Honeywell AQUASTAT Adjustment?

Joe.G

Hi, I have a few ? about my triple aquastat honeywell. I was told that it should be 180 hi and 160 low, I have 205 hi and 140 low with a 15 DIF, I have a coil in my new peerless boiler but I do not use it, I use a indirect hot water tank. Should I leave them there?

When my boiler is calling for heat and it reaches the 205 it kicks off? and what temp does it come back on? when my boiler reaches 140 does it come on then? and if so when does it shut off? thanks a lot

Bill Nye_2

When

when there is a call for heat it comes back on at 195°, 10° below the high limit. This is a fixed differential.The pump continues to run until thermostat is satisfied.

It shuts off the burner when the call for heat is satisfied and the boiler is above 140°.

When there is no call for heat, it shuts off at 145° when you have a 15° diff.

Is that clear as mud? I could try again. I know what I am talking abiut, just hard to say it.

Sweet_2

triple aquastat

Normally thelow limit has 10-25* adjustable limit differential the high limit is fixed at 10*. High limit is set to shut down boiler when set point is met low limit is lowest temp desired for boiler operation.

Joe.G

So when the boiler is making heat, the boiler kicks off at 205 and comes back on at 195. when the boiler goes below 140 for what ever reason (say not making heat) it kicks on and shuts off at 145? does this sound like a good setting? I don't want to run out of DHW either,a nd if the temp is this low it will take longer to get the indirect up to temp right? right now it is not a problem becasue the temp does not egt that low.

oil-2-4-6-gas

.

the high is the boiler high limit the differential is the temp that it will come back on at (so 180 hi w/10 diffential off at 180 and back on at 170--more differential if adjustable would be changing the on temperature so if at 20 --off at 180 and on at 160*etc..)the low is the pump shutoff if the boiler is running for heat and hot water without priority the low shuts the pump for heating at set temp so still have a hot boiler for domestic

eleft_4

What the diagram I posted shows. Call for heat is in the HI limit control area. Check the foot note (1). read it over several times.
"SWITCH MAKES R-W AND BREAKS R-B ON TEMPERATURE RISE.WHEN WATER REACHES PROPER TEMPERATURE,

1) THE BURNER SHUTS OFF OR THE CIRCULATOR PUMP STARTS (IF CALLING FOR HEAT)."

"The call for heat" , in the diagram, is called out in the HI Limit area....... So which, The Low or the High limit turns off the burner when demand is met?..... The text in the diagram says the High Limit controls the call for heat.

al

Joe.G

My inst say there is a 10 dif built in, so if my dif is on 15 does that mean I have added five? for a total of 15 or do I now have 25?

So in the summer my boiler will maintain 140 deg? if so is that enough to make sure my indirect can keep up with my DHW use? ( I think I have a 40 gal tank )I hate to run out of hot water.

another ? when my indirect calls for the boiler to make hot water does it kick the circulator on and wait for the boiler temp to go below 140 before it fires up? and if for some reason it gets up to 205 will it kick off and keep the circulator running itill the indierct is happy? thanks

P.S when the boiler kicks off but is still heating my houes, I don't think my gauge is reading 205, which is more accurate the gauge or the aquastat? thanks

eleft_4

Joe, Honeywell AQUASTAT Adjustment?

If you are referring to the high limit, it's differential is fixed at 10.
ONLY the Low Limit has an adjustable differential.

Read foot notes and diagram notes over a few times, you'll get it.

al

Joe.G

Hi, ok let me see, if I set it to 180 hi and the dif on 15 the boiler will kick off at 180 and back on at 165? if I have the low on 140 it will kick on at 140 and kick off at 165? or the high only has a ten dif and the low is the one with the adjustable? what are some good settings to start with? Does anyone have anumber I could call them at to talk about this? or could someone call me? thanks a lot

Joe.G

Anyone else?

Ron Schroeder_2

Joe,

Only the Lo has an adjustable diff.

If you have the high set for 180, the low set for 140 and the diff set for 15 and there is a call for heat,the boiler will go up to 180 and the burner will cut off. If there is still a call for heat, when the boiler drops to 170 (the Hi has a fixed 10 degree diff) the burner will come on again. So basically, the boiler will cycle between 170 and 180 degrees durring a call for heat.

If there is no call for heat, when the boiler cools down to 130 degrees (always 10 degrees less than the Lo setting) the burner will come on again. If there is still no call for heat, the burner will stay on until the boiler gets up to 145 degrees (Lo setting minus 10 degrees plus the differential setting).


When there is a call for heat, the boiler stays "near" the Hi setting.

When there is not a call for heat, the boiler stays "near" the Lo setting.

Also, when the low setting is running the burner, it is also preventing the circ. from running.

I hope this helps.

Ron

Joe.G

So if the low is set at 140 and a diff of 15 it will drop to 130 and run up to 145, so if it was set at 10 it would stop at 140 and if teh diff was set at 20 it would go up to 150? is that right?

Also the temp gauge and the aquastat are off about 10 deg which is more accurate? the boiler is only 3 or 4 month old, thanks

Ron Schroeder_4

Hi Joe,

You have it right. The attachment on eleft's post shows the relationship too.

The accuracy of the temp gauge and the aquastat are probably about the same but the temp gauge is only accurate when the circ is on.

Ron

Joe.G

So how does 205 ho and 140 low sound? and with a 15 dif? what is a good dif and what is the max hi you can go? I could also turn the low all the way down since I am useing a indirect and not the coil right? the only thing with it staying at 140 is that if I run low on hot water it will heat the indirect fast due to it already being hot right? thanks

Ron Schroeder_4

Hi Joe,

Set the Hi to as low as you can get by with and still heat your house at the cold design temperature but at least 20-25 degrees higher than you have your indirect set for.

Set the Lo to at least 15 degrees above the concensing temperature for the fuel type that you are using. Probably the worst thing that you can do for a boiler is to make it a "luke-warm" start. Either keep it above the condensation point or make if a full cold start. Since you have an indirect, you probably should set the differential at the maximum to keep it from short cycling durring standby.

What tyoe of boiler do you have? What is the fuel? Are you running baseboard?

Ron

Joe.G

Hi, iam running raditors old cast iron ones, I am useing fuel oil and I have a ec seriers peerless boiler. I am unsure of the condensation point of my fuel, the tanks are inside. I should run a 25 deg dif? thanks

Ron Schroeder_4

Joe, starting Aquastat settings suggestions.

Hi Joe,

The condensation temperature of oil is about 115 degrees so don't set the Lo below about 125-130 degrees. Set the Lo diff to 25.

Your high limit could then be set somewhere between 150 and 205. The lower that you set it, the more oil you will save but it will slow down your DHW recovery some and also if it is too low, it might not keep up with your house heat loss on the coldest days. My gut fealing is to set the Hi to 160 and see how it works for you. Your circulator should need to run at least 50% of the time but not 100% of the time on a very cold day.

Ron

Joe.G

So what dif should I set it for? Thanks

Ron Schroeder_4

Set the low dif to 25.

Ron