I'm heating with a wood furnace (first timer here)!!! But...

[Nelson2]

But I like to fiddle and have some questions about the fan limit control. The fce is a wood only PSG Caddy. The fan limit is a honeywell something or other, with fan limits, fan on @ 150, fan off @ 100, fan limit @ 250. Now, I don't have a plenum yet, so I'm just dumping the hot air in the basement and trying to convect it upstairs.

So the questions - I haven't had the limit hot enough to get to 250°. What's supposed to happen then? I would think that at 250 plenum temp, the design assumption would be that the fce is overfiring, which should shut off the servo motor and kick the motor on high to dissipate heat. No such thing though! The wiring diagram shows that the servomotor is only controlled by the t-stat, and would remain open in a 250°+ plenum.

As it's wired, and I need to fiddle and check a couple things, but the 'fan on' switch on the side of the fce is a nice quiet fan speed. When the 150° limit kicks in, the fan kicks in high(er) speed. I would think the opposite should happen. Perhaps it's wired wrong, and I will check this tomorrow.

Thoughts?

 

[anymanusa]

Wow. U said a mouthfull. My insert comes on at low, kicks in to medium, and if it goes high speed, I've over fired. Don't know if that's any help or not.

 

[laynes69]

Our isn't wired to run on low constantly. Ours when the limit control hits 140 activates the blower on the furnace. If the plenum would hit 250 then the limit control will kill power to the servo on the damper and close it. That 250 isn't there to control the fire. For us we will load our furnace and open the damper for 15-30 minutes depending on where the fire is at. At that point we close the damper and let the furnace take over. If your running with the damper open at all times, you are letting alot of heat out the flue. The limit control is wired into the transformer along with the thermostat. No matter what, if you hit the high limit, then the blower will continue to run while the damper closes.

 

[tupmoore]

When you say you open the damper you mean the barometric damper? We have a caddie that we have had for 3 years now, it works okay, not impressed. I have a digital manometer that I measure the draft at the flue discharge right after the heat exchangers and set it to 0.05. 2 year seasoned oak wood, I get good secondany burning above the wood,

The reason I am writing this is I was cleaning the exchangers last night and forgot to push the steel plate back when finished. The furnace was putting off real heat. I'm not sure what is considered over fired however I am thinking that my furnace is not working as hot as it could be, wasting wood and living a bit less than comfortable in the heat department. We have about 2000 square foot home that we spray flamed last year? It's very hard to get help on the caddie where I live no one is familiar with it.

Any thoughts?

 

[laynes69]

When the baffle is forward, your putting flames directly into the heat exchanger. I'm sure it will put out more heat, but at the expense of burning out the heat exchanger. The damper we open is not the barometric damper, but the damper in the firebox. A spray foamed home that's 2000 sqft should not have a heavy heating demand.

 

[Whitespider]

OK... I looked at the manual/wiring diagram and I'm assuming yours is the standard wood furnace.

The "FAN ON" switch (on the side of the furnace) will turn the circulation blower on at low speed even if there's no fire in the firebox. It does not have to be "ON"... it's used only if you desire a continuous circulation blower running.

The "fan controller/limit controller" serves two separate purposes.

1. When plenum temp reaches 150°, the "fan on" setting turns the circulation blower on at a high speed (or kicks it up from low speed if you have the "FAN ON" switch in the "ON" position). When plenum temp falls to 100° the "fan off" setting turns the circulation blower off (or kicks in down to low speed if you have the "FAN ON" switch in the "ON" position). It's a furnace man, you don't want the circulation blower running if it ain't makin' heat. All functions of the circulation blower are independent from the "limit", and the "150° on/100° off" is independent from the "FAN ON" switch (on the side of the furnace).
   
2. The 250° "limit" setting is a safety feature designed to protect the duct work in your home (and by extension it protects the furnace from over firing). If plenum temp reaches 250° it cuts 115v power to the 24v transformer, which will cut 24v power to the servo and thermostat. Basically, the "limit" causes the combustion air inlet to close, shutting down the fire until plenum temperature falls to a safe level. The "limit" does not, and should not, affect the circulation blower in any way... the circulation blower is controlled by temperature alone... and/or the "FAN ON" switch (on the side of the furnace).

Hope that helps...
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[Whitespider]

Oh... I almost forgot.
Your circulation blower is actually a 4-speed blower (according to the diagram). It is "factory" wired to use the lowest speed with the "FAN ON" switch (on the side of the furnace), and the second speed when the plenum temp reaches 150°. When you get the thing hooked up to duct work you may have to move the wires on the terminal board to utilize higher speeds depending on the set-up. For a forced air heating system to work properly you need a certain amount of static pressure or there won't be enough flow at the far ends of the ducting... and you need a return air connection also.
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[brenndatomu]

I wonder if he ever sorted it out before sayin screw it? http://www.arboristsite.com/community/threads/psg-caddy-3-years-old.271827/

 

[Whitespider]

I didn't notice this was a resurrected thread last night
My beer goggles must'a been fogged-up.
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