triple aqustat settings

mph

Looking at the L8124A schematic, if there is no call for heat the boiler will maintain the temperature set by the low limit, plus or minus the adjustable differential. On call for heat, the circulator will not run until the low limit is satisfied, and then the boiler operates off the high limit, plus or minus the fixed 10 degree differential. If, at any time during call for heat, the boiler temp falls below the low limit, the circulator is shut off. When the heat demand is satisfied, the circulator shuts off and the boiler will cool down to the low limit.

It's not clear if the on-off is at plus or minus one half the differential, or plus or minus the full differential.

Personally, I think these aquastats are energy wasters. Unless you have a side arm tank there's no reason to hot-fire the boiler.

Jeff

jonathan_6

triple aqustat settings

I have two zones and dhw off my burnham oil boiler. I run the dhw into an electric water heater, so the boiler is just preheating.
I have a triple aquastat L8124a . I am confused about the high setting. Somewhere I read that it is some kind of safety setting and not an in operation setting. Meaning no matter what happens circulator on, call for heat, the boiler tries to be in the range of the low setting plus or minus.
Elsewhere I read that the water should go to the high setting when there is a call for heat.
Before having this aquastat, I needed to run 180 water in order to heat the house during the very coldest days. What settings should I have? Also I had a Beckett heat manager installed, does this effect the settings?

Big Ed

settings

Set the low at 160 ,the high at 180 and the diff at 5 . Not sure about the Beckett control have not had the chance to play with one.

soot_seeker_2

triple aqustat settings

thanks

Terry

diff lo

is 5 diff not a little too tight?

I think a 5 diff will cycle the boiler a little more than wanted.

I would expect a 10-20F Diff.

jmo
EIN

soot_seeker_2

With the high setting at 180, what will be the range of boiler temperature?
I am still unclear about my original question.
"Somewhere I read that it is some kind of safety setting and not an in operation setting. Meaning no matter what happens circulator on, call for heat, the boiler tries to be in the range of the low setting plus or minus. Elsewhere I read that the water should go to the high setting when there is a call for heat. "
Thanks
Jonathan

Ron Schroeder

When there is a call for heat, the boiler will try to be between the the High Limit setting and 10 degrees below that. (if the Hi Limit is 180, the boiler will stay between 170 and 180)

When there is no call for heat, the boiler will try to stay between 10 degrees below the Low Limit setting and the Differential setting above that. (if the Low Limit is set to 160 and the Differential is set to 15, the boiler will stay between 150 and 165 degrees.

Ron

Joe Brix

The differential

When the temp hits low limit - 10°, the burner will fire the boiler back up to low limit + differential.

JOHN_103

beckett recomends 150 for a low and no less than 170 for the high with a 15 diff they don't want the boiler below 145

Burnerman

Where are you reading your temp from? Most boiler temp gauges are not that accurate with respsct to the aquastat. Is you aquastat temp bulb FULLY inserted (Manufactureers ATTENTION most factory bulbs are not even in the copper tube)? The high limit is the Max temp the aquastat will allow the burner to run up to.

PJO_5

I have nearly the same ...

hot water set-up. I have the differential at the maximum setting, and when there is no call for heat it runs very long cycles for domestic hot water.

I manually adjust my temp. settings through the shoulder seasons (like now and the spring) between 160 to 180 hi-limit and 135 to 155 lo-limit.

I am not a contractor, but have learned from this great website that those settings are the approximate limit for my oil-fired, cast iron unit.

Hope this helps. Take Care, PJO

Mike Beaulieu

I strongly agree with the 10 degree differential.The 180 high setting is an operating setting.

Ron Schroeder

<It's not clear if the on-off is at plus or minus one half <the differential, or plus or minus the full differential.

Hi Jeff,

It's neither. The High Limit differential is fixed at -10/+0 from the setting.

The Low Limit on is always -10 from the setting and the off is the differential above that point. For example with a 10 degree differential it would be -10/+0 and with a 25 degree differential it would be -10/+15.

A wider Low Limit Differential will save energy by allowing longer run times (and longer off times) when there is no call for heat but it will delay turning on the circ when there is a call for heat. Unfortunatly, the Hi Limit Differential can't be increased to give the same savings durring a call for heat.

One old retired heating tech always used 3 seperate single aquastats and a couple of relays whenever a boiler had enough tapings. One with a 5 degree differential set at 125 degrees for circ control, another one set at about 140 degrees with a 25 degree differential for the tankless and the last one set gor 180 degrees with a 20 degree differential for the high limit.



Ron

mph

Ron,

Thanks for the clarification.

Jeff