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Balance Point

Balance Point. North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed. When the outside temperature is zero degrees this house loses 60,000 BTUs per hour. This is its heat loss. To keep the house 70 degrees, the heat pump must put out 60,000 BTUHs.

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Balance Point

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  1. Balance Point North Seattle Community College HVAC Program Instructor – Mark T. Weber, M.Ed.

  2. When the outside temperature is zero degrees this house loses 60,000 BTUs per hour. This is its heat loss. To keep the house 70 degrees, the heat pump must put out 60,000 BTUHs.

  3. When the outside temperature is zero degrees this house loses 60,000 BTUs per hour. This is its heat loss. To keep the house 70 degrees, the heat pump must put out 60,000 BTUHs. When it is 70 degrees outside and 70 degrees inside, there is no heat loss so we draw a straight line like this.

  4. Most heat loss calculations for the City of Seattle use a delta T of 50 degrees. You figure the heat loss as if it were 20 degrees out. For this house, the heat loss at 20 degrees is about 43,000 BTUH When it is 70 degrees outside and 70 degrees inside, there is no heat loss so we draw a straight line like this. For this house, we would use a 4- ton unit (48,000 BTUHs)

  5. Heat pumps are made to put out their maximum capacity at 47 degrees. (SEER 13) For this house, we would use a 4- ton unit (48,000 BTUHs)

  6. Heat pumps are made to put out their maximum capacity at 47 degrees. (SEER 13) A SEER 13 heat pumps’ output will be about like this. At 47 degrees it is putting out 48,000 BTUH. At zero degrees it is putting out 20,000 BTUH.

  7. Where the heat loss of the house and the output of the heat pump meet is called the balance point. A SEER 13 heat pump’s’ output will be about like this. At 47 degrees it is putting out 48,000 BTUH. At zero degrees it is putting out 24,000 BTUH.

  8. To meet the heat loss of the house the heat pump must be running 100% of the time. Where the heat loss of the house and the output of the heat pump meet is called the balance point. In this case, our balance point is about 26 degrees.

  9. As an installer, it is seldom you will know the balance point. If the salesperson did their job correctly, they would have figured the heat loss for the house and it would be on the installation paperwork. Good luck with that. When programming the thermostat, knowing the balance point is important. But, most of the time you just have to go with what you know from previous installations. Let’s take a look at a heat pump with electric auxiliary heat.

  10. This how I would program this thermostat 38 37 36 35 34 33 32 31 30 29 28 27 26 25 At 37 degrees I would lock out the auxiliary heat. So, no matter how much the thermostat is turned up, the auxiliary heat will not turn on. Between these two points, both the compressor and auxiliary heat can operate depending on the required rise in temp. Assumed balance point At 27 degrees, I would lock out the compressor. As long as the temp remains below this point, the compressor will not turn on and only the auxiliary heat will work.

  11. For more information please contact Mark T. Weber At North Seattle Community College WWW.NorthSeattle.edu Mark.weber@seattlecolleges.edu

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