[Equest-users] Appendix G System 4 PSZ-HP Supplemental Electric Heat ( Section G3.1.3.1)

[Dan Russell]

My LEED baseline model is HVAC system type 4 - PSZ-HP and Section G3.1.3.1 states:

"Electric air-source heat pumps shall be modeled with electric auxiliary heat.  The systems shall be controlled with multistage space thermostats and an outdoor air thermostat wired to energize auxiliary heat only on the last thermostat stage and when outdoor air temperature is less than 40degF."

So, the auxiliary heat remains off until the heat pump can no longer do its job and is activated only if the OA temp is less than 40degF.  Is the intention to allow the heat pump to continue running simultaneously with the auxiliary heat?  Or, at the moment the heat pump can no longer handle the space heating requirement does it shut off and allow the auxiliary heat to do the entire job by itself?  If it is intended that both functions operate simultaneously is there an OA temperature limit where the heat pump should be turned off?

Does anyone have some insight as to what eQUEST is doing for the control sequence of this system type?  Is it meeting the criteria of this Appendix section inherently or do I need to fiddle with the values in the screenshot below to make it compliant?

The eQUEST heat pump supplemental heat window looks like this:

[cid:image003.jpg at 01CB2F3C.CF3BFF30]

There appears to be only two inputs:

*         Minimum HP Heat Temp (Turns heat pump off when OA temp is below this temperature.)

*         Maximum HP Supp Temp (OA temp at which supplemental heat becomes available.)

The latter, seems to match with the intended 40 deg OA setpoint specified in the Appendix G section above.
What's more unclear to me is how the Minimum HP Heat Temp input should be utilized.

Thanks,

Dan Russell
[cid:image001.png at 01CB2F39.542DCC40]

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20100729/c3046a06/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.png
Type: image/png
Size: 29839 bytes
Desc: image001.png
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20100729/c3046a06/attachment.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image003.jpg
Type: image/jpeg
Size: 32144 bytes
Desc: image003.jpg
URL: <http://lists.onebuilding.org/pipermail/equest-users-onebuilding.org/attachments/20100729/c3046a06/attachment.jpg>