Turning a window unit into a mini split?

[jeff5may]

Units a ton and a half or smaller can be fitted with a reversing valve and a defrost control, leaving the original metering device to control heat flow. Old school twisty knob units can be used with the original thermostat, modern button boxes benefit from adding a single stage heat pump thermostat. The whole retro fit can cost less than 100 dollars.

[AC_Hacker]

Originally Posted by Stoker

Obviously they could go reverse cycle to melt the ice, but efficiency would plunge...

Have you watched a reverse cycle in operation? It happens pretty quick.

Another approach is to not do an air source, but to use a large source of water, or to use the ground as your heat source, rather than air.

Be brave.

-AC

[Stoker]

Originally Posted by Mikesolar

defrost is the price you pay for an air source heat pump. Some reverse direction, some use hot gas directly from the pot to defrost, some have electric heaters (not many anymore)

Done right, defrost is 3 min out of an hour, averaged out over the season.

I'm guessing that your average season in Toronto is a little different from mine. (I haven't parked my motorcycle yet... Though I see it was a balmy 4 deg C (39 F) in Toronto today).

Am I wrong to suspect that if conditions were let's say 3 deg C (37 F) and 100% humidity ie: perfect ice making conditions, the defrost penalty would be much higher?

[Stoker]

Hi AC,
I've been following the Manifesto for some time and I fear that the Geology at my place is not favourable for GSHP. My area is basically a glacial moraine. Pretty much a shallow sand slope on a hillside of granite. Only test drilling would tell for certain, but I believe the water table in old water wells in the area is 60 ft or better.

A good friend of mine lives in a beautiful swamp. I want to try a GSHP system for his place next year. I'm sure that location will be a winner.

[AC_Hacker]

Originally Posted by Stoker

Hi AC,
I've been following the Manifesto for some time and I fear that the Geology at my place is not favourable for GSHP. My area is basically a glacial moraine. Pretty much a shallow sand slope on a hillside of granite. Only test drilling would tell for certain, but I believe the water table in old water wells in the area is 60 ft or better.

A good friend of mine lives in a beautiful swamp. I want to try a GSHP system for his place next year. I'm sure that location will be a winner.

In spite of recent posts, you don't need to make your loop field in the water table. A swamp would be nice, but it's not the only way.

Granite is tough for sure, but hard glacial cobbles are the very worst... They will move around and make things really difficult. Granite will not move, so drilling is possible.

So you live in BC?

What is the annual rainfall in your area?

-AC

[Stoker]

About 45 inches. Pretty similar to Portland, and probably only a few degrees cooler on average.

[AC_Hacker]

Originally Posted by Stoker

About 45 inches. Pretty similar to Portland, and probably only a few degrees cooler on average.

The reason I asked is that you might be able to extract heat from your abundance of rain.

It rains the most when you need heat the most.

-AC

[Mikesolar]

Originally Posted by Stoker

I'm guessing that your average season in Toronto is a little different from mine. (I haven't parked my motorcycle yet... Though I see it was a balmy 4 deg C (39 F) in Toronto today).

Am I wrong to suspect that if conditions were let's say 3 deg C (37 F) and 100% humidity ie: perfect ice making conditions, the defrost penalty would be much higher?

Unfortunately, "she who must be obeyed" is afraid of motorbikes so mine got sold years ago......bummer.....

Many winters as long as it was clear and dry I would be out riding in below freezing temps and loved it.

Last few days here have been -6 to -18 so HP is not defrosting much but I have a fujitsu on the shop which froze up the bottom 2 inches of the coil because the drain is so small. It got warm enough to melt a day or two later so all is well but I'm thinking of putting an electric stick on pad with an ice sensor to control it, just in case.

[Stoker]

Originally Posted by AC_Hacker

The reason I asked is that you might be able to extract heat from your abundance of rain.

It rains the most when you need heat the most.

-AC

That's a very good point AC. Perhaps I'll do some more research on my ground before writing off GSHP. I think my city has a Geotechnical Engineer on staff. Test drilling would be the best proof of course.

I've been lurking here for a long time and have learned a lot. Thanks to you and the other major contributors sharing successes and other "learning opportunities". I've been inspired. I have collected most of the tools of the trade, and I wrote the Canadian CFC certificate last summer. I've also scrounged 2 1 ton ac's to practice on.

This winter I have thrown down the gauntlet and torn out my oil furnace, so the time for procrastination is dwindling with my meagre woodpile.

Regards,
Stoker

[AC_Hacker]

Originally Posted by Stoker

This winter I have thrown down the gauntlet and torn out my oil furnace, so the time for procrastination is dwindling with my meagre woodpile.

Well, sound like you're about to take the big jump.

The bro-region we are in is very favorable for heat pumps, since the winter temperatures are moderated by the Pacific weather system. This give us a limitless supply of good quality, low-temperature heat for us to upgrade to home-heating levels.

As you must already know, (and I am saying this not only to you, but to anyone who is interested in embarking on a low-exergy (low-temperature) heating project), reduce your heating requirements as much as possible first, before you start into designing and building your heating system.

The lowest hanging fruit is infiltration. Have a blower door test done on your place to see where the heat is leaking out.

Then go all-in for insulation opportunities that may have been overlooked. If possible, beg, borrow, or rent a thermal imaging camera and take a good look at your place on a cold night. I'm sure that you will find neglected heat leaks (I sure did).

These steps will be the least expensive part of your project, and will produce the biggest bang for the buck. Also, insulation is very reliable.

Then, after your heat-loss reduction phase, get a realistic idea of what your home's heat loss really is. Build It Solar has a calculator that will do the math for you. There are also heat-loss calculating computer programs, some are even free. My favorite is Watts Radiant RadiantWorks. Even if you're not going for radiant heating, there is a preliminary section of the program that will lead you through the steps, and calculate your heat loss.

You can also get a good estimate from your utility bills.

* * *

Good luck to you on your project, there are a lot of people here ready to help you, and for the most part, their advice is quite good.

Please share your progress on your project, include lots of photos!

BTW, don't burn up all of your firewood, a source of low-tech backup heat is always a good thing!

Best,

-AC