Help with Geothermal quote

After reading many of the posts I realise that its hard to answer whether a proposal is correct or not given all the variables involved.

Basically, based in Westchester County, NY
2750 sq ft house
R15 insulation in all walls
R38 ceiling (cathedral ceilings)

air filtration is 2554 CFM50

contractor's calcs ended with a 40k BTUH @ 10 deg

During the last 12 months we have used ca 1000 gallons of oil (on a 15yr+ 80% efficient oil furnace)

Based on this, contractor has proposed a 3 ton system.

Other feedback, and looking at other numbers posted in various forums, has suggested that a 3 ton system is not sufficient so I pushed back on the contractor. He stands behind his numbers and has offered a guarantee (in the contract) that if more than 5% of the the electricity costs in running the system comes from the back up heat source, he will, out of his own pocket, cover any expenses that increasing the tonnage would incur. My expense would be that I need to pay for a system (ca $300) to monitor the electricity usage but he will install.

The contractor has been very diligent during this sales process. He is very responsive to all questions, providing references, proof of relevant licenses, insurance coverage details etc. All this contractor does is geothermal systems.

I'm inclinded to go ahead with him (he wasn't the cheapest), especially since he's prepared to offer the guarantee (only good if he stays in business of course!) but have a nagging doubt about the size of the system due to other quotes we received (4-5tons) and what I have read here.

Would appreciate any feedback on what other folks would do in this situation. Thanks!

 

We have a contractor standing behind his work vs. anecdotal information? Did the other quotes do a HLHG?

If really in doubt, have someone experienced and independent of the process do your Heat Loss/Heat Gain.

 

after a while, you can't see the wood for the trees. Thanks for helping me see the wood again!

 

It appears that NY metro area has a design low of 15 so he appears to have put in a little fudge. Questions: do you make hot water with fuel oil as well? Is 1000 gal/yr typical or just last year? What is the average consumption?

 

We have only been in the house one year so do not have a reference point, although the previous owners indicated they were spending ca 5k on Oil. We had the house insulated & airsealed last September which obviously helped tremendously in getting that oil bill down.
Hot water is also provided by the oil.
Thx.

 

If your consumption data is correct, 40 KBTU/h matches about 1000 gal of heating oil matched with NYC weather data and an 80% efficient furnace. If you have a contractor who can run those numbers, you likely have someone who understands how this works. Yes, 40 KBTU/h heat loss would indicate that a 3 ton unit will run most economical and most comfortable, more so than a 4 or 5 ton.

 

It appears that 1,000 gallons of oil would be about right for a 40,000 btu loss and hot water production in a reverse operating cost model I built. That would make his calculations reasonable and the heat pump a little big for the job.

I'm curious as to the source of this "Other feedback, and looking at other numbers posted in various forums, has suggested that a 3 ton system is not sufficient so I pushed back on the contractor."

 

Thanks for the feedback. Its been very helpful.
We got 3 other quotes; 4, 5 & 7 (!!) tons respectively. The contractor i'm querying also originally came in with 4 tons but downgraded to 3 after doing the calcs. I got particularly nervous when we had a contractor out when our well failed who is active in many geothermal projects (and has geothermal themselves) who stated, based on what he had seen for similar sized houses in the area, that 4-5 tons was more typical. Given that geothermal systems are still relatively rare here I haven't been able to 'ask around' with those that already have geothermal (and given the chunky price tag involved with geothermal) I started to get cold feet & started second guessing. Figured given the quality of the discussions given in this forum, that this would be a good place to come to get a sanity check. Thanks so much for the quality feedback.

 

Jens must have been typing while I was.....
In the old days, open loop installers favored larger equipment with less auxiliary input. So it's easy to see why a 4 or 5 ton would be within the well guys experience.
I'm working with a homeowner now who's original installer used a six ton. I guessed sight unseen that we would be installing no more than a 5 ton and after doing the math we are quoting a 4 ton.

I'm encouraged by your observation that the installer had a size in mind that he later changed once he'd done the math. (That has happened to me. Most of us are pretty sure what size a house will need when we measure it, but some of us have been suprised by the math which is why we keep doing it.) This tells you he really did the math on manual J or reverse modeling as Doc and I did.

 

Thanks Joe, Chris & Jens. The deposit check will be making its way over to the 3ton guy with the signed contract (incl the guarantee) this week. I'm excited!

 

Just to update that the system is in, but not yet finished. The drilling and initial installation went well and was wrapped up in about 3 weeks and, as per the contract, we made a chunky payment on system start up. Only the last 10% payment remains.
However, the contractor has since pretty much disappeared leaving the crawlspace a complete mess (including the contractor's tools), with not all the duct work fully sealed, wires hanging down everywhere, cover not on the heat pump, debris from packaging, old parts etc lying around. Emails, texts, voicemails go mostly unanswered with the odd message from time to time saying he will shop up on date x, but doesn't appear.

Its pretty cold now (21F) and the heating does work but the system is struggling to maintain 65F in the house and is pretty much running 24/7. Its hard to tell at this stage whether this is due to remaining work or the expected way the system should work.

Too early to pass judgement on the quality of the installation but not having seen the contractor in 2 months is not a good place to be.

 

You're in Westchester, I'm on Long Island, so we're experiencing the same weather. My conditioned space is less than 2000 sq. ft, my blower door test had twice the amount of air infiltration as yours. I wound up with a 4 ton split system. Last winter my system couldn't keep up with single digits, so I had auxiliary heating added to my air handler (should've been installed from the start). There's lots of talk on this forum about the reasoning for having this option. Do you have it?

My guess would be if you have the mess that you describe, your system is not going to be able to work well unless you resolve some of those issues. Leaky ducts are a killer. Who knows what else may be impeding performance? Our electric company, PSEG, offers free home energy assessments, which includes duct sealing. Not sure if they service your area too, but similar programs probably exist.

I had a very bad experience with my geo contractor (they went chapter 7), and have spent a lot of time here getting help to improve my situation. The responses have been very valuable. I'll share more of my experience if you'd like.

 

The auxilary heat has not come on (we have an energy monitoring unit - TED5000 - that measures this and has shown 0 usage; I presume it comes part of of the bosch SM036 unit rather than being an optional extra; it was certainly part of the original bid/design) and I'm pleased it hasn't. Its not 'that' cold yet. My understanding is that it is required when the temps get down to the single digits.

I'm not super worried yet (the unit ran for 14hrs yesterday costing ca $1.24) but am getting concerned about a) getting the last few parts of the job finished up b) getting to talk to the contractor about how to best run the system over the cold winter and c) getting a completion certificate so we can get the tax credit!

 

Could you try putting the cover on? It could be sucking a lot of air into the cabinet, mostly bypassing the coil. I would guess that much of your heat is being provided by the aux strips in this state.

 

What do you mean by "struggling". Is 65 your set point? I would expect one of my systems to run most of the time at 21F. A well designed geo should not cycle on and off when its cold. I t should upstage and down stage (meaning run in first til it loses ground then second til it gains then back to first......). That's true of multistage gas units as well.

 

How do I figure out if the system is correctly 'upstaging' and/or 'downstaging'?

By struggling, I meant the heat (due to a window being replaced) fell to 60f and its taken the best part of 36 hours to get back up to (and stay at) 65

 

"I'm not super worried yet (the unit ran for 14hrs yesterday costing ca $1.24)"

14 hours of run time cost $1.24? If that were true for me I'd be thrilled. I had an extremely high electric bill last January (single digit temps). I guess I'll have to see if aux did most of that damage.

 

Maybe the contractor reads these posts because he showed up after learning of my concerns (its the first email he's responded to in a while). Turns out the Aux heat is not yet installed, so that's why that hasn't been running and has promised to be here the first week of December to finish off. Here's hoping.

He advised to reduce the temp variations that we had on the thermostat (63 overnight, 65 during the day, 67 in the evenings) and keep it more constant. We'll see how that pans out but its warmed up some here (40) and we're back a nice 67 this evening.

the charge for Wednesday ended up at $1.75 for the day (21.1kwh). it wasn't cold in the house but maybe this is part of the learning curve of living with the geothermal; it will just run longer (22hrs in the end) but that won't necessarily break the bank like it would if the Oil burner was on that long.

 

Heat pumps are like the turtle, slow and steady wins the race.

 

One thing I have learned and verified is that setbacks are a reason for your system to work harder, and thus should be avoided/minimized. "Set it and forget it" was told to me and really ring true, I believe.

$1.75 for 21.1 kWh sounds to me like you're paying less than 9 cents per kWh. That's very good. Since we're located near each other, I'm trying to apply your experiences to my situation. I take my total electric bill (including taxes and other) and divide it by my total kWh used. My cost per kWh over the past year was 15 cents at its lowest and got up to 20 cents. Are you using the same logic?