Honeywell Aquastat Settings???

Paul Fredricks_2

With an 8124, the low limit setting is the temperature the boiler will maintain when the heat is not calling. Set at 140 with a 15 degree differential, the boiler will kick on at 130 and run till it reaches 145.

The high limit is the temp the boiler will attempt to reach when the thermostat calls. It has a fixed differential of 10 degrees.

The high limit is set to give you enough heat on cold days. If it seems to take forever for the house to warm on a cold day you should raise the setting, 200 is about as high as you should go.

The differential is set to keep the unit from short cycling and to give you somewhat consistant hot water temperatures if the boiler has a tankless coil. 15 degrees is fairly typical.

As far as the boiler not getting over 160, I assume you are reading the temp on the boiler guage. This may not be accurate so a different methed of determining the true boiler temp may be necessary.

If you are happy with the hot water temp and the house heats well leave it alone.

Paul

Rodney Summers

Honeywell Aquastat Setting Questions??

I have a Honeywell 8124 Aquastat with HI, LO & DIFF settings. I am trying to determine the most optimal, fuel efficient settings. Currently, I have the HI at 180, LO at 140, & the DIFF at 20.

I know that I can set the HI & LO to suit my domestic hot water & heating needs accordingly, but it is the DIFF setting that confuses me. Is a higher DIFF better?

Also, I'm not sure if this problem has anything to do with my settings, but the boiler shuts down at about 160, never reaching 180, even if the thermostat is still calling for heat. I even raised the HI to 200, just to see if the boiler shuts down at or near this setting, but it still shuts down around 160, even if the thermostat is still calling for heat.

I"M CONFUSED!!

ChasMan

Its easy to get confused. These elkementary controls are so old in design dont try to read too much logic into them. In any case, you have to remember that the sensor on the aquastat is not the same gauge as the one on the front of the boiler. There can be a wide variance between what the guage on the boiler shows and what the aquastat thinks the temperature is.

Rodney Summers

Honeywell Aquastat Settings??

Your right, I understand that there could be a difference, but even so, the difference should somewhat track on the temperature guage when I set the HI to 200 versus setting it to 180.

That's why I'm still confused as to what might be wrong.

Terry

actually...

if the Low is set to 140 & diff is at 20. the highest temp you will see is 160.

The HI setting is the HI Limit Temp (fixed 2F diff), safety setting in case LOW side fails.

The LOW setting is your operator which winds around your Diff setting.

SET HI to 200+
SET LO to 160
SET DIFF @ 20F

watch a few cycles and adjust. you will get it.

Gl,
EIN