Proper Aquastat setting??

I have an old American Standard natural gas boiler with 3 zones to hydronic baseboards. Question is that the boiler fires until the temp gauge reaches 210 degrees. This seems high to me. There is a Honeywell aquastat on the boiler with what looks like 2 limit dials. Is 210 degrees correct or should it be lower?

The reason I ask is that it seems the room (especially right above the boiler) heats up too quickly so the other rooms haven't had a chance to warm up as much. Seems if the aquastat high limit is lower then the circulators will work longer and the temp should be more balanced throughout the house.

Any sense to this?? Thanks...

Gene

 

That is high for sure. Most boilers are set that they come on at 160o and off at 180o

ED

 

Ed.... thanks VERY much!!!

 

Hi,

I set the limits as you suggested then noticed a 3rd dial for differential. It's on 10 right now - is that the right setting?

Thanks
Gene

 

Trying to fine tune this system for fuel savings and wondered if I set the low limit down to 120 deg would that be a good idea. The system does not supply domestic hot water.

Thanks

 

Not a good idea. Bad, in fact. 120F is too low. At that temp, flue gases will condense in the boiler and it will corrode out. Acid rain in your boiler. Not good.

I believe 160, 180 and 10 are the correct settings, though I will admit not being familiar with this kind of aquastat.

In no case do you want the low limit less than 140F. 130F is where condensation starts and with an old boiler you don't want to push it.

 

Thanks Xiph. Seems like it's a fine balancing act trying to determine what the optimum settings are between fuel savings, boiler longevity, and room comfort control. I guess I'll just leave it at 180/160 and 10.

 

The weather is still somewhat mild now so I got the setback on my outdoor reset set to the lowest setting. (It goes from 1 to 5 and i have it set to 1). So now the temperature at the boiler will in fact go as low as 120 or so. Thats what the setback on that outdoor rest is designed to do based on the chart curves on the paperwork for it. You think this may damage the boiler in the long run?

 

George, it depends on your fuel type and what boiler. You can go to 120F with oil. Can't with gas. Some boilers are designed to work at low temps.

The reset (and its manufacturer) assume that you are providing proper boiler protection if you let/set the reset that low.

That said, I recently had a new boiler installed that can handle low return temps, and also use an outdoor reset control. I think it's the greatest thing since sliced bread.