Calculation Of Heat Generated By Control Panel Elements

The manufacturer's catalogues give these values usually. Here are a couple of samples from ABB....

They are measured, not calculable usually. Lots of experimental data is always available with good manufacturers.

Maybe with new Thermal FEA software, one can perhaps calculate, but in my days, we did not achieve any high level of confidence in the calculation.

Please remember, manufacturers give pessimistic values. Actual wattloss figures are likely to be lower.

i think you need to give more information.

What is the AC (i assume you mean an airconditioner) supposed to cool...the whole control room? or the control panel?

For the purpose of deciding the AC, you say you need the wattloss figures of components used in the panel. Why? And, what about busbars, enclosure class(IPxx) etc. ?

Details, with proper punctuation, will help.

Calculate the power flowing into the panel and the power flowing out. Subtract one from the other and that figure will be the power dissipated within it.

Air conditioning is to provide comfort control.

Cooling is provided by increasing the ventilation, perhaps using (a) fan(s).

In either case, basic data such as the local ambient atmospheric conditions is a cornerstone to the sizing!

http://www.engineeringtoolbox.com/indoor-temperature-humidity-d_114.html

No-one can answer the question without knowing the resistance of the contactor coil.

The calculation can be done right now!

• Power dissipated is the voltage squared divided by the load resistance.

As an order-of-magnitude first estimate, take the incoming voltage and multiply it by the panel's measured current.

Do the same for the power leaving the panel to various loads. The difference is the power dissipated.

The Switchboard/MCC/Control panel manufacturer should calculate and provide ventilation facilities for his panel considering ambient conditions.

http://cr4.globalspec.com/thread/71067#newcomments

Schneider Climasys

go to download documents & then download the software...

or go here schneider enclosures

i think these should help u out assuming you are asking about cooling the panel and not the entire room.....and why do u want to provide AC ? ventilation Fans are enough for control panels.

Quickest way is to assume the worst case and provide enough cooling to take care of it.

If you have a control power transformer or DC power supply, ASSUME that 100% of the rated capacity of that device is turning into heat INSIDE of the control panel. The only thing that would not be is anything that the control circuit is powering that is OUTSIDE, such as solenoids or external sub-control assemblies. So if you have a 1000VA CPT and nothing being powered outside of the panel, you ASSume that you have 1000W of heat rejection inside. Might be overkill because rarely are CPTs fully loaded, but it's a safe bet for A/C sizing. Alternatively if you use line power for your controls look up the data on each and every coil or power supply or pilot light in the panel and look at the watts consumption or rating. Again, 100% of that energy is going into the control panel in one form or another.

Then look at the power devices such as contactors, switches and circuit breakers and ASSume 0.1% voltage drop across each of the power contacts, anything more and the mfrs are in trouble (the value should always be in milivolts). Then calculate the resistance that represents and using your expected line voltage, calculate the worst case watts loss that represents.

If you have circuit breakers or overload Relays that have bi-metal thermal sensing elements, they are figured at 9W per phase each, that's the maximum design allowances for manufacturers, anything more and they get in trouble with regards to component sizing. If you use solid state OLs or CBs, don't count them, no heat losses to speak of.

If you have VFDs or other types of drives, assume 3% of the max power rating of the drive as heat rejection into the box. So if it is a 10kW VFD, assume 300W of heat rejection.

If you have a soft starter or other SCR based power device WITHOUT a bypass contactor, assume 4W per running load amp per phase; with a bypass contactor, assume it is the same as any contactor per the above.

If it is anything big enough to have bus bars, most likely it's a switchboard or Motor Control center, and the mfr will have guidelines on determining heat rejection.