To fuse or not to fuse

[titan1021]

I relocated this transformer setup for a client that owns a pressure washer sales and service business. They use the plugs on these transformers to power various pressure washers that they service. They have been using this setup for years, and just recently some tech they hired is insisting that the 60amp 460v receptacle on the right should be fused down to 30amp as most of the units they test are max of 30amps. He even thinks that the fuses should be changed to match whatever unit they are testing at the time, however this would be a bad idea to expect employees to remember the steps needed to do so safely.
His concern is that if the unit pulls too many amps it would be damaged before the breaker feeding the transformer trips.
This seems highly unlikely to me and I believe the pressure washer would have there own fuses for such circumstances.

Anyone have any thoughts on this?

Thanks

 

[Coppersmith]

Usually the receptacle maximum amperage is what the receptacle is fused at regardless of the equipment plugged in except in the case of a dedicated piece of equipment. It's the wires from the OCPD to the receptacle that are being protected. However, it would not be difficult to have several extra receptacles fused at various sizes to accommodate the various equipment. Just a training issue for the staff.

 

[pjones]

I relocated this transformer setup for a client that owns a pressure washer sales and service business. They use the plugs on these transformers to power various pressure washers that they service. They have been using this setup for years, and just recently some tech they hired is insisting that the 60amp 460v receptacle on the right should be fused down to 30amp as most of the units they test are max of 30amps. He even thinks that the fuses should be changed to match whatever unit they are testing at the time, however this would be a bad idea to expect employees to remember the steps needed to do so safely.
His concern is that if the unit pulls too many amps it would be damaged before the breaker feeding the transformer trips.
This seems highly unlikely to me and I believe the pressure washer would have there own fuses for such circumstances.

Anyone have any thoughts on this?

Thanks

When you say they are concerned that the “unit” will pull to many amps and fail before the circuit breaker trips I’m assuming the unit you are referring to is the pressure washer and not the transformer.

If they are worried about the transformer then fuse the transformer to protect it at its rated VA. No need to adjust the fuses each time.

If the unit you are talking about is the pressure washer then install a digital amperage readout for each test receptacle. The worker can monitor the amperage as they try it and turn it off themselves if they see a need for concern. I think if they fuse it for the FLA of the motor then they will be replacing a lot of fuses because sometimes the inrush current on those can be quite high and be quite slow to start. Let the circuit breaker protect the wires on the circuit and the receptacle. It was never designed to protect the equipment.

The pressure washer motor should have a thermal safety on it ( may not be resettable) or a built in circuit breaker or fuse integral to its design. It should trip on those before needing to rely on an additional fuse.

Without knowing exactly what their scope of work is on a day to day basis it’s hard to really make a perfect judgment as to weather or not it would be beneficial to them, but from the outside looking in it seems like a wasted bit of money to me.


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[pjones]

Wait, is that just a single outlet off of each of those? Or do those feed a row of bench outlets?


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[titan1021]

Wait, is that just a single outlet off of each of those? Or do those feed a row of bench outlets?

Yes, there is a single outlet on each transformer. They change the cord ends on the pressure washers that come into the shop accordingly to match the plug and power source they need. Good call on the inrush.



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[petersonra]

no reason you cannot add several different rated receptacles with different rated OCPD on the same circuit so they can just plug it in to the appropriate receptacle.

 

[steve66]

no reason you cannot add several different rated receptacles with different rated OCPD on the same circuit so they can just plug it in to the appropriate receptacle.

That would also be my suggestion. I agree with the comment that the pressure washer should be protected per its rating, or at least per the rating of branch circuit allowed for ts attached cord and plug.

Since I assume you can't predict the MOCP rating for every pressure washer they might service, I would refer to table 210.21(B)(3) and provide receptacle ratings listed connected to the circuit ratings listed. For example, you could put both a 15A and 20A receptacle on a 20A circuit. And you can put both a 40 and 50A receptacle on a 40A circuit. But a 30A receptacle has to be on a 30A circuit. And a 60A circuit requires a 60A receptacle.