heat pump

[chuck172]

How should I pipe my geospring heat pump hw heater to run in the winter when I fire up the tarm solo40?
I also use a 30 gallon super store piped into my 500 gallon storage.
Should I use the superstore as a pre-heater for the geospring?
Right now, all summer for that matter I've been using the geospring by itself. It's great.

 

[Fred61]

How should I pipe my geospring heat pump hw heater to run in the winter when I fire up the tarm solo40?
I also use a 30 gallon super store piped into my 500 gallon storage.
Should I use the superstore as a pre-heater for the geospring?
Right now, all summer for that matter I've been using the geospring by itself. It's great.

I have the Geyser plumbed in to my Superstore and so far it's been great but it will be shut down when the EKO is fired up. Preheating water will help but it doesn't do anything to make up for standby losses in your Geospring. Normally you won't need the dehumidification byproduct in the winter.

 

[chuck172]

But adding 50 more gallons to storage might help wouldn't it? Even if it's domestic hw storage. Preheat is also important.

 

[Fred61]

Preheat is good but it's not a replacement for DHW that is totally produced by wood without having to top it off with electric or any other fossil fuel source.

In my system when the storage reaches 110 degrees, the superstore pops out of the loop. No water flow, no oil fire and no heat pump. I guess it depends on how your system is plumbed.

For me, 500 gallons is more than sufficient for 24 hours of heat and all my DHW after a 4 or 5 hour batch burn each evening.

 

[woodgeek]

Preheating the geospring doesn't really make a lot of sense. The COP (efficiency) is very high when the water is cold, and lower when it is hotter. Why not run the Tarm in the winter, and the geo the rest of the time?

 

[tom in maine]

If the space is warm from the Tarm, then the HP makes some sense. It would help keep your firewood a bit drier.
I operate my heat pump only in the warm months when not burning wood, but would use it year-round if the basement was really warm. The sweet spot for these units is basements above 45F (70F is ideal) and water temps up to 120F or so.

 

[woodgeek]

To be more technical, I guess you could price out a cost of a wood BTU (perhaps pricing your labor if scrounged) and an electric (resistance) BTU (3414 BTU/kWh). If the latter was more than 4x the former, it would prob never make sense to run the geospring, since its COP (BTUheat/BTUelec) is never going to be that high. If is less than 2x, you should run the geospring all the time (since the seasonal average COP ~2). Between 2 and 4, I guess you could mix it up a bit (run in the summer, not in the winter), but frankly, when the costs are that close, the savings/motivation for worrying about it are minimal.

 

[tom in maine]

To make the conversation more interesting. The heat pumps are $365 delivered (new old stock--not Geospring) at (broken link removed)
If you use a dehumidifier, then the heat pump is a no brainer, because the DHW is free for the cost of dehumidification.

 

[Clarkbug]

Tom, thanks for that link! I have been tempted by these types of units before, but this makes it even more tempting... Do you know anything about either of these two brands? I would think the one running R-22 might be easier to service, since most A/C techs would have the equipment to charge the system if needed, but would welcome any thoughts.

 

[woodgeek]

Tom, thanks for that link! I have been tempted by these types of units before, but this makes it even more tempting... Do you know anything about either of these two brands? I would think the one running R-22 might be easier to service, since most A/C techs would have the equipment to charge the system if needed, but would welcome any thoughts.

R-22 is getting really tough/$$ to service in the last couple years.

 

[tom in maine]

There are R-22 drop in replacements that are available.
The mechanical parts on these systems seem to be very robust.
The controls have been a little tricky at times. I have had my hands on a LOT of these.
They are actually pretty simple.

Here is an article by a scurrilous character on the topic:
http://www.homepower.com/articles/solar-water-heating/domestic-hot-water/heat-pump-water-heaters

 

[Clarkbug]

From doing a little digging, my guess is these are the leftovers from the CT lawsuit against Nyletherm....

WWW.docstoc.com/docs/139408087/030101RE-032906doc

I just wonder if they have the more robust controller. Very tempted to nab one of these, but I know I won't have time in 5 days to try it out.....

 

[tom in maine]

That is my understanding. There was a big lawsuit against Johnson controls who made the controllers.
The relay that let go was controlling the electric element.
These units have new beefed up controllers. They also can be used without the electric backup elements, which
eliminates the original issue.
I have used one for about 7-8 years, without backup. They are fine.

I think there are about 2000 units available!

 

[Clarkbug]

Thanks for the reply. (Note, I now realize there is a parallel thread going in the Green Room....whoops!)

If I pull the trigger on it, I might pick your brain since you seem to be one of the best as far as institutional knowledge on these units

 

[pybyr]

This- the Nyle closeout- is really interesting.

I have a stand-alone oil fired HW heater that is at the age where the tank is probably on borrowed time.

Are there any efficiency ratings available for this Nyle HP unit that would let me compare (sort of) apples to apples on operating costs compared to the existing or a replacement stand alone oil-fired HW heater or a propane stand-alone HW heater? My incremental cost of electricity is 21 cents per kWh.

PS, I understand that the HP unit is not going to necessarily pay for itself as compared to my existing unit- please assume, as I do, that I need to replace my existing unit relatively soon, and that I can and will do install myself, which should put outlay roughly the same between various fuel replacement water heaters.

 

[BoilerMan]

My incremental cost of electricity is 21 cents per kWh.

PS, I understand that the HP unit is not going to necessarily pay for itself as compared to my existing unit- please assume, as I do, that I need to replace my existing unit relatively soon, and that I can and will do install myself, which should put outlay roughly the same between various fuel replacement water heaters.

21cents? Holy schnikes batman, that's EXPENSIVE electricity. A HPWH may be quite expensive to operate at those rates. What do you mean by incremental cost BTW?
If your water is not hard, you may want to look into a propane tankless unit like a Rinnai if you have good access to propane, dryer, and range are good candidates for propane as well, especially with your high electric rate.

TS

 

[pybyr]

21cents? Holy schnikes batman, that's EXPENSIVE electricity. A HPWH may be quite expensive to operate at those rates. What do you mean by incremental cost BTW?TS

Yes, it's an ouch. My utility is an electric coop; the first 200 kWh per month are at 9.4 cents/ kWh and everything above that is at 21 cents kWh... so for people with moderate or high electric usage, the "incremental" cost per additional kWh (since you've already used up/ gone above the cheap "block") is EXPENSIVE. It's partly a result of the fact that they serve a very rural territory and partly a product of what power supply and demand-side measures the utility has prioritized, many of which are "worthy"... but... well, the numbers are what the numbers are...

 

[BoilerMan]

Personally I'd go as much propane as I could then. I've never had an electric bill over 200Kwh here. I have propane dryer, and range. Oil for HW in the summer and wood only for heat in the winter. I do have 2000w of electric baseboard to keep the homeowners insurance happy. I do have a well, and an 86 gallon tank, this keeps pump run time long and minimizes startup locked rotor current draws. PM me if you'd like more ways to save on electricity. I'm an electrician, among other things.

TS

 

[woodgeek]

My HPWH elec usage is so low that I didn't see it on my bill. At 15cents/kWh, I think my DHW for a family of four big users is ~$150/year. A lot of folks around here are reporting $10-15/mo costs. If you are worried about 'heat stealing' in your climate, maybe figure $200-250/yr even with your expensive elec, less if you have a small family.

If your tank is nearly shot, just get an all in one HPWH like the geospring from Home Despot, on sale, look for rebates from the state and on your fed taxes. You might be surprised how cheap the unit will be after rebate. Propane tank HW heaters have lousy efficiencies due to flue losses, and propane is expensive per BTU to begin with.

 

[woodgeek]

Ok, let's be more precise....let's go to the hearth.com fuel cost calculator...

https://www.hearth.com/econtent/index.php/articles/fuel_cost_comparison_calculator/

and put in 21 cents for elec, and 200% for efficiency (given that HPWH have EF>2, where EF is BTU out/ BTU in), then I put in 62% for the eff on propane (the EF of a typical cheap propane tank heater I googled), and then I found the price balance to be at $1.75/gallon propane. Typical residential retail price I found was ~$2.50/gallon, so the HPWH is nominally 30% cheaper to operate on a fuel basis, despite your ridiculous elec cost. YMMV.

Issues:

1. Note that for low volume users, the EF on the HPWH will go up a little, and the EF on the propane will fall a lot (due to its high standby). If you use a niagara level of DHW, the propane might be cheaper, if you are 2 normal people with normal shower habits, the HPWH looks like a win.

2. If your space heating is expensive, then heat stealing by the HPWH will cost you extra relative to the propane. Roughly speaking, though, you would need to heat your space with something more expensive than propane before this would become worth worrying about.

3. If you run a dehumidifier in your basement, then a HPWH can offset that energy usage, and make it a no brainer.

4. If you have cheap propane in your area (there are large variations) then it may be better, if there is a big tank fee or other nonsense, then the reverse is true.

5. Can you shop around for cheaper elec?

 

[pybyr]

If your tank is nearly shot, just get an all in one HPWH like the geospring from Home Despot, on sale, look for rebates from the state and on your fed taxes. You might be surprised how cheap the unit will be after rebate. Propane tank HW heaters have lousy efficiencies due to flue losses, and propane is expensive per BTU to begin with.

If I do this I would probably rather go with a separate unit like the Nyle closeout (my frugal side) combined with a Marathon tank that won't ever rust out (my side that likes to but and do something once and never again (cheapest in the long run and I dislike throw-aways)); I'm not so keen on having a combined unit where a failed HP negates a still-good tank or a corroded tank negates a still-good HP unit. Good point on the rebates- will need to look at that and run the numbers some. Thanks for all of the input!

 

[woodgeek]

If I do this I would probably rather go with a separate unit like the Nyle closeout (my frugal side) combined with a Marathon tank that won't ever rust out (my side that likes to but and do something once and never again (cheapest in the long run and I dislike throw-aways)); I'm not so keen on having a combined unit where a failed HP negates a still-good tank or a corroded tank negates a still-good HP unit. Good point on the rebates- will need to look at that and run the numbers some. Thanks for all of the input!

I originally thought the same way (marathon tank), but the EF is lower for the two piece unit, so you end up paying more in the end. IMO the engineering and stratification/recovery is better for the one piece. The HPWH I got (AO Smith) has an active (rather than sacrificial) electrode, so I expect the tank to last a good long time with little maintenance.

 

[BoilerMan]

When I was talking propane, I mean that all big electric consumers that can be propane should be to save money. Also I stated a tankless unit like a Rinnai, efficiencies are typically in the 90% and that's still hard to quantify as there are no standby losses.

Personally if propane were not an option for hot water (I do not use it) I'd go HPWH. Separate units if you are mechanically inclined, as I think it will work out cheaper and avoid Chinese stuff. The systems that Tom sells have a long track record for reliability, the all-in-one units do not as of yet, and some have had teething pains which have not been time proven yet...........

IMHO, time tells the story about all equipment.

TS

 

[woodgeek]

Would you buy a two piece refrigerator for the same reasoning? A GE HPWH costs less than most fridges at this point, a lot less with rebates. As for reliability, get/check the warranty on the HPWH. Have never heard good things about the tankless propane units re reliability or hot water 'quality'.

 

[BoilerMan]

I had a Bosch (Aquastar) tankless unit and was quite happy with the performance. Aquastars are not known for being the best, Rinnai has that category. I wish I had kept the unit, it worked well, but I sold it for what I paid for it back when propane was expensive relative to oil. Now we have competition in the propane market here and it's significantly cheaper than oil/btu.

I also stated if his water quality was good the tankless units are good.

If your water is not hard, you may want to look into a propane tankless unit like a Rinnai

TS