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Posted By: sccat Staircase Pressurization Fan Motor Overload - 09/22/11 06:41 AM
Is there a Thermal Relay in a DOL starter for "staircase pressurization fan"?
When motor overload happens,will the Thermal Relay cut off the contactor?
Your second question: Thermal OLs 'open', and the motor starter opens (Off).

First question may require more than the NEC, as staircase pressurization is Building & Fire Safety Codes. I suggest that you contact the local AHJs in whatever area you are working in. My opinion would be no OLs, just short circuit protection as this is a life safety item, perhaps like a fire pump. Just my opinion.

Posted By: sccat Staircase Pressurization Fan Motor Overload - 09/27/11 04:57 AM
Is there a Thermal Relay in a DOL starter for "staircase pressurization fan"?
When motor overload happens,will the Thermal Relay cut off the contactor?
Only ONCE did I have to build such a circuit.

The AHJ determined that such a blower is NOT a life essential device.

So the OL heaters were left in place.

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Each situation is going to be a Life Safety issue. It's outside the NEC.

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WRT smaller ( 1hp or less ) thermal overloads lead directly to integral drop-out from the load.

Not uncommonly, they reset, automatically, when the temp drops they re-trigger. They DO NOT interact with any contactor what so ever.

These beasties interrupt line current -- and then restore it.

These motors are so small that contactors are uncommon.

Originally Posted by sccat
Is there a Thermal Relay in a DOL starter for "staircase pressurization fan"?
When motor overload happens,will the Thermal Relay cut off the contactor?


In a Direct On Line starter, your only real protection is thermal via the overloads at the base of the contactor.
This should by rights open the control circuit and shut everything off, unless it has been poorly designed or wired.

This is first year apprentice stuff, why do you ask?
Some people think that "staircase pressurization fan" is a Life Safety Equipment as "fire pump".
Sccat:

You have this posted in the NEC section from 9/22/2011, which has one response. I'll merge the two together.

You're right!! Now, it will depend on 'who' the 'some people' are!!

The best solution I would suggest is to speak to the local AHJ about this. IF the ventilation system is considered 'life safety' or not.
NFPA 92A-2006 Standard for Smoke-Control Systems Utilizing Barriers and Pressure Differences

Annex D Fire Fightersí Smoke-Control Station Considerations

Control actions issued from the FSCS should not override or bypass devices and controls intended to protect against electrical overloads, provide for personnel safety, and prevent major system damage.

Is "Staircase Pressurization Fan " a part of "Smoke-Control Systems"?
Again, I say...talk to the local AHJ!

BTW, you profile states your location as "CHN", would you care to elaborate on that please?

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