# motor protection



## MSSI (Mar 25, 2006)

Tuesday I have to wire an exhaust system in a restaurant....The 3 115v. 15A motors are to be wired through the ANSUL fire extinguishing system.(N.C. Microswitch) series with on/off . What knd of motor protection if any would you guys suggest??


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## mdshunk (Mar 13, 2005)

Probably none. A motor that small will have thermal overload protection, surely. Just double check. The typical route is to use that ANSUL microswitch to pull a contactor in and out. Those fans will be served by their own ciruit(s), which will run through that contactor. A 3 pole contactor, with one fan on each pole. There's not much inrush for an exhaust fan, as it starts basically unloaded, other than the weight of the fan blades. 

Sometimes you need to use a double-throw contactor if you have makeup air fans. When the ANSUL trips, the makeup air needs shut OFF, and the exhaust fans need to come ON, if they aren't already.


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## MSSI (Mar 25, 2006)

Thanks MD.. That is the way I was leaning. I cant recall ever seeing overloads on that type of circut before. I just wanted to make sure I wasnt missing something.
They way I understood it though, was that they want the exhaust fans to turn off if the bottles blow. I need to talk to the manufacturer to be sure.... Also this 3rd fan is for the vents in the front of the exhaust hood..Could this be the makeup air you speak of? I have yet to find a overall system drawing for this unit. Thank you for your time.


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## MSSI (Mar 25, 2006)

On second thought That 3rd fan must be Intake air...There is a filter on the rooftop assy...Duh


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## mdshunk (Mar 13, 2005)

MSSI said:


> I cant recall ever seeing overloads on that type of circut before. I just wanted to make sure I wasnt missing something.


Yep, no need for overloads when you're dealing with a thermally protected motor.



MSSI said:


> They way I understood it though, was that they want the exhaust fans to turn off if the bottles blow. I need to talk to the manufacturer to be sure....


You sure do. Might not hurt to try to get that in writing. When the system activates, the makeup air fan is to turn OFF (to eliminate fanning the flames) and the exhaust is to turn ON (to take out smoke). A double throw contactor is what people typically use (activated by that Cherry switch in the ANSUL). Most of those ANSULs have three leads on the Cherry switch (Com, NO, NC), in case you don't want to use a double throw contactor. You can use one contactor for the makeup air, coil connected between com and NC, and one contactor for the exhause, connected between com and NO. You need to arrange it so that the wall switch for the makeup air won't keep the makeup air running when the ANSUL is activated.


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## Sparky Joe (Apr 29, 2006)

So what is the dividing point between 'fused disconnect' and 'non-fused disconnect'?

You will need a toggle switch on the roof for each motor, or some sort of disconnect within sight.


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## MSSI (Mar 25, 2006)

10-4 Thanks....


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## RobertWilber (Mar 5, 2006)

MSSI said:


> Thanks MD.. That is the way I was leaning. I cant recall ever seeing overloads on that type of circut before. I just wanted to make sure I wasnt missing something.
> They way I understood it though, was that they want the exhaust fans to turn off if the bottles blow. I need to talk to the manufacturer to be sure.... Also this 3rd fan is for the vents in the front of the exhaust hood..Could this be the makeup air you speak of? I have yet to find a overall system drawing for this unit. Thank you for your time.


The systems we have worked on have required that the exhaust fan continue to operate to spread the ansul product through the exhaust duct to extinguish any fire in the duct.
We have been required to trigger the F/A system and shut the gas off, as well, when the Ansul activates.


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## MSSI (Mar 25, 2006)

yeah .. I got some third hand info about how this sysem is supposed to operate when I first looked into it. So I did a little research. I couldnt find anything requireing the exhast to come on when the system trips, but it does say the exhaust should be allowd to operate. The Gas Intake air and any outlets or lights under the hood must be interupted though. I made the drawings with the option to activate exhaust upon fault. 
To make a long story longer...another "electrician" friend of the owner told me I was over complicating things.. Gave me the old 746 watts story, Told me he would take care of it "No contactors, just wire it through the microswitch those motors dont draw 15A each 746 watts blah blah blah"
So I get a call from the owner around 4 today wondering why the single pole 30A breaker trips 10 minutes after he turns the fans on.....No I wont explain to your friend how to wire it and guess what my price just went up $400 
I dont usually say things like that but he has given me alot of run around and I told him(owner) his method was wrong and not to call me if the friggin thing goes up in a mushroom cloud(lol)


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## mdshunk (Mar 13, 2005)

MSSI said:


> I dont usually say things like that but he has given me alot of run around and I told him(owner) his method was wrong and not to call me if the friggin thing goes up in a mushroom cloud(lol)


I'm still laughing. You did the right thing. You don't monkey around with life-safety stuff like that. 

I had no idea that the lights were to shut down too. Thanks for that tidbit. I knew about the gas valve, but I never saw an electric one. All the gas valves I've ever seen are operated off the same cable pull that triggers the ANSUL (or the spring loaded pull mechanism in the ANSUL if the ANSUL goes off automatically). Learned something new today. Thanks. MSSI and RobertW (aka grumpy old guy).


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## Sparky Joe (Apr 29, 2006)

MSSI said:


> he has given me alot of run around and I told him(owner) his method was wrong and not to call me if the friggin thing goes up in a mushroom cloud(lol)


:clap: :clap: :clap:


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