LeftieBiker
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Re: Share Your Home Electrification/Efficiency Improvements

Thanks. I just posted my question there, about one of the Mr. Cool standalone heatpump units. Trying to get an estimate for a sub-$8k job is not easy. I mostly get calls from people wanting to sell me more expensive, complete systems.
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ripple4
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Re: Share Your Home Electrification/Efficiency Improvements

LeftieBiker wrote: Thu Nov 11, 2021 1:48 pm I've been looking for an air source heat pump that is affordable for us ... and that will directly replace the 13.0 EER central A/C unit on the North wall of the house, sending heat as well as cold to the A coil in the furnace. The two units were sold and installed as a pair, and the furnace manufacturer says that while they no longer sell heat pumps, what I suggest is quite possible.
I am researching a similar idea to make a split heat pump heater for DHW and also my spa, both which are now NG. according to one single youtuber guy who made his own split DHW tank claims that the indoor unit is nothing more than a length of pipe. So a plate/plate exchanger or your A coil would not be different. Two cravats, a traditional AC unit might have an expansion valve right at the evaporator, so that would need to be bypassed as the split system heat pumps have all that inside the outdoor unit. also he used the indoor unit in his install, using just the outdoor unit by itself would require a hacker-level control system with a thermostat ( a quick google seems to indicate that the indoor unit communicates with the outdoor unit via a pulse modulation signal on the single non-power wire that connects the two units) The big upside is there are 24-36Kbtu outdoor units from mini-splits by themselves for only a few hundred out there.

https://www.youtube.com/watch?v=g5y-_Axl284
LeftieBiker
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Re: Share Your Home Electrification/Efficiency Improvements

That sounds like some creative wiring and programming is required. I was hoping that I could find an outdoor unit that doesn't have a linked air handler inside the house. The ones I was directed to in the above post seem to be of the latter type.

https://iwae.com/shop/heating-air-condi ... age-units/
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dmacarthur
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Re: Share Your Home Electrification/Efficiency Improvements

That sounds like some creative wiring and programming is required. I was hoping that I could find an outdoor unit that doesn't have a linked air handler inside the house. The ones I was directed to in the above post seem to be of the latter type.
Because all of the mini-splits coming out in the last few years have been designed for max efficiency and for working in colder temperatures, and because the 2 components (indoor and outdoor) need to work together, I will be surprised if you will find a stand-alone unit or if you do if anyone will be willing to hook up the tubing. Best of luck..... my son has 2 outdoor units sitting in his driveway, taken out of building projects, and has not been able to find indoor units to match them correctly. (maybe you and he need to talk....)
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LeftieBiker
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Re: Share Your Home Electrification/Efficiency Improvements

The problem is that my housemate isn't going to go for a $9k project in which we have people working inside the house for days, taking apart half of the furnace (which we will be needing any day now) and exceeding their estimate by thousands of dollars. The only ways I can get a heat pump this year are either by doing what I propose above, or by doing another mini-split install - this time with 3 or 4 air handlers. I barely managed the last one with one air handler, and I'm much more feeble now. It's looking like I'll just be hooking up the portable heat pump in the dining room, and running that very loud piece of...technology when it won't disturb us. I really hate that we're still burning fuel oil (she is terrified of gas furnaces) in 2021, as the world begins to burn.
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dmacarthur
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Re: Share Your Home Electrification/Efficiency Improvements

We finally installed an on-demand propane boiler (a combi, does DHW also) after heating solely with wood for fifty years. It only runs for a brief period in the AM 'till we get the fires going.... It is elegant and efficient but still burns stuff that should be left in the ground. Not entirely sure that mini-splits are that much better......
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LeftieBiker
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Re: Share Your Home Electrification/Efficiency Improvements

I think that mini splits are a bit like EVs: they have enough embodied pollution that you have to run them for a few years to "break even" on pollutants, but they do reduce the pollution in the locale in which they are used.
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danrjones
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Re: Share Your Home Electrification/Efficiency Improvements

LeftieBiker wrote: Tue Nov 16, 2021 5:48 am The problem is that my housemate isn't going to go for a $9k project in which we have people working inside the house for days, taking apart half of the furnace (which we will be needing any day now) and exceeding their estimate by thousands of dollars. The only ways I can get a heat pump this year are either by doing what I propose above, or by doing another mini-split install - this time with 3 or 4 air handlers. I barely managed the last one with one air handler, and I'm much more feeble now. It's looking like I'll just be hooking up the portable heat pump in the dining room, and running that very loud piece of...technology when it won't disturb us. I really hate that we're still burning fuel oil (she is terrified of gas furnaces) in 2021, as the world begins to burn.
I'm not really an expert (just play one here) and had to learn as I went on my project, but I really do think you would need a new furnace and A coil and outside unit. But you should be able to keep your old lines, though its possible pulling bigger or new properly sized lines would be more efficient. And they would need vacuuming and refrigerant weighed in.

Excluding some really crazy janky stuff, a new forced air furnace (you want NG? Or keep Oil?) would likely be needed, and that acts as the blower. If I recall correctly, when you have the furnace acting as the blower, the A coil must go above (up stream) AND they can't both run at the same time in heating mode, because the furnace is too hot, and trying to run the furnace and the A Coil (in heat pump mode) is too hot for the coil. Which is a bit disappointing because the coil still produces heat, just diminishing returns as it gets colder outside. With an all electric setup you CAN run both the heat pump and the emergency heat - but that is because first the heat pump heats the air through the coil (which is BEFORE the blower) and then the warm air is then heated more by the electric heat strip kit. So that is an important difference - in your setup you PUSH the air through the coil. In mine, the air is pulled through the coil first. Just something to remember.

But can you technically keep your old oil furnace, replace the A coil and outside condenser? I think so. Most furnaces have a blower speed setting and you might need to adjust it. A new oil furnace on its own is probably 2-3k? I actually looked at this route for myself - replacing my NG furnace, adding the A coil on top and condenser outside. But it added substantial cost because now I had to get a new furnace AND the A-coil and condenser kit. Plus the DIY pre-charged line kits were only compatible with the AC ONLY A coil/condenser kit (or the full heat pump kit, but no NG furnace), and I wanted a heat pump. Add in that I realized when the NG furnace was running the heat pump was forced off, and I decided to go all electric. We don't get that cold anyway, so the heat strip will likely never run. I installed it basically as a backup in case my heat pump ever dies. That all sounds a bit confusing, sorry. In other words the DIY kits (when I got it) was AC and furnace, or Heatpump only. But if you don't want to go DIY, there must be a A-coil and Heatpump setup using your old furnace as the blower.

Not sure any of this helped, but good luck!
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goldbrick
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Re: Share Your Home Electrification/Efficiency Improvements

I'm just following along since I'm trying to decide how to upgrade my system as well.

First, I have a question: what's an A coil?

Second, I imagine just about any forced air system has a switch on the thermostat to just run the blower with no heat or AC used. I know mine does that and I'd guess just about any system will. Not automatic by any means but using the furnace blower without (oil) heat should be easy.
LeftieBiker
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Re: Share Your Home Electrification/Efficiency Improvements

It should be, but isn't. The units I was considering are not compatible for what I wanted to do, according to the HVAC business above, as they are designed as self-contained systems.

An A coil is a heat exchanger coil that is installed in the furnace air plenum. It is connected to lines from a central A/C unit. It may be possible to do what I want, but I'm not going to find anyone to do it. I'm likely looking at the nightmare of having a mini split installed with multiple air handlers, or at having a $10k heat pump system installed parallel to the furnace or replacing it with backup heating strips. That means another Winter of oil heat and about six electric heaters.
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