Maximum Breaker Size

[James A]

I looked at a customer's pool equipment and am not sure I have come to the right conclusion if anybody knows for sure a little help would be nice.
1st off all the pool equipment is fed from a sub-panel that is piped to the main panel and a set of #6THHN conductors are terminated on a 2 pole 60a breaker.
Heat Pump 37a (the largest)
+ 125% = 46.25a (as per 430.24 conductors feeding several motors)
1 1/2hp pump= 7.8a
.5hp blower 120v= 8a
For a grand total of 62.05a which trips the breaker and it should.
If 310.16 says that #6THHN @75Degree's C has an ampacity of 65a and that is not a standand circuit breaker(240.6) can I legally breaker this circuit with a 70a breaker?

 

[augie47]

I looked at a customer's pool equipment and am not sure I have come to the right conclusion if anybody knows for sure a little help would be nice.
1st off all the pool equipment is fed from a sub-panel that is piped to the main panel and a set of #6THHN conductors are terminated on a 2 pole 60a breaker.
Heat Pump 37a (the largest)
+ 125% = 46.25a (as per 430.24 conductors feeding several motors)

what is the 37 amps ? Is the RLA or is it the MCA ?
If it's MCA there is no need to add the 25%

1 1/2hp pump= 7.8a
.5hp blower 120v= 8a

By Code you should use the values in Table 430.248, not nameplate

For a grand total of 62.05a which trips the breaker and it should.
If 310.16 says that #6THHN @75Degree's C has an ampacity of 65a and that is not a standand circuit breaker(240.6) can I legally breaker this circuit with a 70a breaker?

If your calculated load is 65 amps or less, you can legally use a 70 amp breaker

 

[chris kennedy]

What Gus asked.

 

[bob]

Are you saying that you connected the pool pump to the 60 amp Heat Pump breaker? The actual load is

Heat Pump 37a
1 1/2hp pump= 7.8a
.5hp blower 120v= 8a
For a grand total of 45 amps not 62 amps.

45 amps will not trip the breaker but the starting of the Heat Pump or the 1 1/2 HP might if all of the other load is on.

As far as changing the 60 amp breaker, the name plate on the Heat Pump should have the Max OC device allowed and it might be 60 amps.

 

[James A]

I didn't actually connect anything it's an existing installation all the current readings are off my amprobe which matches the nameplates of the equipment

 

[James A]

War Eagle! Bob, 37+7.8+8=52.8 which is over 80% of a 60a breaker

 

[James A]

The nameplate on heat pump max overcurrent size is a 60a but it's fed with a 50 from the sub-panel and is not the breaker thats tripping.

 

[James A]

37 is the RLA off the name plate and the actual current the equipment it's drawing.

 

[benaround]

James,

I think conductor size and load calc are being mixed together in your o.p.. IMO, the heat

pump needs to be 125% for largest motor, and the pump & blower needs to be 125% for

continious load. That would be 37+8+7.5=52.5 , 52.5*125%=65.62 amps, this would be the

starting point for sizing the conductors not the breaker, #6 is too small.

 

[augie47]

If 37 is your RLA, using that plus the motor FLA from 430.248 I get 66 amps. (37 x 1.25 + 10 + 9.8)
That, of course, makes your #6 slighly undersized,
If you read 440.22 you will find that your OCP can be 175% of the largest
+ sum of the other RLA so you could go to an 80 amp breaker based on loads.
Since you need to increase your #6 to a #4 you could then go to a 90 amp breaker anyway.

 

[klrogers2]

I
1st off all the pool equipment is fed from a sub-panel that is piped to the main panel and a set of #6THHN conductors are terminated on a 2 pole 60a breaker.

Surely this is a sub panel feeder question, the amp draw of the heat pump and other loads are somewhat mute.

Kevin

 

[Dennis Alwon]

Forget about calculations and put an amp meter on the sub panel.