Geyser DHW owners

[Redbarn]

Then consider that whatever air you pump out of the house will have to come back into the house somewhere (you aren't going to maintain negative pressure after all) so you will be pulling in the same volume of outside air - which will be even colder so the net effect of venting the unit outside may well be to cool the house even more than if you just vent the unit into the home (assuming the temp outside is lower than inside).

I agree with Slow1.
I researched and considered this for my installation but reached the same conclusion.

 

[GaryGary]

Hi,
This is just a idle, off the top of the head thought on whats going on in water heating with the HPWH:

1 - The heat pump extracts heat from the house air, cooling the house air and heating the water in the water tank.
This is not so good in the winter, since, to some degree, you end up reheating the air that the HPWH cools with your furnace.

2 - The water from the hot water tank goes to a shower. The water enters the shower head at (say) 100F, it goes does the drain at 95F taking most of the the heat that the HPWH added to it with it. That is, you heated the water from 55F up to 100F, then actually used about 10% of it, and sent the rest down the drain.

Isn't there some clever way to use the heat in the drain water to heat the air in the area where the HPWH is operating, so that the HPWH operates more efficiently and does not cause your furnace to come on as much due to the cooling from the HPWH?

Gary

 

[Slow1]

Isn't there some clever way to use the heat in the drain water to heat the air in the area where the HPWH is operating, so that the HPWH operates more efficiently and does not cause your furnace to come on as much due to the cooling from the HPWH?

There are in fact some methods of recovering waste heat going down drains. Most involve coils of copper or other pipe wrapped around the drain pipes which you then run the inbound cold water through before running it into the hot water heating elements/tanks thus pre-warming the cold prior to heating by cooling the waste water. Basically these are water heat exchangers. Not really practical for home use but there is some benefit in settings that have large hot water use - think gym showers or perhaps commercial laundry or other high demand use where you are likely to run the hot water for long periods of time at the same time as you are draining hot water.

 

[woodgeek]

Gary,

The thing to remember (and that you know well) is that compared to space heating, the BTU load we're talking about for DHW is pretty small, and for a HPWH only about half of those BTUs come from the space, with the other half coming from the grid via the compressor work on the refrigerant.

Drain Water Heat Recovery systems (DWHR) are water-water heat exchangers that I guess are getting pretty common in new construction in canada, but are still pretty rare in the US. It also appears that in many places there are code compliance concerns and inspection hassles (due to the threat of mixing gray and potable water streams, I guess). Most importantly, they only recover ~50% of the DHW BTUs, which hurts the payback. With a HPWH, your best DHWR configuration would be to preheat the cold supply stream before it enters the tank, not to heat the space for a comparatively small benefit to COP. I looked at DIY drain water to air exchangers (on paper), but it didn't look good...the peak powers are very high (several kilowatts), requiring a biggish blower, the drain pipes are not very big (requiring something like a massive finned heat sink)....and then it runs <30 min/day. Oh yeah, and the air system would only be used during heating season (but the water one would save year round).

When I looked at this, I decided that going to a HPWH would save me 50% over a conv elec tank (in my mid-atlantic climate), adding a water-water DWHR would get me to 75% savings. But in my case the additional DWHR savings would be ~$100/yr for a family of four and it was hard to get excited about tearing out the finished walls containing my drain pipes, installing a huge, spendy hunk of copper, and cleaning up afterwards. New construction, we could talk.

 

[GaryGary]

There are in fact some methods of recovering waste heat going down drains. Most involve coils of copper or other pipe wrapped around the drain pipes which you then run the inbound cold water through before running it into the hot water heating elements/tanks thus pre-warming the cold prior to heating by cooling the waste water. Basically these are water heat exchangers. Not really practical for home use but there is some benefit in settings that have large hot water use - think gym showers or perhaps commercial laundry or other high demand use where you are likely to run the hot water for long periods of time at the same time as you are draining hot water.

Hi,
I'm aware of the GFX style grey water heat recovery devices that preheat the incoming cold water, but I was thinking about something simpler and cheaper that might just heat the air in the general area where the HPWH is.

As a rough example, in the crawl space half of my house there is an exposed PVC drain pipe from the shower area that runs diagonally across the whole crawl space -- perhaps 40 ft. I've never measured the temperature drop over its length, but I'd guess its giving back a significant portion of the shower drain water heat to the crawl space (its a conditioned crawl space).

I guess the general thought is that the HPWH will deliver a better COP when it has a warmer heat source, and the heat in the drain water is heat we are just throwing away -- seems like using it for the HPWH would be a win-win -- just need a simple, practical way to do it

Gary

 

[hemlock]

While I'm sure anything is possible with a bit of creativity, I am not sure it would be worth it. Consider the fact that the air you pump out of the house (venting it out) while cooler than the room temperature is still likely to be warmer than the outside air in the winter. Then consider that whatever air you pump out of the house will have to come back into the house somewhere (you aren't going to maintain negative pressure after all) so you will be pulling in the same volume of outside air - which will be even colder so the net effect of venting the unit outside may well be to cool the house even more than if you just vent the unit into the home (assuming the temp outside is lower than inside).

I'd considered that. My solution for "make up air" to compensate for the air that would be pumped outside would be to remove the exhaust air duct from the heat recovery ventilator that shares the same room as the Geyser, thus the Geyser would then act as the exhaust. Hopefully, this would somewhat balance out any negative pressure situation that would otherwise occur.

 

[Slow1]

I'd considered that. My solution for "make up air" to compensate for the air that would be pumped outside would be to remove the exhaust air duct from the heat recovery ventilator that shares the same room as the Geyser, thus the Geyser would then act as the exhaust. Hopefully, this would somewhat balance out any negative pressure situation that would otherwise occur.

Solves the negative pressure all well and good. However, then consider that the HRV (assuming you keep it running) is now wasting power pumping the cold air into the house - same problem, you are cooling that room with cold air. The HRV is essentially a heat exchanger - it helps to ventilate the room with fresh air without affecting the temperature (much) by heating the inbound air with the warmth from the air it blows out - thus the exhaust is colder than the room air. If you disconnect the exhaust and blow it into the room you will be blowing this colder air into your room. The 'wasted power' I'm referencing of course is the fan blowing for no real purpose - let the negative pressure draw the cold air in itself if you are going to have it come in anyway.

 

[DBoon]

Hi Slow1,

I have a Geyser HPWH. I bought it for about $1100 delivered to my house direct from the company that makes them. I wouldn't pay more.

I have had it for a little more than a full heating season. I live in a cold climate in upstate NYU with a well-insulated basement, and desired to lower my (already low) electricity usage for hot water direct electric heating and provide some dehumidification for my basement. It has worked well on both counts with some caveats.

First, I have a day/night electric meter and ran my hot water direct electric tank on a night timer and used approximately 220 kWh/month for water heating in the winter, 170 kWh/month in the summer and about 200 kWh/month in spring/fall. My HPWH is on a 115V circuit and I have metered it with a Kill-a-Watt meter and I have the following data to report:

Summer 2011 - 85 kWh/month
Fall 2011 - 110 to 120 kWh/month
Winter 2011/12 - 200 kWh/month (this led to a lot of changes, discussed below)
Spring 2012 - 150 kWh/month (colder incoming water than fall? Also, I made changes, discussed below)
Summer 2012 - 60 kWh/month

First, I tried to run the HPWH like my direct electric heater with a night timer and storage throughout the day. I heated the water to 130 degrees F overnight and used it during the day. Worked well that first summer. However, this didn't work in the winter - 8 hours wasn't enough time to heat the tank.

So, in Winter 2011/12, I let it run whenever it needed to, and it was running a lot. By the end of the winter, my basement was 50 degrees F and the COP seems to really go down at that temperature. I put an electric resistance element on backup and was still using a lot of energy for the HPWH and it was running a lot.

In Spring 2012, the performance didn't improve as much as I thought it should have by May 2012. I think that it was partly because the basement was a good 5 degrees colder than the previous May (HPWH had done that). I also worried that I had some scale in my heat exchanger (I have since installed a water softener). So, I reduced the temperature to 120 degrees in the HPWH from 130 degrees. That helped a lot. Also, I had noticed that my wife would run straight hot water when rinsing dishes - using the same hot water at slightly lower temperatures reduced the usage a bit as well.

In Summer 2012, I started out by getting about 110 kWh/month usage. I think this was because of the colder basement. Also, I noticed that the insulation on my outlet pipes was not what it could be. I did a better job of thoroughly insulating all of my pipes, and double insulated the pipes between my tank and the HPWH and my usage dropped to 60 kWh/month.

The bottom line for me is the following:

1. You will probably find that in the northeast, the basement will get too cool in deep winter with this thing running, and you will want a backup heating plan for the hot water.
2. My unit runs about 6 hours a day in the summer, and 12-15 hours a day in the winter, and we don't use a lot of hot water compared to most people. If you have a large family, I don't see it supplying all of your need in the winter - you will need a backup element (even I did last winter, but maybe not this coming winter due to extra insulation and settings changes).
3. You will get a fantastic dehumidification side-benefit from this - that was actually the main reason I installed it. I was tired of running a dehumidifier in the basement 8 hours a day in the summer with all of the attendant costs and heat generation.
4. Plan on using it at 120 degrees F (the factory setting). The HPWH seems lose a lot of COP/efficiency in going from 120 degree water to 130 degree water.
5. You must be meticulous in insulating all of the pipes coming out of the hot water heater, and if you don't have great insulation on your tank, insulate that with more. Don't setting for the single layer of insulation on the hoses connected the HPWH to the tank. Double-insulate thos with more insulation. Don't allow one bit of exposed pipe surface anywhere - tape everything up thoroughly to ensure it stays in place.

PM me if you have any specific questions. FYI - I am only checking this site about once/week, so a reply could take that long.

 

[Ehouse]

I Think drawing the heat from your septic tank (if you have one) is an idea worth exploring. Start with a simple DX fan coil set up and an insulated tank. Before you pounce, I said explore. I'm aware that the powers that be will shriek in outrage, but if you think about it the potential problems don't seem insurmountable.

Ehouse

 

[Slow1]

Thank you DBoon - I really appreciate the detailed write up. I don't have the humidity in my basement - likely due to it being half exposed (on a hill so we have a walk-out the back). The other down side is that it is already colder in winter so less heat to draw on - likely get the feeling I'll have to either turn off the DWHP in winter or provide heat to the basement in another form which has been under consideration but makes for an odd way to heat the water eh?

 

[maple1]

DBoon, are you able to quantify or estimate the electricity savings realized from reduced dehumidifer operation?

 

[DBoon]

Hi Slow1 - you may have more humidity than you realize. Just about any below ground area - even partially below ground - will have overall high humidity levels in the summer. I would be very surprised if your humidity is below 60% in the summertime.

Hi Maple 1 - I used to run a dehumidifier 8 hours a day (overnight) for about 5 months a year. The dehumidifier rating is 115V @ 5.4A = 621 watts/hour. For 8 hours, power consumption would be 4968 Watts - let's round it off to 5 kWh per day. For 30 days, that is 150 kWh/month, or over 750 kWh a year. My night rate (I ran the dehumidifier only overnight) was 11 cents/hour, so the cost per year was $82.50. This might be low - my wife would often run it more - not because it needed it, but because she was sensitive to mold and worried that I wasn't running it enough.

Now, I will admit that this certainly helps with the payback of the HPWH. I figured that (overall) I would save ~100 kWh/month using the HPWH versus electric resistance heat, or 1200 kWh/year. Add that to the 750 kWh/year by not running the dehumidifier, and I would be at a 1950 kWh/year savings - lets round that up to 2000 kWh/year at 11 cents/kWh and that is $220/year in savings, or a 5 year simple payback on the HPWH (6 years counting installation).

I'm not sure that I'll get this savings - given my earlier post, I'm not sure that I'll really see 1200 kWh/year in savings. I think it is likely to only be about 800 kWh/year due to wintertime inefficiency. Electric rates have also gone down a bit - especially in the non-peak electric season (anytime but summer), so 11 cents/kWh is probably a little high, overall. But, I'm an efficiency nut always trying to reduce my usage, and I get a nicely dehumidified basement year round that never smells musty. Knowing what I know now, I would still buy the Geyser again.

 

[begreen]

What is the repair history on these units? In order to get the expected ROI are they expected to be repair free for 10-12 years?

 

[Redbarn]

There was a long thread on Heat pump water heaters in 2009. Reads a bit dated now but some usefull data there.

https://www.hearth.com/talk/threads/heat-your-water-with-a-heat-pump-50-electric-savings.30309/

 

[begreen]

Thanks for the back link. I checked into a HP for hot water for our house but was discouraged with the repair record for the all in one units. That's why I asked how the Geyser's track record has been.

Our electricity is a bit cheaper and we use less hot water than average. The extends the payback period for us.

 

[Redbarn]

Thanks for the back link. I checked into a HP for hot water for our house but was discouraged with the repair record for the all in one units. That's why I asked how the Geyser's track record has been.

Our electricity is a bit cheaper and we use less hot water than average. The extends the payback period for us.

The person with a lot of history with the Geyser and its predecessors is Tom in Maine.

He installed Geyser ancestors called Nyletherm.
He is a Geyser dealer so may not be unbiased but could give some history.

We have owned ours for 15 months so cannot really comment.

 

[tom in maine]

I don't usually check this forum, but just came across this thread.
I have had my hands on a lot of Geysers and their predecessors, the Nyletherm.
Also know the principals in the company from way before they started making these units.

Don Lewis, who is the chief engineer, is an extremely conservative engineer, who prides himself in making dependable, durable products.
That being said,the units are pretty solidly built. The latest changes they have made are upgrades in the controls and a slight efficiency bump.

The current controls are hand wired and use contactors and time delays that are all readily available online and from Grainger.
The controls used to be potted in epoxy which were decent but not serviceable.

What separates these units from the all in one units is the fact that they can be swapped out from one tank to another in case there is a tank leak.
All in one units cannot be re-used. They use a copper coil that is wrapped around the outside of the tank.

Here in Maine, our electric cost is 18 cent a kwhr. In my household, we use about $20 a month to operate the Geyser. This has been consistent
for several years. We use a fair bit of hot water daily.

There are downsides. My home unit is only operated from May through October. My basement is small and insulated with spray foam, so the unit tends to steal energy from the first floor of the house. This is great in the summer. It gets to be less fun in the late Autumn.

The recovery is 1/2 that of an electric water heater. This could be annoying. I heat a 350g tank that we sell. We do not run out of hot water.
A 40 gallon tank can be tolerable and manageable. If you have a teenager and can beat them to the shower, you are guaranteed to not have them in for too long.

We offer these as the preferred backup to our new solar DHW system.

As someone mentioned, we do sell them. That could make me biased. I am biased in that they are made here in Maine, but I would not sell them if I did not
think they were a good investment.

My long 2 cent worth!

 

[hemlock]

Bought a Geyser, and it arrived today (a big thanks to Tom in Maine). Hopefully, I'll have it hooked up in a day or so. I do have a question however - it says to use Pex and crimp fittings, but would "Sharkbite" fittings be acceptable with the Pex? I don't have the crimping tool for the traditional Pex pipe installation.

As an aside - thanks for all of the responses. It helped in making my final decision. I'll be anxious to see my next few power bills after the install.

 

[tom in maine]

Sharkbites are fine. Nyle just assumes that everyone would want to use crimp connectors!
I am actually amazed that so many people have access to crimp tools.