Carrier 3 ton, Infinity Geo - Trying to optimize our system to be as efficient as possible. I monitor the incoming/exiting water temps with sensors at the unit in the attic. Its not uncommon to see a swing in incoming water temps dependent on the weather outside. The 4 wells are 60 ft from where the pipes exit the house, only 36 inches down, but not insulated. I keep wondering if the 60 ft of uninsulated pipe is sapping efficiency by giving me warmer water in the summer and cooler water in the winter. It would be a chore, but I could insulate to the tops of the wells. What is everyone's thoughts?
What temp is EWT at it’s highest in summer? Lowest winter? May not be worth it if temps stay between 90F and 30F
My lines have an 80 ft run from my wells to where they enter the house, buried 4+ feet deep (frost line in 36" so minimum depth is 42") to get below the frost line. A friend of mine, who lives about 20 miles from me, has a very similar house (40k btu/hr heat loss to my 38k btu/hr heat loss) with an identical system installed by the same contractor. His wells are about 10-20 ft from where they enter the house. We both keep our houses at similar temperatures and have very similar EWT numbers, with mine generally be slightly higher. Our wells are the same depth (2 x 300 ft drilled by the same contractor). The only difference in our wells is that mine start in bedrock, while his go through about 15-20 ft of dirt/sand before hitting bedrock. Other than that, they are the same. We both monitor our systems with different monitors, but we regularly compare our numbers when it gets cold. Based on the above, my vote would be to not bother. You may be losing a little bit of heat, but its probably not enough to make any real difference. You are probably losing fractions of a degree in EWT, if anything, and keep in mind, that works both ways. In the winter, as your LWT piping is running through the ground, and the LWT gets low, it is probably picking up some heat before it enters the wells. I would think the opposite happens in the summer as the ground will be cooler than the LWT and the fluid will start shedding heat as it travels to the wells.
It's not standard practice to insulate the supply and return lines. They don't exchange very much heat with the ground, and certainly should not be influenced by the air temperature. Your EWT will be driven by the loop field. I don't think your EWT is varying due to outside air temperature. I expect it's varying due to increased usage of your heat pump. My supply and return lines have a 160' run to the loop field and are ~3' deep with no issues. It was 15 degrees outside this weekend (below the design temp for the area), the system has been running 24 hr/day, and my EWT is sitting at 40F.
We generally stay between 60 and 90, I think I just expected it to be a little less correlated with air temp/day night cycles. I appreciate everyone's input.
The thing is, when it’s colder outside the heat pump takes more heat from the ground, lowering your loop temp. When the weather warms up the heat pump doesn’t run as much leaving more time for the loop to get replenished.
I'm assuming the temperatures you are referring to being 60 to 90 degrees are your EWT and you are running primarily AC. I haven't had my monitor running in the summer, so can't speak from experience, but at least for heating I see a significant increase in EWT when the sun is out because the heating load on the house is reduced (solar gain of the house) and the ground is warmed up by the sun some small amount. I would expect something similar in AC, as the system works harder to cool the house and the ground temperature increases.
