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michael · 12-03-13, 06:02 PM

Originally Posted by AC_Hacker
"I talked with a local hydronic guy who told me that around here, feed water temperatures are:
80 to 85 degrees for tube in slab
100 to 110 for on top of floor heating
120 to 130 for below floor (AKA: staple up) heating"

First, a question: can someone explain what the terms "part load" vs. "full load" mean with regard to heat pump performance? I've been reading a PDF from roth-usa.com on their RWT Series Water-to-Water Heat Pumps, and in the performance data under the column titled "capacity," they list values for part and full load. Are they modulating heat pumps, or to what do the terms apply?

PEX tubing just arrived along with the manifolds, so things will be happening on the new house site very soon. Photos will follow.

A quote from quite a while back appeared and is re-quoted above, and the temperatures surprised me. In our current residence, the heating part of which has a 1.5" concrete slab and 1/2" ceramic tile with 1/2" polybutylene pipes at 6" centers, entering water is 110 degrees, and it returns to the heat exchanger at 85 degrees. I suppose entering temperatures (in the quote above at 80 to 85 degrees vs. our house at 110 degrees) depends a great deal on the pumping rate. I've been monitoring ours, and the water flows through the floor at the rate of 7 liters per minute (1.85 gpm). There are 2000 LF of tubing in the floor containing 23 gallons of water, so there's a complete change of water every 12 minutes or five times per hour, so 115 gallons of water could flow through the floor every hour if the pump ran continuously. At 115 gph and a 25 degree temperature drop, the set up could provide close to 24000 Btus per hour to the house. The house is 2000 SF; the central radiant portion is 1000 SF, and the rest is carpeted and unheated. In the weather we're having right now, the house is demanding 140K Btu per day, so the pump is running less than 6 hours per day. This is from data I've collected, not from heat loss calcs. The inside temperature is 70, and outside it is 65 during the day and 35 at night.

Heat loss calculations done in 1988 when we designed and built the house predicted a 32663 Btu per hour loss with an outside design temperature of 34 degrees. Just sayin'.

12-03-13, 06:02 PM	#344
michael Michael Join Date: Feb 2013 Location: mendocino, california Posts: 67 Thanks: 7 Thanked 2 Times in 2 Posts	Originally Posted by AC_Hacker "I talked with a local hydronic guy who told me that around here, feed water temperatures are: 80 to 85 degrees for tube in slab 100 to 110 for on top of floor heating 120 to 130 for below floor (AKA: staple up) heating" First, a question: can someone explain what the terms "part load" vs. "full load" mean with regard to heat pump performance? I've been reading a PDF from roth-usa.com on their RWT Series Water-to-Water Heat Pumps, and in the performance data under the column titled "capacity," they list values for part and full load. Are they modulating heat pumps, or to what do the terms apply? PEX tubing just arrived along with the manifolds, so things will be happening on the new house site very soon. Photos will follow. A quote from quite a while back appeared and is re-quoted above, and the temperatures surprised me. In our current residence, the heating part of which has a 1.5" concrete slab and 1/2" ceramic tile with 1/2" polybutylene pipes at 6" centers, entering water is 110 degrees, and it returns to the heat exchanger at 85 degrees. I suppose entering temperatures (in the quote above at 80 to 85 degrees vs. our house at 110 degrees) depends a great deal on the pumping rate. I've been monitoring ours, and the water flows through the floor at the rate of 7 liters per minute (1.85 gpm). There are 2000 LF of tubing in the floor containing 23 gallons of water, so there's a complete change of water every 12 minutes or five times per hour, so 115 gallons of water could flow through the floor every hour if the pump ran continuously. At 115 gph and a 25 degree temperature drop, the set up could provide close to 24000 Btus per hour to the house. The house is 2000 SF; the central radiant portion is 1000 SF, and the rest is carpeted and unheated. In the weather we're having right now, the house is demanding 140K Btu per day, so the pump is running less than 6 hours per day. This is from data I've collected, not from heat loss calcs. The inside temperature is 70, and outside it is 65 during the day and 35 at night. Heat loss calculations done in 1988 when we designed and built the house predicted a 32663 Btu per hour loss with an outside design temperature of 34 degrees. Just sayin'.