project super

[project super]

what is the calculation for getting the amp draw from a 35kw A/H

 

[infinity]

What is a 35 kw A/H? Phase?

 

[Ingenieur]

what is the calculation for getting the amp draw from a 35kw A/H

A/H air handler?
most have a nameplate with required ckt ampacity and ckt protection

heater?

either way

need voltage and phase

 

[project super]

project super

3 phase
208

 

[project super]

project super

wouldnt I just divide my kw by the voltage

 

[jumper]

what is the calculation for getting the amp draw from a 35kw A/H

Roughly: kW is smaller or equal to kVA.

kVA = V x A
kW = V x A x PF, power factor.

So assuming a good PF, .9 or greater, kW/V/PF = ~A

Best is get info off nameplate or spec sheet.

 

[Ingenieur]

3 phase
208

The amp draw (not code ckt requirements)

35000/(1.732 x 208) = 98 A

 

[infinity]

35000/208/1.73=97.27 but all of the pertinent info should be on the nameplate.

 

[jumper]

3 phase
208

wouldnt I just divide my kw by the voltage

3 phase. Multiply Voltage x 1.732

 

[project super]

Project super

Project super

I am having to design build with only a kw rating

 

[jumper]

I am having to design build with only a kw rating

Well, you are gonna need the MCA and MOCD info at some point and that is on the nameplate/spec sheet.

 

[project super]

project super

thanks guys, yall are amazing
love this forum

 

[iwire]

Well, you are gonna need the MCA and MOCD info at some point and that is on the nameplate/spec sheet.

A lot of unit heaters only provide voltage and KW.

You need to calculate it in the feild.

 

[Sahib]

A lot of unit heaters only provide voltage and KW.

You need to calculate it in the feild.

For combination type load such as air conditioner having motors of different sizes, it may not be possible to calculate such as MCA in the field.

 

[Besoeker]

A/H air handler?
most have a nameplate with required ckt ampacity and ckt protection

heater?

either way

need voltage and phase

Voltage, number of phases and power factor. Efficiency would be good too.

 

[jumper]

A lot of unit heaters only provide voltage and KW.

You need to calculate it in the feild.

Are you referring to the various strip heat packages that may be available for a AHU?

If so yeah, those would be voltage and kW only.

I have just have never been told to size wire and breaker for a total unit (fan motor, dampers, heat, etc) and just given kW and volts.

 

[Ingenieur]

Are you referring to the various strip heat packages that may be available for a AHU?

If so yeah, those would be voltage and kW only.

I have just have never been told to size wire and breaker for a total unit (fan motor, dampers, heat, etc) and just given kW and volts.

I have
sometimes in a bid with public money the mfgr is not spec'ed
must be open bid, sometimes a basis of design
cfm, tons clg, kw htg, etc
I would pick the a unit that met demand
calc the kva from mca and throw 10-15% at it
on the panel schedule AHU kva would be listed
never got bit
usually had to size down, no cost impact (in fact back pocket credit)

 

[ActionDave]

Are you referring to the various strip heat packages that may be available for a AHU?

If so yeah, those would be voltage and kW only.

I have just have never been told to size wire and breaker for a total unit (fan motor, dampers, heat, etc) and just given kW and volts.

A unit heater is a stand alone heater with a small fan. The only rating given is the kw.

 

[Besoeker]

A unit heater is a stand alone heater with a small fan. The only rating given is the kw.

View attachment 16843

Is that kW in or kW out?

 

[ActionDave]

Is that kW in or kW out?

Kw in, heat out.