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#1 Posted : Saturday, December 13, 2008 3:53:32 AM
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Hey Jim,wow sounds like a nice heat transfer system you have..You're using methanol/water as a heat transfer medium,good choice!I think if you wanted you could also use ethanol/water too though I dont know if ethanol has any better/worse heat transfer capacities than methanol does.In some of our chilling equipemnt we build we have to use a proplyene glycol/water mix and I have to tell you the dayum glycol cuts the heat transfer down by a third at least...makes my life tough,lol.OK what are you using for refrigerant,r-134 or 404a? I hope 404a,you'll get better suction pressure(better heat transfer thru your evaporator/condenser) at lower ambients.Are you using Sporlan valves or Alco's?How many coils in your exchangers?Ya the lockouts are because of low suction pressure on cold days,this usually is because of r-134 having sucky heat transfer the lower pressures you get and thats why we use 404a or r 507.507's' extremely pricey though.Yes indeed,there's nothing wrong with putting in more capacity than you need,see most dont understand that if you put in a large condenser & evap.&if you have a small compressor  running the system,if you have the right ambient controls(and the right amount of refrigerant) for the compressor so it does'nt flood with liquid,you'll be fine.Makes it easier to up the compressor when you want to add xtra capacity to the system,it's already there..

Jim in Sherrard WV
#2 Posted : Saturday, December 13, 2008 1:56:01 PM
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using r-22, the methanol was a great choice, but I was going to add a solar panel to hybridize the loop, but methanol is not a good choice with solar. It would have been neat to see what could have been done with one panel of solar for temp boosting in the winter. Jim
#3 Posted : Sunday, December 14, 2008 3:20:16 AM
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Yes it would be;you know you could always add another exchanger between the water loop and the solar,throw a flatplate in to separate the methanol from the 50/50 mix in the panel,though that would cut down on transfer but you may be able to get away with a 70/30 mix or 80/20 in WV.

Ouch watch your r-22 level,I hear thru the grapevine the stuff's going to be awful hard to come by after this year ends..EPA's making it illegal to use in new installations after 2008 I thinkin it's going to get pricey too after this year..

Jim Duke
#4 Posted : Sunday, December 14, 2008 3:20:16 AM
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My wife and I started a geothermal do it yourself project about 4 years ago, we got it up and operational in July. Background info, 2200 feet 1.25" loop with 178 gallons of methanol mixture in a trench 5 feet deep by 1100 feet long. Most of my trench was clay, with springs. Two weeks ago a got my monitoring system installed, it is composed of two rtds on the incoming and outgoing lines. I live in WV and it has been a cold winter so far and what I have learned so far is worthy of being shared. My loop should be about 7 tons in capacity and my unit is a vt030 climate master with a hwg and copper nickel heat exchangers. The loop being more than double the size needed is in my opinion worth considering. My incoming temperatures have been between 43-45 degrees F depending on load. when its cold and the unit runs most of the time it runs 43 F. It warmed up for a two day spell to 50 F and the incoming loop ran at 45 F. All the geothermal people I have talked with consider 32-34 F good. At 30 F my system charts show the units capacity to make 18,700 BTUH heating and generate 1700 BTUH for hot water and have a system COP of 3.7. At 40 F the charts show 23,600 BTUH heating and 2100 BTUH hot water, and a system COP of 4.5. I have tested what happens if you shut off half the loop for one hour on a cold day, this resulted in a temp decrease of 3 degrees, when I restored the loop to normal the temp went back to 43 F. The capacity of the system I built and the unit have run flawlessly for us. I have talked to a lot of people that have had there systems for a while and some have had problems with compressor lockouts on very cold weeks. I would think because the loop runs out of capacity. I was even ask to go to court as an expert witness in a law suit over a 20 ton system that ran out of loop capacity. I hope this data can help. I always tell anyone investing into geothermal to put in extra capacity if they can, none have ever out of cost. I now have proof of the value of extra capacity. Jim
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