# Aquasense Heat Pump Water Heater



## maple1 (Nov 20, 2012)

http://geyserheatpump.com/aquasense.htm

This is the first I've seen of this - is it new or I just didn't know about it?

It looks like the ideal water heater - can plumb solar or hydronic right into it. Almost looks too good to hide in the basement too. Wonder what it costs?


----------



## woodgeek (Nov 20, 2012)

Looks nice, i.e. the 3.0 EF (my HPWH is 2.5). Believable if you think these products will improve over time.

But it lacks a price, a certification of its performance, a reliability track record or warranty info, or any info re what kind of tank is inside.


----------



## Jerry_NJ (Dec 9, 2012)

Suppose it is just a tank with a heat pump, takes heat from the room (i.e.,cools the room) an "compresses" it into the water tank.  These seem like a good thing in a basement in the summer when the cooling and dehumidification is needed.  Not so good in the winter when the air is dry and the basement cold... seems this one offers the opportunity to exhaust to the outside eliminated both the plus and minus above.

I have a geothermal HP with a COP of 3 to 4 depending on which "speed" it is operating in.  The subject unit may well have a 3 when working into air at 70 degrees... I bet it is lower than 3 when working into air at 20 degrees (like winter outside air).  I suppose the subject using also has a resistive boost when one needs more water than the HP can generate - most are puny...my electric water heater has 5K Watt resistive heater, thats over 18K BTU/Hr., I'll estimate my HP will deliver about 2K BTU/Hr. to the hot water when running on high.


----------



## woodgeek (Dec 9, 2012)

I've got a HPWH, and have given the whole heat stealing issue a good deal of thought. Remember that a lot of the BTUs come from the compressor work. The stealing does pull down your savings a bit, but so long as your space heating BTUs cost less than electric resistance, the HPWH will still be cheaper to run in the winter than a conventional electric. Exhausting the cool exhaust air outside doesn't help....you pull even colder outside air in to replace it. Running the unit on outside air is not possible....they're not designed to run on air below 45-50°F, as they have no defrost cycle/control. They will switch to resistance below those temps.

Another point. EF does not equal COP. EF includes tank losses. Conventional elec tanks (COP=1) run EF=0.90 or so, and a HPWH running EF=3 would probably have a COP 10% higher, like 3.3. or so, at least at the air temps used in the test, probably 70°F.

A little OT, but the stuff I have been reading lately has been beating up on geos. Basically saying that the COP figures are all nominal from the manufacturers, and do not include blower or pump usage, only compressor. It seems that tests of installed geo units with pump and blower work included are all less than COP=3. Have you metered your total usage and estimated a COP by any chance??


----------



## Jerry_NJ (Dec 9, 2012)

Yes, I've made mostly Volt Amp (VA) measures on the input and assume the power factor is close to 1... in any case the power in is measured to include that to the loop pumps, the compressor and the circulating fan. Using the VA I always have an overstatement of the power being used. VA is always greater than or equal to Watts, so the ture COP is in fact a little higher In any case, the resistive back-up and supplemental is fused separately as those units use a lot more power (amps) I have a two stage resistive backup which isn't suppose to run unless the outside is zero and I'm holding the inside at 70. Neither is the case here... it may have been zero a night or two in the last 20 years but not more than that.

The best measure I have of the BTU output is to measure the air temperature at a duct well removed from the plenum and then switch in a 5KW (17 KBTU/Hr) resistive heating element and measure the delta temperature... with the circulating fan running at the same speed. This allows me to estimate the number of BTU/Hr it takes to give the temperature rise without the resistive supplement. This number comes out very close to the factory specified heating BTU. Using this and the VA (more than Watts) input to get those BTUs I get a COP approaching 4 on low (compressor and fan, and only one loop pump) and 3.5 on high. This will depend on the ground loop temperature, but the factory rates the units with the loop at 32 degrees best I can recall, colder than it ever is I believe. The loop has antifreeze in it just in case. My loop is a twin 250' vertical loop which hits the water table at about 30 feet, so it has very good heat conduction with the earth.

Given my electric usage, I can check but think it is about 1,000 KWH per month average (12K KWH per year). Said another way with an all electric, including hot water, cooking, washer/dryer and heat/cooling my annual electric cost is about $1,800 ($150 per month) for a 2000 sq ft (well insulated) house. I have neighbor, with a 3,000+ sq ft house who uses over $1,000 in oil in one winter month. They spend more than my total energy cost just to heat during the 3 month winter high heat period.

The high cost of oil is the big problem in the above, when I had my Geo installed I estimated it would cost me about the same as oil - oil must have been about $1 gallon then and electricity about 10 Cents/KWH. Now it is $3.50 a gallon verses 15 Cents/KWH in NJ, one of the higher cost electricity states. The 350% increase in heating oil and a 50% increase in electric makes the big difference. Happily Obama didn't get his Cap and Trade legislation through, but he's working on those goals via the regulatory end and I may see the electric rates rise to make it as expensive as oil when heating with an electric HP. In NJ electricity is generated with about 50% nuclear and with a large component from coal, not oil or natural gas.

Hope I didn't ramble too much, or make too many typos... all the numbers above are from memory I haven't consulted any notes.

My HP is approaching 20 years old, the newest has slightly higher COP and EER, but mine works on. I had no maintenance in the first 15 years other than changing the forced air filters, no service calls or maintenance. In the last 4+ years I have had to spend about $2,000 on repairs, including loop pumps and circulating fan. Still, averaged out the maintenance cost have been only $100 a year, that's less than an oil furnace tune-up I will guess.

As for the subject water heater using outside air, I assumed a closed loop, not just exhausting - of course that's not good for heating water if that makes the input air at 20 degrees or less.


----------



## woodgeek (Dec 9, 2012)

Cool.  Thanks for the info.


----------



## woodgeek (Dec 10, 2012)

Jerry_NJ said:


> Suppose it is just a tank with a heat pump, takes heat from the room (i.e.,cools the room) an "compresses" it into the water tank. These seem like a good thing in a basement in the summer when the cooling and dehumidification is needed. Not so good in the winter when the air is dry and the basement cold... seems this one offers the opportunity to exhaust to the outside eliminated both the plus and minus above.
> 
> I have a geothermal HP with a COP of 3 to 4 depending on which "speed" it is operating in. The subject unit may well have a 3 when working into air at 70 degrees... I bet it is lower than 3 when working into air at 20 degrees (like winter outside air). I suppose the subject using also has a resistive boost when one needs more water than the HP can generate - most are puny...my electric water heater has 5K Watt resistive heater, thats over 18K BTU/Hr., I'll estimate my HP will deliver about 2K BTU/Hr. to the hot water when running on high.


 
The HPWH I bought this spring (AOSmith Voltex) has an 80 gallon tank, a roughly 1.5 ton compressor and the usual 4.5kW resistive element. Looks like they sized the HP and element so that HP recovery would be slightly faster than pure resistance recovery. Reading about the design/control, they didn't want anyone to switch it to conventional to get faster recovery (bypassing the energy savings). While the recovery does still take hours, like conventional electric, the tank is amply sized for my family of 4 (with nice low-flow showerheads). Seems that first hour rating, or recovery is a problem in a lot of the smaller HPWHs, and those run a lot of conventional backup under heavy load (i.e. more than ~2 people or 2 heavy users), aka 'hybrid mode'.

The takeaway, unless you know your loads are low, going for a bigger tank HPWH seems to result in much lower energy usage overall. The tanks are all very well insulated (I had hot water after 3-4 days without power). All kinda the opposite of the 'tanks are bad' demand water heater idea.


----------



## Jerry_NJ (Dec 10, 2012)

One and a half ton, that's the same as 18,000 BTU, right?  In the summer that would do a great job cooling my basement when water is being heated.  Thinking (if I do) while typing, I now note that is equivalent (approximately) to the heating from a 5KW resistive heating element.  My 40 gallon tank, guessing, can recover from cold (60 degrees assumed) to 125 degrees in about 30 minutes - so I'd guess a dedicated HP of 1.5 Ton would not run very much.  Doing the math, approximately in the head, the HP consumes about 1,800 watts while heating.  What temperature is the set upper limit?

When I'm home alone I use almost no hot water, yes I do bath, but the dish washer and the cloths washer are silent most of the time and the HWH is turned off, that's how I have an estimate of how long it take for the resistive to recover the tank, my tank has upper and lower heating indicator lights so I can tell, if I watch closely, when it has finished a heating cycle.


----------



## woodgeek (Dec 10, 2012)

My unit is in an attached two car garage with a 10 ft ceiling, and I think the unit cools the space by ~1°F on average. The temps in there previously dropped below 40°F during good cold spells, below the 45°F HP cutout, so I will prob run conventional several weeks in the winter. I'm tracking that with a wireless thermometer.

I used to run a dehumidifier in there, and this past summer I shut it down. And frankly, the dehumidification was 'ok' but marginal. The Voltrex has a bigger fan than the GE units, making it louder, but also increasing the running temp of the fins. This is good for EF/COP, but bad for dehumidification and noise. When I went on vacation, the garage got musty...no DHW, no dehumidification. Next year, I'll turn on the dehum when I leave.

Upper temp? On the water, I run it at 120°F for safety and eff but I think it can go a lot higher. On the air side it is happy with air well over 100°F, since some folks like to put such things in their attics. At 1100 lbs loaded, not me so much.


----------



## sesmith (Dec 12, 2012)

woodgeek said:


> A little OT, but the stuff I have been reading lately has been beating up on geos. Basically saying that the COP figures are all nominal from the manufacturers, and do not include blower or pump usage, only compressor. It seems that tests of installed geo units with pump and blower work included are all less than COP=3. Have you metered your total usage and estimated a COP by any chance??


 
I've read some of the same things, and based on our experience with our 3 ton Climatemaster system over the last year, I suspected our numbers are much better, and that the installer and installation is what makes or breaks efficiency on these systems.

The engineer who did the design and installation of our system calculated average COP to be 3.9 for our system. Based on calculations I made comparing our increase in electric use with the heat pump during last heating season, with prior years, when we heated with our oil furnace, I came up with a COP guestimate of between 4.4 and 5.3. Lots of room for error here, especially estimating furnace efficiency (I used 60% for our forced air furnace which had an 80% combustion efficiency). I recently did some testing of the heat pump using this method:

https://docs.google.com/viewer?a=v&q=cache:6grtKZV3sd4J:www.geoconnectionsinc.com/geothermal_resources/geobookstore/downloads/how_to_measure_GSHP_efficiency_for_forced_air_units.pdf &hl=en&gl=us&pid=bl&srcid=ADGEEShOFLjtg_msdzBmSJNxAkUCPrytVQlNuaHPjpT6QfDW86eLNuUgVdZTM1d3gsc4-pOUAgcpfqHpuV6jZ8IGtIQlSBidvKMSUroZt6lrEIxBqG0o7_E9_42hWvLeHL_IZVHrqEkk&sig=AHIEtbTqE82rT-Xij5h6XnuN0IOIm-Q_zA

2 separate tests this evening gave a COP of 6.3. I made my electrical measurements at the breaker panel using known good current probe and Fluke meter, and temp measurements are from calibrated TC's on the input and output ground loop lines. I did not measure flow, but used 6 gal / min that the installer said he set the flow to (no reason to question that...he knows his stuff). Even if the flow was set to the minimum of 1.5 gal / ton the COP would still calculate to 5.0. So that's my story, and I'm sticking to it  I think this at least lends credibility to the 3.9 COP estimate from my installer. His other calculations, such as winter design temp, have been right on the money (actually a little conservative).

Footnote: a little more checking with another temp probe found that 6.3 COP was as unbelievable as I thought it was.  The 6 degree delta I measured with the 2nd probe is a little more realistic, making the COP 4.35, a little more believable for this time of year.  So much for my TC's.


----------



## woodgeek (Dec 12, 2012)

I think both things can be true....a properly installed system can perform at spec, and an inexpertly installed system, that no one ever checks can be running way off spec.  Goes for geos, solar DHW, ASHPs, HPWHs, boilers, etc. 

Kinda justifies the compulsive measuring 

In my case, I estimate the COP from home power monitors and estimated BTU loads at different temps. I mostly do this at 30°F, which is my average January temp, under dry conditions.  As installed, I got COP~1.5.  Switching a jumper on the defrost timer got me to 1.9.  Additional mods to the defrost controller got me to ~2.3.  Estimating a seasonal average is harder but probably closer to 2.5-3.


----------

