Ansul System: Exhaust Fans wont Stay On

[Kcook]

Im currently converting an old vent hood control box from 3 phase to single phase with all new exhaust fans and make up airs. Everything is going smooth up until today. I pressed the micro switch in the ansul system control box and the exhaust fans came on as expected, but shut off after about 5 seconds. No breaker tripped and no other obvious pop fuse or reset triggered. After this, the fans wont come on for about 10 minutes via the micro switch (N/O). Only the relays (N/C) can be heard clicking. Manually pressing the contacts (Siemens Brand) still activates the fans.

I have two separate lines in from the panel, and two loads going to a disconnect on the roof where they then seperate to each fan. The nuetrals are twisted together and dont pass through the contacts. The contacts have a couple adjustments but Im not familar with them. One is a screw adjustment with a range from "2.4a to 4a". I have it set in between. And the other is a screw adjustment from "M to A" which I assume is manual to automatic. I have it set to A.

Is this a sign of a bad set of contacts? Bad Relay? Or bad wiring? Note: Im working alone so I wasnt able to put a meter on anything while the ansul microswitch was being pressed today.

 

[gadfly56]

Im currently converting an old vent hood control box from 3 phase to single phase with all new exhaust fans and make up airs. Everything is going smooth up until today. I pressed the micro switch in the ansul system control box and the exhaust fans came on as expected, but shut off after about 5 seconds. No breaker tripped and no other obvious pop fuse or reset triggered. After this, the fans wont come on for about 10 minutes via the micro switch (N/O). Only the relays (N/C) can be heard clicking. Manually pressing the contacts (Siemens Brand) still activates the fans.

I have two separate lines in from the panel, and two loads going to a disconnect on the roof where they then seperate to each fan. The nuetrals are twisted together and dont pass through the contacts. The contacts have a couple adjustments but Im not familar with them. One is a screw adjustment with a range from "2.4a to 4a". I have it set in between. And the other is a screw adjustment from "M to A" which I assume is manual to automatic. I have it set to A.

Is this a sign of a bad set of contacts? Bad Relay? Or bad wiring? Note: Im working alone so I wasnt able to put a meter on anything while the ansul microswitch was being pressed today.

If you have them, it sounds like the heaters in the motor are tripping. After cool down, they'll operate again, then trip.

 

[Kcook]

If you have them, it sounds like the heaters in the motor are tripping. After cool down, they'll operate again, then trip.

That could be an issue, its very hot in Texas and on that roof. But I am still able to manually press and hold the contacts in for the exhaust fans and they run for as long as I hold the contacts in. Even immediately after a failed test of the ansul system.

 

[hillbilly1]

As @gadfly56 said, it’s probably the automatic reset causing part of the problem. Did you reuse the old three phase starters? They are probably too small, as the single phase motors would have a much higher amperage for the same HP motor.

 

[Kcook]

As @gadfly56 said, it’s probably the automatic reset causing part of the problem. Did you reuse the old three phase starters? They are probably too small, as the single phase motors would have a much higher amperage for the same HP motor.

Yes Im reusing the old 3 phase starter. Im guessing thats what that adjustment screw on the starter contacts is? 2.4 amps to 4 amps. Im pulling about 22 amps through it now. The reset doesnt pop to reset. Unless there is an internal breaker.... Im going back saturday to try swaping the relays in the box, and run the nuetral through the contacts to see if anything changes.

 

[hillbilly1]

The adjustment screw sets the trip point for the overloads. You are way undersized for that motor. You do not have to run the neutral through the starter if the motor is 120. Unusual for a manufacturer to use 120 for that size of motor, ( going on the amps you provided) unless it has been field converted to 120. You will need two separate starters for the fans.

 

[LarryFine]

Rewiring won't help anything. If you don't know why the contactor is dropping out, you need to do a troubleshoot and figure out what is opening in the control circuit.

I also agree that re-configuring the motor for 240v if possible would halve the current it uses. That would then be the time to run both motor lines through the contactor.

 

[hillbilly1]

Rewiring won't help anything. If you don't know why the contactor is dropping out, you need to do a troubleshoot and figure out what is opening in the control circuit.

I also agree that re-configuring the motor for 240v if possible would halve the current it uses. That would then be the time to run both motor lines through the contactor.

Don’t forget, you would not want to run both motors through the same contactor, one has to run, the other shuts down upon activation of fire suppression. (Unless you shuntrip the make up air fan)

 

[Kcook]

The adjustment screw sets the trip point for the overloads. You are way undersized for that motor. You do not have to run the neutral through the starter if the motor is 120. Unusual for a manufacturer to use 120 for that size of motor, ( going on the amps you provided) unless it has been field converted to 120. You will need two separate starters for the fans.

That makes the most sense. I'll start shopping for some 120v starters. The amps are the combined amps. Individually they run at 11.2 or something close to that.

 

[hillbilly1]

That makes the most sense. I'll start shopping for some 120v starters. The amps are the combined amps. Individually they run at 11.2 or something close to that.

If the motors have internal protection, (since they are single phase), you can get away with just contactors, but be mindful of the hp rating.

 

[Krusscher]

with the reset set to A(automatic) it will reset after a certain amount of time and allow it to run again. M(manual) means you have to go in and physically press the reset button which is ideal when you are a maintenance electrician at a industrial facility and want to be notified when things trip. You definitely need bigger overloads for these since you went to single phase and 2 starters would be ideal. If the motors do have protection on them I would still rather have an overload trip on the starter rather then have to go to the motor to reset it.

That makes the most sense. I'll start shopping for some 120v starters. The amps are the combined amps. Individually they run at 11.2 or something close to that.

do not use the combined amps for your overload setting as it will be looking for overloads on each individual phase/pole of that starter

 

[LarryFine]

Don’t forget, you would not want to run both motors through the same contactor, one has to run, the other shuts down upon activation of fire suppression. (Unless you shuntrip the make up air fan)

Absolutely. I missed that there was an intake fan.

 

[Kcook]

Don’t forget, you would not want to run both motors through the same contactor, one has to run, the other shuts down upon activation of fire suppression. (Unless you shuntrip the make up air fan)

Currently the exhaust fans are wired through the same set of contactors. The make up airs run through another set and are on shunt trip breakers as well. I will seperate them in case my local supplier doesnt have a 2 pole 120V set of contactors and starter.

 

[Kcook]

with the reset set to A(automatic) it will reset after a certain amount of time and allow it to run again. M(manual) means you have to go in and physically press the reset button which is ideal when you are a maintenance electrician at a industrial facility and want to be notified when things trip. You definitely need bigger overloads for these since you went to single phase and 2 starters would be ideal. If the motors do have protection on them I would still rather have an overload trip on the starter rather then have to go to the motor to reset it.

do not use the combined amps for your overload setting as it will be looking for overloads on each individual phase/pole of that starter

Thank you! That actually makes a lot of sense. Saved me a stupid question at the supply store.