Pool Controller AIC rating

[bphgravity]

Pool control panels are very popular around here. They usually consist of a timer, some relays and switches, a transformer, and a small panelboard. All your pool power and control needs in one package.

My concern is in regard to when pool heating equipment is served from this controller panel. One in particular has a 100A rated bus and a 5,000 AIC rating. The heater supplied from this panel is a 240V, 38A RLC heat pump. The branch circuit to this heat pump is about 7' long and consists of 2-#8 awg and 1-10 awg EGC, and is protected by a 50A breaker. (10,000 AIC rated)

What is the potential the AIC rating of the panel will be exceeded with this installation? What characteristics are calculations can be performed to determine the available fault current the heater unit may provide?

 

[pierre]

Re: Pool Controller AIC rating

Bryan

Typically dwellings are supplied from the utility with fault current in the neighborhood of 3-6,000 amps. Remember, I mentioned this is in general.
Depending on the location of the panel (distance from transformer supplying the building) there may be enough impedance in the feeder that the fault current will be well below 5,000 amps. Of course this can be calculated, but in general I think this would be a safe installation in regards to AIC ratings.

 

[bphgravity]

Re: Pool Controller AIC rating

Florida Power and Light will only guaranty to limit the AFC to 10,000 A for residential services. However, like you state, it could be much less.

On the same line of questioning. Lets say I have a commercial occupancy where the AFC is calculated at 10,200 A at the line side of the unit panelboard. This panel is fed from a main disconnect where the line side AFC is calculated at 26,500 A. Standard 10,000 AIC rated equipment and breakers are installed for this occupancy.

Are there any problems here?

 

[ron]

Re: Pool Controller AIC rating

Brian,
Calculations for fault current are the responsibility of the designer. If you are the designer, and you feel that the calculated fault current with all appropriate impedances and source total 10,200A, then you should go up to the next higher AIC rating for that equipment.
Many fault calculations do not include all impedances, and must be interpreted by the designer and/or AHJ to determine a close call.

 

[LarryFine]

Re: Pool Controller AIC rating

Bryan, there are several free fault-current calculators available on-line, some are free trials. Do a search for "fault current calculator".

To do a calculation, you need some info from the POCO: the available fault current and impedance of the supplying transformer and the service cable type, size, and length.

Then, you need the feeder info: again, cable type, size, and length. Each piece of equipment along the way must have the capacity the calculations show for that point in the chain.

[ December 03, 2005, 12:35 PM: Message edited by: LarryFine ]