Please explain heat pumps to me like I'm an 8 year old

Jan White wrote:For people heating their houses with supplemental heat because the heat pump can't deal with the temperature differential in the winter, is it possible they'd be better off putting some kind of insulated shed around the outside portion of the unit and heating the air in there?

No. If you have supplemental heat use it directly within the envelope of the house.

These heat pumps work by passing huge amounts of mass of air over the heat exchanger. They need unimpeded air flow.

If you put a shed around your heat exchanger you will restrict the available air and the shed will rapidly cool down, like a refrigerator.  So then you add supplemental heat to the box to compensate, raising the box above ambient temperature. But now you losing heat from your box to the surroundings, so instead of gaining energy from the air passing by you now have to supply ALL of the heat to the air that your heat exchanger needs.

You have just created a really inefficient heater, with extra energy wastage, extra expense, and extra steps.

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Alternatively, use your heat pump to supply enough baseload heat during a normal winter, and then light the fire indoors on the dozen evenings a year your need to top it up.

You get to choose a smaller, cheaper heat pump because you are not 100% dependent on it. And still stay cosy warm in winter while using less fuel than before.

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Downsides of heat pumps - they tend to provide low energy density heat. Here in the UK houses are designed with water filled radiator panels. The water circulates room to room at about 60 degrees C. The radiators are sized with that in mind, and usually only run intermittently.

Heat pumps provide a base load of warm water, but at substantially lower temperature. They tend not work so well when directly installed to our existing infrastructure. They are better when installed in well insulated underfloor heating. In our particular property - old, drafty, impossible to insulate well - they would be suboptimal. We'd never be able to get the living spaces warm enough because the heat intensity isn't there. In a more modern, well insulated, place they would be great.

The bulk of our winter heating is from our wood stove, and will remain that way for the foreseeable future.

Phil Stevens wrote:  It starts to drop off if the outside temperature is really cold, but we can fix this by using the earth instead of the air as a source of heat...of course this will cost more to install and set up but in places with proper cold winters it's a viable way to roll.

Thank you.   I am just going through the rest of the posts, ( did not have time last night to read them all) and it seems like alot of people have made the bad decision to install air sourced heat pumps in cold climates.  Problem is, you cannot get heat out of cold ( cheaply ).

My ground source heat pump heats my house too 72 degress with capacity too spare all winter.  Just keep in mind, in my area, a general rule of thumb is 600 feet per ton ( 12,000 btu ).  My unit is a 3 ton ( 36,000 btu ) system, and while they were installing it, added another 600 feet due to rocky, sandy soil ( the wetter the better ).
If you have a pond or year round stream nearby, you can drop a loop of pipe in there for heat.

Nissa Gadbois wrote:, How would it be to DIY an installation for an old farmhouse?  

Aaaaand... go!

This is a loaded question....  that depends on your personal skill level.  Are you comfortable wiring 240 volt systems ? How big of a system do you need in b.t.u s ?  You are on a farm, so you probably have lots of space.  Do you have a body of water near by or a stream ?  Lets assume you go ground sourced heat pump.
Lets break this down into sections.
1.  Ground loop.  It HAS TO BE below your areas frost line.  In my area, the frost line is 3 too 4 feet below grade level.  Remember, you cannot get heat out of cold - hence, below frost line.
My buddy put his 4 ton ( 48,000 btu ) system in the same time i did, and since it was a drafty old farm house, he says his heat pump ran non-stop on the coldest days, so size accordingly.
Do you have the backhoe or equipment too dig a 5 foot deep trench 200 or 300 feet long ?  You could lay the pipe in straight lines 12 inches apart as long as you use equal lengths for each loop.  Which brings us too the manifold.  A heat pump installer has a double sided heater, which clamps onto each side of the pipe physically melting the plastic.... pull out the heater, clamp em together... and you have a joint that is actually stronger than the pipe itself.
Maybe contact a heat pump installer and ask if you can do the bulk of the digging and filling ?
Once the two pipes of the manifold enter the house, it goes into a pump unit - seperate from the heat pump.  This is what circulates the fluid underground.  It gets wired to the heat pump itself and comes on with the unit.
The pump unit attaches to the heat pump, and then the whole thing is filled and purged of all air bubbles with a powerfull tank and pump arrangement.
After that, with the heat pump attached to the ground loop, you have to figure out how to deliver the heat.
My buddy chose an air forced system attached to exsisting duct work ( a radiator attaches on top of the heat pump and has a heat exchanger in there. With a seperate fan blowing the house air through the rad.
Me, i chose a water to water boiler, and installed my own radiant floor heating system.

Pictures of my install are attached.  Questions ?

Now for the horror stories...

Did lots of research before i spent the 11,000 $ to install this system ( many years ago 😁), and there are 2 homes close to me that used a well know company to install their heat pumps.  Problem is, this company believed that you did not need 600 feet per ton ( 12,000 btu ) - instead they installed 200 feet per ton.

If you went into the back yards of these homes at the time, you would see a 2 foot deep trench wherever  the pipes were buried.  What happens is, the heat pump is pulling the heat out of the ground, and will continue to do it for as long as it can.  So if the ground loop is not big enough, the pump has to work harder, run more ( continuously ) and creates a tube of solid ice / ground around it.  When spring comes, the whole thing melts into mud, and collapses in on itself.  One guy kept backfilling for 3 years in a row - no change.  He had a 4 ton downstairs and a 3 ton upstairs - ON A 2,000 FOOT LOOP.  7 ton x 600 feet = he should have had AT LEAST 4,200 feet of pipe.

When the guys actually came in to install my system, they shared more stories.... i liked the one about the house in downtown Toronto.  Installed a heat pump in their front yard 50 x 50 feet square.  Dug down 10 feet, coiled the pipe in there in 2 or 3 layers, backfilled it 2 feet, and coiled another 2 or 3 layers, then filled and leveled.  Owners could not figure out why the pump would not shut off, high hydro bills, and there was not heat.
My guys tell me, they had to go in with jackhammers to break up the solid block of ice that was the front yard.

This is why i prefer the 600 feet per ton rule, and lay the pipe in a straight run - do not try to save space by coiling the pipe in loops, as EVERY INCH of that pipe is meant to pick up heat, so overlapping them in loops does not make sense.  If they are installed properly, they are a nice way to heat your home.

As for the hydro bill, i have had people tell me it must be nice having a solar system, that means i have no hydro bill !   Wrong !  For 4 or 5 months of the year, it makes very little power, since solar panels only work with sunlight.  In November, December and January ( cloudiest times of the year ) , my 2,000 watt system makes 20 watts.
Others tell me ... " well, you can bank the power and save it for the winter.... "  and yes, my utility does allow that, but, my system is nowhere near big enough to overgenerate, AND every 12 months, the bill goes to zero.  Anything banked in the account at that time is gone.  No cheque, no money, just .... gone.
In case you are curious, my entire house is based on hydro.  Heat, on demand water heater, everything.  
I use about 1 Megawatt a year for hydro... roughly.

Hope this helps.

Looking at the options for a diy geothermal heat pump, and there are kits out there for the ground loop portion, but with all the options available, i would strongly recommend making friends with a local installer.

Someone who does not mind giving you advice ( and also a source for the equiment....)

Lots and LOTS of research sized and tailored for your area as well.

Edit : the little stubby things in each picture are the underground manifolds each equal length of pipe ties into one of those.  - i just followed the link, and their "6 ton kit" only comes with 600 feet of pipe - that is only 100 feet per ton ! Way too short for cold climates.

Jan White wrote:
For people heating their houses with supplemental heat because the heat pump can't deal with the temperature differential in the winter, is it possible they'd be better off putting some kind of insulated shed around the outside portion of the unit and heating the air in there?



I've brought this up several times, and each time, I'm met with blank stares... I think it's worth looking into.

I'm wondering how you will be heating the air in the insulated shed part

Sid Deshotel wrote:I'm wondering how you will be heating the air in the insulated shed part

Just a shelter around it, to keep the wind off would go a long way, but a small heat source inside the shed would suffice. The idea here, is that just keeping the temp a bit warmer in a small, outdoor space could warm the entire house. So, a small brick 'emergency' cooking rocket would, theoretically, keep the main house well above freezing, to at least prevent pipes from freezing, if there's no other heat. Yes, someone would have to go out, to check on it, frequently, so it's not ideal, but in an emergency, (like winter before last, where folks in tropic and subtropical regions, who don't normally need their heart pump to work in below freezing temps *were* freezing) would prevent that little rocket from causing carbon monoxide issues, avoid the need for new construction in the house, and not void insurance policies.

Sid Deshotel wrote:

Jan White wrote:
For people heating their houses with supplemental heat because the heat pump can't deal with the temperature differential in the winter, is it possible they'd be better off putting some kind of insulated shed around the outside portion of the unit and heating the air in there?
I've brought this up several times, and each time, I'm met with blank stares... I think it's worth looking into.

First, you have to look at the numbers.  I have had a few people tell me that i did not need to add 600 feet per ton of ground loop when i installed my ground source heat pump,  but, the way i look at it, the more warm area you have to draw from the less the machine will run ( low hydro bill ).
Now, take the shed idea...
An air to air heat pump that is trying to get heat out of cold will just burn alot of hydro constantly running ( you will get some heat out of burning the hydro ( running the machine), but there is no more heat to draw from.  It is still trying to meet the heating demand on the system, but cannot do it.

By building a seperate enclosure, you have to buy the materials for that, as well as the insulation to insulate it ( or you waste more heat - heating the unisulated walls )
Then you have to run the equipmemt to transfer the heat already made - inside the building.  I am assuming that you are just warming the air a " little bit" ? - in that case, the heat pump will still run more than necessary, giving you a high hydro bill, as well as having to monitor your secondary heat source outside the building - unleass you give the heat pump a nice warm source too draw from - which brings me back to my first statemenet...
On top of that, what do you do in the shoulder seasons with an insulated shed around your heat source ?  Move the entire thing out of the way ? Would it not be far more efficient to install a heating source directly inside the building you are trying to heat ?
Be far cheaper, easier to get a few electric resistance heaters and plug them in - inside the house - me, for emergencies, i have a couple of 10,000 BTU kerosene heaters - that i have never had to use .... yet.

Hope this helps.

A few ideas that helped me to understand heat pumps. Caveat: These ideas are not exactly correct in terms of the science and engineering.

1. You'd think that the best efficiency possible to heat a space would be to dump energy into the volume that you want to heat. You'd think that this would be 100% efficient because all of the energy is being converted to heat. However, with a heat pump, you are exceeding this efficiency by not 'creating' heat, but rather by moving it ('pumping' it) from one place --outside, or underground (geothermal) -- to another place (the space you want to heat).

2. A heat pump and an air conditioner are theoretically the same system except the space you care about is opposite. In an air conditioning system you care about the place the heat is being pumped from (your house). In a heat pump system you care about the place that the heat is being pumped to (your house).

3. The closest thing to an air conditioner that you typically interact with are those Air in a Cans for cleaning keyboards. If you turn it upside down and hit the trigger, you will see a fluid (refrigerant) come out of the tube (thermal expansion valve) and evaporate (evaporator) and get very cold. In an air conditioning system this evaporated gas is recollected and recompressed into a fluid (condenser and compressor) and the cycle repeats continuously.

I'm late to the game on this topic, but it's very timely for me in that I'm looking into getting an air source heat pump installed in my old (1855) small house. Both the federal and the provincial governments are offering grants of up to $10,000. I couldn't understand how they work, either, so I've visited one family to learn about their system, and I'm visiting another later today. I'm in climate area 5B, southern Ontario, so cold winters and hot summers.

Two other people around here who have heat pumps are thrilled with theirs and coincidentally both said that they spent only $200 on propane last winter. The kicker seems to be the electricity cost. This house is oil heated now, so I could use the current ducts in the cellar and ground floor, but there are no ducts or heat upstairs and no air conditioning at all. I imagine I'll get a mini-split in the small two-room upstairs. The person I've visited said that the only thing he'd do differently now is to have a one-to-one system, rather than the three-to-one ductless system he has.

I have a wood stove (replaced my old one a few years ago and wish I hadn't as it worked much better than the new one), but I doubt they'd permit that as the back-up heat source. We'll see. My fingers are crossed hoping that this will all work out.

Going through my files, and came across a video i took , of them repairimg my heat pump pipes.  I had to get them in to fix my pipes after i hit them with the back hoe - digging the hole for the hobbit home.
Screen shots are just as good, i guess...
1. Attach pipe coupler using heater block too melt plastic on both sides.
2. Heat coupler and other side of pipe with heat block.
3. Squeeze together, and the melted plastic coupling/pipe is stronger than the actual pipe.

This is how all the ground loops are joined together to make a larger loop - so my 3 Ton system has 4 - 600 foot loops attached to it.  ( i asked them to install an extra loop, just for efficiency )