As many of you are already aware, I'm working hard to find a circumstance in which I can justifiably install a 2-ton Geo system in my 2000 Sqft ranch with 1000 sqft finished basement, located in Essex MA. Using HVAC-calc I found a scenario in which the load for the first floor would be 19,000 btuh and the basement would come in at 4,000 btuh. I'm planning on having 3-zones. That scenario requires the insulation of my foundation using re-claimed foam insulation somewhere around R-14, and insulating the floor above the unconditioned half of my basement.

The major hesitation I get from the installers I am working with is that during the coldest part of the winter, EWT can be in the mid 30's. Using the climate master tranquility as an example (http://www.climatemaster.com/share/Res_All_Products_CLM/Section_3_TT27.pdf), performance at that EWT is somewhere between 18-21,000 btuh. I would also have a 5kW strip installed, but the installer feels I may be pushing the limits resulting in an uncomfortable heating season. The installer is calling for 110-130' per ton of Geo and is quoting me 360' for a 3-ton system. I am pushing to make improvements that allow for the 2-ton system. What do people think of this scenario, am I pushing too hard to save $2500?

Make sure you are aware of the duct sizing and/or efficiency downsides to zones.

I thought you got 510' of well depth on the 3 ton you already have the quote on. What happened? Is this new quote from a different contractor?

I would think 110-130' per ton is pushing it on the too short end of things and your EWT will be very low and not give good performance. Not wanting to use rules of thumb as a guide, but I thought verticals should be closer to 150-200' per ton depending on local soil conditions.

With the added insulation and sealing your doing, and having the wood stove and baseboards, I think the 2 ton would give the best ROI. But you need to loops sized right and good duct design for it to perform good.

Sorry for jumping around. I have two contractors I feel somewhat comfortable with, one is calling for 130' per ton the other is calling for 170' per ton. At this point I'm struggling to find enough comfort to spend $35K, but I'm trying really hard. As a scientist I'm very irritated that I've yet to find a contractor who let's the data drive their decisions. Of course, it is possible everything I read (especially on the internet) isn't true... I spent 6 months trying to find someone to install horizontal loops but failed to find anyone to take me up on it. In my fantasy world, I would take advantage of my 2.3 acres (one of which in in front of the house), put in a nice horizontal loop but the contractors here have beat me down into going vertical.

With $35K at stake, I wouldn't go with any contractor that I wasn't quite comfortable with. Including a clear explanation as to why a horizontal loop isn't the best choice. Ie, keep shopping and asking questions (we aren't tired of you - yet :-)).

Is there any reason a horizontal loop cannot be installed?

We are running 133'/ton, but the trick is to use 1.25" pipe, which has higher volume of water and a larger surface area. Here is a house with a 42KBTU heatloss, 3 ton system, and the 400' loop actually over performs, the min EWT was around 33F, it was designed for 30F.

http://welserver.com/WEL0478/

It is important to understand that a 3 ton unit with the same load does not require an increase in loopfield size, the amount of heat pulled out of the ground is the same, the only difference is the amount of supplement heat which now comes from the strip and not from the ground. Usually a few % more.

Everyone around here thinks there are too many rocks in the ground to go with horizontal loops, so the canned response is that it probably is just as expensive to excavate around boulders than it is to drill. I have about 200' x 100' of my front yard that could easily be used to trench. Both contractors plan to use 1.25" pipe

What do you pay/kwh. The only place I endorse oversizing is where cost/kwh is high.
If your guys aren't doing the math then they have no idea what fits your job best.

The prices here are 14 cents/KWH - very high

Operating cost models would help decide whether 2 or 3 ton was the better fit for you, but with an upfront difference of less than 10% the 3 ton might be more attractive, however with (did you say OMG) 3 zones I don't know how anyone would accomodate required air flow.
Given the high upfront cost, you might want to revisit other alternatives- air source or even greater insulation and 98% furnace etc.

Maybe you have some neighbors with geo that have some input on boulders, installers, etc.

I can probably move down to 2-zones if necessary. In terms of alternatives, I only have access to oil or propane so I don't find those to be attractive optons. Furthermore, without ductwork currently in place, they won't be very different in $$ from Geo. Air source would also be tough for me with my floor plan, not to mention the need to retain a backup which would be electric baseboards. I want the baseboards to disappear....

Sounds like I should backoff and settle with a 3-ton even though my load indicates 20,000 btuh for the first floor, and 4000 for the basement?

I dunno know I like the 2 ton, but that's me and I haven't run any models. I'm skeptical that anyone can get 3 zones to work correctly in your house with a 3 ton without a lot of bleed or dump.
Why is your floor plan a problem for an ASHP? There are ducted airsource heatpumps with electric or propane (ducted) back-up. Sure it will cost a little more to run then the geo, but it will cost a whole lot less to install.
Bank the difference and use the savings to pay the higher utility bills.

Across the board, duct work is $12K no matter what the heat/cooling source. I have a quote for a Bryant ASHP coming in for $8,000 extra. I don't have a ductless mini-split quote, but that's what I'm referring to when I say my floor plan isn't amenable. I probably will need 4-5 heads to cover what I need. I can imagine it not being a stretch to ~$8k for a propane. For Geo my quotes are $22K for ducts , heatpump, and flowcenter. Drilling is coming in around $12K. After 30% tax credit I end up around $25k for Geo.

It looks like this:
$20k for ASHP
$25K for Geo
I'm estimating about $20k for propane/AC

The extra $5k is worth it to me for not using fossil fuel (directly at least). The ASHP is a concern for me since I need to retain a backup heat source, which will not be electric baseboards.

Let me know if my logic isn't sound.

Joe, if you want to run a model for me I'd be happy to compensate you, assuming the price is fair (that goes for any pro's that want to help me out).

Agreed. IMO, a reasonable zoned duct design would be something like building all the ducts 25% oversized and then allowing a zone thermostat/damper to close off only 25% of a duct. Plus transfer ducts if this could unbalance the supply and return (ie, depressurize closed off room(s)).

You need auxiliary heat with a properly designed GSHP as well. I guess those numbers are faintly familiar I must be circling this conversation. It's not a big deal to run op cost model with known load, you can do it your self with freeware.

run op cost model with known load, you can do it your self with freeware.

can you point me to some freeware that does this?

Looks to me like adding $12k  worth of ducts is  a dead-end.  My 4 head minisplit cost about $8K and heated 6,000 square feet down to about 27F. That's when we had to turn on the 3rd head..... If you have rooms you are worried about you can put an electric resistance wall heater in there for backup.

After reading a bit through here again (and some of your other threads) and giving your usage data at "60-68" F thermostat settings, which you deemed uncomfortable, and the fact that you burned wood as well, and even after the airsealing insulation your own electrical consumption data indicates 21.5 BTU/H, PLUS the "stove on on the weekend". It is hard to see how you could design a system for less than 3 tons and be comfortable at a constant indoor temp of 68-70F. Consider cutting down your loop size to 400' and use the saved money for a zone controlling strategy like WF Intellizone, which can slow down the blower to serve single zones as small as 25% airflow, or even go with a variable speed HP (7-series), which can go down to 15% (with Intellizone 2).

I also would question the $12K for ductwork for a 2100 single story house. Any specific obstacles?

I'll be happy to run an operational cost model for you, but your numbers seem off anyway.

You are 100% correct. My load is 3-tons right now, 34,000 to be exact. However, prior to installing anything, I want to make further improvements. Specifically, after using HVAC-calc, I noticed a large amount of my load was being lost through the floor of my conditioned space into the unconditioned/uninsulated basement. After changing the calculation to include an insulated basement, my load dropped to about 20,000. I started this weekend by picking up factory second insulation for my basement



Yes I made it home without incident. Any help is greatly appreciated. Let me know and I can PM my email address