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Old 12-08-2008, 10:23 PM   #1 (permalink)
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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)...

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Old 12-08-2008, 10:56 PM   #2 (permalink)
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Quote:
Originally Posted by Xringer View Post
Anyways, this is heat, pumped from the air outdoors, without any electrical heating elements for boost..
Not directly at least.... They do have defrosters which is why the data has this footnote

Quote:
Above data does not take Defrost Operation, Overload Prevention Protection, and/or Cold Air Prevention Protection during heating operation into account. For this reason, the value may vary from the actual heating characteristics.
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 But that said - electric heating elements have less losses than any heat pump
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Old 12-09-2008, 12:04 AM   #3 (permalink)
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Quote:
Originally Posted by trebuchet03 View Post
Not directly at least.... They do have defrosters which is why the data has this footnote



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 But that said - electric heating elements have less losses than any heat pump

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..
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Old 12-09-2008, 03:19 PM   #4 (permalink)
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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.
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Old 12-09-2008, 04:40 PM   #5 (permalink)
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No cold blast with the mini-split

Quote:
Originally Posted by JMags View Post
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.
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 57.2F (14C).
Defrosting operation lasts 12 minutes (maximum).
2 minutes after it is stopped, compressor is ON.
4-way valve is ON. Outdoor fan is ON.
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Old 12-09-2008, 06:31 PM   #6 (permalink)
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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.
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Old 12-09-2008, 07:02 PM   #7 (permalink)
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Quote:
Originally Posted by JMags View Post
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..
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Old 12-09-2008, 07:47 PM   #8 (permalink)
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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.
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Old 12-09-2008, 08:06 PM   #9 (permalink)
Old Retired R&D Dude
 
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Quote:
Originally Posted by JMags View Post
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..
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Old 12-09-2008, 08:18 PM   #10 (permalink)
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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.

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