Protection for two air conditioners is questionable

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Vic9319

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I have an old office where the protection for two air conditioners is questionable. The air conditioners help to reduce the temperature of a computing system installed into a small cabinet. There is no much room in the cabinet for additional equipment. These air conditioners don't have independent protection, but they both are connected to a terminal strip and the terminal strip is connected to a 20 A two pole 120/240 breaker. The length between the terminal strip and the breaker in the panel board is 12 feet. I normally see each air conditioner unit with its own individual max breaker and disconnect. They are having air conditioner issues so professionals are already going to be recommended. I would appreciate others insight and opinion as to this situation. Thank you

Background: The air conditioner units are installed on each door of the cabinet. Each unit has internally a 15 A class T fuse, works at 208 VAC phase-phase, but it is rated to work at 230 VAC on the label, and the load is: 5 A nominal current and 10 A starting current. Wiring conductor is # 12 AWG THHN/THWN copper stranded.
 
Are they part of a UL 508A control cabinet?
Is there a label with the amps and max over current protection size?
Is it possible to install one larger AC?
 
Sounds okay to me as far as overcurrent protection goes. I don't see anything in what you're describing that would make me think that the wiring is a problem other than the possibility that running on 208 volts is not especially good for them as they're rated at 230 volts. But often such things are rated to work at both voltages and will work fine. I don't understand the part about nominal current 5 amps and starting current 10 amps either. Where did that come from? I would expect more starting current than that if the running current was 5 amp.
 
Welcome to the forum. (Where in VA?)

Vic9319 said:
These air conditioners don't have independent protection, but they both are connected to a terminal strip and the terminal strip is connected to a 20 A two pole 120/240 breaker.
Click to expand...
Is this part of a factory assembly, or thrown together in the field?

They are having air conditioner issues so professionals are already going to be recommended.
Click to expand...
What are the issues?
 
petersonra said:
Sounds okay to me as far as overcurrent protection goes. I don't see anything in what you're describing that would make me think that the wiring is a problem other than the possibility that running on 208 volts is not especially good for them as they're rated at 230 volts. But often such things are rated to work at both voltages and will work fine. I don't understand the part about nominal current 5 amps and starting current 10 amps either. Where did that come from? I would expect more starting current than that if the running current was 5 amp.
Click to expand...

I agree this needs investigation. Single-rated 230V (motorized) equipment can experience problems when operated on a 208V system, especially if the voltage is a bit low.
 
tom baker said:
Are they part of a UL 508A control cabinet?
Is there a label with the amps and max over current protection size?
Is it possible to install one larger AC?
Click to expand...
The air conditioners are not part of a UL 508A control cabinet. No label with the max amps for wires and max overcurrent external protection size. No possibilities to install one larger unit.
 
petersonra said:
Sounds okay to me as far as overcurrent protection goes. I don't see anything in what you're describing that would make me think that the wiring is a problem other than the possibility that running on 208 volts is not especially good for them as they're rated at 230 volts. But often such things are rated to work at both voltages and will work fine. I don't understand the part about nominal current 5 amps and starting current 10 amps either. Where did that come from? I would expect more starting current than that if the running current was 5 amp.
Click to expand...
Starting and nominal current readings were performed on each unit with a clam amperemeter.
 
Vic9319 said:
Starting and nominal current readings were performed on each unit with a clam amperemeter.
Click to expand...
Normal digital ammeter readings are averaged so you won't see the actual starting current unless your meter has a peak reading function. The peak starting current only lasts a very short period of time so it gets buried in the average.
 
I don't see an issue either-- 5 amps each... 10 amps x 125% of one is 11.25 amps.

Only concern may be if they have overload protection or whether they need it. 15 amp fuse is higher than the usually175% of the FLA
 
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