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Heat Pump Water Heaters - GE vs. Rheem  Rating:  Rating
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 Posted: Sun Feb 12th, 2012 02:26 am
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Bluzman
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Heat pump water heaters can be very efficient and reduce operating costs significantly. They have a compressor unit (refrigeration machine similar to what a household refrigerator uses) that absorbs heat from the surrounding air using a fan with a tube and fin coil on top of the unit. The heat pump then moves that heat to the water in the storage tank. The GE model uses tubing coiled around the storage tank underneath the foam and jacket to do this, hot refrigerant gas is pumped through the coil. A. O. Smith, Stiebel Eltron, American, State and most other manufacturers use this same type of wrap around coil design. Rheem uses a water-to-refrigerant heat exchanger on top of their unit. It’s a tube inside a tube coil. The Rheem unit has to have a pump to move the water between the tank and the heat exchanger.

The compressor unit is a far more efficient way to heat water (well over 100% efficient) but the heating capacity or recovery rate of the compressor unit is often lower than standard electric heating elements. Heat pump water heaters are equipped with standard heating elements as a backup heat source for times when demand (showers in the morning) is high and the compressor unit cannot keep up. The control system will automatically switch to heating element operation when it sees the tank temperature dropping too far below the thermostat setting. When a heat pump water heater is using its backup heating elements it is no more efficient than a standard electric water heater (below 100%). So the idea is to use the compressor more than the heat elements.

This GE unit has 50 gallons of storage; Rheem has a 50 gallon and a 40 gallon model. For a heat pump water heater to provide any real savings it needs to have more storage so the compressor unit can store heat it absorbs during low demand periods and have it ready for your morning shower load. Added storage acts like a battery and improves overall efficiency (savings) by allowing the compressor unit to run more often than the backup heating elements. It also provides more hot water for more showers.

The mistake many people are making today is they remove a standard 40/50 gallon electric water heater that can make 21 gallons of hot water an hour (using heating elements) and replace it with the same size (40/50 gallon) heat pump water heater that will only be capable of making 8-10 gallons of hot water an hour much of the time while using its compressor. They should be installing a 60 or 80 gallon model to maximize the efficiency and savings. The difference in cost between 40/50 gallon models and 60/80 gallon models is well worth the investment. Stiebel Eltron makes an 80 gallon model. A. O. Smith, State, American, Kenmore, Whirlpool, Reliance, U. S. Craftmaster all have 60 and 80 gallon models.

I wouldn’t pay attention to those yellow Energy Guide stickers either. The estimated operating costs on those are calculated based on outdated test procedures that do not factor a typical morning shower load; the time when a heat pump water heater is most likely to resort to heating element operation. See the chart below. The Energy Guide estimated operating costs work fine for standard efficiency products but they need to be revised before they will ever make sense for heat pump water heaters. Same for EF (Energy Factor) ratings both EF and Energy Guides rely on the same outdated DOE test.

The National Renewable Energy Laboratory (NREL) conducted a test on the 50 gallon models from GE and Rheem and the 80 gallon model from A. O. Smith in 2011. Unlike the tests used to calculate Energy Factors and Energy Guide estimated operating costs this NREL test put the water heaters through a real world test with four shower draws in a 90 minute period. Typical morning shower load for a family of four. The results of these tests were published in a report in July of 2011 which is available to the public.

Here is the link: http://www.bpa.gov/energy/n/emerging_technology/pdf/HPWH_Lab_Results_Advisory_Team_7-14-11.pdf

In the summary findings of this report (page 18) NREL states that “tank storage capacity has a significant effect on efficiency” and that “larger tanks have more thermal storage which allows equipment to supply hot water for large draws longer and then recover tank with compressor only.” The NREL test showed that the 80 gallon model from A. O. Smith was able to deliver 4 showers before the heating elements came on or the water temperature dropped below 105°F (average shower temperature). The GE model was only able to deliver 2 showers. The Rheem was the worst of the three, it was only able to deliver one shower before the heating elements came on.

Attachment: doe_vs_real_world_draw_profiles.jpg (Downloaded 81 times)

Last edited on Sun Feb 12th, 2012 08:48 am by Bluzman

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 Posted: Sun Feb 12th, 2012 04:19 am
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eleent
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Hello  Bluzman:  Good information.  The report you gave a link to reads (unintentionally) like an ad for A O Smith as their unit performed better under so many conditions.  The breaking out of COP (coefficient of performance) according to circumstances around the units was particularly useful and nice to see :cool:

Yours,  Larry

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 Posted: Sun Feb 12th, 2012 08:36 am
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Bluzman
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Larry,

I know what you mean but any decent quality 80 gallon model would have shown similar results. The 80 gallon Stiebel Eltron will deliver far greater efficiency performance compared to any 50 or 40 gallon unit also.

That was the point of my post, its not about brand its about the nature of slower recovery "renewable energy" water heaters. Solar water heaters need more storage for the exact same reason.

The first rule of water heater sizing is recovery + storage = demand.

Think about tankless water heaters for a minute, they don't have any storage so what did they do with the heating capacity? They raised it through the roof and most need 3/4 inch gas lines to support the heat engines that start around 150,000 Btu/hr. They had to do it so they can meet demand without any storage.

With heat pump water heaters people wont notice as much because there are backup heating elements that will come on to supplement the compressor. But the whole point of a heat pump is to run the compressor as much as possible.

The GE unit will probably work fine for a young couple without kids or a retired couple who's kids are grown and gone. But what happens when they sell the house and the next owner does have kids? People need to size the water heater for the number of bedrooms/bathrooms in the home, not the current number of occupants.

Last edited on Sun Feb 12th, 2012 08:40 am by Bluzman

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 Posted: Sun Feb 12th, 2012 05:21 pm
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eleent
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Hello:  Gary Klein likes to boil it down to needing either a "big burner and small storage" or "small burner and big storage".  It looks like many of the heat pumps have a small burner and modest storage.

COPs dipped under one in that paper you brought, yet in Japan, the Eco Cute heat pumps can achieve four or more.  I know that's looking at the facts in a selective manner, but it's clear we can do much better than we are doing now.

Also, work is being done at ASHRAE to change Energy Factor (EF) to better reflect the real world.  Hopefully it will happen in our lifetimes so we can get some benefit from those yellow stickers ;)

Yours,  Larry

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 Posted: Wed Feb 29th, 2012 05:28 pm
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jongig
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I just found this thread after doing a search on the GE heat pump because mine has broken. Mine was installed in November of 2009.
I am very interested in green living and we use solar-DHW, heat recovery, Geothermal-DHW and lastly in line is the third tank the GE Heat pump. I have data loggers installed and can always tell what's going on.
My first problem I noticed with the GE was that it seemed to run much more in the last year and since we didn't have a hot summer or as much solar as usual I wasn't sure what to make of this. Recently I noticed the elements turning on even though the unit is in eHeat mode. I can tell by both the current draw as well as the noise the water heater made.

I was never given an option for an extended warranty and I sure wish I had one. The warranty is only on parts at this point and I was a bit concerned since a lot of times repairs can be so high as to not make it feasible to fix.

I was however fortunate that GE was kind enough to pick up the tab for the entire repair, parts and labor.

The unit should get fixed in the next couple weeks but I thought I'd like to put this information out there because at $1,300 this was a purchase that will take me about 6 years to recoup and my original thinking was that this should last 20 years but maybe I'm wrong. My thinking was that heat pumps are very old technology and like refrigerators this GE should be a good purchase.

My unit is installed in a warm 67 degree 2,400 sq-ft basement. Because this is the third water heater in series this unit rarely gets cold water. In the last year I’ve become unhappy with this unit turning on at nighttime even though we were not using water and it would run for hours. I called GE last August and asked about this and they said it was normal. The unit is set to 130 degrees. We don’t have insulation in our first-floor because of the temperatures in the basement being kept within a few degrees of the upstairs and the basement walls are insulated. The unit just happens to be installed below our bedroom, which makes listening to it at night unpleasant. I wish GE would put some additional thought into this and let us program an on/off time. I do cut the electricity to the unit at night so that we don’t have to listen to it but when we originally bought it I didn’t notice the noise at night that often. Our huge Geothermal unit sits next to the GE and we can’t hear the Geothermal.

I will update this when it gets fixed and please note that I'm so far happy with GE and we have a house full of GE. I can't say for sure why they are paying for labor but hats off to them for this.

John

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 Posted: Wed Mar 14th, 2012 02:10 am
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EdP
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Noise is an issue for me, but apparently Noise is not a standard specification. A few of the hybrid hot water heaters do have the Noise rating.
Stiebel Eltron ACCELERA 300 is loud at 64 dB
GEH50DNSR is like 52 dB
Rheem HP50RH is quietest at 48 dB

I haven't been able to find the Noise ratings for the Whirlpool HPE2K80HD045V (WP), or Kenmore 153.32118 versions or any of the others for that matter, but haven't searched as much for the others.

GE is coming out with the new model (GEH50DEED w/ EF 2.4) in April 2012, so the older model GEH50DNSR is on sale now for about $1000. Mostly the Stiebel Eltron ACCELERA 300 runs for about $2600-$3000, but a couple of places have it currently for ~$2162, but at a $1000 difference and more noise the Stiebel only saves about $18 per year for me, so would never pay the difference back. Although maybe the Stiebel is more reliable than the GE? Haven't decided which one to go with, because noise and reliability are big issues for me, and there is little info on those.

I also note that some heat pump water heaters give set backs of 3 ft, 5 ft, and 2 ft on different sides which makes it really tough, and others don't mention that, so be careful, if you currently have the water heater in a small room or near a wall now.

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 Posted: Wed Mar 14th, 2012 02:18 am
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EdP
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Most heat pump water heaters tend to have larger capacities because they are slower to recover. So, you really have to up the tank size to get the same amount of hot water out of many of the heat pump water heaters compared to a normal one. I think the Rheem circulating the the water through the heat coil at the top also mixes the water up more rather than leaving it stagnate with hot water at the top and colder at the bottom. Most water heaters take the hot water off the top, and this gives hot water longer, so anything that mixes the water in the tank too much will tend to give less water before getting cold.

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 Posted: Wed Mar 14th, 2012 02:26 am
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EdP
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Not exactly sure how the anode works and whether the tape on the threads might create undesirable electrical insulation between the two pieces of metal, thus changing the anode protection level. Not sure if that would make it slower or faster, or even if it matters, but if it did not say to do that in the instructions, I would check with the company.

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 Posted: Wed Mar 14th, 2012 07:14 am
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elenano
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Teflon tape does not do this. Remember that when you tighten it, the threads bite through the Teflon. In any case, we've tested with a voltmeter and there is electrical continuity.

Also, when you pull an anode that was installed with Teflon and it's mostly consumed, you know the Teflon didn't stop it from working.

Randy Schuyler

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 Posted: Thu Sep 27th, 2012 02:57 pm
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jkasben
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Is it a forgone conclusion that the HP water heater is definately better than nat gas??

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 Posted: Thu Sep 27th, 2012 09:25 pm
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eleent
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Hello and no.  If you have low hot water use, it would be a strike against using a heat pump.  If you have very high electric rates, the same applies.  If the filter on the heat pump is unlikely ever to get cleaned, or if the unit lives in a cold place, performance will drop off. 

Heat pumps are best installed where the owner is just a bit technical, where a bit of cooling and dehumidification would be welcome, where any noise from the unit wouldn't bother the people and where gas rates are high and electric rates are low.

We don't like forgone conclusions.  They get in the way of good troubleshooting ;)

Yours,  Larry

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 Posted: Wed Nov 28th, 2012 11:37 pm
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terryk
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New member here and I joined because of this discussion regarding heat pump water heaters. I want to thank everyone who contributed here. There is a lot of good informaiton that I have not found else where. I had almost given up putting one of these in because it is going in my basement and I was worried about the noise but someome mentioned a refrigerator like noise and a light dawned that we already have a refrigerator down there so the noise issue shouldn't be a problem.

Here is my chance to give back. One of the posts in here mentioned that GE was going to build their heat pump water heater in Louisville, KY. Well, I never saw that confirmed so I'm posting that it is confirmed. I found it yesterday after reading through this forum. Also, if anyone wants to search the web for it here is the model number: GEH50DEEDSR. It looks different than the original GE heat pump model.

Again, thanks to all for this forum.

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 Posted: Wed Jan 16th, 2013 06:12 pm
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Filam
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I like the information you have presented and I agree.

I am looking at this at a slightly different angle. I use a Carrier / Climatemaster geo- thermal heat pump (open loop) and my heat pump has the additional second optional heat exchange coil (desuperheater).

When I first installed it in 2008 I tried using a low boy 50 gallon tank, and it was "tricky" trying to get the original water heater to provide hot water economically year round. With a single electric tank it just doesn't work well, because you have to lower the temperature of the bottom and top thermostats so you are not feeding electrically heated water to the inlet side of the desuperheater coil in the geo heat pump.

When I purchased my GE geospring (which is currently awaiting repairs for a leaking evap coil), I installed it in the house and began using the original 50 gallon unwired electric water heater to store the heated water produced by the desuperheater in my heat pump.

Heating incoming water in the first tank is efficient and there is no danger of heat being transferred back out of the tank back to the desuperheater. Effectively, when all is working, the water temp in tank #1 is boosted 10 - 30 + degrees above incoming water temperature. That heated water then goes in series to the 2nd heat pump water heater.

So coupled with even a smaller capacity heat pump water heater, incoming water comes in relatively warm and overall water temperature does not cool down too quickly, as I /we shower.

Of course the larger both tanks are, the better everything works. Another important observation: if the first and or second tank is outside in a non conditioned space, you will always be fighting heat loss. The other important things are the use of appropriate check valves in water lines to prevent through the pipe loss when hot water is not being used, (more critical on the inlet side) and if possible getting insulation between the bottom of the water tank and the ground surface.

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 Posted: Thu Mar 28th, 2013 02:17 am
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maxshiff
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Hi All,

I have a question concerning the height requirements of the GEH50DEEDSC. It seems to recommend that the unit (60 1/2" high) must have a minimim of 6" clearance to be able to remove the filter. This is fine, since I have about 75" vertical clearance in all.

My question is ... if we're supposed to remove the Anode rod for maintenance and inspection, how could they only suggest a 6" clearance? Don't we need a whole lot more space to be able to lift the rod out vertically?

Has anyone else run into this trouble? The only other way I can think of doing it would be do drain the tank, disconnect the fittings from the top, and awkwardly tilting the whole thing over to remove it?! Seems like a lot of work for an annual procedure??

Thoughts?


Max...

Last edited on Thu Mar 28th, 2013 04:37 pm by maxshiff

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 Posted: Thu Mar 28th, 2013 03:37 am
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elenano
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You need about 44 inches to fully remove an anode, but you can inspect it and get a good idea of its condition in about a foot. As to replacement, when the anode is depleted, it will remarkably bendable, but you'd need at least 12 inches to put in even a flexible anode.

Randy Schuyler

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 Posted: Thu Mar 28th, 2013 01:55 pm
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Filam
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My two cents worth. Yes, you need "enough" room to remove the anode from the top AND the proper socket, breaker bar etc. I have never done this in any water heater. People rarely do. My guestimate is that I wouldn't mess with it for at least 3 - 5 years unless you are very consciencious.

Also some area codes require the water heater to be XX inches above the floor. In coded areas these stands are purchased from plumbing houses etc, or built.

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 Posted: Mon Apr 22nd, 2013 05:44 pm
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floydo
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FWIW as part of pre installation I called GE on the GEH50DEEDSR, and they indicated the anode is 39", so generally one would drain and tip the unit to replace.  Inspection could be made with minimum clearance specified.
I also asked about the reported leakages to the coolant heat pump system in the earlier model.  The GE rep was familiar with the issue of "welds" that were not robust.  Based on the forum comments it sound like solder connections were the issue.......She stated the new model has a different (I can't remember the word she used but it was similar to radiator) manufacturer for that part.

Right now in the Pacific Northwest these units have a series of rebates that can take the price to $0....$999 less 200 instant rebate at Lowes.  Local utility (PSE or Seattle City Light) has a 500 rebate, and the fed tax credit is 300....So you are out labor and sales tax in Washington....WOW.:)

That is some inducement.

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 Posted: Mon Apr 22nd, 2013 06:26 pm
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elenano
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Thanks for the update. As to the anode, a number of times we've seen that the factory anode is not as long as it might be. We'd like to see it extend nearly to the bottom of the tank, so if it will take a 44-inch anode, you shouldn't be thinking of cutting the thing just because GE uses a shorter one.

Paying a few bucks extra for a loose-link flexible anode is better than disconnecting the plumbing, draining the tank, and tilting it to replace with a solid anode.

Randy Schuyler

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