Thanks in advance for the help!

I have received 3 estimates (from 2 installers) to retrofit my house with geothermal heating and cooling and I am having a difficult time sorting throough them.  There are lots of experts on this forum so I am hoping to get some advice.  Information is as follows:

House Info:

• 2500sf (2 story 9' ceilings on 1st floor and 8' on second).  We are also finishing a bonus room over garage (additional 312sf)  and basement (additional 900sf) this spring for a total of 3712sf
• Full spray insulation (walls, ceiling, joists, etc.). House rates as 5 star plus in the NYS Energy Star Audit
• Blower door test came out at 1156
• Rochester NY location
• Clay soil

Design Data: (provided by 1 of the estimates.  2nd contractor will only provide detailed design data if I sign contract with him)

• Heating Load = 61,735 BTU/Hr
• Htg load temp Diff = 65 Deg F
• Cooling Load = 22,929 BTU/Hr
• Clg Load Temp Diff = 25 Deg F
• Winter Design = 2 Deg F
• Summer Design = 90 F
• Bldg Balance Temp = 55 Deg F
• Avg Internal Gains = 10, 697 BTU/Hr

Estimate 1 (From contrator who did NOT provide design data)

• 4-ton ClimateMaster Tranquility
• Modify ductwork to accept increased air flow
• 3,200 linear feet (slinky) in horizantal trenches (depth 6 feet)
• Designed for 100% heating and cooling.  Aux heat will kick in at -3F

Estimate 2 (from contractor who provided design data)

• 4-ton ClimateMaster Tranquility
• Modify ductwork to accept increased air flow
• 2,950 linear feet in horitantal trenches (depth 7-8 feet)
• Geo 98% heat and 100% cooling.  Aux 2% of heat.  Aux balance point 12F

Estimate 3 (from contractor who provided design data)

• 5-ton ClimateMaster Tranquility
• Modify ductwork
• 3,550 linear feet (7-8 feet depth)
• Geo 100% heating and cooling.  Aux 0%

References for both contractors check out but I am leaning towards the contractor who provided more data.  (I love data!).  The question is should I go with the 4-ton or 5-ton?  When i factor in the 30% federal credit and 10% NYS rebate the price differential for the two systems is only $1000.  The contractor is recommending the 5-ton as it will allow for more set backs and less aux heat.  It will also not run as much and I have to admit, the concept of the furnace running 24/7 has me a little spooked.

Sorry for the long post, just wanted to provide detail!

Thoughts??

5 ton will likely cost more to operate.
Did the contractor that kept data to himself measure the house for load calcs?
I'm interested in why there is such a great disparity in balance points of 4 ton.....it's gotta be load.
j

Probably a long shot, but can the installer provide a reference for a similarly sized and insulated house?

Joe.Ami,

This contractor used a rule of thumb based on blower door test and experience in area (installed 12 systems within 10 miles of my house.).  Honestly this is one of the reasons I am leaning against him.  The other contractor (also did multiple installs in my area) asked for blue prints and audit data which I provided and then did a manual J calc and Bin Temprature analysis.

The estimated operating cost for the 4-ton is $1,332 and the 5-ton is $1,327.  Contractor states these are conservative and when I factor in setbacks with the 5-ton I will actually save more.  He also indicates that the most complaints he hears from customers is the fact that geo runs to long.  The 5-ton will reduce this concern.

 

Posted By geome on 08 Feb 2011 08:58 AM
Probably a long shot, but can the installer provide a reference for a similarly sized and insulated house?

Both contractors provided a number of references to similar sized houses.  None however are insulated as tight as mine.

Complaints that geo runs too long indicates a contractor that is not educating his customers.
I dunno.
I sure wouldn't go with the 5 ton.
Have you any other estimates planned?
j

No additional estimates planned at this point.  I had a 3rd contractor provide an estimate (5-ton Water Furnace) but his references did not really check out.  References for both of the remaining contractors rave about them.  I know several of the references personally so I am confident they are not plants. 

I am leaning towrads the one because of the greater detail he has provided.  While he recommends the 5-ton, he is not pushing it so hard as to raise red flags.  He is basically saying my house is at the high end of a 4-ton and the low end of a 5-ton.  Either will work, he just thinks long term I will be happier with the 5-ton.

Based on your experience, do the load numbers bear out for a 4-ton?  Is he accurate in saying it could go either way?

You aren't too far from Buffalo. Doc participates on this forum, and he really seems to know his stuff. He has mentioned that he offers a performance guarantee in the past. You may want to contact him to see if he can help you. If he was a stone's throw from me, I'd ask him to come out (if I needed another system.)

Any idea what Doc's contact info is?

Could it go either way? In my mind no but we are getting into design philosophy, and their may be idosynchracies I'm not aware of in your area (though it looks a lot like mine design wise).
j

www.buffalogeothermalheating.com

His user name here is docjenser.

I have no idea if he really goes by "Doc". :-)

Posted By lax18 on 08 Feb 2011 10:04 AM
Any idea what Doc's contact info is?

You got mail. I love data, too!

Joe,

I think the chief difference between your AO and Rochester may be significantly higher electricity rates - NYS is a high tax nanny state.

I lean toward 4T, based on info provided.

Based on your info, running it thru my ClimateMaster designer and looking at it from a southerner perspective, I like the 4 ton also.  My reason would be the proper upsizing of the duct system to accomodate 5 tons of airflow vs. the 4 tons and during the summer and high humidity periods, the 4 ton will run longer in the first stage and give you superior dehumidification.  Too much cooling power will cause the unit to short cycle and can sometimes lead to a cold and clammy feeling in the house.

Posted By engineer on 09 Feb 2011 09:49 AM
Joe,

I think the chief difference between your AO and Rochester may be significantly higher electricity rates - NYS is a high tax nanny state.

I lean toward 4T, based on info provided.

Electric rate is probably the only difference. With that in mind I would be less reluctant to design in significant auxiliary use.
As I said before, I dunno on this one. I couldn't kill either design.
The economics would seem to make the 5 ton less attractive vs payback.
I'd be curious to hear doc's assessment if he has a look.
His propensity to add loopage may make the 4 ton a perfect fit.
J

I concur.

Posted By joe.ami on 11 Feb 2011 08:57 AM
Electric rate is probably the only difference. With that in mind I would be less reluctant to design in significant auxiliary use.
J

I should have said I would be "more reluctant" to add in significat aux use....... 
The ole' double negative.......

Posted By lax18 on 08 Feb 2011 08:30 AM

  When i factor in the 30% federal credit and 10% NYS rebate the price differential for the two systems is only $1000.

Thoughts??

How are you getting 10% from NYS? We installed a Climatemaster system in New York last year. I would have taken an attaboy. But I didnt even get that. Did they add Geo as a rebate? anyone?

It all comes down to the load calc, I still lean toward 4T, but it is hard to make such a call via the internet

Before choosing 5T I'd want to be absolutely certain the ductwork will handle the flow. If it won't you'll be forever sorry at the noise and inefficiency

Here is some feedback. I told him before that he is a bit too far away for me to consider this as a job, but I would be happy to help. I was in Rochester, so I did swing by him.
Just as an example how the heatloss can be off. House is 100% sprayfoam.

He uses 1000 gallon of Propane each year (plus minus 10 gallons!) currently, which puts him at 33000 BTU/H at -3F design temps with a 93% efficient furnace and Rochester NY BIN data, and with his current build out status. Now add 4.5 KBTU for the basement he will finish (he already has open dampers there, a generous 4.5K BTU for the bonus room over the garage, because it is above unconditioned space but will be sprayfoamed, account 2 KBTUs capacity for the DSH. Now he runs the house at 66 degree, and his wife would like to have it up to 70, so there are another 2 KBTU, for a worst case scenario of 46 KBTU at -3F.

A 4 ton CM 27 would take 98% of the load, 2% aux heat. A 3 ton would run 12% Aux heat, a bit too much with our electricity rates, a 5 ton would run him $50 more to operate annually despite no aux heat, so that does not make much sense either. A 4 ton seems to be a perfect fit for him. Lots of variables, but at the end of the day, same result.