Thanks for your reply, so if I understood what you wrote this is how it should be:
Single family
Standard: Largest motor X 1.25
Optional: Nameplate
Multifamily
individual unit within building
Standard: Largest motor X 1.25
Optional: Nameplate
For all building
Standard: Largest motor X 1.25
Optional: Nameplate
is it true?
also, (in red above) if largest motor is heat ill have to calculate Largest motor X 1.25 in all options?
Thank you
As I interpret it, the selection of Nameplate under optional will apply unless
both of the following are true:
1. The largest motor is the one in the AC,
AND
2. The heating load was used in the general calculation (one of the heating lines was used instead of one of the A/C lines of the six options shown specifically under Heating and Air Conditioning). [
emphasis is mine]
Heating and Air Conditioning
The largest heating and air-conditioning load must be chosen from six options:
100 percent of the nameplate rating of the air conditioning and cooling
100 percent of the nameplate rating of the heat pump when it is used with no supplemental electric heating
100 percent of the nameplate rating of the heat pump compressor and 65 percent of the supplemental electric heating for central electric space-heating systems (If the heat pump compressor is prevented from operating at the same time as the supplementary heat, it does not need to be added to the supplementary heat for the total central space heating load.)
65 percent of the nameplate rating(s) of electric space heating if less than four separately controlled units
40 percent of the nameplate ratings of electric space heating if four or more separately controlled units
100 percent of the nameplate ratings of electric thermal storage and other heating systems where the usual load is expected to be continuous at the full nameplate value.
You avoid having to add 25% to the A/C motor load because it will be intermittent rather than continuous and yet you are adding it in at full value rather than applying the demand factor to it as part of the General Load total. IMHO, YMMV
PS: If the largest motor load is the heater (heat pump), then you do
not have to add an additional 25% to it, based again on the special rule for Heating and Air Conditioning. You have again added the heat pump motor in at full nameplate rating instead of adding it the General Load where it would be reduced by the demand factor.
And there is no provision telling you to add 25% of the
second largest motor load instead if the largest one is in Heating and A/C.
