GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Heat Loss vs Heat Pump Ratings

Rob Shuman | Posted in Energy Efficiency and Durability on

Given an estimated heat loss rate, how should the listed capacities for heat pumps be used to select a unit that is capable of meeting my heating needs.

For instance, given a heat loss rate of 18,000 BTU/h for a house where the design temperature is 1 deg F, should I ensure the maximum capacity of a given heat pump at a temp close to my design temp, say -5 deg F, is approximately equal to the estimated heat loss? Or is that approach too conservative (given the small probability of those temps occurring) and likely to cause me to oversize the unit? And if it is too conservative, what are some reasonable alternatives. 

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.

Replies

  1. Jon R | | #1

    Your operating cost won't go up much if the heat pump doesn't quite meet the Manual J load and you use supplemental resistance heat to make up the difference.

    On the other hand, fully meeting Manual J load (at design temp) or slightly exceeding it per Manual S isn't "over-sized", at least for heating.

    In either case, you are likely to have problems if the heat pump shuts off from being too cold (below design temp). Or even if output drops significantly - such weather happens, sometimes for extended periods. Consider 100% backup heat.

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |