Polaris Short Cycling

hot_rod

has a very tight differential. 3 degrees as I recall. Crank it all the way up and add a basic setpoint control to the 120V supply. Then you can adjust the diff and use the factory aquastat as a high limit protection.

The 3 degrees was built to keep the unit in a tight condensing mode. Nnot friendly for radiant.

hot rod

Brian Seickel

Short Cylcing Polaris

I have a PG10 34-100-2PV that is short cycling. I would like to create a larger delta for the ICM to activate but can get no help from AWH Company. The module is manufactured by Robertshaw and Fenwal Part No. 1018-525. Any suggestions?

Brian Seickel
Seickel Heating

kinglerch

Improve the Polaris efficiency by

increasing the temperature differential. It's pretty easy. It is stupid that there is just about 3 degrees between the water temp and temp setpoint before the heater turns on again. And for radiant heat, my polaris was cycling on then off then on just a minute later. Such a waste...well, here's the easy answer:

 



When the burner is on, 120VAC is present on the ignitor. I am using this to power a (very important spec) 120VAC powered relay coil. So just wire this relay to the HSI and HSIG inputs of the Ignition Control board.

 



I then take one side of the relay output contacts and wire it to the thermostat board (orange wire, there it says 'POT') and the other side through a 7500 ohm resistor and also to the thermostat board (other orange wire).

 



What happens is that when the burner is on, the resistance to the thermostat board will be reduced, causing a temporary increase in the temperature setpoint of about 20 degrees. i.e. at 100 degree setpoint, the increase is 28 degrees (128) at 120 setpoint, the increase is 20 degrees (140), at 140 setpoint, the increase is 16 degrees (156 degrees)...you get the idea. You can calculate the resistance, but with the polaris thermostat they are all approximate anyway. Just remember your higher setpoint will be about 20 degrees above what the thermastat says.

 



Once this higher setpoint (128, 140, or 156) for the water is reached, the burner turns off and the 120VAC relay opens. Then the setpoint is back to the original value (100, 120, or 140). This should reduce the cycling significantly and make this more efficient for space heating. Also, this may reduce the condensation problem since you are firing the burner always at a higher temperature, even though the water temperature can fall 20 degrees lower....all for less than $10.

Piper

just saw another similar post

with another solution. hotrod is right, they only have a 3* differential. i hate those things... luckily i only installed 1 - the first system i ever did.