I have a Tectco 3 ton closed loop system. My flow rate is about 6 GPM. EWT is 40 and LWT is 35. Air return temp is about 66 and supply is 86-88 (delta 20-22). Are these numbers reasonable for this size unit? Appreciate any comments!
Re: EWT/LWT question 6 gpm x 5°F x 500 BTU/hr-gpm-°F = 15,000 BTU/hr extracted from the loop, plus another 5000 BTU/hr from the electric company (assuming a COP of 4), for a total of about 20k BTU/hr That sounds about right for a "3 ton" dual-speed unit running in stage1. For stage2 (or a single-speed unit), it should be around 30k-35k BTU/hr.
Re: EWT/LWT question Hey guys, Thanks for the replies! Based on Looby's formulas and finally finding the manufacturer's spec formula it looks like the unit is working within the lower spec range of air temp rise of 20-30 degrees (mine is 20-22). Output is around 36K BTU. I have tried to increase water flow and air flow but it only results in lower output temps. It seems the unit is operating as designed. Is there anyway to expand such a unit, like adding additional loops or is it limited by the compressor? Thanks again for the feedback!!
Re: EWT/LWT question Increasing air flow will lower lower output temps (delta T) Decreasing air flow will raise output temps. Your pretty much limited by unit capacity. Higher EWT (larger loop) will increase capacity slightly but not worth the investment. EWT of 40F is good for this time of year, although I don't know your location.
Re: EWT/LWT question Are you measuring return at a grill in the house or right at the unit's coil? Likewise with the supply side. A loss of 5+ degrees in the return or supply ductwork makes a big difference. It may be caused by uninsulated ducts in an unconditioned space or duct leaks. Your EWT and waterside delta Tee look good, so I'd be looking at the airside for any possible improvements.
Re: EWT/LWT question Engineer makes a good point, all air temps should be taken at the unit not the registers.
Re: EWT/LWT question Thanks Engineer. I am measuring air temp at the unit but I do think I have supply ducts that are uninsulated. Here's a crazy idea I had :idea: ; tell me what you think: My ground loops are (4) 600 foot loops for a total of 2400 ft. It seems that my 3 ton unit only would require 3 loops? If so, could I use the extra loop to supply a 1 ton unit at the other side of the the house? Right now, my current unit is at one end of the house and the supply ducts have to travel over 40 feet! Seems I could loose a lot of heat before it got to the far side.
Re: EWT/LWT question It's not so much the loop quantity; rather more about total ft. in the ground. Keeps loop temps higher in winter. You could but loop temps will drop due to more load. Measure temp at unit and register to see how much you are losing. I think I would a proper HE done on the unit by a quaified tech before making that decision.
Re: EWT/LWT question I'm a homeowner. If you have sufficient total loop for two appropriately sized units, you may be able to share one loop rather than separate the existing loop into two distinct loops. There may be advantages in doing this. For example, if one unit runs more than the other unit due to differences in thermostat settings or house orientation relative to the sun, the unit that runs more can take advantage of the larger overall loop. Are you sure about 2400 feet of loop? That seems like a lot of pipe for a 3 ton system (800'/ton). Horizontal or vertical? What is your closest major city? We have 600'/ton for a horizontal loop in VA. Probably oversized by 20% from what I understand, but it came in handy this cold winter (loop temp is currently 37-39f depending on load).
Re: EWT/LWT question Thanks Teetech and Geome. My loop size is definitely 2400 feet since I did the install myself (lots of fun). The ground type is very moist, I live North of Baltimore, MD in a deep valley. EWT is holding at 41 degrees. I'm going to shut off 1 loop and see how the current unit handles the change. Wish me luck!
Re: EWT/LWT question By the sound of it you must have an inside manifold. That makes for a sweet set up. I wish you luck!
I want to come look at you stuff It is a bad day if I do not learn something new. My kid lives inside the beltway. I may go see the cherry blossoms
