If your below grade basement walls (NYSoap..) is 5’, say, then only about 2’ of that is significantly above freezing in the dead of winter. The freeze line in Upstate NY must be at least 3’. So you have little or no wall sourced by the earth at 50 degrees or better in the winter. I’d expect you’d see a noticeable drop in room temp in the basement due to HP water heater. That may not be a problem, just reduce the efficiency of the HP, not freeze the plumbing, I’d guess, I don’t have any real empirical numbers - but I do recall some study data in one of the early mentioned links that talked about drop in room temp.
Good point - I’d guess on average we’re about 6 feet below grade. Without any heat or A/C in the basement, we stay around 50-55. Maybe some of that is coming from the house above being warmer, and part could also be the fact that the boiler is on and likely leaks some heat to the basement. Shutting down the boiler maybe would drop us lower if it’s actually providing enough heat to overcome conductive losses out the walls.
I know the freeze lines are supposed to be fairly deep, but then again, I keep fish in a 2 1/2 foot deep pond outside the house and I usually only see this freeze a few inches thick. I was really questioning the need to bury my porch piers over 4 feet deep
I hadn’t thought about the risk of putting the copper tubing directly in the hot water tank, but that simple approach is what makes the AirTrap so economical. EDIT: I did watch the video for installing the AirTrap, and as the copper tubing is “T’ed” into the hot water exit pipe it can be removed and reinstalled in a new tank if the tank needs to be replaced.
As for getting my goe-hp working again, I hadn’t given any though on an aux tank as a pre-heater, any suggestions on where to get such a tank, Chris? The current arrangement is full stop, but I can just leave the drain stopped up as the pre-heat tank will be in series with the cold water feed. As I can no longer flush the electric tank it may need to be replaced before long...it must be approaching 8 or 9 years old anyway.
Wow, must have some serious minerals up there…
I would consider a 50 gal regular electric water heater as a preheat tank ahead of your regular water heater. Let the desuperheater or heat pump warm up that tank to 100-110 or so and let your regular heater bring it up the rest of the way. That way, if you have a heavy demand, you will still have a full heater available. Quick and dirty, disconnect that pipe from the drain valve and tee it into the cold water inlet. It’s almost the same thing, but no chance of clogging.
There are solar storage tanks available up to about 120 gal, but they are very expensive. 50 gallon heaters are very popular and therefore more price competitive. You don’t really need to save up an entire day’s worth of hot water as the heat pump will cycle many times a day to keep up. You just need to cover a load of laundry or a shower for maximum effectiveness.
Being so new to the market, they don’t have much of a track record yet, but I think they will. They will definitely see more use in the southern parts of the country than up north. Since they are not really designed for outdoor use, you will have to pull heat out of your home to put into your water heater. I suspect that putting one in the basement is going to pull the air temperature well below 55 degrees in the winter as most seem to have about a 6000 BTU compressor in them. That amount of cooling can drop a good size room down 20 degrees in the summer and I suspect that your basement might end up dropping into the 30-40 degree range unless you duct the cool air somewhere else. Maybe it could be ducted into the room with the wood stove? Just a thought.
This would seem to be one of the major questions that I need to do some calculations around. The units I have been looking at are 12,500 BTUs. Our basement is about 1,000 SF fully open, and below grade block walls with no insulation. From what I read on here, it is fairly challenging to heat such areas with 30,000 BTU woodstoves as the heat just sinks away quickly, so this is why I’m thinking it may be even harder to cool that space with a much lower BTU compressor system. But that is something I need to size carefully.
I run my woodstove 24x7 and still need a little extra heat on cold days, so I don’t want to duct cold air into the house I actually need a net addition of heat on some days, but probably not more than 10,000 BTUs at any given time, which has me interested in these.
Agree with comments of others that such an approach really necessitates using radiant whenever possible - then the 110-120 F water output is just about perfect. I would assume that I’d have to go down this path throughout the first floor to make it work, and would use higher temperature resistance-heated water only when using 2nd/3rd BR heat on baseboards, and even there, it would only be low supplemental load to the wood heat that hits most of the house fairly well.
-Colin
Careful with the specifications on a heat pump as there is the heat of absorption or the cooling BTU rating and the heat of rejection or the heating BTU. The difference will be the heat of compression and is basically motor heat. Assuming reasonable efficiencies, that 12,000 BTU unit will absorb about 9000 BTUs of heat from the room and use about 1KW of electricity to do it. The equivalent electric element would need about 3.5 KW to do it and give you a COP of about 3.5. I am basing this on the typical AC compressor rating of 45/130 delta. These are rough numbers and will depend on the compressor and heat exchangers used.
How much will this drop the temperature in your already chilly basement? I suspect that it is proportional to the temperature rise if you were to add heat, but there will be differences. I’ll let others debate this, but if you did a heat loss calculation for the basement, you would be in the ballpark. If 12000 BTUs raises the temp from 55 to 65, then the same amount of cooling would drop the room from 55 to 45. That 50-55 degree number is typical in basements as the earth will moderate at this temperature below 4-6 feet in practically all areas of the country. This is why GSHPs work in the first place!
I’m not sure why you would want to use electrically heated water in a baseboard, but it is possible. I have never seen a heat pump used on radiant flooring, but it is also possible, though I have never found anything designed for this. I have been considering a radiant floor in our walk out family room and I think a heat pump would be a great way to take the chill off in the spring and fall when the stove isn’t lit.
Chris,
Thanks, I hadn’t given a thought to another hot water tank in series with my existing electric water heater, but sure that would work. What I figured would be available was a smaller insulated tank of say 10 gallons that had an upper inlet and lower outlet that would connect to the HP loop, then the tank would have a lower input (could be a tub inside the tank as is the case on water heaters) for connection to the cold water feed, and an upper outlet that would feed into the existing water heater. As to why the existing “T” in the drain of my hot water heater plugs up I don’t know we don’t have real “Hard” water, no stains in the sink/toilet/etc and soap lathers well, still the HP (Waterfurnace) supplies “T” that was installed in the existing water heater plugged up soon after installation, then a couple of years later I replaced the water heater, made sure the “T” was clear and reinstalled. It plugged up rather soon too...don’t remember how long it took, a few months perhaps.
Now if we were to use another water heater tank we’d be short one tap (I/O) as I see it, we’d have the known three, not the needed four. The three being: cold in, hot out and drain. As I think the HP heat exchanger isn’t free flowing enough to handle the full flow of the hot water demand, it has to “set” on the side and pump heat into the HWT as a parallel function. Hope this makes sense, the point is I don’t see how I can use a second standard HWT as the parallel pre-heater using the HP waste heat (A/C assumed for this test).
I don’t think it really makes a difference. The drain tap on the heater goes to the bottom of the tank just like the cold inlet. The only difference is that there will be less of a pressure change if you are running water through the heater for the house. I have seen gas water heaters with extra taps for space heating, but that is a different application and I’m not sure it really means much anyway. I’d try connecting the inlet of the desuperheater to the cold inlet of the existing water heater and see how it works. It HAS to work better than that drain that keeps plugging up, right?
My suggestion on adding another tank in front of the heater is to maximize efficiency on the desuperheater. Having the electric element come on when the desuperheater might be able to take care of the high demand isn’t as efficient. I would also go as large as possible within reason as the preheat tank is going to even out the difference between demand and production. Just a guess, but the average shower is going to drain that 10 gallon heater pretty quick and force you onto electric resistance sooner. The A/C will be able to warm it up fairly quickly, but you will already be out of the shower. More storage for the “free” heat is a good thing! Besides, price out that 10 gallon heater; I doubt it’s 1/5th the cost of a 50 gallon heater.
Thanks, still missing something here on the plumbing and fluid dynamics subject. I believe the desuperheater has to have the ability to circulate water when there is no demand for water so that it can heat the stored water during slack usage periods. The plumbing you suggest would, as I read your suggestion, pass water through the desuperheater only when there was a demand for hot water. The desuperheater has to have a “parallel” in/out path to the storage tank, and at the bottom would be best as it would draw the cooler water into the desuper.. and if the hot output was also low, no big problem, the heat would rise. That’s the idea behind the factory method of putting a concentric pipe inside a 1/2” pipe that can be stubbed into the drain hole… with a “T” to allow draining, that’s what I know know to be clogged.
My 10 gallon ideas was just a “number”, thinking there may be some special small tank designed to work with a HP desuperheater. I haven’t asked Waterfurnace, I may do that.
Thanks, still missing something here on the plumbing and fluid dynamics subject. I believe the desuperheater has to have the ability to circulate water when there is no demand for water so that it can heat the stored water during slack usage periods. The plumbing you suggest would, as I read your suggestion, pass water through the desuperheater only when there was a demand for hot water. The desuperheater has to have a “parallel” in/out path to the storage tank, and at the bottom would be best as it would draw the cooler water into the desuper.. and if the hot output was also low, no big problem, the heat would rise. That’s the idea behind the factory method of putting a concentric pipe inside a 1/2” pipe that can be stubbed into the drain hole… with a “T” to allow draining, that’s what I know know to be clogged.
My 10 gallon ideas was just a “number”, thinking there may be some special small tank designed to work with a HP desuperheater. I haven’t asked Waterfurnace, I may do that.
The simplest and most straightforward way to do this is to tee into the lines going in and out of the water heater. Cold goes into the tank as well as the DSH and hot leaves the tank and DSH, assuming the DSH has a circulator of its own. When you are not actually using hot water, the circulator pulls water back up the dip tube on the cold inlet and returns it warmer to the top of the tank on the hot outlet. I have no idea how you would do this without a circulator; maybe some kind of sidearm arrangement? Could you post a pic of this concentric fitting? I haven’t seen anything like you describe. Maybe this is why it has been clogging up?
Yes, a “T” could work, the DSH has a low capacity circulation pump that runs, when enabled, whenever the compressor is running. I’ll take some pics of the outside of the existing connection. The pipes are 1/2”, so the pipes have the capacity and I assume the design takes into account it is working as a circulatory in a closed storage system that is under pressure, i.e., the well pump/tank pressure.
Here are a couple of pictures of the connection between my electric hot water heater and my geothermal heat pump. The two insulated pipe lines going to the right go the the HP and the line to the left is the drain line, a third use for the old drain connect on the water heater. I suspect the drain is just the input side of the lines going to the HP.
Nope, can’t say I’ve ever seen anything like that before! Is this a Waterfurnace part? I’m not sure what the purpose is, other than to make it easier to tap into an existing heater. Since you’ve had problems with it, maybe it’s time for a rework? Free heat’s wasting as we speak…
I"m not sure how much guidance the installation firm got, but Waterfurnace provided what’s at the right side of the pictures, including a desuperheater and circulation pump with a defined “in” and “out” and a suggestion that these be connected by pipes to the hot water supply, and in parallel, not series. So, on the left, the installer put a three-way tap into the drain hole of the water heater. This provides for water to be circulated between the HWH bottom (seem good, the hot water will rise) and the dsh while still allowing the third-way on the tap, just a hole in the portion of the tank feeding the desuperheater, with a faucet to allow draining the HWH. As it now sets, I can open the drain faucet and nothing comes out, also nothing circulates in the dsh circuit, best I can tell. My test method over the years has been to measure the pipe temperature, under the insulation sleeve, on the water going to the dsh and on the water being returned, assuming water was moving in the pipes. I believe the expected delta T is only a few degrees, but I would measure none to a heat loss and concluded water was not flowing in that circuit either.
Yep, sounds like it is stopped up to me. I assume the ball valves were open while you were checking? I’m not sure I would want to go disturbing it if it is 8-9 years old. I’ve found the tappings on a DHWH tend to rot out after a while. If I were you, I would consider adding a 50 gal tank in series in front of this thing and pipe the DSH into this. That way, the heat pump can heat the entire water heater up before you even begin to use hot water. Pull the cold water back up the dip tube through the DSH and pump it back into the outlet of the first heater. Just for yuks, put a thermometer on the line in between the two heaters and you can see how much heat you are recovering. I think it’s possible to hit 180F on a desuperheater without much effort.
My reasoning for the second heater is to separate the electric heat from the “waste” heat. If you were to overcirculate the cool water back up to the top of the electric heater, it might bring on the electric sooner than necessary. At least if it doesn’t work out, you will have a spare heater!
Trying to put in a “three hole” tank in front: cold in (tube to bottom of tank), hot out (top dip tube, or flush with top) and drain/flush (bottom of tank). If I put a “T” in the cold water line into the new pre-heater tank, on the cold that has the dip tube to the bottom of the tank, I could run the other leg of that “T” to the input of the DSH. Then I’d return the DSH to the drain hole of the new tank, here I assume the water pressure in the tank is balanced top/bottom so the DSH circulatory pump doesn’t have to work against any back-pressure. Then the hot out line would simply connect to the cold input on my regular/normal electric water heater. This would allow me to use the full 1/2” pipe cross section area in the loop through the DSH. Sounds like:
1) a lot of plumbing
2) should work, if the existing system can/did work as it too has to work to circulate water in/out of a tank that has water under pressure stored in it.
Here I note I never verified the original system worked, as there were no easy ways to measure...when I began to wonder and started measuring the surface temperatures of the pipes to/from the DSH I think the system was already plugged up. Other tests I made, while my wife was away, she’d never go for periods without hot water, I turned off the hot water heater when the A/C was being used and didn’t use any hot water for the whole day, then measured the hot water coming form the tank...this was all long ago, but I think the first time I did this there was some elevation in the temperature, later there was not.
That would work, but I think it would work better if you piped the DSH back into the hot outlet. This will promote stratification which anyone in the “Boiler Room” will tell you is a good thing when it comes to heat storage. This way, the hottest water is always available to the regular heater.
Don’t worry about the pressure difference across the DSH as the pressure is in the positive direction while you are drawing water and will only increase the flow rate, if it changes anything at all.
Ok, you’re suggesting using “T” connections on both the top cold/in and hot/out. I’d then run the cold to the input of the DSH and return from the DSH to the hot. My intuitive on fluid dynamics isn’t working (may not exist) well, but it seems that in the static state the DSH circulatory pump would draw water from the “T-ed” tank, not the cold feed/well, and return water to the “T-ed” hot, this water would flow back into the top of the tank as space would be available due to the water flowing to the DSH. Then, as I’m dumping hot water in the top, where it wants to set anyway (stratify level), and drawing cooler water from the bottom of the tank where it sets (stratifies) to feed the DSH there will not be much thermal churn. The cold feed isn’t supplying any of this flow. Now when there is a draw on the system, I suppose most of the water flowing into the DSH would be the cold water input to the “T”, feeding some of the demand through the DSH and some through the “normal” dip tube into the storage tank.
