Heat strip sizing question
What is the correct way to size aux/emergency heat strips for residential geothermal heat pumps? Are there any code requirements?
Yes there can be code requirements. Sometimes code is that aux heat must cover the full heat load others have no requirements. I typically size to cover most if not the full heat load of the home since they are there as a backup only in most homes we design since I am in a mild climate. In other homes such as more northern climates often the heat strips are sized as auxilary so you can size your compressor to cooling load and then use heat strips to meet your heat load.
Example 1: Heat loss 66K BTUs Heat Gain 36,000 BTU's
House has a 3 ton geothermal that puts out 36K BTU's of cooling and 36,000 BTU's of heating(not real world conditions BTW) so heat strips are sized to provide the additional/auxiliary 30K BTU's of heating needed.
Example 2: Heat Loss 36K BTU Heat Gain 36,000 BTU's
House has 3 ton geothermal that puts out 36K and 36K for heating and cooling and has heat strips sized for 36K incase of a loop failure, pump failure or total system failure of some sort so the house can fully heat on heat strips in an emergency.
and a manual J of 80 degree design and zone and a manual J of 80 degree design and zone 6 and with th systems that have been with tw with two compressors small then large then both doing th small then large then both doing three staging we took the liberty of sizing for 5 and 10 below zero with a little larger loop because it matched the loads for coolingor heating more efficiently wasn't so ba since the next ti since the next Ton size was only a few hundred dollars and a little more loop
Backup heating has a few different philosophies then 1 then 10 kilowatts even in 60,000 BTU 60,000 BTU heat loads for 35000 be t for 35000 btus to allow our home to drop 10 degree
If I can say some average even still built homes of 3500 square feet
6000 to 7000 degree and 15 below zer might barely have 15 k n in a 20 to 25 kW requirement
Electric 60 to gt units 3 stage 100%
Only single speed systems such as corner consoles or other console units upflow Systems are size 75% to 85% of a manual j InZONE 5&6 but the ground loops are sized for 100 to 110 percent of the manual J
Last edited by GT1980; 11-28-2013 at 08:13 AM.
no strip heat at all and 120% gt worked
Also there are homes all over from the 70's that had 7 ton intent on geothermal in 3000 and 4000 square foot homes single compressor that no one in the north air conditionin air conditioning because of some two and three and maybe 5 weeks of cooling up by Lake
Last edited by GT1980; 11-28-2013 at 08:18 AM.
Reason: add 70's that had 7 ton intent on geothermal in 3000 and 4000 square foot homes single compressor that no one in the north air conditionin air conditioning because of some two and three and maybe 5