Geothermal HVAC

BB.

Re: Geothermal HVAC

GreenPowerManiac wrote: »

Furnace is 93% efficient. 83700 btus output. Duct work are not insulated in basement (about 53 lineal feet) 1x2 rectangular. Same with return lines in basement.

Basically, heating your basement--May be a good thing or a bad thing. On a cool day, turn on the heat and let it stabilize. Measure the furnace outlet temperature vs the outlet temperature at the grill in your home. The temperature drop will tell you quickly how much heat you are losing...

My guess (I always like the math):

110F - 90F duct-work = 20F drop
110F - 70F room = 40F drop

20F drop / 40F drop = 50% efficiency

-Bill

LucMan

Re: Geothermal HVAC

I would probably go with the 064 unit with the optional sequenced electric strip backup heater. Definitely glycol in the loop.
But it all depends on who did the manual J calc.

GreenPowerManiac

Re: Geothermal HVAC

The 064 unit is a 5 ton. The chart is from 3-6 ton. What made you decide to go with a 5 ton unit and why?

The Manual J was done by yours truly. I've got the software and the time.
All of the house was insulated with blown in. 2x4 walls and some 2x6, except for attic which is R-38 blown insulation. Don't know what the R-value was for that. Assumed R-50 at least.

Like said before, I've well insulated this place. 95% of windows have inside clear treatments for minimizing draft leaks.

Oh, and if I don't heat the basement at all throughout winter, never gets any lower than 58-60 degrees. Now is being heated a bit since the duct vents are open.

LucMan

Re: Geothermal HVAC

GreenPowerManiac wrote: »

What made you decide to go with a 5 ton unit and why?

40 Yrs as a HVAC & refrigeration contractor designing & selecting equipment.

GreenPowerManiac

Re: Geothermal HVAC

Not trying to insult anyone.

Would that be enough tonnage for the water heating and radiant floor?

And looked up the circulation pump Grundfos UP 26-96 F. Says up to 28gpm.
Got lines 8' down in ground, and climbs about 4' to make it 12' head pressure. Chart says 18-20 gpm.
5 ton unit says 15-16 gpm and 6 ton 16-18 gpm. Question is: is running the pump at the higher range too much for the pump to handle?
And the other question of minimum temperature is 35.6 assuming their rating is with pure water, not antifreeze water solution. ??

LucMan

Re: Geothermal HVAC

GreenPowerManiac wrote: »

Not trying to insult anyone.

Would that be enough tonnage for the water heating and radiant floor?

And looked up the circulation pump Grundfos UP 26-96 F. Says up to 28gpm.
Got lines 8' down in ground, and climbs about 4' to make it 12' head pressure. Chart says 18-20 gpm.
5 ton unit says 15-16 gpm and 6 ton 16-18 gpm. Question is: is running the pump at the higher range too much for the pump to handle?
And the other question of minimum temperature is 35.6 assuming their rating is with pure water, not antifreeze water solution. ??

Your calculations for total head loss look way off! That pump may be OK for radiant but for the loop you will need a 1.5- 2 hp pump.

GreenPowerManiac

Re: Geothermal HVAC

Hmmm.....That pump works for my solar water heating just fine. About 20' head loss and 5 collectors. About 19 gallons total on that one.

There is a flow center for the unit which my contractor must order with the furnace. Maybe should let them work out the details.

When the lines are installed (laid and buried) must the lines be filled with fluid before buried or can they withstand the pressures of earth and be filled/purged from inside the basement ?

LucMan

Re: Geothermal HVAC

160 PSI poly pipe is pretty tough unless you drop a 100# bolder on it, it needs to be filled and purged after installation.
Hopefully your contractor will have 0 connections under ground. All connections should be made at a proper header in the basement for easy repair. 99% of leaks in ground loops are at the fittings. If you use a header system if a loop ever goes bad you can just disconnect the defective loop and continue using the system with a slight loss of capacity instead of digging up the loop looking for the damaged area (Not fun).
Calculate head by going to engineeringtoolbox.com

GreenPowerManiac

Re: Geothermal HVAC

Yes about the connections underground, understood. All connections with be heat fused with a new HDPE heat iron coming in the mail.

There will only be one supply and return pipe as far as the way it was described by this contractor. He wanted 1.25" 150' to fro and 3/4" lines in loop field. With all the head pressure losses, thought staying with 1.25" throughout to save on pump size. Heat transference would work better with more IPS size and saturated soil. Also thinking about lengthening the field another 600' to 3600' for 6 ton.

The only concern for a 6 ton unit when MJ says 5 ton, is that it has the HWG (hot water generator) and will not do two things at same time (according to specs). Water Furnace says the 6 ton CAN do both regardless of specification. Still skeptical about it cooling too quickly and short runs, and poor humidity control.