Duct temp limit switch

Duct temp limit switch

PostBy: markm4 On: Thu Nov 15, 2007 5:00 pm

Is anyone aware of a sensor / switch that could be installed in your duct(s) that would turn off the stove if the duct temperature exceeded say 200f?

I was thinking of something really simple that would turn off all power to the stove in the event the ductwork got too hot for whatever reason. Maybe some kind of bi-metal switch or "snap disk" (dont really know much about snap disks).

Any ideas? Once we add ductwork, and fans, we are kind of making a furnace, perhaps there is a furnace control that would work.

I am thinking of this as a safety precaution, and not something that would see regular use. For instance if your fan(s) blow out, the reduced circulation may make the ductwork hotter, and if it got too hot, you would want your stove to shut itself down fore safety.

Mark
markm4
 

Re: Duct temp limit switch

PostBy: Matthaus On: Thu Nov 15, 2007 6:45 pm

Mark,

You can find a good selection on Granger.


http://www.grainger.com/Grainger/categories/hvacr/controls/fan-and-limit-controls
This link is broken, either the page no longer exists or there is some other issue like a typo.


You can also use a fan limit control, but that is kinda expensive. If you hook the main stove hot lead through the snap switch it will shut it down till it cools off. You just need to mount it so the wires are not an electrical hazard and make sure interrupting the process doesn't cause any problems.

Hope this helps a little. :)
Matthaus
 
Stoker Coal Boiler: Leisure Line WL110 Dual Fuel, natural gas
Hot Air Coal Stoker Stove: Leisure Line Lil' Heater (rental house)
Coal Size/Type: Rice and Buckwheat Anthracite

Re: Duct temp limit switch

PostBy: WNY On: Thu Nov 15, 2007 7:39 pm

Yes, I actually just got one for my FLUE Switch for LOW Temp stoker cutout at around 80 degrees, so it doesn't keep pushing coal if it thinks the stove has gone out.

These are very simple Snap Acting Temp. Switches

http://www.thermodisc.com/

You can get in just about any temp and/or configuration

We just had that scare Sat. Morning, I could smell something HOT and the convection blowers hooked into the Rehostat didn't come on and the stove got a bit hot, I unplugged from the stove and plugged directly into an outlet and they worked. The rehostat must have burn up or something? My pipe temp going upstairs was almost 200 degrees !
WNY
 
Hot Air Coal Stoker Stove: Keystoker 90K, Leisure Line Hyfire I
Coal Size/Type: Rice
Stove/Furnace Make: Keystoker, LL & CoalTrol
Stove/Furnace Model: 90K, Hyfire I, VF3000 Soon


Re: Duct temp limit switch

PostBy: e.alleg On: Fri Nov 16, 2007 11:25 am

The most common is the Honeywell L4064 B xxxx combination fan and limit control. (the xxxx # is determined by how long a probe you need) Check Ebay for deals as they are about $60 at the hardware store. It is basically three switches in one unit, either low voltage or line voltage. The high limit shuts down the burner but not the fan at your preset temperature of anywhere between 200 and 250 degrees to safeguard against meltdown, you set the dial to when you want the fan to come on and when you want it to shut off, I have mine set at 140 on, 90 off, so the duct has time to heat up nice without short cycling the stoker and fan stays running after the stoker has shut off to dissipate the heat in the ducts but not so much that cold air blows out. Installation is simple.
e.alleg
 
Stove/Furnace Make: EFM
Stove/Furnace Model: 520

Re: Duct temp limit switch

PostBy: Matthaus On: Fri Nov 16, 2007 7:57 pm

Just a couple more ideas on the subject:

The snap switches are from $8 to $12 so they are cheaper than a fan limit such as e recommended. These devices are not as much a control as a safety as Mark was originally thinking of. There are also non resetting fan limits that insert into the duct like the Honeywell, they are basically a trip device that cuts power and require manual reset, they run around $30.

So bottom line is there are many solutions to provide an interlock and/or control to limit duct temperatures. ebay is an excellent source once you know what you are looking for. I usually peruse the manufacturers web sites and get the specs and manuals to figure out how they work and then look on ebay to find one cheap. :roll:
Matthaus
 
Stoker Coal Boiler: Leisure Line WL110 Dual Fuel, natural gas
Hot Air Coal Stoker Stove: Leisure Line Lil' Heater (rental house)
Coal Size/Type: Rice and Buckwheat Anthracite

Re: Duct temp limit switch

PostBy: traderfjp On: Sun Nov 18, 2007 8:54 pm

I think this is on topic. I have a stoker. I would like to get a snap disc switch in case the feed motor goes haywire. Can anyone suggest which model/temp to get and where is the best place to mount it? That way of the stove over fires it will shut down.

Thanks
traderfjp
 
Stove/Furnace Make: Alaska
Stove/Furnace Model: Channing 3

Re: Duct temp limit switch

PostBy: Matthaus On: Sun Nov 18, 2007 9:03 pm

Depending on what stack temps you are seeing I would get a 250*F unit and mount it on the stack about halfway between the baro and the stove. That way it would open when overtemp was achieved and then close when the condition no longer existed thereby not letting the stove go out.

The only concern is that I would leave the convection fan run to wash the heat off the stove. If you shut power off to everything it will actually get hotter for a bit before cooling off. :P

The other solution is a SW 1 fume switch by Field Controls ($50) that actually installs in the stove and shuts everything off if there is not sufficient draft to carry the heat off. It installs by drilling a hole in the back of the stove. Most older Alaska stoves came standard with one. If I get a chance I'll post a pic of one.
Matthaus
 
Stoker Coal Boiler: Leisure Line WL110 Dual Fuel, natural gas
Hot Air Coal Stoker Stove: Leisure Line Lil' Heater (rental house)
Coal Size/Type: Rice and Buckwheat Anthracite

Re: Duct temp limit switch

PostBy: coal berner On: Sun Nov 18, 2007 9:06 pm

Matthaus wrote:Depending on what stack temps you are seeing I would get a 250*F unit and mount it on the stack about halfway between the baro and the stove. That way it would open when overtemp was achieved and then close when the condition no longer existed thereby not letting the stove go out.

The only concern is that I would leave the convection fan run to wash the heat off the stove. If you shut power off to everything it will actually get hotter for a bit before cooling off. :P

The other solution is a SW 1 fume switch by Field Controls ($50) that actually installs in the stove and shuts everything off if there is not sufficient draft to carry the heat off. It installs by drilling a hole in the back of the stove. Most older Alaska stoves came standard with one. If I get a chance I'll post a pic of one.
Hi matt get back to work and stop posting :lol: :lol: :P
coal berner
 
Stoker Coal Boiler: 1986 Electric Furnace Man 520 DF
Stove/Furnace Make: Electric Furnace Man
Stove/Furnace Model: DF520

Re: Duct temp limit switch

PostBy: Matthaus On: Sun Nov 18, 2007 9:08 pm

I'm done, tired of Chinese water torture from working outside in the snow! :mad2: Besides I have to post a few so I can be ahead! :taz:
Matthaus
 
Stoker Coal Boiler: Leisure Line WL110 Dual Fuel, natural gas
Hot Air Coal Stoker Stove: Leisure Line Lil' Heater (rental house)
Coal Size/Type: Rice and Buckwheat Anthracite