Mini-split ductless question..
 

I've been looking at a (somewhat) new breed of heat pump to supplement
my home heating system and these new imported (China?) Mini-split HP
systems seem to be the cure for high oil bills..

Here's the service manual link for the Sanyo 24,000 BTU AC & Heater.
http://sanyohvac.com/assets/document...SeriesRevB.pdf

Found at: 24KHS72 - Sanyo 24,200 BTU Heat Pump Air Conditioner Kit

Anyways, my question pertains to page 28 in the manual.
The chart seems to indicate that when it's 18 deg F outdoors,
the until will still deliver 20,850 BTU of heat (indoors @ 70deg)..
I find it amazing that 18,000 BTU can be had when it's 8 degrees outdoors!

Anyways, this is heat, pumped from the air outdoors, without any electrical heating elements for boost..

It seems like the perfect little heating system for New England type winters.
(Plus the AC looks pretty nice too).

Question:
What is the draw-back to installing a Mini-split ductless??
I know there has to be something wrong, or everybody would have these..
(They seem too good to be true)...

Not directly at least.... They do have defrosters which is why the data has this footnote :thumbup:

Page 41 explains the frost detection and defrost cycle (up to 12 minutes max).

I like these cooling systems - much more efficient than window units and are scalable :thumbup: But that said - electric heating elements have less losses than any heat pump :p

The way I understand Reverse-Cycle Defrosting, is they turn on the AC mode
for a while to pump heat to the outdoor coil, melting the ice.
(No electric heating elements needed).
Which, it seems would only frost up if it was both cold and humid outside.
Around here in the winter, it stays pretty dry when it's cold..

From what I've read about regular heat pumps, it seems like they add on
some 10 or 20 KW heating elements to turn on when it gets real cold..
(Making your electric meter spin like crazy).

----
I don't understand what you mean by, "But that said - electric heating elements have less losses than any heat pump".

Isn't a heating element is just a direct 100% conversion of electrical power to heat??
Whereas a heat pump is just moving existing heat?
Comparing power usage vs BTU out, a space heater is 100% efficient
and a heat pump is about 300 or 400 percent efficient.?.
(At least this is what I've read)..

That low power use per BTU is the main reason heat pumps are so
popular these days.. Electrical baseboard heat around here (20 cents per KWH)
will do a job on your paycheck..

The reason whole house heatpumps have those heat strips at 5k+ watts is to prevent a "cold blow" when the unit has to defrost. The average homeowner is unwilling to accept that happening.

No cold blast with the mini-split
 

Even when they tell him that it's going to cost him a bundle for the power?


I like the way the mini-split units defrost. They just skip turning on the indoor fan. I guess they have better firmware programmers.?.

Reverse-cycle defrosting operation

Compressor 1 minute after it is stopped,
Compressor is ON.
Outdoor fan OFF
Indoor fan OFF
4-way valve OFF

Operation lamp
Repeatedly switches between red
and orange illumination.

Releasing of defrosting

Outdoor heating exchanger temp. is over 57.2°F (14°C).
Defrosting operation lasts 12 minutes (maximum).
2 minutes after it is stopped, compressor is ON.
4-way valve is ON. Outdoor fan is ON.

Manufacturers seem to be reluctant to add inverter technology to whole house heatpumps. You can buy a 23 SEER AC only system but only about 16 SEER if its a heatpump. I hate trying to deal with the HSPF ratings because I'm just not familiar enough with them.

Split ductless has had the inverters for a little while now I don't know why whole house systems are behind.

Yeah, I've been wondering about Whole House systems too.
They seem to be stuck in a time warp for some reason.
Maybe I should write to some of those manufactures and tell them
I'm paying 20 cents per KWH and the price isn't going to drop like gasoline..

However, since my home uses forced hotwater baseboard heating,
we are basically ductless..
So, a $1,000-$1,500 mini-split 24,000 BTU ductless that can heat my whole house
for most of the winter (and comes w/ a nice AC), looks pretty dang attractive..
Heat or cool my whole house on 2.5KW?? That's about 50 cents an hour when it's running full bore..
Not too bad compared to heating with oil.

I've read these mini-splits are simple to install. But you do need to call an AC
guy to vacuum pump the lines and flip the valves to release the refrigerant.
(I see those vac pumps aren't that expensive)..

----

But, with gas prices falling, home heating oil can't be far behind.
Maybe I'm worried needlessly.. :rolleyes:

Is your house an open floor plan because its very difficult to heat/cool an area with any confined openings, doorways etc. A large archway or no wall at all is little problem but a standard doorway size opening will be a large restriction. Also make sure you do a load calculation to get the right sized unit.

I've found the best location for the inside unit. We do have a large open area.
The wall unit will be right next to a fireplace where I once used a wood stove
(with a integral blower) to heat the whole house, so I'm in luck with this location.
(No plasma TV that will need to be moved etc).

I've done the load cal and it looks like 2 tons will do the job with a tad over-kill.
But, these new inverter models can slow down their motors and run
at low power/BTU levels..
So, we shouldn't be wearing it out in 2 years.. :thumbup:

If 24k BTUs is slightly oversized you might go to a 1.5 ton unit then since your only going to use it in milder weather for heating. And cooling is better undersized to remove lots of humidity so even if it doesn't drop the temperature much its comfortable.

The neat thing about inverter technology is it's not just on or off, or a 2 speed blower, it's variable..
Cooling output is variable from 4,000 to 24,200 BTU.
Heating output is variable from 4,400 to 29,000 BTU.
(from the 24,000 BTU model specs).

So, if it's pumping out 25,000 BTU of heat early in the morning,
it might be down to 5,000 BTU by 9 AM..

Not to sound condescending but I'm aware of that. Unless there is a humidi-stat you can set you wont necessarily be able to get maximum efficiency still.

Haha.. This is all new stuff to me. I find it all very fascinating.

Anyways, one of the operating modes listed in the manual is Dry .
And there is a humidity sensor listed as a component.
I'm not sure how it works, since there isn't much detail in the users guide.

It seems like Dry mode might be useful for mild nights when it's really damp,
but not very warm. I think the low temp limit (for DRY) is around 56deg.

We have a humidifier and a dehumidifier, so I've got some idea of how the sensors work.
I just remembered, our new model tiny window AC has a DRY mode too.
Never felt the need to use it, the last two summers, since Cooling is mostly
why we got it.. :)

I thought I would share my experience with you.

I live an a 1920's stucco Tudor in Minneapolis. The house has been updated with insulated windows and celulose blown in the walls, but it still isn't and can't be (without massive remodel) tightened up the way a modern house can be.
I have an older forced air furnace in the basement and central air which rarely gets used.
The house is a 1.5 story with a master bedroom and office on the second floor. The second floor has been the problem. This area gets poor airflow from the furnace and often experiences extremes of heat in the summer and cold in the winter.

In October I purchased an Amcor Air mini split inverter heat pump (12000 btu cool, 15,000 heat) from Kingerson's online.
http://www.minisplitacunit.com/12000....html#features

As you can see like many inverter units the specs were impressive. Living in Minneapolis I was most concerned with the heat output and cost of operation.

Here's what I can tell you after 3 months of use and a couple of utility bills and some really cold weather....

The unit functions GREAT as a supplemental heat source, and GREAT as a massive air conditioner.
The specs on mine state that it is a SEER 20 with a HSPF of 10.1
The operating temperature range (outdoor) for heating goes as low as -4 degrees (F)!!
My unit was 90% installed by me. I needed an impact drill (rented at Home Depot) to make a hole for the wires and pipes. I mounted the unit on the wall, and ran the pipes down the outside wall to the compressor which is mounted on my cement patio. I hid the wires and pipes inside of a rain gutter and it is hardly noticable by anyone who isn't specificly looking for it. I ran an ad on craigslist for an HVAC man to help me set it up and double check my work. I found a great guy who even re-did my flare fittings with a special gooey thread compound instead of the teflon I used. He then vacuum'd the lines and tested it out. I have him $120 for 90 minutes of work and we were done. The electrical hook up was a simple 120v affair and the wiring was simple. The manual sucked, but it wasn't rocket science.

I had good experience with Amcor customer service and shipping as well. The Energy Guide Sticker stated it was only a SEER 19; so I called to ask about the descrepency. They were great, and told me that they made up the stickers before getting the results back from testing. The unit did better than they thought. He offered to send a new sticker, but I didn't really care. I was just happy that the service was competent and friendly (and fluent in English).
The unit cost about $1200 and was delivered to my door step in 3 large cardboard boxes. Total cost for unit plus equipment rental, electrical stuff and HVAC guy was under $1500. I'll post photos of the install if anyone is interested.

So far, I got to test it in some 80 degree (outdoor) weather in October. The A/C works incredibly well. It is not only far quieter than the noisy window units, it moves much more air at much greater velocity. In late afternoon, the second floor receives direct southern sun on the roof and knee-walls which are only insulated with 3.5" of celulose. Often the temps can reach into the 90's indoor without A/C. This unit can cool the area in about 10 minutes under the worst of circumstances. The area is about 600 sq ft.

In December we got a string of sub-zero days. I was really curious to see how the heat pump would work. Normally we turn the temp inside down to about 64 degrees at night and I pump it up to 75 degrees during the day (I work in a home office at the other end of the floor, and keeping it hot helps make sure the heat reaches all the way back to my office).

Here's what I found regarding the heat output.
1. The unit puts out good heat (at least 80% of max capacity) until outdoor temps drop to about +5 degrees (F). Below that the temperature of the air coming out begins to drop. Higher fan settings just blow more 'less hot' air.
2. The unit shuts itself off when it is too cold to generate usable heat. This temp seems to change with relative humidity. While it is certainly 'dry' by our standards in the freezing cold winter of Minnesota, the relative humidity may create a dew-point that is not too far below the ambient outside temperature. When the outdoor compressor unit is running (even when it is cold outside) you can put your hand in front of the fan and feel that the escaping air is even colder than the outside ambient air. Even when it is only 10 degrees outside you can still feel that difference, which is pretty amazing. With a dew point close to ambient outdoor temperature this can also cause ice or frost on the coils, causing a defrost cycle. Eventually the unit is doing too much defrosting and it just shuts off completely until it can efficiently start back up again.
This is key, and I couldn't get an answer about this before I bought. I was worried about the heat pump chugging inefficiently along all night burning electricity on a permanent defrost cycle if I left it on some night and outdoor temps really dropped. The good news is that it is smart enough to shut itself off!
3. The outdoor unit is inverter-run, and you can tell because the fan and the compressor change speeds. Its pretty cool to watch. The indoor unit, however, is an AC motor fan. It runs at one of 3 speeds. I wish it also changed dynamically as a variable speed fan, but it doesn't. Still- it works fine and is a major improvement over a window unit.
4.Bills: In October I couldn't even tell that we were running it. It is probably at least 200% more efficient than the window units, and much larger capacity- so it didn't need to work real hard. The bill increase was not discernable, even though we ran the fan every night. I expect that will save some serious electricity next summer.
In December my electricity bill was about $145. With no HVAC or other seasonal loads I expect this number to be around $70. We pay about .10 kwh here. I haven't gotten a chance to log in to the power company's website to compare actual usage, but I'm very happy with it.
An added benefit is that when our outdoor temps are a little more 'moderate' (average winter temp is +20 degrees) and the heat pump is producing at full capacity I put a fan at the top of the stairs and blow hot air down to the first floor. This keeps my gas furnace from turning on as often. My gas bill in december dropped about $30 (from same time last year). Not much, but I also like to consider that I am essentially conditioning an extra 600 sq ft that wasn't really being conditioned before. If the house was properly ducted and the gas furnace could reliably heat it I'd estimate that my gas bill would increase by about $100.
Net savings isn't enormous, but the moderate savings coupled with much more comfortable square footage has been great.

Final Thoughts:

I think this is a game-changing technology for three reasons:
1. Low cost for a unit (bought over internet) coupled with simple install that can be 90% DIY can keep costs LOW.

2. Many people in older homes need fairly radical remodeling work done if they replace furnaces or boilers- which is why there are so many older homes in cities with 30 year old inefficient 60-80% aflue units around. A Mini split allows you to keep them running, but supplements their heat with something very efficient. Hopefully you are only using inefficient heat on the coldest days.... in my mind that's a reasonable compromise. Also adding decent A/C to houses with radiant heat (radiators) is wonderful.

3. It is simply amazing to me that I can use an air source heat pump with better efficiency (HSPF 10.1) than almost any ground source heat pump out there (without the expense and engineering of digging up your yard), and it will work in 95% of the temperatures I am exposed to (even here in Mpls), for 1/20th the cost!!

My last two ideas:
- start putting this technology in all HVAC and refrideration units. The difference in efficiency is just too large, and the technology is not all that complex. Imagine if homes in the future had one large really efficient heat pump compressor outside. It fed anything that needed heating or cooling. Small minisplit units in the rooms, and units in refridgerators and freezers. All having their heat efficiently moved around from where its needed to where it isn't.

-an air source heat pump could be made into a cheap gound sourcer with this technique:
PVC "earth tubes" are laid underground to warm ambient air up to a range that works for an air source heat pump. Simply run several of them in a shallow trench for 40-50 feet and have them exit in a manifold around the outdoor compressor. They would warm ambient outdoor air temp slightly. It wouldn't take much to increase temperatures below zero temps to +5 degrees. Since these earth tubes don't enter the conditioned space of the home, you don't need to worry much about condensation or mold or permits. They would increase efficiency by cooling air in the summer as well. Here's a link to a story about someone who did it with an older air source heat pump in Nebraska:
Earthtoys - Emagazine

I'd like to hear other people's experiences if they try these out.
Thanks for the discussion-

WOW!! That's what I'm talkin about!! Thank you Forty Two for the great review!

The first time I looked at the specs on an Inverter Mini-split, I was just amazed by the cold climate heating abilities. I had to wonder if this was for real!

I am very encouraged by your experiences with your 12,000 BTU system in heating and cooling modes.
Please post anything you have found out about the AIR PURIFICATION and DEHUMIDIFICATION modes, if you get time.

If you have pictures, please post some..

----
We have about 1,000 sq feet of area that I want to heat (and cool) with a Mini-split. Just like yours, this unit will supplement our regular heating system. (Oil-heated-forced-hot water).

I think a 24,000 BTU system should handle the job, since most of the winter our temps aren't super cold. 20 degrees in January is very typical.

I guess I'll have to start building the outdoor pad in the spring!

Right now, heating oil is only about $1 more than gasoline, but I don't expect it's going to stay that low in the coming years.

Our power bills are high (.20 per KWH), but I have locked in that rate through December 2011. Knowing they aren't ever going to go down.

I guess the amount of oil vs KWHs we use will depend on what's currently cheaper. (My guess is oil will not remain very stable).

Since my boiler can also burn wood (or rolls of junk mail), we could get by without oil, IF we get that mini-split installed! :D

Thanks again! :thumbup:

I'll put together a small photo album shortly.
This morning I woke to 3" of snow and negative 10 degrees F. Chilly!
The heat pump was off, so I turned it on to see what would happen. At this moment it is running for the past 50 minutes and has defrosted once. It isn't blowing much heat, but it's a little. I suppose as much as a small electric fan ceramic heater on low.
It'll be a cold day to work in my office, so I'll work from the dining room instead- something that I don't mind doing a couple days a year.

As to air purification and dehumidication-
the unit has a plastic mesh screen filter that seems to grab dust and such very well. I've rinsed it out in the sink once. There are no other 'ion' charged filter gimics with this unit- just the mesh screen. It is similar to what you would find in the front of a modern window a/c unit.

I can't say I've tested dehumidification. I'll get a chance this summer, as Minnesota's 10,000 lakes can make our area a little steamy.

Something else I discovered that may be of help:
in Mpls our electric utility is Xcel Energy. They offer a 'dual fuel' program for reduced electric rates.
Basicly if you have gas or other fossil fuel 'back up' heat and install electric resistance or heat pumps (for space or water heating) you can (at a cost of about $1500) intall a second electric meter. This meter provides power at a cheap $.045 kwh but has a 'saver switch' which allows it to be shut off at any time. Last year it was only shut off twice for a couple hours during some peak demand.
I haven't installed this yet, and I am contemplating some remodeling and need to consider where to route additional wires, etc. I think this sort of program often exists in other parts of the country and could be a great way to really drop the costs down.

I'd like to add the big heat pump to the basement or main floor, and the heat pump water heater as well, and then install the extra meter.

another thing- the outdoor unit only weighed about 70 lbs and is about 1/3 the size of my central air unit. You don't need to build 'much' in the way of a pad. A couple of patio bricks would easily suffice. I actually had wood 2x4s embedded in my concrete patio to separate the panels. I just screwed the unit to these.

It would be cool to figure out cost per million btus of heat for these machines at different electric rates. These calculators are often on sites for pellet and corn stoves. I've never tried to figure it out for heat pumps with this level of efficiency.

Sorry to hear it's so cold there this morning.. (Prelude to global warming?) ;)
It's about 20 here right now. It would a fine day for a Mini-split ductless.
But, I'm burning up gallons (1GPH) with my old multi-fuel boiler..
http://i46.photobucket.com/albums/f1...HSTARMOT35.jpg
This thing needed a large pad. It was a messy DIY job. :o

The 24,000 BTU outdoor unit is 130 pounds, so I can likely get away using stuff that I have on hand. But, I do wont to avoid any complications if the city inspectors have to come by.

Can't wait to see the pictures. Want to see how you did the AC wiring,
conduit etc..

Got to head for the bowling alley..

42, Love the idea of using earth tubes. Have looked into them in years past and always wondered why no one is doing this. I was looking for inexpensive cooling to supplement a solar (evacuated tube) hydronic infloor radiant heat system. As you can tell this is an older article as the prices today are probably a little higher. After reading about problems you mentioned with direct air exchange I gave up on the idea. Though I still think decoupling it through an outside exchanger would work great. Should keep the outdoor unit right in it's sweet spot year round and save alot. Look over the link.
My thought is to use this setup and add one more set of 90 degree elbows to make almost a complete rectangle. Build both ends of the tubes into an insulated box. Place the outdoor unit inside in a fashion so it's fan would suck from one side (return) and blow out the box (supply) completing the loop in a push pull fashion. Not sure of the cfm of the outdoor unit though this is probably still overkill built in.

Free Home Air Conditioning! - Save Money on Air Conditioning Bills

Mine does not do that; I avoid using the heat strips, so whenever they are used you can definitely smell them.

Hey 42!
 

It's been a about a month and it's been cold as well digger's butt.
How has that mini-split been working out on these cold days?
Have you had any problem with the outdoor unit frosting up?

Thanks,

This thread has led me to think that I should get one of these with my tax return.

Here's the situation. We have an oil furnace driving a single-pipe steam heat system (steam goes up to radiators, condenses, and uses the same pipe to return to furnace) that does a good job of keeping the house warm, but at a rather high price.

One of these units looks like it would be PERFECT for my downstairs. I could mount the compressor unit in what was a flowerbed beside the house right by the dryer vent - thus having a relatively good supply of hot air for it to work against in the cold, and the wall unit right above it in the "middle" room of the house.

There is an archway between the front room (stairs and TV) and the middle room (table and toy area) that is about 10 feet wide and 8 high. The rooms I'm looking to heat/cool with it are roughly 14' x 21' for a total of 588 sq. ft.

Is one worth it for me, living in Pennsylvania? Probably 85% of our time is spent in those two rooms, and having A/C would make the summer VERY nice.

Being able to *cheaply* heat those two rooms and leave the furnace set low would help our oil bill - but would it make a big impact? Would I save enough on heating/cooling over the next 4 years to pay for the unit?

What size unit should I go with for ~600 square feet if I were to get one?

The first 5 pictures are the two rooms to heat/cool.

Picasa Web Albums - Nevyn

You need to check out some of the AC websites. Many have programs or charts to help
you size your system. My guess is about 12,000 BTU..

4 years to pay back? Right now, my oil is about $2 a gallon. When and if it goes up again,
will it stop at $4 a gallon? Or $5 ?? No one knows the payback on these things..
(Solar panels, hybrid cars etc)..


Edit:
Here's a URL with some info about BTUs needed for sq foot.
http://www.ductlesshvacsupply.com/btu-sizing.html

Mine has been running really well. No complaints- only happy with the purchase.
I never notice if its frosting up. It just shuts itself off. Its pretty easy to tell on the really cold nights that it will gradually stop working at around zero degrees.

As far as sizing- another thing to think about is this: those charts are mainly for cooling. As far as heating- it depends on your climate. When its zero degrees outside I think my hp still puts out heat, but much less.... maybe 7500 btus instead of the 12000 it is rated for. If heat is your main concern- I'd oversize. Because these are DC powered, they will throttle up and down a lot more than most of us are used to with conventional A/Cs.
My 12000 btu (15k for heat) will comfortably heat about 800-1000 sq feet with heat to spare if I use a fan to blow it downstairs. But its also running constantly as opposed to a 60k btu furnace cycling on and off. I would try one out. I'm also looking forward to the A/C as an extra benefit.
My bill depends a lot on the weather. If its really cold (below zero)- not much benefit. Above that- it makes everything more comfortable. And if I take the time to put a fan in the doorway and crank the HP it'll heat the downstairs partially as well. Your situation sounds much more ideal than mine- I'll bet it would cut your oil bill in half and probably bump the electric by $30-50 in the winter.

Thanks, that's got a lot of what I wanted to hear in it. it's rare to see temps that low here, but it does happen occasionally. I'd be mounting the compressor in front of the dryer vent, which I figure should help with air temps for it to work against a little bit. My area to heat/cool is ~588 square feet, which is kind of on the line. I'd love to oversize, but I'm also looking to minimize cost.

If it halved my oil bill then it might pay for itself by springtime. That's a MAJOR bargain! I just have to be sure to get one that is inverter powered, correct?

I would look for one that has an inverter (which will cost slightly more) and uses 410a as the refridgerant. The one I got is this one:
mini split air conditioner - ductless split system
it seemed to be the most efficient I could find. I've been happy with it so far.
It is only 120v so the install is not that hard for a DIY. You will still need someone to vacuum the lines, but craigslist is a great place to look.
Good luck!

I would make sure it's an Inverter model, and a brand name you've heard of.
I would also download the manuals and be sure the heating mode worked well, when the outdoor temps are low. IIRC, some of the Mini-splits I've seen for sale, don't publish any data below 30 deg F.



Placing the outdoor unit near the dryer vent might be asking for problems,
with little micro fibers of lint building up in the coil.


I looked at the $ price per BTU out on the Sanyo systems and found,
Sanyo Ductless Mini Split Heating and Air Conditioning
that the price per BTU for the 24,200 BTU model ($2111.00) comes in at the best rate,
about 8.723 cents per BTU.. The other sized Sanyo models range from 10 to 15 cents per BTU.

With the free stuff, it's too good of a deal for me to pass up..

FREE FREIGHT to your local FedEx Freight Terminal US Continental deliveries $129.00

FREE 20'-Interconnecting LineSet with UV Protected Wiring $219.00
FREE Service Disconnect Box and Power Whip $56.00
FREE Condenser Mounting Block Risers $37.85
FREE Wall Sleeve and 10' Drain Hose
$14.00
FREE Warranty,Technical and Installation Support Priceless


Yeah, I'm going to be ordering soon.. :)

Thanks for the report.. That's just what I wanted to hear!
We have had a few Zero degree spells this year, but about 89% of the time,
we could have been using a mini-split.. (If we had one)!

I plan to start on the pad and pre-wiring the 220V this month.
I will be placing my order for the 24,200 BTU Sayno very soon.
We should be able to get it installed soon enough to use the heater mode,
since spring time seems far away right now..

Dang! Now you got me looking at the AmcorAir 24000 deal...
It does have a 25' line set, instead of the 20' with the Sanyo kit..
Comes with a wall thermostat too. (In case I lose the remote)!
The HSPF of 9.8 is better than the Sanyo's 8.5 HSPF...
And, the price is better. Hummmmm..

42,

I know the link I left a few post back may not have stood out so here it is again.

Free Home Air Conditioning! - Save Money on Air Conditioning Bills

I realize it is a long read and the person sounds a little pompous but what he describes seems well thought out. If given the yard space and initiative I would think one could keep their outdoor unit close to it's SWEET range year round using this closed loop setup with the outdoor compressor driving it in a kind of push pull configuration.
You mention adding on another large heat pump for basement or main floor or both, are you familiar with multi splits. One of the most reputable brands sells here now and while I'm sure would cost more than your 12k unit x however many rooms, it still may offer many benefits for your additions as opposed to multi smaller units. Especially after you put in the cheaper electric supply meter you spoke of. Expensive I know but 3-4 ton from one outdoor unit and up to 8 indoor units of varying capacities.

http://www.daikinac.com/residential/...-%20Daikin.pdf

Just zone the whole system so it can condition the area your in at any time of day. Just look over the specs and see what you think. Now think about the one outdoor unit driving a closed loop earth tube system and what do you think you could save now.

Just a thought Paul

Something I just thought of as I looked through the mini-splits on ebay.... many are only Seer 13, and these don't seem to function at temps below 15 degrees F. Make sure you get something in the SEER 18-20 or with a HPSF(?) that's as close to 10 as possible. These seem to be the ones that function best in cold weather.
I saw a 24000 BTU mini split on ebay for only $1000 but it was only a SEER 13 and couldn't function well at low temps.

I LOVE the idea of using earth tubes to feed the outdoor compressor on an air source heat pump. You get rid of any issues of mold, and in really cold environments you only have to get the temp up to around zero. Plus, you wouldn't need to trench it as far- probably a regular trencher would do the trick instead of a backhoe. Around here you have to go pretty low to avoid frost for water lines- but in this application you only need to raise the temp up to a good operating range for the heat pump. Even if you don't do it right away, keep that in mind when you mount the outdoor unit. You might want to add something like that later. I know I'm thinking about it.

Placing the outdoor unit near the dryer vent might be asking for problems,
with little micro fibers of lint building up in the coil.

I second the warning, not only lint, but humidity.

I do thank you for your concerns, they were things that I hadn't really thought of in a large way. I was looking at it a little more over the weekend, and I won't be putting it RIGHT in front like I thought was a good idea. It'll be near it by necessity, but I'll put it next to my basement doors instead - about 3 feet to the left of the vent. The vent points towards the backyard, and I'll be mounting the unit on the front side, so it'll actually be blowing away from the unit.

I wonder if I can move my dryer vent underground and heat my garage with it....? :)

I wish I could come up with a positive reply. Under ground would not be good either. I'm afraid we are getting too far off subject for this thread. If you know how to PM then leave me one and I will try to explain something I did that seemed to help utilize a little of the heat. Otherwise you would be asking for trouble again by putting it under ground. The cool ground would condense the humidity, leaving the inside walls very wet and cause a lint trap and a probable blockage. NOT GOOD. Not to mention, there probably wouldn't be much heat left to exit anyways.

Paul

That's why I mentioned it - I figured there was SOME problem I'd forget about.

Anyway, we're looking at going with a 12,000 BTU unit over the 18,000. It says the 12k is for 300 to 500 square feet.

We're more concerned with heat than cooling. Would putting that in a space around 550 square feet be over-taxing to the unit? It's job wouldn't be primary heat, but merely to help hold temperature once the furnace has the area up to temp (from overnight low).

I really hate to see people waste their money sooo.

People often discount or totally ignore stratification of air when heating/cooling two story homes. As silly as this may sound, (IF!) you have an open (no door at the bottom of) stairway and you are considering only one unit (mini split) and are looking purely at saving money as opposed to requiring more comfort (as was 42's initial concern) you may be better off putting the unit upstairs in as open an area as possible. Over heat the upstairs a few degrees with the combined output of your boiler and this unit set a few degrees higher which would in effect cause an insulating buffer zone akin to adding more insulation in your attic. I can only guess that is why 42 is so happy with his. Well that and it was quite a find as far as specs and price are concerned.. (KUDOS to 42 for the find) I would buy three of those separately over a three zone multi split.
Excuse the over explaining but, my Mother owns a over under duplex. My brother currently rents the upstairs and keeps his heat at 62 all the time. They both have the same make and efficiency furnaces except for size. Hers being forced air gas 93% AFUE 75000 btu out. His the same , but 48000 btu out. She needs to keep hers set at 70-72 to keep it comfortable downstairs. Last month (DEC) here in central NY was cold as usual. He used exactly half the therms gas as her 92 his vs 184 hers. These apts are not open to each other so I can only surmise that the 8-10 degrees delta T and the fact that he has some insulation over head in attic where as there is none in her ceiling between apts that her heat is indeed supplementing his. They are both same sq ft same layout.
My mother saves everything and I was able to prove this with old bills when previous tenants lived there and kept a much more reasonable 70-72. The difference was only 67% on average as opposed to 100%.
Now this can be used for A/C as well. At my previous house (I am currently back home with Mom) I was able to cool one upstairs bedroom and the whole downstairs from 88in 92out to 66in bedroom 78downstairs all with one 6000BTU window unit running max. I covered all the registers, supply and return with cardboard and tape. Placed a box fan at the bottom of the stairway in a fashion that blew the cool air in a complete circle around the downstairs. I watched in amazement with a lit cigarette as the heat was brought around and went up the stairway with an almost chimney like draw as the cool air flowed down the stairs like a waterfall.
NEVYN.
This is why if you use only one unit (and I would buy 42's 12000btu Amcor) I would suggest an upstairs open area with room doors open if possible over downstairs. At least for the first unit. Who knows, maybe next year another for downstairs!! and No boiler.
One thing I thought of, but have no answer to is if it would be cost effective to have your boiler kick down (setback) overnight as I am not familiar with how quickly one pipe systems can recoup. If your bedrooms are upstairs this may be another money saving option we use in CNY with forced air. I do know that with boilers and radiant floors it doesn't work well.
Anyways I just have this feeling that if you put the indoor unit downstairs as you propose, you will not only be asking a 12000BTU unit to heat your 588sq ft downstairs, but also effectively half of your upstairs through convection. In which case YES you would be over taxing it. In which case I believe you would be better off taking the $1500 (per 42's install) and renting a blow in cellulose machine and putting as much as feasible in you attic. Caulk any infiltration areas. It would be money better spent.
As always my opinion is just that. I always appreciate any feedback as that is how I learn. With the exception of the statement about resistant heats efficiency vs heat pumps JMags has been (in my opinion) spot on and maybe he can add or subtract from all I've suggested.
As the great philosopher Forest Gump said, "That's all I got to say about that, I think I'll go for a run."

PAUL

Thanks, there's a lot of info there.

My upstairs is very oddly shaped - see the slideshow in my first post. There's a small foyer area, a bedroom, and the computer room that sit above the two downstairs rooms I want to put the unit in for. Above them is a crawlspace, no real attic. It's full of R-38 insulation ON TOP OF some R-13/R-19 that was there. We had to add the insulation to be able to get a gov't grant for first time home buyers. The rooms upstairs often hold heat 3 to 5 degrees warmer than downstairs.

The floors downstairs have R-19 between them and the basement.

I'll get some better pics and measurements over the weekend, but I hope that this info helps. I'd feel better with the 18,000; maybe we should just scrimp the extra $500 together for it?

Excellent and yes it helps. How serious are you about this and have you thought the total costs through. Are you thinking of the Amcor or looking elsewhere. I keep trying to see how serious you are. I spend way too much time trying to help people and they end up doing something totally different or end up cheaping out a couple dollars and unhappy. Then somehow blame me so let me know if this is just a thought or a goal because I think if you do what I propose you could save quite a bit over oil. Payback definitely. How long, can't say. Do it wrong, never, plus waste of your up front money.

PAUL

Sorry about that, just had something happen before I sat down previously. Anyhow. This Amcor deal looks too good to pass up. You can find what looks cheaper to start, then add in all the other stuff that this one includes and it is more expensive with worse specs.
NEVYN:

I would go with nothing less than this...

mini split air conditioner - ductless split system

For many reasons. Look at it and the price and if your still with me tell me what you think. Also I found this...

http://www.youtube.com/watch?v=PdMRVO_NOz4

How much of this do you think you can do on your own?

Also try as I might I can't find the room pictures at your link. I find pictures, but not of rooms.

PAUL

Kingerson's what where I planned on ordering from, and the Amcor was my plan too. I'll post the link again, if it doesn't get you to the "House!" photos PM me and I'll direct link you.

Picasa Web Albums - Nevyn - House!

We're highly serious about this. My wife and I agree that we *NEED* to do something to reduce what we spend on oil, and this looks to be the best bet.

I have no trouble doing, well, just about anything for a home. I grew up in a DIY house, and with an extended family that gave me all the opportunities a boy could wish for (My mom's side runs a farm - and they have a sawmill + full woodworking shop, AND a full machine shop for equipment repairs). I have no problems with household wiring, piping, plumbing, ducting, etc.

We are looking to use the mini-split for several reasons:

1. Save money by buying less oil.

2. Provide an alternate source to the oil furnace for maintaining the temperature of the main two rooms downstairs (rest of the house is not important). The furnace will boost the temperature once in the mornings throughout the whole house, and then be turned back down and the mini-split will heat only the rooms that are occupied.

3. Provide small to moderate cooling in the summer. We're not looking for something that will cool 90 down to 70, but for something that would be able to take 85 down to 75 in the "main occupancy rooms."