Electrical load calculations with heating and cooling loads

[balddude]

When connecting a mechanical split system (outdoor compressor / indoor fan unit with electric heat), but is the best way represent this in the calculations? Since they won't be operating at the same time, the overall electrical service size doesn't need to have both loads, but both loads need to be accounted for at the panel level.

[fabiosato]

Hello,

You have do create a load classification that uses and appropriate demand factor to estimate the actual load.

[dyp4f]

Regarding split A/C units, Cooling and Heating loads should not be both registered independently, because split units work either in cooling mode or in heating mode.

• You have to register the load as a unique “A/C Load” = 12816 VA, in one single row
• You have to keep the demand factor to 100%

In real split units though, the nominal cooling load is not the same as the nominal heating load.

Look at manufacturers catalogs.

In such a typical case, you register as “A/C Load” the bigger of the two loads.

[balddude]

To explain the issue a little further,...

Usually the outdoor unit and the indoor units are connected to different panelboards. Therefore, each panelboard (and the associated feeder) need to have the load taken into account.

However, at the distribution panel, only one of the loads (the larger of the two) needs to be accounted for.