Low flue temp fan control for my GARN

[Jim K in PA]

OK - I am now looking at the opposite end of the burn cycle for my GARN. What kind of thermocouple/controller would I need to interrupt power to my draft inducer fan on my GARN when the flue gets cold? The GARN operates on a simple Intermatic timer that keeps the big Dayton 3/4 hp fan going as long as I tell it to. However, if I over estimate how much time is needed to consume the load of wood, once the fire goes out I am pulling outside air through the tank and cooling it off. I would like to avoid this waste of energy (heat loss).

I just need suggestions for the correct component(s) to add that level of control. Anyone already have this in their GARN or Switzer?

 

[Blevesque]

I don't have mine installed on my boiler yet but this is what I got to shut my fan off when my stack temp drops below setpoint.

http://www.lightobject.com/Dual-Display-PID-Temperature-Controller-P43.aspx

 

[TCaldwell]

jim, i am working on some new control parameters, based on o2, but one change will be that the process is not run by a timer, rather a toggle that will start the motor,enabling a program based on o2 targets throughtout the burn, when the plc senses a specific flue temp and declines for a period of time,it will end the process and 1 hr later it will tell the motorized damper on the intake air to close 80%!

 

[Jim K in PA]

Tom, you are my hero . . . :coolsmile:

Look for a PM.

jim, i am working on some new control parameters, based on o2, but one change will be that the process is not run by a timer, rather a toggle that will start the motor,enabling a program based on o2 targets throughtout the burn, when the plc senses a specific flue temp and declines for a period of time,it will end the process and 1 hr later it will tell the motorized damper on the intake air to close 80%!

 

[hkillam]

Posted: 22 January 2009 10:17 AM

...The GARN operates on a simple Intermatic timer that keeps the big Dayton 3/4 hp fan going as long as I tell it to. However, if I over estimate how much time is needed to consume the load of wood, once the fire goes out I am pulling outside air through the tank and cooling it off. I would like to avoid this waste of energy (heat loss). ..

I can sure confirm this cooling off effect. My fan didn't shut off at the end of its burn two days ago. I didn't get near the shed till almost 48 hours after I lasted loaded her. Water temp had dropped to about 90 degrees. Ouch. I estimate she would have been at 180 - 185 degrees at the end of the burn, so I lost 85 to 90 degrees of storage. Well, I got some heat out of her before she dropped below about 130, but, WOW, that is a lot of BTU's lost in 1850 gallons of storage. Sadly, this is the 3rd time that this has happened, it just took longer till I discovered it this time. It's a lot of Amps wasted, too. I think it is an 8 or 9 Amp motor, right? Switch finishes its counterclockwise rotation, but doesn't ... quite ... break ... the electrical connection.

Anybody else experienced this problem? Replacing the timer switch shouldn't be too hard, but I'm not sure how readily available they are. I'll have to contact Garn for replacement, probably.

 

[Jim K in PA]

Hugh - that is a bummer. The timer is an Intermatic brand unit. I have not looked for a p/n on it, but think it is a readily available part from other suppliers, but I am sure you can get a replacement from GARN/Dectra. Give them a call. How old is the unit?

This is another reason to get the second cut out circuit based on low flue temp. The only thing is that you will have to reset the control after the GARN is up to temp when you start the burn.

 

[hkillam]

Hugh - that is a bummer. The timer is an Intermatic brand unit. I have not looked for a p/n on it, but think it is a readily available part from other suppliers, but I am sure you can get a replacement from GARN/Dectra. Give them a call. How old is the unit?

Unit is about 6 months old. I'll try to contact Garn and figure out a solution.

 

[heaterman]

Posted: 22 January 2009 10:17 AM

...The GARN operates on a simple Intermatic timer that keeps the big Dayton 3/4 hp fan going as long as I tell it to. However, if I over estimate how much time is needed to consume the load of wood, once the fire goes out I am pulling outside air through the tank and cooling it off. I would like to avoid this waste of energy (heat loss). ..

I can sure confirm this cooling off effect. My fan didn't shut off at the end of its burn two days ago. I didn't get near the shed till almost 48 hours after I lasted loaded her. Water temp had dropped to about 90 degrees. Ouch. I estimate she would have been at 180 - 185 degrees at the end of the burn, so I lost 85 to 90 degrees of storage. Well, I got some heat out of her before she dropped below about 130, but, WOW, that is a lot of BTU's lost in 1850 gallons of storage. Sadly, this is the 3rd time that this has happened, it just took longer till I discovered it this time. It's a lot of Amps wasted, too. I think it is an 8 or 9 Amp motor, right? Switch finishes its counterclockwise rotation, but doesn't ... quite ... break ... the electrical connection.

Anybody else experienced this problem? Replacing the timer switch shouldn't be too hard, but I'm not sure how readily available they are. I'll have to contact Garn for replacement, probably.

You can get it from Garn, the local dealer you purchased it from or from any WW Grainger store. It's nothing special or expensive, just a standard wind up timer. Send me a PM if you have trouble locating one.

 

[hkillam]

Posted: 22 January 2009 10:17 AM

You can get it from Garn, the local dealer you purchased it from or from any WW Grainger store. It's nothing special or expensive, just a standard wind up timer. Send me a PM if you have trouble locating one.

Thanks!

 

[brad068]

McMaster-Carr p/n 7014K5 or 7014K9 29.76 or 22.54

 

[hkillam]

Anybody else experienced this problem (Intermatic switch failure)? Replacing the timer switch shouldn't be too hard, but I'm not sure how readily available they are. I'll have to contact Garn for replacement, probably.


You can get it from Garn, the local dealer you purchased it from or from any WW Grainger store. It's nothing special or expensive, just a standard wind up timer. Send me a PM if you have trouble locating one.

Problem solved. I contacted someone from Garn, and they got the identical timer in the mail to me immediately. Had it two days later. Installed and working as expected.

 

[Jim K in PA]

Fantastic. Glad to hear that Dectra responded so promptly.