Daikin unit

[Indy]

Hi,
I have a question regarding a daikin REMQ16 unit and the manual says that the Rated load amps is only when the indoor temperature is 27’c dry bulb/19’c wetbulb and the outdoor temperature is 35’c dry bulb so does this mean that if the temperatures are out with this range then the unit will draw more current than the rated load amps ?

Thanks

 

[lukaiENG]

yes. Catalog data is a guide, You need to have your rep to run selections at design conditions.

 

[Indy]

Thanks for this. Just to be clear if the temperature outside is for example 18’c and the indoor temperature is say 22’c then the unit will operate with a higher current draw?

Thanks again

 

[moideen]

Indy :Current draw will be varied as per the outside air or condensing temperature. When outside air goes high the electrical consumption will go high and thermal capacity will come down and vice versa.

 

[IRstuff]

If it has to work harder, it will burn more power.

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[Indy]

Thanks for this but I’m still not 100% clear if the device has a RLA when the outside temperature is 35’c and the outside temperature is less than this then the unit will draw more current, is this correct? I assume if I take the MCA then this will be a worst case scenario.

Thanks

Thanks

 

[lukaiENG]

If the temperature outside is lower then the unit is not having to reject to as high of a heat sink (the ambient). This means it is not having to work as hard to change the properties of the refrigerant . This in turn means lower power at lower ambient temperatures.
Conversely, if the indoor temperature drops (or the outdoor temperature increases) the compressor has to work harder, and therefore use more power.

Basically, the bigger the temperature difference, the more work/power required to overcome it.

 

[Indy]

Got it thanks. The numbers for the daikin REMQ16 unit is it just the difference between those two eg rated load amps at a difference of 35’c-27’c.

Thanks again.

 

[lukaiENG]

I was really oversimplifying above. Don't expect linear changes if you change the deltaT. As I said in my first response, get selections from your rep

 

[lucaspenalva]

Always consider MCA and MFA for selecting cables and circuit breakers.

For expected power demand, use performance tables for worst case scenario.

 

[lukaiENG]

Good point above, but I wouldn't treat the catalog performance tables as worst case - these are just at common/standard design conditions which may be more or less stringent than the design need.
Always get a selection from your rep at your design conditions.

 

[Indy]

Thanks for the replies. So as the MCA is a worst case and switchgear/cabling should be designed to this current?

Thanks

 

[lucaspenalva]

Indy,

Yes. But your switchgear must be designed for lower than MFA.

Example:
MCA = 55A
MFA = 80A

Your cable must be designed for at least 55A.

And your switchgear must be designed for maximum 80A.

OBS.: ALWAYS design cable/switchgear for MCA and MFA, respectively.
NEVER for power input !
(That's what manufacturer requires)

Power input is useful for calculating building power demand.