Air handlers - once again

[tonype]

New Home - has 5 air handlers - each lists max. OCPD of 15 amps (220 volt).

All are connected to one 20-amp breaker. Putting aside the obvious problem of an over-sized breaker, is there any limit as to how many air handlers can be on one circuit?

 

[chris kennedy]

New Home - has 5 air handlers - each lists max. OCPD of 15 amps (220 volt).

All are connected to one 20-amp breaker.

Yup, violation of 422.11(A)

Putting aside the obvious problem of an over-sized breaker, is there any limit as to how many air handlers can be on one circuit?

I would be looking at 210.23 and 430.24.

 

[kwired]

what is the rating(s) of the air handlers?

If anything they can be fed from one feeder and have overcurrent protection at the unit disconnect.

 

[LarryFine]

All are connected to one 20-amp breaker.

Whose idea was that?

 

[Jim W in Tampa]

Are there no heat strips or are they gas for heat ?
If 15 is max then the 20 needs replaced.
Even if legal your asking for a problem if all 5 start at same time after a blackout.
Perhaps install a sub panel 10 circuit and feed it with a 50 if problem is breaker space.

 

[tonype]

Are there no heat strips or are they gas for heat ?
If 15 is max then the 20 needs replaced.
.

Just a plain vanilla a/h - heating is from a boiler

 

[tonype]

what is the rating(s) of the air handlers?

If anything they can be fed from one feeder and have overcurrent protection at the unit disconnect.

Unfortunately, a photo I took was blurred - I think the ratings were 3 to 4 amps each (a/h's were for systems 2 1/2 to 5 tons).

 

[Jim W in Tampa]

Just a plain vanilla a/h - heating is from a boiler

OK but the 20 amp is still over the 15 max. Concern is the start up amps we would need to know the running amps per unit. And we must figure them in as continuous load so that is 125%
help us out a bit, why would you do it this way ?

 

[augie47]

As long as you meet the requirement for max OCP, there is no limit other than the obvious need to allow for starting current, etc.
If you happen to have (5) units that had a FLA of 2 amps and they would operate on a 15 amp breaker, it would be allowable.
The 20, would not be allowed for any (1) through (5) as it exceeds the mfg. limit (unless you had independent OCP at each unit)

 

[kwired]

If they have ECM motors the starting current will not cause problems, not that this justifies an improper install.

As I said before overcurrent device at each unit may be acceptable. Anything ahead of that is a feeder. If the calculated load for the feeder is less than 20 amps then there is no code violation.

 

[Jim W in Tampa]

Unfortunately, a photo I took was blurred - I think the ratings were 3 to 4 amps each (a/h's were for systems 2 1/2 to 5 tons).

Then yes 3 to 4 is normal. Now we are looking at 5 x 3= 15
or 15 or 5x4 =20 and that won't work on 15 amp breaker. I believe you will need to do them at 125 %
Having hard time understanding why with this much invested in AC that we would get to cheap to run dedicated circuits to each unit. You might get by with 3 of them on 1 circuit but this looks like a hack job.

 

[kwired]

I believe you will need to do them at 125 %

125% of largest plus 100% of the rest. 430.24 For sizing the feeder overcurrent device see 430.62(A)

If done properly you could have calculated load of 20 amps or less and overcurrent device that calculates to over 20 amps and still install a 12AWG feeder. Each individual unit of course will need a 15 amp or smaller overcurrent device.

Just because you don't like it or have not seen it before does not make it wrong.

 

[Jim W in Tampa]

125% of largest plus 100% of the rest. 430.24 For sizing the feeder overcurrent device see 430.62(A)

If done properly you could have calculated load of 20 amps or less and overcurrent device that calculates to over 20 amps and still install a 12AWG feeder. Each individual unit of course will need a 15 amp or smaller overcurrent device.

Just because you don't like it or have not seen it before does not make it wrong.

If its going straight to the disconnects then it is not a feeder.

 

[chris kennedy]

If its going straight to the disconnects then it is not a feeder.

If the disco has OCP its a feeder.

 

[tonype]

If the disco has OCP its a feeder.

Each a/h only had a switch - no OCPD

 

[Jim W in Tampa]

Each a/h only had a switch - no OCPD

exactly my point, so it is a branch circuit not feeder. You will need a disconnect for each. Might still be worth while idea if you install ones that have a breaker. Cost differance might only be $10. I would suggest running something bit larger if you do take this route.
Is there a reason behind your not wanting dedicated breakers ? It is legal if done right but leaves customer with a problem if 1 of the units has a problem or develops a short. They will not thank you for shutting all 5 down without a trip to attic to shut the defective one down.

Just noticed that this sounds like already is installed. Would change switch to breakers.

 

[tonype]

Just noticed that this sounds like already is installed. Would change switch to breakers.

Jim: You are correct - all the stuff I see has already been installed by others (I am just an Engineer). Thanks for the input - I have learned more on this site than I could ever have by any other means!

 

[kwired]

exactly my point, so it is a branch circuit not feeder. You will need a disconnect for each. Might still be worth while idea if you install ones that have a breaker. Cost differance might only be $10. I would suggest running something bit larger if you do take this route.
Is there a reason behind your not wanting dedicated breakers ? It is legal if done right but leaves customer with a problem if 1 of the units has a problem or develops a short. They will not thank you for shutting all 5 down without a trip to attic to shut the defective one down.

Just noticed that this sounds like already is installed. Would change switch to breakers.

I don't claim that it is necessarily a good design, but if done right is an option that will meet code, that is what we are about on this site.

There are things that could be done to have similar install and make it a better design, like selecting branch circuit overcurrent devices that will likely open faster than the feeder overcurrent device.

 

[Dennis Alwon]

Hold on --- doesn'y 422.12 come into play. It's an air handler but it is for central heat.

422.12 Central Heating Equipment.
Central heating equipment other than fixed electric space-heating equipment shall be supplied by an individual branch circuit.
Exception No. 1: Auxiliary equipment, such as a pump, valve, humidifier, or electrostatic air cleaner directly associated with the heating equipment, shall be permitted to be connected to the same branch circuit.
Exception No. 2: Permanently connected air-conditioning equipment shall be permitted to be connected to the same branch circuit.

 

[A/A Fuel GTX]

Hold on --- doesn'y 422.12 come into play. It's an air handler but it is for central heat.

I agree.........the air handlers I see are part of a central heating/cooling system and I say each AH needs its own dedicated branch circuit.