5000 sq ft home geothermal 6 ton - adequate?
Last Post 16 Feb 2011 09:27 AM by opsman. 21 Replies.
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opsmanUser is Offline
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08 Jan 2011 01:23 PM

I think I have some sizing issues with our geothermal.

We have three floors, the basement, main floor, and 2nd floor (5,000 sq ft total). We did not go cheap on insulation. 2x6 exterior walls, cellulose, low-e windows, R49 attic, sealed very well. Brick exterior.

The main floor almost always has the aux heat on. The upstairs can not seem to get to 70 degrees (outside temp of 20 deg F). It gets to 68, but can not get to 70.

The airflow coming out of the 1st stage in basement seems good. The airflow coming out of the 2nd stage in the main floor seems good. The airflow coming out of the 3rd stage upstair is almost non-existent. So... of course, the 2nd floor can't get up to temp.

Now, I am wondering if the Waterfurnace, NDV072, six ton system is adequate. We only have the one unit in the basement.

We had someone here recently and he said the returns may need some adjusting. I enjoying working with this crew during construction, but now I am a bit skeptical of the advice/recommendations. I like working with them... but want to make sure what I have is the appropriate system.

Steve

Palace GeothermalUser is Offline
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08 Jan 2011 03:51 PM
Hi Steve,

In order for us to help you, we need the info detailed in this thread
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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08 Jan 2011 06:27 PM
Steve, Was your ductwork existing? Do you have Zoning (thermostats on each floor)?
As Dean stated above the info above in the thread is needed to get an accurate starting point.
engineerUser is Offline
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08 Jan 2011 09:42 PM
Steve - please post as many answers as you have to the ten questions at the top of the thread Dewayne linked
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>
Paul AuerbachUser is Offline
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12 Jan 2011 02:11 AM
Steve

Did your contractor do a manual J? I don't know where you live - but you're looking at less than 15 BTU's per square foot. This may be OK for mid-Atlantic or down South, but not anywhere in the Northeast. The manual J will tell the story. - and you'll likely find the system is undersized.

Paul
www.TotalGreenUS.com
DX Geothermal Specialists
engineerUser is Offline
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12 Jan 2011 09:01 AM
It MAY be undersized, but I wouldn't be willing to bet on that given the construction details.

If there is doubt about the return air system, then a measurement of static pressure across the unit is in order. If it can't make designed airflow then it can't make designed capacity and efficiency will plummet in heating mode while it tries.

I'd want to know the room by room and zone by zone required airflows per Manual J and then measure each supply register airflow and compare.

Need entering and leaving air temps, entering and leaving water temps.
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>
joe.amiUser is Offline
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12 Jan 2011 09:34 AM
Is the basement part of the 5000SF? I'm not so convinced you are undersized vs poorly ducted.
J
Joe Hardin
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engineerUser is Offline
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15 Jan 2011 08:25 PM
Paging OP Steve...

Steve?

Steve?
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>
opsmanUser is Offline
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15 Jan 2011 08:35 PM
Sorry, I had an emergency I had to leave.

I have the installer coming back on Monday to go over it with me.

Here is what I know:
1) Where you live

Chicago, but on three acres. BTW, the 5,000 sq ft includes the basement.

2) Heat loss/gain calculations for your home

I don't have this information and wasn't given it.

3) Brand, size (model), age and type of heat pump

WaterFurnace, NDV072, 6 ton Envision

4) Type of loop field (open/closed/vertical/horizontal) size and design parameters

I know it is a closed loop, horizontal field primarily running through sand.

5) Average cost/Kwh of electricity and consumption

December gas usage was 45 therms average outside temp of 32.
3,263 kwh used cost which cost $257

6) Entering and leaving air temperatures (EAT, LAT) measured immediately upstream and downstream of the heatpump

Don't know.

7) Entering and leaving water temperatures (EWT, LWT) measured at the geo system

Don't know.

8) Percent of load to be covered by geo and balance point

Don't know.

9) Installer's assessment of your systems operation.

Finding out on Monday.

10) Projected operating costs, actual operating cost and previous heating and cooling costs
opsmanUser is Offline
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15 Jan 2011 08:38 PM
I'll add the system has three zones. One for the basement. One for the main floor. One for the 2nd floor.

I just found out today that if I turn off the main floor, turn on the fan to the 2nd floor, very little (VERY) air comes through the 2nd floor vents while a lot of air comes through the main floor despite the main floor being off.

opsmanUser is Offline
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15 Jan 2011 08:38 PM
I'll add the system has three zones. One for the basement. One for the main floor. One for the 2nd floor.

I just found out today that if I turn off the main floor, turn on the fan to the 2nd floor, very little (VERY) air comes through the 2nd floor vents while a lot of air comes through the main floor despite the main floor being off.

engineerUser is Offline
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15 Jan 2011 09:08 PM
Sounds like a damper, zone board, or thermostat wiring problem.

Each room and zone has a required amount of airflow needed. That should be compared with measured airflows.

We really do need most of the 10 questions answered to be able to dig much deeper. Ask the installer to measure / answer the questions you can't
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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15 Jan 2011 09:37 PM
3,263 kwh used cost which cost $257
Really?

Isn't that less than $0.08/kWh?

How do you guys get it so low there?
opsmanUser is Offline
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16 Jan 2011 09:38 AM
Thanks, Curt. I will find out more information tomorrow.

As for the rate, we get a special rate if you have geothermal or solar. The house we came from was 1400 sq ft and it cost about $180 a month for electric/gas. This house runs about 280 for both.
joe.amiUser is Offline
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16 Jan 2011 09:54 AM
Yep sounds like a zone problem.
I'm 99% certain your heat pump is right or oversized not undersized as basement square footage adds much less load than above ground squares (~20%).
j
Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort!
opsmanUser is Offline
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23 Jan 2011 12:01 PM
I am wondering what is happening. I asked for the information, but I havent' received it yet.

I've had two visits. The first time the blame was on the returns. This past week it was the thermostats.

The 2nd floor is still not warming up. The 1st floor is iffy. I have been keeping track of G, Y1, Y2, Y3 and the thermostats appear to be working fine. I am beginning to question the expertise I am being given, but don't know these systems. Sorry for the lack of information... but I am not getting any myself...
joe.amiUser is Offline
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23 Jan 2011 12:56 PM
Might want to hire another opinion.
j
Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort!
engineerUser is Offline
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23 Jan 2011 01:47 PM
Agreed.

I did a J and D calc as well as an actual airflow for a client who was uncomfortable after having an ASHP removed and replaced with one 1/2 ton smaller. My calc proved the need was in the other direction...original contractor bumped the outdoor unit back up to the original 4 tons without charge. Airflows were out of whack as well.

You need the same thing - anything less is just a guess.
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>
opsmanUser is Offline
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15 Feb 2011 11:26 PM
Well, I made a little progress, but no J or D calcs.

Water temp in: 36
Water temp out: 32
Pressure in: 72psi
Pressure out: 64psi
19GPM

Return air temp: 73
S/A temp: 94

WaterFurnace, NDV072, 6 ton Envision
Closed loop, sandy soil

December gas usage was 45 therms average outside temp of 32.
3,263 kwh used cost which cost $257

The installers assessment of the system, is hey, its running.

Is there a way a laymen can do a manual J/D? I can see what we have and know how to use a tape measure. Actually, my math skills are pretty good: differential equations would not be an issue.
engineerUser is Offline
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16 Feb 2011 12:30 AM
There are free load calc utilities online

For $50 you can use a well-regarded professional grade package for 60 days...Google HVAC-Calc
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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