Do AC units require both fuse and breaker?

[Jeff Greef]

A rooftop HVAC unit is replaced. The label says:
-Max fuse 90 amp
-Max breaker 90 amp
The old unit had a 125 amp breaker on it, and 125 amp fuses.

?-If the fuses are replaced with 90 amp, but the breaker is left at 125, does the installation meet NEC?

?-Does a fuse provide all the protection required for the unit, or does it only provide overload protection, and the breaker is required for protection of shorts and ground faults in the unit itself?

?-When the label says (as this one does)
-Max fuse 90 amp
-Max breaker 90 amp
does this mean that BOTH are required to be at that amperage, or only one or the other? The label never says....

JG

 

[mdshunk]

?-When the label says (as this one does)
-Max fuse 90 amp
-Max breaker 90 amp
does this mean that BOTH are required to be at that amperage, or only one or the other? The label never says....

No, just pick one or the other. Once in a blue moon, mainly on older equipment, you'll see different values for each overcurrent type. Other times, it'll just say one or the other, which means that one type is excluded from use.

 

[George Stolz]

Once in a blue moon, mainly on older equipment, you'll see different values for each overcurrent type.

I just got done wiring a new heat pump thingy (looks like an A/C to me!), and it had a 30A fuse / 25A breaker nameplate on it, or vice versa, I forget. First time I'd seen it though.

 

[Jim W in Tampa]

A rooftop HVAC unit is replaced. The label says:
-Max fuse 90 amp
-Max breaker 90 amp
The old unit had a 125 amp breaker on it, and 125 amp fuses.

?-If the fuses are replaced with 90 amp, but the breaker is left at 125, does the installation meet NEC?

?-Does a fuse provide all the protection required for the unit, or does it only provide overload protection, and the breaker is required for protection of shorts and ground faults in the unit itself?

?-When the label says (as this one does)
-Max fuse 90 amp
-Max breaker 90 amp
does this mean that BOTH are required to be at that amperage, or only one or the other? The label never says....

JG

Are the conductors good for 125 if so your fine

 

[stickboy1375]

I just got done wiring a new heat pump thingy (looks like an A/C to me!), and it had a 30A fuse / 25A breaker nameplate on it, or vice versa, I forget. First time I'd seen it though.

I heat pump basically is a AC unit, it just works in reverse...

 

[infinity]

?-If the fuses are replaced with 90 amp, but the breaker is left at 125, does the installation meet NEC?

Using 90 amp fuses would make this code compliant since the nameplate allows either fuses or a CB.

 

[Jeff Greef]

Thanks guys

Thanks guys

thanks guys

 

[acrwc10]

I would replace the less costly of the two , the fuses or the breaker. Just because some breakers can be pricey.