PSG Caddy blower speed

Is his a Max Caddy, perhaps?

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.

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.

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.

laynes69 said:

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.

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

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.

laynes69 said:

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.

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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.

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.

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.

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.