[emassey]

There is a machine which requires both 480V and 110V for operation. Maintenance has been asked to bring both 480V and 110V into one panel rather than setting up a step down transformer. Is this safe or permissible?

[KISS]

Panel may be somewhat of a misnomer. Bringing the HV and the LV to 2 separate lockable disconnects near the machine makes sense. From those disconnects they can enter the machine.


I believe that's noting unusual, typically you can have 3 phase motors powered from a 3 phase panel and 120 coming from a 120 V panel.

The kicker is the disconnect(s). Those, I beliive, have to be located very close to one another and clearly labeled. The equipment also needs to be lableled that it' powered from two power sources.

Make sure that the equipment is happy powered by one.

We had pieces put together that way, Has a large rack of 240 V power supplies , maybe like 12,000 W connected to a machine which had a 50 A 4 wire power supply. A breaker panel was placed on a the rack and plugged into the wall.

There was a contactor on the wall that made sure the power supplies were off on a power fail of the main system.

Safety wise they need to co-exist and disconnects need to be close by. Emergency stops even better.

We had systems powered from everywhere. Three safety panels in three different rooms, tox and hydrogen monitoring. Partial UPS and generator backup. Anyone of those safety panels went out, the system went into a safe state. It was also connected to a monitored fire alarm contact closure, so that's yet another power source.

Pumps required yet their own power source. Most were OK and independent as long as they had a purge set and were isolated,

Some parts of the safety system was on a UPS, others were not. The toxic gas detection came up after the generator started. About 2 minutes.

Shut downs came from panics, emergency stops fire alarm, velocity alarms, hydrogen alarms, toxic gas alarms etc. One PLC was put on a UPS and was dedicated for safety control. It had o run dillution for about 20 minutes after an abrupt shutdown. Other systems had to shut down too and they were isolated.

It's not uncommon. Just make sure disconnects are properly labeled and accessible and can kill all power and can be locked out.