Kitchen Hood Shunt Trip Equipment

[mbrunner]

Ok, I have a hood that has a number of equipment that is 208V which we are sending to its own panel for the shunt trip. Here comes the BUT, the Kitchen Designer also placed a couple pieces of equipment that are 480V under same hood, and he cannot get that type of equipment in lower voltage.

How should I shunt trip the 480V along with the 208V with (1) push button to shut everything down?

 

[augie47]

You can use 480v breakers with shunt trip or contactors. The coil and shunt trips can be the same voltage as your 208 shunt trip.

 

[gadfly56]

You can use 480v breakers with shunt trip or contactors. The coil and shunt trips can be the same voltage as your 208 shunt trip.

Exactly.

I will insert my usual comment here on kitchen system shutdowns. We prefer to use contactors when possible. With shunt trips, you have to worry about the source of voltage for the shunt coil, unless you tap that from a hot off the breaker itself, which may or may not be kosher. With a contactor, if you have a power failure generally or at the contactor coil, the system will fail safe. If you lose your shunt coil circuit, you may not know that until it's too late.

 

[Tyler C]

With shunt trips, you have to worry about the source of voltage for the shunt coil, unless you tap that from a hot off the breaker itself, which may or may not be kosher. With a contactor, if you have a power failure generally or at the contactor coil, the system will fail safe. If you lose your shunt coil circuit, you may not know that until it's too late.

Agreed, plus even if you tap off the breaker you are trying to trip, you still have the risk of poor splices, terminations, etc. causing the system to fail, all of which is removed with the fail safe properties of the contactor as you mentioned.

Another benefit is you don't have to waste a pole for the ST, and you can locate the contactor elsewhere in some dead space.

The biggest counterpoint I see to the contactor is energy usage.

 

[gadfly56]

Agreed, plus even if you tap off the breaker you are trying to trip, you still have the risk of poor splices, terminations, etc. causing the system to fail, all of which is removed with the fail safe properties of the contactor as you mentioned.

Another benefit is you don't have to waste a pole for the ST, and you can locate the contactor elsewhere in some dead space.

The biggest counterpoint I see to the contactor is energy usage.

Fair point. I just looked up an Eaton definite purpose contactor, the sort you might use for controlling kitchen equipment. A double pole contactor for 240 volts and 50 amps with a 120VAC coil has an inrush of 41 VA and holding of 6.5 VA, or 3 "maximum sealed watts", whatever that means. If we take the 3 watts, the vampire load over the year is 3 x 24 x 365 = 26,280 watt-hours/yr or 26.280 kW-hr/yr. At $0.15/kW-hr, that would be $3.94/yr. I hope I got the math right.

https://www.eaton.com/content/dam/eaton/products/industrialcontrols-drives-automation-sensors/definite-purpose-motor-control/definite-purpose-conactors-for-construction-quick-selector-guide-td03501001e.pdf

 

[augie47]

You can also use a latching contactor (they make 2 wire control modules if needed) and avoid the energy usage and hummm.

 

[farmantenna]

I've used NC contactors for under-the-hood power shutdown. If you have GFCI requirements you can't get GFCI and Shunt trip CBs and lead time for anything is long. I've come off the hood fan control, that integrated everything, EX fan and MUA etc, which is tripped by the Ansul system and will latch off and has to be reset by a human to continue.

 

[hillbilly1]

You can also use a latching contactor (they make 2 wire control modules if needed) and avoid the energy usage and hummm.

Murphy USA does that on their gas stations, multiple Estops to unlatch, with one reset button at the cashier station to latch. The problem is, it can be years before it is used, and the grease dries up causing the contactor to be unable to latch.

 

[Tyler C]

If we take the 3 watts, the vampire load over the year is 3 x 24 x 365 = 26,280 watt-hours/yr or 26.280 kW-hr/yr. At $0.15/kW-hr, that would be $3.94/yr. I hope I got the math right.

I think you've got it right, although I'd say 3W and 15¢ are both on the lower end. I've done this sort of math before and found it really varies a lot per installation depending on the sealed power consumption (I have often seen values in the 5-10W range but as you pointed out, lower exists), electricity rate, number of contactors needed, etc. I've also run into the issue where some contactors only give you the current draw or VA, which are not helpful in determining real power consumption.

One instance I can recall - put the contactor on the kitchen panel feeder and dump the whole panel, because many of the circuits would have needed shunt trips. It ends up costing a lot up front for the contactor (although all the shunt trips may have been just as much if not more expensive) but then you are not too worried about energy usage of just the one (albeit bigger) contactor.

If you have GFCI requirements you can't get GFCI and Shunt trip CBs and lead time for anything is long.

This was another issue the whole panel contactor got around, you can then use standard GFCI breakers. I've also seen the GFCI issue overcome by using external hardwired GFCI protection that gets wired inline with the branch circuit conductors.

 

[MTW]

Ok, I have a hood that has a number of equipment that is 208V which we are sending to its own panel for the shunt trip. Here comes the BUT, the Kitchen Designer also placed a couple pieces of equipment that are 480V under same hood, and he cannot get that type of equipment in lower voltage.

How should I shunt trip the 480V along with the 208V with (1) push button to shut everything down?

Something else you may want to look into for a fire system cooking line equipment shutdown.

In my area, the fire marshals require that the hood air make up unit, for the hood supply, shuts down with a fire system trip. At the same fire control head trip time, it is required for the hood exhaust fan to remain running or automatically turn on if it is off when the fire system trips. They also require a fuel gas solenoid shutoff if there is any gas fired equipment under the hood.

if that is the case in your area, you don't want to supply the exhaust fan from the panel that you are going to put the shunt trip breaker on.

The fire suppression installer/contractor also supplies a reset relay that prevents turning on any equipment or circuits until the fire system head is reset and the reset button on the relay is pushed to enable the electrical system reset.

The purpose of the air makeup shutdown and the automatic exhaust fan run is to help avoiding feeding air to a fire and pushing it away from the hood and equipment, while drawing the fire into the solid welded exhaust stack. to help prevent the fire from spreading out into the building. Check with the fire contractor installing the job and the fire Marshall to be sure before you start.