Posted By ICFHybrid on 07 Sep 2013 09:53 AM

Tamar has the high temp geo which can go to 130 or so.

I realize that. My question had to do with how high a temperature the heat pump was being asked to deliver to a radiator system that was designed for much higher temperatures. Your answer seems to be that such a system would push the heat pump to what, maximum output?

At the risk of saying something dumb...let me see if I can answer this. The initial intent of the install was for the hi-temp W2W to be first stage, running constantly and maintaining a temp of 140 degrees (based on outdoor temp setting). On a call for heat that water would start circulating through the radiators. Instead, the installer lost sight of that and set up the controls so that the SpacePak highvelocity air was first stage. The high temp unit did not even start heating water until the HV couldn't keep up. With this control setup, the high temp unit ran in vain until gas kicked in to supplement, because it was trying to raise the loop temp from 70 > 140 and couldn't do it in a reasonable amount of time.

Posted By Bill Neukranz on 06 Sep 2013 08:13 PM
...I've learned how hard it is for companies to offer performance guarantees, and thus why
you don't see it being done much, and virtually not at all in the residential market.

Well, some residential contractors provide performance guarantees as part of
their normal bid submission. I can't imagine signing a $30k+ contract without
a written statement including some plain-language performance benchmarks.
Here's what was promised in our contract with a WaterFurnace GeoPro dealer,
for a 3-ton residential retrofit in a 60 year old PA home (including conversion
from oil-fired hot water baseboard to a forced air system with all-new ducting):

"When maintained and operated in accordance with the manufacturer's operating
and maintenance manuals, the system will maintain (within a 3-degree swing at
the thermostat):

- When cooling: 74 degrees on a 96 degree summer day
- When heating: 70 degrees on a 10 degree winter day

If within five years of installation those temperatures are not achieved, we will
make any modifications, repairs, or replacements necessary to achieve those
temperatures...AT NO ADDITIONAL CHARGE."

Also promised (in a less legalistic, bulleted list):
- 70% energy savings over oil (at 2009 prices)
- Lifetime air distribution guarantee (i.e., the ductwork)
- Ten year parts & labor on WaterFurnace heat pump
- Five year parts & labor on ALL peripheral parts
- Fifty-five year warranty on outdoor ground loop

Plus operational projections/estimates:
- Minimum loop temperature: 35.1 F
- Average heating efficiency: 3.88 COP
- Maximum loop temperature: 96.3 F
- Average cooling efficiency: 20.25 EER
- Total annual heating cost: $403
- Total annual cooling cost: $160
- Total annual DHW (w DSH) $233

IMO, only the first two items (indoor temperature guarantees) and last three
items (annual cost projections) were really necessary. Efficiency guarantees
(COP/EER) are interesting, but not easily measured or presented in evidence.

BTW, the dealer's projections were eerily accurate. Geo reduced our annual
heating/cooling/DHW costs by an astonishing 80%+ (not to mention the
many intangible benefits: quiet, odor-free, soot-free, combustion-free, etc.).

... the high temp unit ran in vain until gas kicked in to supplement, because it was trying to raise the loop temp from 70 > 140 and couldn't do it in a reasonable amount of time...

Slow responding systems don't make good second stages.

The initial intent of the install was for the hi-temp W2W to be first stage, running constantly and maintaining a temp of 140 degrees

Heat pumps don't like to deliver 140F water and it is evidenced by how the COP falls off the higher it goes. Have you looked at what the COP is for that unit when trying to deliver 140F? It looks like you are taking what could be a nice efficient heat pump and making it work where it is least efficient.

Have you looked at how much of the time you could meet heat demand with lower temperature water, say 120F?

Posted By ICFHybrid on 07 Sep 2013 11:23 PM

The initial intent of the install was for the hi-temp W2W to be first stage, running constantly and maintaining a temp of 140 degrees

Heat pumps don't like to deliver 140F water and it is evidenced by how the COP falls off the higher it goes. Have you looked at what the COP is for that unit when trying to deliver 140F? It looks like you are taking what could be a nice efficient heat pump and making it work where it is least efficient.

Have you looked at how much of the time you could meet heat demand with lower temperature water, say 120F?

I haven't heard that hi-temp units don't perform efficiently at higher temps. What I was told in one second opinion was that once the temp is attained, maintaining it is "easy". As far as looking at options for controlling the system in different ways, that is what our installer has supposedly been doing all summer, though they refuse to share their findings/thoughts/plans with me yet.

Posted By tamar on 08 Sep 2013 01:06 AM
I haven't heard that hi-temp units don't perform efficiently at higher temps.

Sorry, but it's an unavoidable fact of physics & thermodynamics that heat pump
efficiency must fall off as the source-to-load temperature differential increases.

However, you previously mentioned that your system senses and responds to
outdoor air temperatures. Hopefully, that means that it only tries to achieve its
maximum 140 F output temperature when outdoor temps are at their coldest.

What I was told in one second opinion was that once the temp is attained, maintaining it is "easy".

Substantially untrue. What that person may have been referring to was the apparent control issues with your system regarding hand-off between stages. That is probably a matter of minutes.

Over the term of hours, the longer a geo heat pump is asked to deliver that high temperature, the harder it becomes to do so because the source (loop) temperature drops lower and lower as heat is extracted. The harder it is to move heat up that growing hill, the more your efficiency decreases. Many heat pump performance charts top out at 130F. They can deliver a higher temperature, but the efficiency is abysmal. Sometimes, the marketing department wins over engineering and the product is actually marketed that way (our product delivers 145F!), in an effort to appeal to untapped clients, such as homes with radiators designed to run at higher temperatures. Look at your particular unit's performance charts and see if you want it to operate at that COP all the time.

Posted By Looby on 08 Sep 2013 01:42 AM

Posted By tamar on 08 Sep 2013 01:06 AM
I haven't heard that hi-temp units don't perform efficiently at higher temps.

Sorry, but it's an unavoidable fact of physics & thermodynamics that heat pump
efficiency must fall off as the source-to-load temperature differential increases.

However, you previously mentioned that your system senses and responds to
outdoor air temperatures. Hopefully, that means that it only tries to achieve its
maximum 140 F output temperature when outdoor temps are at their coldest.

Slight correction...the Carrier high temp is designed to respond to outdoor air temperatures. That's not how our system was installed. This is (possibly) one of our issues and hence the question about industry standards.

That's not how our system was installed.

Right. Because how low a temperature of water are you going to run through radiators designed for 170-180F and get anything useful out of it? If you did a total energy makeover on the home and dropped the room by room heating demand way, way down, I'd say that had a chance, but otherwise....

I don't know what this means, but maybe 3-4 reads will help it start to make sense. Comments on this forum give me key words to search on, which is how I "self study" and learn more:

The Carrier 50YEW series water-to-water heat pump is unlike
any other heat pump on the market. The large operating map of
the scroll compressor allows high temperature operation, up to
145°F (63°C) leaving load water temperature (even at 32°F [0°C]
entering source water temperature). The combination of a coaxial
(tube in tube) heat exchanger for the source (ground loop) side
and a brazed plate heat exchanger for the load (heating/hot water)
side provides very high efficiencies. Integral controls for hydronic
heating and domestic water heating avoid the need for external
microprocessor-based controls for outdoor temperature reset,
warm weather shutdown and staging. Below is a summary of the
key components of the 50YEW series internal controls, followed
by a list of control features.
“Smart” module (MPC): Every 50YEW unit includes the Carrier
MPC controller. The MPC is a programmable controller that
takes inputs such as buffer tank temperature, domestic hot water
(DHW) tank temperature, outdoor air temperature, and other
inputs to “decide” when to operate the compressor, pumps
and hot water valve. The MPC is factory-wired to the CXM
compressor control module and user interface.
Part IV: Controls
Outdoor temperature reset: The heat pump capacity and water
temperature delivery to the heating system must be designed
for local weather conditions, usually at the 99.6% outdoor
temperature. Therefore, 99.6% of the heating season, the
heating load is less than it is at design conditions. As the outdoor
temperature decreases, the heat loss of the structure increases,
which requires more capacity from the heating system. If the
water temperature is reduced as the outdoor air temperature
increases (and vise-versa), the heat pump operates at higher COP
most of the year. The MPC has a built in algorithm that adjusts the
buffer tank temperature based upon outdoor air temperature to
maximize effi ciency and comfort. Temperature settings may be
adjusted at the user interface if factory defaults are not suffi cient.

ICF. Again all your questions are answered in Tamars other thread. Your latest question again ignores information already available to you here i.e. old homes with cast iron radiators are near universally over radiated and often energy retrofitted. Since one can determine the output of a given radiator at a given temperature one can make perfectly good use of a radiator that used to expect 170-180 degrees. The results are predictable and therefore the old radiators are easy to employ.

Tamar the problem is since you have natural gas available, you are likely paying more to heat water to 140 (or 130 for that matter) with the geo than with a boiler. It is possible to calculate at what temp the geo costs more than the boiler (to run).
One of the things that puzzles me is mention of changing the boiler. We all agreed you needed a buffer tank (or at least those of us actually in the biz), but you have a boiler now, yes?

One of the things that puzzles me is mention of changing the boiler. We all agreed you needed a buffer tank (or at least those of us actually in the biz), but you have a boiler now, yes?

I am puzzled, too, but am at the mercy of the installer to feed me bits of information as they see fit (unless this gets to court where they'll presumably have to disclose more). The current Phoenix is a hot water heater that is playing the role of boiler right now. Maybe it is the fact that its max high temp isn't as high as a traditional boiler? Maybe the 50YEW is being removed in one of the plans, which would mean no buffer tank, but a "real" boiler is more appropriate? They may still be thinking of leading with high velocity air.

It's incredibly frustrating to just have to sit and wait for them to decide what they are going to propose, and only get generalized statements like the one at the top of this thread. We have re-hired our kitchen architect to act as an intermediary, because I just can't deal with all the mystery and drama, and I don't deal well with people I've hired refusing to answer questions.

Tamar the problem is since you have natural gas available, you are likely paying more to heat water to 140 (or 130 for that matter) with the geo than with a boiler. It is possible to calculate at what temp the geo costs more than the boiler (to run).

Joe, I'm not ignoring this. I know it's good advice. Is it just a distraction that the SpacePak is running inefficiently due to inattention to installation instructions and that the loopfield has 3 circulating pumps in series? I thought from the other thread that there was likely a control strategy (complex, but out there) that would make sense for us.

I hope that the LEED AP consultant who came out Thursday will provide some insight that takes all our specifics into consideration, and that his report will spell out the most efficient equipment/control strategy.

one can make perfectly good use of a radiator that used to expect 170-180 degrees.

I'm sure you can find an occasional situation where it's a good idea to make a heat pump deliver 140F to an old radiator system (pushing the COP down into the low 2's or below, in order to get, what, a third of the normal output?), but it doesn't seem like a good starting point.

and this application, as described by Tamar, is a prime example;

"I am pretty sure this is the GT-PW W2W heat pump. It was presented to us as one of the only W2W heat pumps that could get the water hot enough to allow us to heat with some geo before switching to gas"

"but the aux kicks in when it drops into the high 20s"

"the gas boiler came on also. The radiators warmed up. Not good considerng the outside temp was 39 degrees and the gas is supposed to be auxiliary"

"And this is what we currently have (no reset controller at all)."


Of what NOT to do.

Yes and again ICF in Tamar's other thread control strategies that would work are discussed. Have a peek if you are interested in how to get it done.

"Joe, I'm not ignoring this. I know it's good advice. Is it just a distraction that the SpacePak is running inefficiently due to inattention to installation instructions and that the loopfield has 3 circulating pumps in series? I thought from the other thread that there was likely a control strategy (complex, but out there) that would make sense for us."

There is a way to control the system to your advantage and that is the problem. Yes the Spacepak was installed incorrectly but that simply makes it less efficient as do the 3 pumps in series. Those things however likely are not adding $100/month to your electric bill. So while they are not inconsequential, I do not think you need to spend all your focus there.
If this is set up to run so that the W to W geo runs first, the air handler second and the boiler 3rd, it will work fine.

Those things however likely are not adding $100/month to your electric bill.

Help me understand how much those factors might be adding to our bills. I think the SpacePak freezing up and/or just blowing 70-ish degree air has been part of the problem. There have been few "normal" months, which has me scratching my head on how to know how bad the bills are off from what they could be.

Here is what we paid in April for heating (I'm excluding other electric and taxes/basic charges). It was cold for April....average temp 38. W2W geo had breaker pulled, so this is all SpacePak + all 3 pumps (and then a bit of gas when geo didn't satisfy call for heat).

Number of Days = 30
KwH = 2444
Fuel Cost Chg 2444 kWh @ $0.028690 $70.12
Energy Charge Winter 2444 kWh @ $0.038460 $94.00
Resource Adjustment $8.00
Interim Rate Adj $13.62

Total Electric for heating $185.74
Total Gas (22 therms) $14.65

I'm thinking the gas should not have come on at all. We had warm radiators one day when it was raining, so was above freezing....

Yes and again ICF in Tamar's other thread control strategies that would work are discussed

You keep saying that and reassuring her that it will "work fine", but what I think Tamar is trying to do is avoid exposing herself to what seems like yet another endless round of promises that can't deliver.

Maybe you could indicate, using what we know about her system, how this could work for her. Try to avoid indistinct generalities like "will work fine", in favor of specifics like energy used or total cost.

For my part, I am having a hard time understanding how a heat pump system that can hardly carry this home into the thirties (at rock bottom COPs) can be made efficient or should have even been installed in the first place.

iced space pack could add to the bill by running a compressor and not heating/cooling, but just the misinstalled duct work in (if icing does not occur) might cost you as much as 10%-15% or so . That means in April perhaps as much as 25$ and perhaps $10 for the pump in a peak month.

Help me understand HOW MUCH those factors might be adding to our bills.

If you want accurate numbers regarding heat delivered and energy used, you need a good measurement system. For example.

Posted By jonr on 10 Sep 2013 11:25 AM

Help me understand HOW MUCH those factors might be adding to our bills.

If you want accurate numbers regarding heat delivered and energy used, you need a good measurement system. For example.

The Web Energy Logger (WEL), noted in jonr's posting above, is the lowest cost, biggest 'bang for the buck' measuring, monitoring and logging system that I'm aware of.  Handles a tremendous number of inputs, implements temp and RH measurement with very low cost yet highly accurate sensors, has a lot of arithmetic computing power 'under the hood,' gives you a permanent web site, stores your data at an off site server location that you can download from at any time (and comes as a spreadsheet so there's no importing effort needed), without any monthly subscription fees.

There are many on this forum who use the WEL for personal and for business purposes.  And the are over 700 using it overall - just click on jonr's 'example' above to see hundreds of examples of WEL implementations.

Best regards,

Bill