Heap Pump Controls

[tmurray]

I know I am in the minority on the board coming from Canada, but I thought some one on here might have a better idea than me of what the intent of the following sentence is;

7) Heat pumps equipped with a programmable thermostat shall be equipped with setback controls that provide temporary suppression of electrical back-up or adaptive anticipation of the recovery point, in order to prevent the unit from resorting to supplementary heat at the time of recovery (see Appendix A).

A-9.36.3.6.(7)-1 Heat Pump Controls for Recovery from Setback. Several techniques of achieving this exist:

• separate exterior temperature sensor,

• gradual raising of the control point,

• controls that ‘learn’ when to start recovery from previous experience.



http://www.nationalcodes.nrc.gc.ca/eng/public_review/2012_1/pcfs/NBC10-DivB-09.36.03.01-07-add-HSB-EEB-Scope_Application_HVAC.pdf

The way I'm reading it is that the heat pump controls have to be able to decipher when it can use just the heat pump to bring the room temperature up after setback, or when it will actually require the electric furnace because the outside air is too cold.

Thanks

 

[Gregg Harris]

That would be correct, most of the new programmable T-stats have the ability to ad an outdoor stat to lock out the auxiliary heat during normal heating or coming out of set back. The high end "smart Tstats' will follow a PI algorithm that when coming out of set back it will measure the time and temperature recovery rate in 1/16th of a degree to determine if the next stage of heat is required to reach the set temperature in a maximum 90 minute recovery.