HVAC Heat Pump

[redpoint5]

This cooling season, the 5-ton whole house AC consumed 357 kWh. 480 kWh for the 1-ton window unit, and a handful of kWh for the window unit in my office that rarely ran. 72 kWh to run the air handler for the whole house AC (about 100 hours of use). Probably 1,000 kWh total for cooling this year, or $170.

Started heating on 10/19.

An HVAC estimator came out yesterday and said it's straightforward to replace the AC with a heat pump and add dampers/rearrange branch circuits in the existing ductwork to create 2-4 zones.

He suggested replacing the furnace with another 80% gas furnace, but I'm thinking to eliminate the gas altogether considering I have 2 gas fireplaces that can supplement heat. He explained the furnace is a comfort thing since heat pumps can blow colder than body temperature when it's very cold out.

He's going to quote a replacement of that wonky return duct.

Found out the furnace cabinet had vents allowing the return to pull in air from the burners, so he taped them over. When I asked him why people would install things this way, he said "I learned long ago to stop asking why and just fix problems".

Also, that upstairs return is 14", not 12". Since the restriction is the intake grill at 17"x20", I'm told I get 500 cfm from each of the returns, which the HVAC guy said was adequate for a 5-ton AC.

[JSH]

Originally Posted by redpoint5

He suggested replacing the furnace with another 80% gas furnace, but I'm thinking to eliminate the gas altogether considering I have 2 gas fireplaces that can supplement heat. He explained the furnace is a comfort thing since heat pumps can blow colder than body temperature when it's very cold out.

People say that. I've never found it to be a problem and I've been living in houses with heat pumps since 2002.

We switched our house here in OR from a 80% furnace to a heat pump about 9 years ago and have never regretted it.

[Isaac Zachary]

I need to read this whole thread when I have time.

Any thoughts as to whether or not it would be worth doing a heat pump where I live? I've got my gas expenses (heating and cooking, all taxes and fees included) down to less than $800 per year.

Trailer house is on a 100 amp circuit. The only thing that could take a lot of that is a 40 amp (or is it 30??) clothes drier that is used a couple times a month in the winter months, although I used to have a 40 amp EVSE on the front of the unit.

[redpoint5]

You're not going to save money with a heat pump over gas, and I wouldn't want to add such a big load to 100A service.

I'd be looking to plumb in a NG dryer. Super cheap to operate, and dries clothing quickly.

In my situation I'm mostly trying to get the upstairs and downstairs temperatures closer to even, and run a quieter variable speed blower.

[Piotrsko]

My 3ton 3year old top of line mitsubishi heat pump is on a 40 amp circuit 220/240 vac 100 amp panel. Give it a minute or so after the 6am start up and it's 100f on the floor vents with enough volume to blow streamers straight up, but we supposedly average 30 most of the winter and not much below. No helper electric coils. Do have a pellet stove, if it ever gets so cold outside that the heater cant find any heat to move. Supposedly like -14f per specs. Haven't used the stoves since installing the hvac. 1100 sqft house, lousy insulation if at all. Your mileage will vary. Also $20K installed

[freebeard]

One of the advantages of not having Internet for 2 weeks, is that among other chores, I weatherstripped the entry door and the fire door.

256 sq ft, running 700/1400 watts in an oil filled radiator. I'm thinking about steam cleaning the built-in radiator, it's dusty so it smells when its on. I think the oil radiator is more efficient?

My current bill shows $0.648/KWH.

[redpoint5]

I've got a bunch of quotes I'll go through and summarize here; all very expensive. I might have the downstairs occupied early next year though, so figuring out how to make it comfortable is becoming a priority.

Originally Posted by Piotrsko

My 3ton 3year old top of line mitsubishi heat pump is on a 40 amp circuit 220/240 vac 100 amp panel. Give it a minute or so after the 6am start up and it's 100f on the floor vents with enough volume to blow streamers straight up, but we supposedly average 30 most of the winter and not much below. No helper electric coils. Do have a pellet stove, if it ever gets so cold outside that the heater cant find any heat to move. Supposedly like -14f per specs. Haven't used the stoves since installing the hvac. 1100 sqft house, lousy insulation if at all. Your mileage will vary. Also $20K installed

Good point of reference.

Originally Posted by freebeard

One of the advantages of not having Internet for 2 weeks, is that among other chores, I weatherstripped the entry door and the fire door.

256 sq ft, running 700/1400 watts in an oil filled radiator. I'm thinking about steam cleaning the built-in radiator, it's dusty so it smells when its on. I think the oil radiator is more efficient?

My current bill shows $0.648/KWH.

I need to get a round tuit for weather stripping as well. Just noticed daylight through a small door that leads from the conditioned "boiler room" to an unconditioned crawl space (that's like 8ft tall).

All resistance heaters are going to be near 100% efficient, it's just that electricity is expensive per BTU unless you're getting above 100% efficiency with a heat pump.

[Piotrsko]

Pretty sure a heat pump doesn't do anything near 100% efficiency because moving air with a fan is horribly inefficient. Think they quoted 85%. In my case I waste 2500 watts just running air through with the all 3 of the fans on: 2 outside, one in the heat exchanger. Add another amount for the compressor if it's needed and your talking serious wattage

[Isaac Zachary]

Originally Posted by Piotrsko

Pretty sure a heat pump doesn't do anything near 100% efficiency because moving air with a fan is horribly inefficient. Think they quoted 85%. In my case I waste 2500 watts just running air through with the all 3 of the fans on: 2 outside, one in the heat exchanger. Add another amount for the compressor if it's needed and your talking serious wattage

But fans usually take up only a few watts. If the total amount of electricity used is in the thousands of watts, but a fraction of that is for fans, and of those fans 15% is of the energy is lost, that's not bad in reality.

[redpoint5]

My air handler fan is 700 watts, single speed. If AC or heat is called, 700 watts. No idea what the AC condenser fan draw is. There's a tiny motor in the furnace to move the exhaust.