Altherma Measured COP

NRT_Rob

Just in case anyone is interested:



measured KWH, Gallons, and temperature change supply/return on our altherma for a full day yesterday.



-Water temps around 85 deg F.



-Outdoor Temp averaged 14 Degrees and the whole day was in the 11 to 16 degree range. 56 degree Days.



-We did see some "snow cake" as it was snowing HARD yesterday, which I think must reduce our output somewhat as it impedes airflow through the coils.



-Calculated heat load on the building is a bit shy of 33kBTUs/hr at a -4 deg F. outdoor design, or about 10,700 BTUs per degree Day.



-Total power draw of the 054 altherma and its backup heater for the 24 hour period: 36.5 KWH



-Total BTUs for the day were 258,772. Remember this was during a snowstorm, and we only had 3 people in the building. For the degree days we had, and our calculations, we'd expect to see 600,000 BTUs for the day. So at least on this day, our load is about 1/2 of what we calculated... And we calculate aggressively. I have to admit, this one takes me aback a bit. Makes me wonder if I'm missing something. Our warehouse level is about 64 average instead of 70, so that helps, but still.... no solar gain. Our infiltration calcs could be reduced but even if I eliminated infiltration entirely that's only half of this differential.



-Assuming we have real numbers though, our calculated COP for the day was 2.08 .



We'll let it run for more days and try a week long number next. since we do have a slab level, our numbers might shift depending on when the slab calls.



Still, pretty cool stuff. Monitoring rocks!

NRT_Rob

day 2

Alright, the numbers I posted above included backup usage which is straight electric. We haven't yet figured exactly how it determines when to use backup, but we are suspecting that it occurs during defrost periods.



Yesterday was sunny and much warmer, 20.1 average temperature for the full day, 49.9 degree days.



Unit produced 259,000 BTUs using a total of 31 KWH, 4.5 on the backup and 26.5 on the heat pump.



so again we used half the BTUs per degree day we expect to see, for one. COP for the heat pump itself is 2.7 for the day, and when backup usage is figured in, it goes down to a 2.45. With Current oil prices ($3.50/gallon) and electric (roughly 0.15/kwh) we only need to exceed a COP of 1.75 to run cheaper than oil.

NRT_Rob

2/4/11

Sensor Error! our readings show the return temp sensor was miscalibrated with the supply by 1.5 degrees.



What does that mean?



at outdoor temperature average of 20, we are actually seeing heat pump COP of about 3.5, 3.2 to 3.3 when you factor in backup usage! That's better.



BTU per DD for the building is still oscillating between 5000 and 7000/DDay.



Yesterday's numbers (2/4/11): another sunny day.



20.3 Average outdoor temp

49.7 Degree Days

246,000 BTUs

19.3 KWH Heat Pump

2.3 KWH Backup Heater

3.62 Heat Pump Only COP

3.34 COP with Backup usage

4954 BTU/DD.

Gordan

That's pretty darned impressive!

What are your supply and return temperatures, roughly?



At that rate, geothermal seems... not very attractive. Especially given all the loop issues that tend to crop up more than occasionally. Of course, finding someone who actually installs these things may itself be a problem.

NRT_Rob

it is pretty cool

though I would think, with a good loop field, sustaining a COP of 4+ with ground source should be feasible, and ground source will be a bit better at cooling.



Still, this is serious contender territory. We're running half of oil's operating cost. of course, the unit was a lot more to install as well, so that's still a long payback. But, it's there... and oil wouldn't have to go up too much more to make that payback very reasonable.



If you factor in needing a chiller or condenser for cooling that goes away with this class of unit, it's even more reasonable.



Interesting stuff.



I forgot to answer the water temp question: we are heating with 85 degree supply temps. DT varies from 1 to about 7 on the 'primary loop' since this is a primary/secondary arrangement out of necessity... mixing requirement for the radiant cooling, dontcha know



I could probably get a bit more out of the unit if this were primary only with wider DT/lower return temp. *dreamy smile*...

Gordan

Thanks!

Those supply temps are pretty low indeed. I wonder how it would do with the temp range that's more in line with radiant ceilings... does Daikin publish any efficiency/output charts, like the geo manufacturers do?

NRT_Rob

yes they do

and they cross reference with outdoor temp.



depending on your climate zone though water temps will have a significant impact on the usage of backup heat in colder weather I think.

NRT_Rob

quick update

we have continued tracking the COPs and so far, the lowest average outdoor temp WHILE OPERATING has been 8 degrees for a day... and under those conditions we're still over a combined heat pump/backup COP of 3.



the 2.7 we saw on the first days of logging appears to be the result of the very heavy snowfall we had on those days: it caked up the outdoor unit during the storm itself, which apparently cost us about half a COP. but immediately after the storm all the snow defrosted out, and we haven't been under a 3 COP yet.

TonyS

That is really impressive

COP of 3 on an 8 degree day. It may be time to remove the LP Prestige from the shop.

Is Daiken sold through the wholesale suppliers? Who do I contact to find who handles them in my Area.. Reading Pa.

NRT_Rob

I'm not sure who handles your area

I believe Lance Dyer of Daikin handles the northeast through wholesale distribution but I don't know how wide his area is or who the distributors are in your area.



they do require a 2 day training to sell/install the units as well. They aren't cheap but up in here in maine it looks like they operate at about half the cost of oil if the COPs hold up.



interesting stuff!

EddieG

Great Info!

Great info. Rob, thanks for sharing. I attended the training and was very impressed. Lance came to our shop a couple times. I have quoted a few, no go's to date. People went with tax credit equipment. But with the majority of the credits gone, I'm hoping to sell some of these. Working with a client now, who is interested. I have been trying to promote them with the solar option, so they qualify for the tax incentives. I was told they had a model coming out with a higher output temperatures that was going to use R-134a. I think they have it over seas now, just waiting for approval here. I wanna say like 150 to 160 degree output temps. Cool stuff! 

NRT_Rob

correction!

we have discovered a sensor miscalibration that has thrown off our numbers. most of our COP calcs were overstated by 0.5 to 1.0 COP or so.



So things are still doing well: we are solidly in the COP 2.5 to 3.0 range under most conditions, but it's a little less great that we thought originally.



Sorry for the oversight and misinformation! if anyone is interested in our data, you can always email me, we're happy to share.

bld999

Updates?

Hi NRT Rob,



I was wondering if you had seen some stability or predictability on performance in your Altherma system since your last post here. Have the sensor calibration problems resolved? I was a little surprised to read above about how sensitive the cop # can be to those kinds of issues. As in everything, measurement is where the rubber hits the road.



I am not a pro, but a builder, and am trying to figure out if a system like this can compete in cost, performance, and maintenance with GSHP running radiant slabs, dhw, and such. Or, from the standpoint of competing with a quality lp fueled modcon system.



How is living with it thus far?

NRT_Rob

I've been busy

so haven't dug into the data recently but have had no observed changed in reliability or noticeable efficiency changes. the measurement was off because we were measuring a low delta-T so a full degree off in measurement was a significant output difference.



basically though operating costs on most systems should blow away LP. for GSHP, operating costs would typically be similar... depending on final heat load... though a little higher, the difference would be small and the initial cost *should* be much lower for the altherma in most cases. plus no one can screw up the well design, deplete the dirt of energy over a few seasons, etc.

bld999

Uncertainty

Uncertainty is what you are talking about, [GS vs AS] and it is foremost on my mind when I think about ground source. As a custom builder, a part of the daily drill is focused on eliminating uncertainty and risk, which makes air source+ hydronics so much more attractive. Here in western washington, there is good expertise in ASHP and hydronics, less so in GS, due to fewer installs. I think about half the GS that gets done in residential here is"because we can, and look green at the same time" My fear is that a failed design or install would make me turn green

NRT_Rob

while I like geo

I have certainly seen a lot of badly performing systems out there. I do like the certainty of air source for sure.

Wayco Wayne_2

Just

Attended a sales class put on by Lance last week. I have a customer who's interested in trying it. To get an installation under my belt I am offering to sell the equipment at cost to him and charge T & M to install it. I'm thinking monoblock to simplify the install. He wants to run an air handler, with domestic water tank (future solar thermal) and add a radiant floor down the road. It's much more exspensive than a traditional heat pump. How do I help him understand the operating price difference between altherma and the traditional Heat pump with back up heat? Our balance point here in MD is 35 F.

NRT_Rob

tricky

Can you estimate usage or cost with the standard heat pump? If it doesn't have software then this would be a manual exercise with bin data for your area, you'd need to know the load you were meeting, and manual COP/Electrical consumption calculations. it's a bit of work but not too bad if you know the heat load and how the heat pump performs at various outdoor temps.



if so the altherma selection software can compare to straight electric, gas, and oil, and it can give you total consumption numbers as well. for part load scenarios, where one altherma can't do it all by itself, I can help if you like. the "hackaround" for the selection software isn't very good for that.

Wayco Wayne_2

So......

It's not just me having trouble. It;'s actually hard to do. My heat loss is 37,000 for heating. My heat gain in the Summer is around 24,000. I could go on my Wrightsoft operations cost software and get the cost estimate for the heat pump I guess, but how do I get and compare the Alterma costs since it maintains capacity well below our usual balnce point of 35 degrees and our design temp is 15. We seldom get down to the single digits. I just need a number to throw at the homeowner so he can measure an aproximate payback on his extra investment.

NRT_Rob

wrightsoft

if you can do the heat pump in wrightsoft, the altherma has its own selection software you can use for its numbers.



If you don't have it, email me the heating/cooling load, water temp at design (heat/cool), and project location and I'll run it for you. won't be able to until monday though.

tim smith

Re: Altherma

Hi Rob, Tim Smith here.  Just wondering what you have seen as max temps capable from the altherma at say 20 degrees out. I am thinking of combo hydro air and radiant floor system.  

NRT_Rob

output charts say

the 030 unit can do 122 degree outlet temp all the way down to 5 deg F... 14.5kBTU on the heat pump plus 3 or 6 kw on the backup available. 122 is the max temp on this unit.



the 054 can put out 113 from the heat pump only (higher, if backup comes into play) down to 19 degree outdoor (29kBTU on the heat pump, plus 3kw or 6kw backup).



I am strongly considering playing with air handlers and fan coils with reset. If Geo guys can run their air at 100 degrees... why not us?