jimbt
New Member
Posts:14
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| 22 Nov 2008 12:36 AM |
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Sorry to double post. Didnt know this forum was here until after i posted in general.
I have recently had a geocomfort system installed in our home. The house is 7 years old with blown in all around. Ceilings have 13 inches and walls are all 5.5. The system replaces, or rather ties into the existing oil hydronic system. The house is around 5100sq ft with a 27 foot ceiling in the center of the house. We live in north central Pennsylvania.
The system is a closed loop, 8 200 foot wells, with two GeoComfort 4 ton units being used with the existing baseboard and 10 MultiAqua wall units ranging from .9 to 2 tons. Hopefully this is a good enough description of the system. All told the system cost was $49,000 installed.
The system has been up and running now for 15 days and i have some questions that i would like answered from someone other than the installer. I have read the post about the noisy unit and how decreasing the flow helped to alleviate the noise from the units. Our unit is about as loud as our old oil furnace was. I can hear the unit from the 1st story when it cycles, but I am more concerned with the frequency at which it cycles. At the current rate of use I would end up using 2160 KwH for 30 days. This equates to about $270 in electricity based purely on KwH not including all the other stuff added to the electric bill. I dont know if this is high, but it seems high to me compared to others in this area with similar geothermal systems.
Currently it has been in the teens and 20s for the last 4 days. My system shows incoming water temp of 49 degrees Farenheit and 48.7 going out. Logic tells me that this is not a very large difference and i am concerned that not much heat is being extracted from the ground with only .3 degrees difference. I REALLY DONT KNOW IF THIS LOGIC IS LOGICAL so please be gently in your responses. Being the homeowner and not a HVAC professional I am looking for some others input.
I completely appreciate and thank anyone in advance for any advice or insight you might have. Thanks |
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tuffluckdriller
Advanced Member
Posts:630
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| 22 Nov 2008 02:15 AM |
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My first question would be what type of loop do you have? It almost seems that you have a possible loop flow problem, but I'm sure we'll need more data. |
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| Clark Timothy ([email protected])<br>Geothermal Heat Pumps: Heating and Cooling that's Dirt Cheap!<br>www.pinksgeothermal.com |
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jimbt
New Member
Posts:14
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| 22 Nov 2008 07:49 AM |
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Closed loop with 8 200' wells. They come into the house to a header. From the header there is a supply and a return that goes to the system. THANKS |
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engineer
Veteran Member
Posts:2749
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| 22 Nov 2008 08:16 AM |
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Given the house size, unit tonnage, system complexity and your description of recent weather, electricity consumption sounds reasonable. May I assume you and your family are comfortably warm in the house?
I'm not sure I quite understand all the details of your system, but I guess that you have 8 tons of capacity via two water-to-water units, and the water feeds both baseboards and water to air coils. Please correct me if that is wrong - maybe the Multiaquas are additional, independent tonnage?
I'm also curious how you managed to mate geo with baseboards - that is normally hard to do because of the high temperature water needed by baseboards.
"My system shows incoming water temp of 49 degrees Farenheit and 48.7 going out. Logic tells me that this is not a very large difference"
I'm highly skeptical of the above data - you are correct to be concerned. There should be a Delta-T (water temperature difference) across the waterside of an operating unit of about 10 degrees, more or less. 0.3 Deg suggests to me the unit is not operating so as to exchange heat with the water lines whose temperature you measured. Other possibilities include thermometer error, or taking measurements at incorrect locations.
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Curt Kinder <br><br>
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
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jimbt
New Member
Posts:14
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| 22 Nov 2008 08:42 AM |
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We are comfortable:) Thanks
Two 4 ton units so capacity is 8 tons.
Baseboard puts out 40% of what it put out with oil. MultiAquas are set to kick on when room temp drops 1 degree below what baseboard is set to. The wall units only run if the baseboard is incapable of providing enough heat.
As for the temperature measuring... The installer placed the temperature probes so i am not exactly sure where they are. When the system was first operating 3 weeks ago there was a difference of 3-4 degrees and it was in the 50s. The delta-t has now dropped as i have indicated. |
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Palace Geothermal
Veteran Member
Posts:1609
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| 22 Nov 2008 08:52 AM |
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Hi Jim,
You have come to the right place for help. I agree that the low temperature difference between Entering Water Temp (EWT) and Leaving Water Temp (LWT ) , is cause for concern.
How are you determining electrical usage?
It would also be helpful if you could measure the pressure drop on the loop across the heat pump. You would do measure this with a pressure gauge inserted into the P/T port located on the in and out lines to each heat pump. If you are not familiar with the P/T ports, I can provide a picture. |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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jimbt
New Member
Posts:14
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| 22 Nov 2008 10:52 AM |
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I had the contractor install a house meter in between the existing panel box and the sub panel for the new system.
I spoke with the contractor this morning. Conversation went as follows:
He agrees that there is something not right...
He said: The field is engineered to actually perform similarly to a 10 ton field. There should be about 1 degree difference for each ton being used, but it will actually be slightly less than one degree because of the larger performance of the field. When temps outside were warmer two weeks ago only one unit was running so only a 4 ton load was being applied to an 8 - 10 ton field so the delta-t was around 1.5-2 half of what it would be with a 4 ton field. He was happy with those numbers. Now that the outside temp has dropped he believes both units should be working so the delta-t should be back to the 1 degree/ton rule. His solution was to come out and switch the units order so that the other unit come on first to see if the Delta-t changes based on which unit is primarly being used. Sounds like a good plan to me, but i dont really know.
I have read about noise in a mini split system like i have. Are the GeoComforts supposed to be nearly silent or should i be able to hear them from the 1st floor when they are in the basement.
THANKS AGAIN... If you have any more advice it would be greatly appreciated. The contractor is very reputable and seems like he is taking care of this, but I just need to start understanding this whole system and how to monitor it. |
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conniepangan
Basic Member
Posts:112
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| 22 Nov 2008 11:03 AM |
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jimbt, i also have geocomfort brand installed in my basement and I had the same issue that being loud. I could hear it running from 1st floor kitchen which is located next to a stair going down to basement. The stairs is about 10 steps down to basement. The contractor says it is normal as described to be like a loud refrigerator . We enclosed it with sliding door and a vent. We also put insulation on the ceiling so it would help the noise as well. It's better now and I guess I got used to it. |
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engineer
Veteran Member
Posts:2749
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| 22 Nov 2008 11:36 AM |
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Perhaps I both misunderstood and misspoke - I understood you to say that the Delta-T across the unit (not the field) was 0.3 Deg. Regardless of field size, the Delta T across the unit should be on the order of 10.
If the field were infinite (AKA open loop) the Entering Water Temp (EWT) from the field into the unit would remain the same regardless of load. In the case of a closed loop, we expect EWT (in heating mode) to slowly drop below ground temperature and eventually reach the design temperature of the field.
In the case of a nominal 10 ton field designed for 10 Deg delta T under full load, I would expect something along the lines of the cited 1 Deg per rule of thumb. For example, if a 4 ton unit were operating alone on that field and running only half the time (as might be the case in mild weather) you might see an average EWT about 2 Deg below deep ground temp. (4 tons X .50 duty cycle)
Hope this helps
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Curt Kinder <br><br>
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
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Palace Geothermal
Veteran Member
Posts:1609
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| 22 Nov 2008 10:10 PM |
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The delta T across the heat pump is not affected by the loop size. The heat pump doesn't know how big the loop is. All the heat pump knows is water comes from the loop. The heat pump will take the heat it needs out of the loop water no matter what the loop size is.
A larger loop will provide warmer water to the heat pump as the heating season progresses, thus making the heat pump more efficient.
A delta T of .3 degrees is not possible if the heat pump is working properly. My guess is that the data is bad. |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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Bill Neukranz
Veteran Member
Posts:1103
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| 22 Nov 2008 11:05 PM |
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Posted By geodean on 11/22/2008 10:10 PM
... A larger loop will provide warmer water to the heat pump as the heating season progresses, thus making the heat pump more efficient. ...
It's taken me a while to understand this. This is an exceptionally significant statement, at least for me. And my instrumentation data ( http://welserver.com/WEL0043 ) this statement, as my EWT swings between a low of about 60° in the Winter to a high of 80° in the Summer, all the while my 'down deep' 'undisturbed' earth temp stays constant at 68°. The more loop pipe in the ground, the less heat extracted from any given point in the earth immediately adjacent to the pipe. Makes it possible for the earth's slow moving heat to replace the lost heat nearest the pipe faster. It's easier to understand now that an undersized loop is going to extract the same amount of heat from the earth as an over-sized loop. But it's going to take longer for the earth to replace the heat lost, nearest the pipe, with the undersized loop. And hence the EWT is going to climb over time, requiring more power to accomplish the same heat injection to the residence. Thanks for posting this Dewayne. Best regards, Bill |
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Energy reduction & monitoring</br>
American Energy Efficiencies, Inc - Dallas, TX <A
href="http://www.americaneei.com">
(www.americaneei.com)</A></br>
Example monitoring system: <A href="http://www.welserver.com/WEL0043"> www.welserver.com/WEL0043</A>
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engineer
Veteran Member
Posts:2749
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| 23 Nov 2008 09:09 AM |
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We've perhaps muddied the waters a bit talking about loop field delta-Ts.
I'm with Dewayne - 0.3 deg across a working geo heat pump is almost certainly bad data - perhaps we can assist Jim with how / where to measure temps.
Dewayne and Bill - do the electricity use numbers seem OK to you two? |
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Curt Kinder <br><br>
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
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Palace Geothermal
Veteran Member
Posts:1609
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| 23 Nov 2008 10:01 AM |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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Palace Geothermal
Veteran Member
Posts:1609
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| 23 Nov 2008 10:08 AM |
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Posted By engineer on 11/23/2008 9:09 AM
do the electricity use numbers seem OK to you two? Heat pumps use roughly 1 KWh per ton. Since this is an 8 ton system, usage will be 8 KWh
If the run time is 33%, then time is 8 hours per day
With 30 days in a month
We have 8 * 8* 30 = 1920 KWh for a month.
So the OP's estimate of 2160 KWh might not be far off.
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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Palace Geothermal
Veteran Member
Posts:1609
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| 23 Nov 2008 10:10 AM |
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Jim,
Are the MultiAqua units tied into your ground loop? |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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engineer
Veteran Member
Posts:2749
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| 23 Nov 2008 10:33 AM |
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Dewayne,
I think Jim's Multiaquas exist only to provide a better / additional way to exchange heat from warm geo water to room air - they are not additional tonnage. They solve the classic conundrum of how to retrofit geo to a fossil baseboard water system. |
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Curt Kinder <br><br>
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
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jimbt
New Member
Posts:14
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| 23 Nov 2008 12:04 PM |
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update:) Thanks for all who have responded. The contractor and i have gone over the system. He assures me that the temp probe on the outgoing pipe must be incorrect. They are coming on Monday to replace the probe. I will let everyone know how i make out. Thanks for all your help.
SECOND QUESTION.
I have been interested to see if running the baseboard all the way to 100% most of the time in the winter or running it less and using the multiaquas more would be more efficient? Basically turn the temp up on the multiaquas and down on the baseboard, or visa-versa? Any thoughts? |
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Palace Geothermal
Veteran Member
Posts:1609
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| 23 Nov 2008 12:12 PM |
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Jim,
I would think using the baseboards as primary and the multiaquas as secondary would make more sense. Since I have no data to support, this is my opinion. :)
On second thought, any idea what the COP is on the multiaqua units? |
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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Bill Neukranz
Veteran Member
Posts:1103
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| 23 Nov 2008 12:38 PM |
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Posted By engineer on 11/23/2008 9:09 AM
Dewayne and Bill - do the electricity use numbers seem OK to you two? I don't know. 2160 KWH for 30 days is 72 KWH daily. What I don't know is the KBTU being transfered here. There are 2 units, w/ each being 4 tons, but what I don't know is if they run simultaneously or separately, and, are are they 1 or 2 stage units. It's difficult for me to compare to my units right now because this is a heating mode subject and my data right now is mixed. My daily KWH average this month is 15, but that reflects both heating and cooling. So what's probably more instructional for my system is to look at just today's data, which is exclusively in heat mode. I've burned through 5 KWH so far today extracting 29 KBTU from the loop. That's 0.17 W/BTU, or 2.1 KW/ton. But this doesn't match up with Dewayne's rule-of-thumb stated above at 1 KWH/ton (for heat pumps). So, in summary, I don't think I have enough knowledge skills to help on this one. Best regards, Bill |
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Energy reduction & monitoring</br>
American Energy Efficiencies, Inc - Dallas, TX <A
href="http://www.americaneei.com">
(www.americaneei.com)</A></br>
Example monitoring system: <A href="http://www.welserver.com/WEL0043"> www.welserver.com/WEL0043</A>
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engineer
Veteran Member
Posts:2749
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| 23 Nov 2008 02:55 PM |
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Need Jim to confirm that Multiaquas are only there for additional heat transfer, NOT additional tonnage, so considerations of COP would not apply.
If Multiaquas are there only for additional heat transfer then my opinion, based on limited facts and some assumptions, it that it makes sense to run baseboards as primary and Multiaquas as secondary. My main assumption is that both baseboards and Multiaquas are working off the same geo-heated water supply fed by one or both units, sequenced somehow (probably need to understand that as well)
My reasoning:
1) Baseboards lack blowers, relying instead on natural convection. Favoring them saves additional electric load from Multiaqua blowers.
2) Baseboards are silent, or nearly so, and assuming proper location along outside walls and beneath windows, do a better job 'attacking load', counteracting cold drafts.
Bill - 29 KBtu from 5 kWh translates to a COP of 1.7. I find that hard to believe given your Envisions and ground temp. Are you sure of those numbers?
Dewayne's rule of thumb works out to a COP of 3.5, perhaps a bit conservative for well-designed systems but useful for ballpark guesstimates. |
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Curt Kinder <br><br>
The truth is incontrovertible. Malice may attack it, ignorance may deride it, but in the end, there it is - Winston Churchill <br><br><a href="http://www.greenersolutionsair.com">www.greenersolutionsair.com</a>
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