# boiler draft damper solenoid



## joeboston (Feb 5, 2010)

I purchased a used outdoor woodboiler this winter and just finished setting it up. It is not a brand name unit. I believe it was built by a start up in western MI that has since gone out of business. The issue I have is the draft damper solenoid. The first time I hooked up the unit the solenid made a very loud buzzing noise. A few minutes later it stopped when it burned out. After removing it I discovered it was a 12vdc unit with a 120vac suply line. I logged onto the grainger website and purchased a new 120vac pull solenoid. The unit arrived today and was installed tonight. When I applied power the unit had the same loud buzzing noise as the original unit. A few minutes later it burned out.

I am now a little confused and wondering if the damper design is flawed. 

The first question I have is, when power is applied to a pull solenoid is it safe to keep the poser applied for a period of time. And it is normally a very loud buzzing noise?

This solenoid is designed to lift and hold the damper up until the water temp reaches the desired temp, then closes. How do other wood boilers do this.

Any help is greatly appreciated.

Thanks joe


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## sgschwend (Feb 5, 2010)

Normally a buzzing sound means a wiring error.  Buzzing is bad and you need to switch the unit off before the relay oscillates itself to death.

Post both the relay part number, I am guessing it has a reset or a latch with reset.  Get you schematic out too and let see what is going on.


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## Gooserider (Feb 5, 2010)

joeboston said:
			
		

> I purchased a used outdoor woodboiler this winter and just finished setting it up. It is not a brand name unit. I believe it was built by a start up in western MI that has since gone out of business. The issue I have is the draft damper solenoid. The first time I hooked up the unit the solenid made a very loud buzzing noise. A few minutes later it stopped when it burned out. After removing it I discovered it was a 12vdc unit with a 120vac suply line. I logged onto the grainger website and purchased a new 120vac pull solenoid. The unit arrived today and was installed tonight. When I applied power the unit had the same loud buzzing noise as the original unit. A few minutes later it burned out.
> 
> I am now a little confused and wondering if the damper design is flawed.
> 
> ...



A lot depends on the solenoid - essentially a solenoid is an electromagnet, and it will suck in when power is applied - how hard depends on the coil size, power applied, and so forth.  The problem is that because a solenoid coil is just a length of wire, it is, or can be very nearly a short circuit when energized if not properly designed and used...

Many solenoids may only be intended for short duty cycles - a momentary surge, and will burn out if energized for to long.

Another issue is that many solenoids are designed such that they take a very high current when initially energized, and pull in, but then need to switch to a lower "holding" power if they need to stay energized - often this is done with an internal switch.  If the switch doesn't make, the high power coil stays energized to long, and will burn out...  If the load is such that either the solenoid can't pull in far enough to make that switch to the low power coil, or if the load is heavier than the low power coil can "hold" then again you exceed the duty cycle on the high power coil and will burn out...

From your description it seems possible that this last might be the problem - the solenoid opens the damper, and switches to low power, which isn't enough to hold so the damper starts to close, causing the high power coil to kick back in, causing your buzz, and burning out the high coil...  Is it possible that some kind of counterweight spring has gone missing from the door, or that the damper is offering more resistance to opening and staying open than it should have?

Gooserider


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## joeboston (Feb 7, 2010)

Thanks for your responses. Part of the issue I have is I did not get a manual for the unit. It seems the company went out of business which is why I was able to pick it up for a reasonable price. I am very pleased with the performance (excluding the damper issue). I burn about a face cord a week with the damper manually set slightly open. Based on the response I now believe the cover for the solenoid/damper may be preventing the damper from opening properly which in turn is preventing the solenoid from pulling all the way in. This would prevent it from reaching the low power setting. The actual damper is not very heavy so I do not believe that is holding it down.

This is the solenoid I purchased which promptly burned out. I will get another one and try it without the cover attached. I do recall looking under it and noticed the damper was not open as far as it should have been. If you have any suggestions on a solenoid I am willing to look at it. 

http://www.grainger.com/Grainger/items/4X317

After doing a little more research it appears the unit I purchased has a 3 minute duty cycle max.

This unit has a continuous duty cycle: http://www.grainger.com/Grainger/items/4X242
Based on the specifications it appears to switch to a lower power usage, called seated amps/watts.

While waiting for the new unit to arrive I will double back and ensure the power line is wired properly (120v).

Thanks for your help.


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## Gooserider (Feb 8, 2010)

The 242 number does look like a better choice, doesn't pull quite as hard, but that shouldn't matter as much as the continuous duty cycle - although you might want to watch the temperature - note the 25°C, or approximately room temperature rating - as the temp goes up the duty cycle will go down, but I don't know by how much, or how hot it gets where you will be putting the solenoid...

Gooserider


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## joeboston (Feb 9, 2010)

Good news, the new unit arrived today (242) and is working great. I left the cover off to prevent it from touching the solenoid to validate this was the issue. The solenoid opened the damper all the way and you can only hear a slight hum. I pulled down on the damper and the loud noise was back. Letting go allowed it to open fully and quite down. I have since modified the cover to eliminate the issue for good.

Thanks for your help!
Joe


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