Quote:
Originally Posted by rhino 660
...one more question in your loopfield after the temp leveled out from running a few hrs there was a 10* rise in loopfield temp as i remember, so i was thinking if that happened in my system it would hurt my cop quite a bit. 70* rises to 80* although 80* is better than 90*-100* my boss had said something about this which had me second guess myself is all maybe i should put another 800' roll underground just to be safe i like over kill
|
I think you are referring to my initial borehole test. Yes, it was interesting that I never reached a 'balance point'.
There used to be a saying that, "a man can't have too much money or too fast a horse." I suppose the same can be said about loop fields. All things being equal, a bigger loop field will yield higher COP. The limiting factor is usually the cost of paying someone to install it for you. If you're doing it yourself, you might as well go for the gold.
My little loop field is much smaller than yours, it is yielding useful heat and the temperature has dropped (since I'm extracting heat). Originally, it started out as 51F and after running my little heat pump 24-7 for about three months, the temperature dropped to around 37F, give or take. Since I put the thermostat the loop temp has risen to the low forties. Part of that is due to the shorter duty cycle, part to the fact that the weather is getting warmer.
In actual practice, I wouldn't expect to extract heat continuously, and this is where I expect the insulation project I am doing to save my bacon.
I still have room to do some more boreholes, if I need to.
But if you have the equipment at your disposal, by all means trench away. It will take more gumption to come back later, trench & fill and patch into your existing field.
The cost of the HDPE is a pretty small part of the total project.
If you have three trenches in parallel, your pump motor power requirement will also be reduced, to obtain the same gpm/Ton. This alone will raise your COP.
There is a strategy to employ when you do your manifold, having to do with first-in, last-out, that will make your loops self-balancing. I'm quite sure your slinky book will give you info on this.
You'll also want to be mindful of potential dissimilar metals corroding due to galvanic action. The less expensive pumps are cast iron... if you don't have any other kind of metal in your loop (don't forget your heat exchanger), you are fine. If you have any brass, your pump will need to be brass or stainless. I think stainless & iron are ok, but you better double-check that one. I know that brass & stainless are ok together.
Since you are in Florida, no need to worry about antifreeze.
-AC_Hacker