PSG Caddy blower speed

[Madkanuist]

I have just replaced my 2007 Caddy furnace with a new one. Long sad story. We reused the electrical and 18 KW heater from the old furnace.

The WETT tech says that his 2010 wood/electric Caddy has staged blower speed in heating mode. He says it starts on low speed, then steps up to the higher speed.

He claims that my furnace is wired incorrectly as the blower only operates at one speed in heating mode (on at 150F, off at 100F, limit 250F). The blower is currently set to medium high. I don't see anything in the old or new manual that supports staged blower speed.

Is mine wired incorrectly as he says? If not, how is he managing to get 2 speeds with his?

 

[M1sterM]

Is his a Max Caddy, perhaps?

 

[Madkanuist]

Is his a Max Caddy, perhaps?

No, his is a standard Caddy. Old version with blower in the same housing as the firebox. He lusts after the Max Caddy though.

 

[laynes69]

I've wondered the same thing since i've owned my furnace. The limit/control has a low side and high side. I've tried to wire with the low, but nothing happened. This is the first furnace i've had that had the 2 speed limit/control. If anyone has any idea's, I'd appreciate it also. Why did you have to replace your furnace? I have the older version with the blower built into the furnace also.

 

[Madkanuist]

I emailed a tech at the manufacturer and was told that my furnace is operating properly. He suggested that my friend the WETT tech must have a Max Caddy. He doesn't.
The old furnace started to produce a very irritating odour this winter and filled the house with almost invisible grey soot. It messed up our breathing. The cause appears to be overheating and it probably started a year or 2 ago when the barometric damper was pinned closed to temporarily boost draft and forgotten.

 

[laynes69]

I've forgotten to latch our door and went to bed with a full load in the furnace. Other than overheating the house, nothing happened with the furnace. I'm guessing repeated over firings would cause some damage. Since our home is almost too big for our furnace, I lowered the high limit setting to 160 degrees instead of the 200. It will hit that temp with a super hot fire, then close the damper till it hits it's on temp. This way it keeps the firebox hot without pushing it too hard.

The limit/control on the older Caddy's were L6064 2 speed controllers. That might be where he is getting the 2 speeds from. I've tried to wire ours where it would blow on the lowest setting until the plenum went up, then kick in its normal speed, but I've had no luck. According to the old manuals, that low hookup is supposed to go to the summer switch, which we don't have.

 

[laynes69]

I found out tonight I had our limit/control wired incorrectly. It now operates with 2 speeds from the limit/control. I have it set on low when it's below 110 degrees and it switches to medium low when it's above that temperature. The only thing that might be a problem is if the furnace goes cold, but in that case, I can hit a switch if it's not needed for heat and it will shut off.

 

[STIHLY DAN]

I found out tonight I had our limit/control wired incorrectly. It now operates with 2 speeds from the limit/control. I have it set on low when it's below 110 degrees and it switches to medium low when it's above that temperature. The only thing that might be a problem is if the furnace goes cold, but in that case, I can hit a switch if it's not needed for heat and it will shut off.

Wont that hurt your secondary action, keeping your fire chamber cooler longer on reload?

 

[laynes69]

I don't think so. The firebox is insulated with a ceramic blanket with firebrick over that, with a c-cast baffle around 1 1/2". With every reload the damper is open until the furnace is hot, then I set the thermostat. I probably won't keep the 2 speeds, but either way the only time the low speed will run is when the furnace is down to coals.

 

[STIHLY DAN]

I don't think so. The firebox is insulated with a ceramic blanket with firebrick over that, with a c-cast baffle around 1 1/2". With every reload the damper is open until the furnace is hot, then I set the thermostat. I probably won't keep the 2 speeds, but either way the only time the low speed will run is when the furnace is down to coals.

That's what I mean, wont your damper stay open longer with the fan on causing you to be adding air at the bottom and the top of the fire. Or does your damper also control your secondary air? I don't now how yours works, mine has best secondary's when damper is closed. When mine starts from cold and has a call for heat the fan comes on and off a few times which keeps the secondary's going good. If it stayed on the damper would open the primary air to get it hotter again.

 

[laynes69]

If the thermostat is satisfied, then the damper is closed. The secondary air isn't controlled via thermostat, it always has a set amount of air. If the damper is open, the fire is hot enough to not produce any smoke, and if it's hot when it closes, then it runs off of mostly secondary combustion. Where the Kuuma runs off of firebox temperature, the Caddy runs off of the home temperature. That way in any condition it keeps the house at the same temp.

 

[STIHLY DAN]

Gotcha, Once the fire gets going it's sustainable with the secondary air so the fan staying on would not over cool it. But when it burns down nothing it will just blow cooler air till reload. I would think your original setup would be more comfortable. Couldn't you add another switch to shut the fan off when temps get low, Then you have best of both worlds.

Your right room temp doesn't effect my box temp, The room temp modulates the fan to keep temps at set point.

 

[laynes69]

I'm thinking of adding a switch like you say to shut down the blower when the plenum gets too low. That way when the fire is burning it's hottest, the fan speeds will be higher, and once the fire dies down, low speed will run. That's pretty much how the Max Caddy operates.