Regarding the idea of putting a HPWH in conditioned space and then exhausting the air to the outside - this is generally not going to be a good idea. For example, in my climate (central VA), the average heating season temperature (Nov.-Mar.) is around 44F, but the average discharge air temperature during a typical water heating cycle will be somewhere in the 50's. Sending out 50-ish air and replacing it with 44F air is an energy waste, not an energy saver.

I second the above. The idea of ducting the cool air outside to save energy makes no sense. The air exiting the unit is warmer than the outside air in winter, and exhausting it would cause even colder air to get drawn into the structure.

The EF of these units is ~2-2.3. This implies that the COP of the compressor is probably 2+ on a seasonal average. IOW, they use <50% as much energy as a conventional electric tank WH.

In a heating climate HPWHs do steal some heat from the conditioned space...but in most homes space heating BTUs are cheaper than electric resistance BTUs, so the HPWH is still cheaper to operate than a conventional tank in the winter, just not as cheap as in the summer.

Posted By woodgeek68 on 08 Feb 2014 05:41 PM
I second the above. The idea of ducting the cool air outside to save energy makes no sense. The air exiting the unit is warmer than the outside air in winter, and exhausting it would cause even colder air to get drawn into the structure.

The EF of these units is ~2-2.3. This implies that the COP of the compressor is probably 2+ on a seasonal average. IOW, they use <50% as much energy as a conventional electric tank WH.

In a heating climate HPWHs do steal some heat from the conditioned space...but in most homes space heating BTUs are cheaper than electric resistance BTUs, so the HPWH is still cheaper to operate than a conventional tank in the winter, just not as cheap as in the summer.

If your HPWH is located in your conditioned space and it is summer and 95° outside.

Where would you want to intake air from? ( Inside OR Outside )

Its summer and your HPWH intakes 95° and exhaust 84° and your conditioned space is 72°. Where would you want to exhaust? ( Inside OR Outside )


If your HPWH is located in your conditioned space and it is summer and 95° outside.

Where would you want to intake air from? ( Inside OR Outside )

Its summer and your HPWH intakes conditioned 72° and exhaust 68° and your conditioned space is 72°. Where would you want to exhaust? ( Inside OR Outside )


If your HPWH is located in your conditioned space and it is winter and 25° outside.

Where would you want to intake air from? ( Inside OR Outside )

Its winter and your HPWH intakes 72° and exhaust 65° and your conditioned space is 72°. Where would you want to exhaust? ( Inside OR Outside )



What are the temps differnce of intake and Exhaust air?

I agree. It seems kind of ridiculous to vent an electric water heater. It adds cooling to the air space in the summer. In the winter, it's such a small amount of cool air being dispelled, that it's hardly worth it. In my case, with the intense passive solar, we actually open windows on most winter days, so it's a moot point.

@JimGagnepain

How about some inlet and exhaust temperatures?

I didn't get the impression that @JimGagnepain has a HPWH...but I have one. Here are the numbers mid-cycle this evening...inlet temperature was 67F, discharge was 51F...outside temperature was 36F.

Assuming roughly 300cfm of airflow for the HPWH and the 15F delta-T between HPWH discharge air and outside air, this would be almost a 5,000Btu/hr heat loss. Granted, there would be a small amount (10%?) of heat recovery by the 300cfm of "make-up" air moving through the building enclosure, but at 300cfm the recovery percentage is going to be pretty low.

In JohnRLee's north-CA coastal area (Arcata area) the mean winter outdoor temp is ~47F, the mean summer temp is 57F. There's effectively zero cooling benefit from keeping the cool air indoors in his case, but also no summertime gain benefit to keeping it outdoors, or in an unconditioned space, but it'll still work in an unconditioneds, and deliver good average performance.

COP is much more sensitive to tank temperature than room temperature, but there's a roughly linear COP derating with room-ambient that occurs with falling temperature. The hit in COP from the cooler operating at temps below 60F in winter is pretty small. A tank maintained at 120F that averages a COP of 2.5 @ 75F room falls to about 2.0 @ 60F, but would still be delivering over ~1.7 @ 45F. See the derating curves with temperature of three different units of page 11 of this document:

http://www.bpa.gov/energy/n/emerging_technology/pdf/HPWH_Lab_Results_Advisory_Team_7-14-11.pdf

(The GE unit in the top graph will still deliver a COP of about 2.0 @ 45F ambient temperature with a 120F storage temp.)

Ducting it outdoors would be more of a room-comfort issue than an energy-use issue in Arcata.

* I don't feel that there is much or any advantage to putting it in my home (in the mechanical room). I don't need the negligible cool air in the summer and I would rather not have to listen to the noise it puts out.

* I cannot put it in my mech room (unless I want to vent the cold air outside which might cost more in materials than simply putting the HPWH in the garage) or it will skew my Title 24 report adn I woud have to find other ways to get into compliance (or I will not be granted a building permit).

so it is a moot point.

However, as much as you guys like to bang around and split hairs on this, I'd rather steer the conversation back to reliable brands of HPWH. So many of the self contained units get some troubling reviews. Some of the bad reviews, you can read between the lines. But there are some serious reliability issues for many brands, specifically some homeowners experiencing multiple failures for the same unit. That is a real concern. Given that if it actually fails, you're SOL for hot water until it gets fixed (unless you have a back up unit)

Posted By JohnRLee on 10 Feb 2014 04:23 PM


However, as much as you guys like to bang around and split hairs on this, I'd rather steer the conversation back to reliable brands of HPWH. So many of the self contained units get some troubling reviews. Some of the bad reviews, you can read between the lines. But there are some serious reliability issues for many brands, specifically some homeowners experiencing multiple failures for the same unit. That is a real concern. Given that if it actually fails, you're SOL for hot water until it gets fixed (unless you have a back up unit)

My daughter and her husband went with a GE Geosprings this past summer and have been very happy with their greatly reduced electric bill. They purchased the unit at Lowes when there was a $200 discount as they are running right now and also went for the 9 year extended protection plan for $99.97. I normally don't believe in these plans but in this case with a relatively new product felt it was well worth the $11 per year for peace of mind. Their power company also has a $200 instant rebate so that makes the purchase even more attractive.

The more recent reviews of these units seem to be much more positive than earlier reviews.

YMMV,

Hugh

I suppose in a hot and humid climate it would be best to install HPWH in the conditioned space. One place which might benefit year round is your pantry, by dumping the cool dehumidified exhaust air in the pantry might would help extend shelf life of stored food and if you have a freezer located in the pantry it would help it out also.

Posted By JohnRLee on 10 Feb 2014 04:23 PM
* I don't feel that there is much or any advantage to putting it in my home (in the mechanical room). I don't need the negligible cool air in the summer and I would rather not have to listen to the noise it puts out.

* I cannot put it in my mech room (unless I want to vent the cold air outside which might cost more in materials than simply putting the HPWH in the garage) or it will skew my Title 24 report adn I woud have to find other ways to get into compliance (or I will not be granted a building permit).

so it is a moot point.

However, as much as you guys like to bang around and split hairs on this, I'd rather steer the conversation back to reliable brands of HPWH. So many of the self contained units get some troubling reviews. Some of the bad reviews, you can read between the lines. But there are some serious reliability issues for many brands, specifically some homeowners experiencing multiple failures for the same unit. That is a real concern. Given that if it actually fails, you're SOL for hot water until it gets fixed (unless you have a back up unit)

Consumer reviews in the blogosphere are all over the place (and not always real.) Data is something else. 

The sample set of 30 AirTap units in this study had three (sites 8, 12, and 15) that were mechanically defective and replaced (probably improper or leaked refrigerant charge, or possible damaged during installation), a ~10%  early defect rate,  and one (site 21) failed during the test period (symptoms unclear) and was removed, not replaced, call it 13% early failure.

Of the participants that answered the surveys, 87% were either "satisfied" or "extremely satisfied" with them  nine months into the data-logging period, and 0% reported being dissatisfied.

How that fares relative to their competitors remains to be seen. There isn't a lot of web-whining about this manufacturer, but they probably have yet to ship even 2% of the total quantities that GE has, over several manufacturing years and multiple manufacturing locations (now concentrated in Kentucky.)

I haven't thoroughly searched the NEEA for other field data on other HPWH units. The NEEA has developed a set of requirements for performance in norther climates, and so far only the AirTap and Electrolux units have cleared their Tier-2 bar, so they may be waiting to do similar testing on other units once they're up to snuff on meeting the spec.  The NEEA page with the most relevant links to HPWH characterization can be found here. 

Given the similarity of the N.CA coastal climate to the Pacific Northwest, the NEEA modeling and test data are more relevant than other more generic test data (such as D.O.E. EF tests.)

I've had a first-generation GE "Geospring" since the end of 2010. I've been happy with the efficiency, and generally satisfied with the recovery time (that is, we rarely run out of hot water). It's quite noisy, though. The 2nd-gen GE units are significantly less noisy....certainly not quiet, though.

I've also heard rumors of problems with the first-gen GE units, but I don't have any data.

Over the past 2 years, I've been involved with ~500 units of multi-family housing across ~9-10 locations and ~50 single family houses that have used the 2nd gen. GE unit that is currently on the market. I haven't heard of any major problems. It certainly seems to be the "go-to" model for most folks I work with...mainly due to the reasonable price. Unfortunately, in the apartments they are almost always installed in a small closet with a louvered door or transfer grille. These installs will certainly see lower efficiencies and longer recovery times.

I have also been involved with four single family houses that used the AirTap units...(both 50 gallon and 66 gallon models). No issues at the moment, though Dana's reference of 13% failure rate in a very important demonstration project for the mfr. has me worried.

I agree that a 13% early mortality is a flag that the Atis might not have been fully ready for release to production at that time- that's more like a beta-test kind of defect level. But it's important to bear in mind that those were all from 2011 production(the first year for the fully-integrated units- the had only been selling retrofit heat pumps for standard electric water heaters prior to that) and the sample size was small. The company is still in business , but probably wouldn't be if 13% early mortality were the ongoing failure rate.

The web-whining about GE units is also overblown- design & manufacturing issues tend to get worked out over time- even if the model name doesn't change the issues under the name-plate get resolved, since the cost of warranty replacement & repair is so devastating to both the gross margin & bottom line. It's arguable that GE probably went too aggressively at cost reducing production early-on, and lost some of the engineering-to-production-to-engineering feedback loop on real problems by sub-contracting production in China, but that's clearly not the case today.

I'm sure tiny Texas based (2008 startup) AirGenerate's feedback loop is MUCH tighter, and even though it's company size relative to GE is a spec on the paint of the battleship, it's a more focused company too, without the layers of bureaucracy found in a giga-corporation that can often slow down the resolution of design & production problems. Their problem last year was in ramping up production to meet surging demand, so unless they really screw it up they'll be in it for the long haul (or sell the product line to a much larger company.) They had over 10,000 of the retrofit heat pump units out there by the end of 2010- it's not clear how many of the fully integrated Ati-xx units have sold to date, or how many engineering revisions have been made since the initial production runs. I doubt they're doing their own manufacturing- they're more like an design/engineering & marketing company than a vertically integrated manufacturing company, but they're almost certain to be built locally, near their Houston location.

Dana,

I'm 99% sure the AirTap units are made in China. I'll ask my clients who have one to 2x check.

Posted By JohnSemmelhack on 12 Feb 2014 12:21 PM
Dana,

I'm 99% sure the AirTap units are made in China. I'll ask my clients who have one to 2x check.

That would be interesting to verify if true. 

Given that the founders all have Hindustani names I would have figured India as the most likely off-shore manufacturing location.

Supposedly, this is the manufacturer in China that makes the AirTap units - http://www.theodoorchina.com/1-3-integrated-water-heater.html

Side note - I was recently surprised to see that some Fujitsu mini-splits I spec'd were also made in the PRC. 

Almost anything can be made and made well in the PRC, but whether it's worth the management overhead isn't always clear. GE obviously had issues controlling the supply chain when they went there on this product. I'm surprised that AirGenerate has the kind of volumes to justify that overhead at this point, but they've been growing pretty fast!

I picked one up from Lowes in the summer to install in my house. However, It is too big for the closet the old one is is and I will have to wait and put it in the closet I am building in the additon. So I need to have the thing heated or at least that closet insulate and drywalled. So in the next month or some, whenever it stops snowing / raining long enough to barrow a truck and go to lowes to do the last interior wall.

My $1600 GE Geospring Hybrid HW Heater failed two weeks ago after only 3.5 years of service. This is an early model (Gen 1?) of this unit, as we bought it when it first became available at Lowes. It has run in heat pump mode all this time, so it saved us some $$, but the evaporator coil developed a leak, causing the filter alarm to come on daily. When I called GE they indicated it was a common problem, and sent a new replacement evap coil, dryer and valve. I had to pay a plumber $150 to add extender connectors to the Hot and Cold water lines to obtain enough clearance (5.5") so that the heat pump shell style case could be removed. Luckily, I paid extra for an extended warranty, as it took 2 weeks and cost $250 to replace the coil and recharge the unit. The HVAC tech had nothing good to say about the quality of the GE parts either. But, if it lasts another 3 years, it will have paid for itself. The troubling thing, in my opinion, is that NO ONE in their right mind would pay $1600 for a 3 year rated hot water heater, but that is what I got. And, that is what others are reporting as well... the same failure scenario with a cheaply made evap coil where all the R-134a refrigerant leaks out (and in my case into my home interior). A class action suit seems in order here, as GE has not done the right thing and issued a recall of these early models that are prone to failure. I am posting this so that those who might be considering buying this unit, as we did, to save money and be more green, are aware that at the Ge GEOSPRING hybrid water heaters are made of inferior components; GE knows it but there is only a 1 year labor warranty on this EXPENSIVE unit. I could have bought 5 regular water heaters for the same $. Sigh. Meanwhile, I have posted to the GE Appliances Facebook page and emailed them and gotten no reply. They just want to sweep this under the rug. I will report this to the US Consumer Products Safety Commission, and like others have posted about it on Lowes website and on Amazon.com. As the tech said, before you buy any major appliances, GOOGLE it first... I did not have that opportunity as an early adopter, but you do.

Hi John: My Gen 1 GeoSpring failed two weeks ago. If you get filter alarms that don't clear, be sure to put your unit into STANDARD MODE, so the compressor does not also fail, as the frequent filter alarm indicates that there is a leak in the evaporator coil and it is freezing up on low refrigerant. GE covers parts only under its 10 year warranty. Just a heads up, because this problem can come along suddenly.