Solenoid on valve caught fire

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Davebones

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North Of Tampa Fl
Just informed that a water valve " Solenoid " caught fire the other night . Guess the fire department was even called in . I haven't seen the solenoid as I have been off . This valve is a normally closed valve , energized to open valve . The valve is mounted about 3 ft below the roof deck in a exposed ceiling about 85 degree fairly clean environment . This is fed from a single pole 120 volt , 20 amp circuit . This valve is pretty much left on all the time and has been in operation at least 8 years like this . I was asked " is there anything we could do to prevent the solenoid from catching fire " . Any suggestions would be appreciated ...
 
Davebones said:
Just informed that a water valve " Solenoid " caught fire the other night . Guess the fire department was even called in . I haven't seen the solenoid as I have been off . This valve is a normally closed valve , energized to open valve . The valve is mounted about 3 ft below the roof deck in a exposed ceiling about 85 degree fairly clean environment . This is fed from a single pole 120 volt , 20 amp circuit . This valve is pretty much left on all the time and has been in operation at least 8 years like this . I was asked " is there anything we could do to prevent the solenoid from catching fire " . Any suggestions would be appreciated ...
Click to expand...

You won’t prevent it from failing but a small fuse should prevent ignition.
 
190318-0800 EDT

Change to a DC solenoid valve, and one where the coil temperature rise is small (design issue), and high temperature insulation is employed.

The current to a DC solenoid is independent of plunger position. Not so in an AC coil.

Failure of magnetic devices is largely a function of temperature rise and ambient temperature interrelated with design criteria.

.
 
What is the purpose of the valve?
It could possibly be replaced with a motorized ball valve that could remain in either position and not powered continuously. Likely costs more, though.
 
Davebones said:
Just informed that a water valve " Solenoid " caught fire the other night . Guess the fire department was even called in . I haven't seen the solenoid as I have been off . This valve is a normally closed valve , energized to open valve . The valve is mounted about 3 ft below the roof deck in a exposed ceiling about 85 degree fairly clean environment . This is fed from a single pole 120 volt , 20 amp circuit . This valve is pretty much left on all the time and has been in operation at least 8 years like this . I was asked " is there anything we could do to prevent the solenoid from catching fire " . Any suggestions would be appreciated ...
Click to expand...


Dave,

It is possible that the electric coil became separated from the actual mechanical solenoid and overheated? We have noticed that if the coil is taken off the post of the mechanical body of the valve and is energized, it instantly starts to overheat as the magnetic reluctance is not limiting the current. Sometimes, we place a wire tie on the solenoid to keep it on the body if the plastic clip that holds it together breaks.
 
I'm curious as to what's going on with this valve. It stays on all the time (for eight years now)?

What is the purpose of the valve? What controls it? Is there an overcurrent device in whatever is controlling this valve?
 
The valve provides water to a Anodizing room with many dip tanks . They set it up this way so if the plant loses power it will shutdown water to this area so we won't have a flooding issue
 
I never heard of a solenoid valve catching on fire. There is nothing there to burn. The coil might smoke a little but it is not going to burn.
 
petersonra said:
I never heard of a solenoid valve catching on fire. There is nothing there to burn. The coil might smoke a little but it is not going to burn.
Click to expand...


Though not likely a plastic encapsulated coil could possibly burn. I'd expect most to melt and drip but not reach point where they burn. Too close to other combustibles may start a fire of those combustibles, or even combustible dust or debris that accumulates on/near the coil.
 
ptonsparky said:
You won’t prevent it from failing but a small fuse should prevent ignition.
Click to expand...
This is your best bet. As stated, there are possible issues with NC valves being held open continuously, but for 'fail safe" situations as you described, there really isn't a good viable solution (that doesn't add even more potential problems). We don't know the reason it FAILED, but most likely the reason it CAUGHT ON FIRE is because when it DID fail, it took far too long for the increased current to make that 20A circuit breaker trip. I would look at the pull-in rating of that solenoid coil and fuse it at a level just above that. The pull-in rating is likely in VA so just divide that by 120.
 
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