Thoughts?

Yeah. Still trying to figure out why I can make do with a third of what you are planning. I heated all Winter running 2 X 9K minisplits and kicked in a third when we had a string of days in the mid-20's. The heating contractor tried to sell me dual 90K gas furnaces......

Go with the 7 series, for 10% more you get units which run 22-25% more efficient, for life. 10 year warranty should put you a peace. (2) 3 ton units should do it, the 7 series 3-ton actually has the heat output of a 4 ton. They also run amazingly quiet.

Posted By docjenser on 05 Mar 2013 01:51 AM
(2) 3 ton units should do it

Do we know the cooling load?

@ICFHybrid, 
Wow, you're running that 6900 sqft (with 1000 sqft of windows) with air-source and only needed 18 kbtu/h? 

@docjenser,
Yea, I'm leaning toward the 7-series, if I can get that rebate they are currently offering.  You say that a 3-ton (036) series-7 will output close to 4-tons of heat?  I can see that for a water loop configuration you are correct, but according to the specifications, for a closed ground loop a 3-ton unit will only put out 2.67-tons (32 kbtu/h).  I wish I had a big pond to sink a water loop, but those are hard to come by in this area.  I could possibly do (2)-048 units, but that could leave me a little short on the main level.

@joe.ami,
Yes, the cooling load for the zones is as follows:

Zone 1 (main level):   19 kbtu/h
Zone 2 (basement level):  11.5 kbtu/h

Good point, and another reason to go with the 7-series... the cooling can ramp down pretty low. 

Cooling
Zone 1 options
Series-7 060:  56,000 - 23,000 btu/h, so it will be able to ramp almost all the way down to prevent short cycling.
Series-5 064:  65,000 - 50,000 btu/h, it seems this one would short cycle a lot.

Zone 2 options:
Series-7 048:  46,000 - 19,000, btu/h, a bit too much cooling for the zone 2 load but much closer than the series-5, below.
Series-5 049:  52,000 - 40,600 btu/h, this also seems it would short cycle a lot.

Wow, you're running that 6900 sqft (with 1000 sqft of windows) with air-source and only needed 18 kbtu/h?

Well, hadn't cut in the garage, yet, so it was only 6,000 sf. And, we did go to a third 9K unit when it got really cold, but,on the other hand, we don't get no stinking high desert solar assistance here and I do have some pretty significant holes in the envelope, still. Nevertheless, the three units cycled on and off.

Posted By therik on 05 Mar 2013 09:43 AM
docjenser,
Yea, I'm leaning toward the 7-series, if I can get that rebate they are currently offering.  You say that a 3-ton (036) series-7 will output close to 4-tons of heat?  I can see that for a water loop configuration you are correct, but according to the specifications, for a closed ground loop a 3-ton unit will only put out 2.67-tons (32 kbtu/h).  I wish I had a big pond to sink a water loop, but those are hard to come by in this area.  I could possibly do (2)-048 units, but that could leave me a little short on the main level.

The 7 series has a higher capacity then the specs suggest, has anyone run the operational cost forcast for you to see the amount of supplement heat you might need? I bet it is almost nothing with (2) 3-ton systems. On the other side, the 4-tons are not very much more expensive, and can modulate down anyway.

Hmmm...No, I have not seen an operational cost forecast yet.  Should my installer have this program to run?  Is it supplied by the manufacturer?  I know that the LoopLink software has this capability, but my installer seemed unaware of the existence of this software. 

Looplink is a great web based design software, but does not model yet the 7 series correctly. You have to go with geolink from Waterfurnace. I'll run it for you tomorrow.

@docjenser I would really appreciate you running those calculations for us (my wife would appreciate it to). Let me know if you need any other input data and I will provide it to you. Thanks.

Posted By therik on 07 Mar 2013 03:00 PM
@docjenser I would really appreciate you running those calculations for us (my wife would appreciate it to). Let me know if you need any other input data and I will provide it to you. Thanks.

I used your load numbers, and guessed the A/C with 60 KBTU peak load given your large windows. I also used your 91 kbtu heatloss. 4 people for hot water (2) 7 series versus (2) 5 series, 2x3 tons, 7 series will save you a bit over $300 annually, you are looking at a maximum of 790' of borehole needed. Loopfield is cooling dominated, 7 series adds less compressor heat, thus also needs 130' lesser loop (660'), might pay for the higher price of the 7 series. Did anyone here mention that we all think your loads are pretty high? So I think you are on the safe side here. Still no need for supplement heat with 2x3 ton units. All done with 1.25" pipe. Cheers!

PS: I do not buy 30 KBTU/H heatgain. Bin data shows 55 hours Annually for 102F outside air, 210 hours for 97F. If it is less, good for you.

Now it gets even weirder. I run the same load (90+KBTU/H heating and 60 KBTU/h cooling, and only with a single 5 ton 7-series. It can easily handle it, only needs 4$/year supplement heat. Again, it is a pretty neat machine. So here is what I suggest: 2 boreholes, 400ft each with 1.25" pipe, (1) 5 ton 7-series, intellizone 2 zone controller. Should cut your current proposal in almost half. Enjoy the most comfortable forced air system money can buy.
I also run the loop at with average rock instead of dense rock, still is less than 800' of total borehole.

Doc- Wow that is some savings. Nice work. I really thought his loads were way bloated. Zoned correctly, that single 5 ton 7 would really save some dough. Now the hard part of getting his contractor to sharpen the pencil.

therik- can your house layout work with a single unit? Good luck!

Posted By chrisbiker on 08 Mar 2013 08:47 AM
Doc- Wow that is some savings. Nice work. I really thought his loads were way bloated. Zoned correctly, that single 5 ton 7 would really save some dough. Now the hard part of getting his contractor to sharpen the pencil.

therik- can your house layout work with a single unit? Good luck!

But even if his loads are correct, which we all doubt, the single unit can handle it. The 7 series is really an amazing beast which performs much better than the rough data suggests. At first I thought that it is overly expensive, but then you realize that it performs so much better, and that it replace actually a much bigger 2 stage unit. Plus no light flickering, no issues with generators, quietness. This keeps going.
I remember when we put our first one in, we looked at each other and never want to put in another kind of forced air unit. I really believe I do people a disfavor by suggesting other 2 stage equipment. I am usually critical and skeptical, and I was that in this case, and it took one unit to win me over once you realize how much better they do things. Now we have more in, still love them. I stop raving now....

@docjenser

Wow.  That is incredible.  I hate to ask since you've done so much for us already...but, could you run it again with the weather conditions of Santa Fe, NM?  The weather conditions at the site will be almost identical to Santa Fe (more heating, less cooling than Albuquerque).  The outdoor design temp for the winter should be about 10 degrees.  Our heat load calculations were done for an indoor design temperature of 72 (we will NOT be setting the stat to that, however). 

I think the average rock is very close to what we will have for thermal conductivity of the soil (1.4), so that looks good. 

Oh, and I posted the cooling loads a few posts ago, I think total was around 30 Kbtu/h. 

This is great, I'll have to talk to my installer about this new data.  And this will make me and my lender very happy.

Thanks,
Erik

...I see that the program doesn't have Santa Fe, NM as an option.  I looked it up and Farmington, NM is very close to the heating degree days that we will experience at the build site.  I think Farmington NM is an option in the GeoLink software. 

Thanks,
Erik

If you have all your load calculations already, and you feel they are correct. You can buy a 1 month subscription to loop link and run all your own options and see the results immediately. It's only $50 for 1 month, and you will have piece of mind knowing you ran all your options. I have not had the chance to use loop link yet personally, but Ryan Carda (the designer) showed it to me at the IGSHPA training class and I must say its Very user friendly.

Posted By Calladrilling on 09 Mar 2013 10:11 AM
If you have all your load calculations already, and you feel they are correct. You can buy a 1 month subscription to loop link and run all your own options and see the results immediately. It's only $50 for 1 month, and you will have piece of mind knowing you ran all your options. I have not had the chance to use loop link yet personally, but Ryan Carda (the designer) showed it to me at the IGSHPA training class and I must say its Very user friendly.

As I mentioned before, Looplink cannot yet accurately model the variable speed 7 series. I am in contact with Ryan about it, he is working on implementing it. Farmington modeling attached, average rock, with your load numbers. PM me your email, I can send you the modeling from looplink as well, it will be for 5 series only