How to adjust L8124A aquastat

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Old 02-08-15, 11:17 AM
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How to adjust L8124A aquastat

Hi, I've done some work on my oil fired burner "Williamson OWT-3" with a Hot Water Coil providing domestic hot water.

I know the dials on the aquastat are not dead accurate, and keeping in mind the HIGH and LOW settings are suppose to be a minimum of 20F difference... HOW do I know they are?

- I set HIGH/180F by using the aquastat dial to make the burner shut off when the boiler TEMP is 180F. The dial on the aquastat says 140F Pretty far off but i won't make the assumption that i can just set the LOW to 120F on the dial thinking it's really 160F...CAN I?

SO, to set the aquastat LOW/160F, should i depend on the aquastat dial markings, or adjust wherever the boiler fires up when there is no heat call?

I've searched about this but cannot find any related info about how to adjust when the aquastat dials cannot be believed.

Would appreciate some suggestions on what to do here!
 

Last edited by Tyannt; 02-08-15 at 11:57 AM. Reason: corrections
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Old 02-08-15, 02:28 PM
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- I set HIGH/180F by using the aquastat dial to make the burner shut off when the boiler TEMP is 180F. The dial on the aquastat says 140F Pretty far off but i won't make the assumption that i can just set the LOW to 120F on the dial thinking it's really 160F...CAN I?
Actually, yes, you can. Then by observation you can tweak the dial up or down to get the desired low temperature just as you did with the high limit. It is time consuming but it certainly does work.

One thing, however. Does the sensing bulb directly enter the water space or is there a "well" it enters? Most common is a well and if you have one there will be a time lag for the sensing bulb to attain the same temperature as the boiler water. Two things can help in this respect, the first to make sure the sensing bulb is pushed into the well as far as possible and the second is to use some non-hardening heat transfer paste in the well to help transfer the heat from the water to the bulb. Also, if the well sticks out of the boiler proper any appreciable length it must me insulated.
 
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Old 02-08-15, 03:00 PM
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Hi Furd, thanks for replying!

Minimal background... replaced expansion tank, auto air vent and boiler guage new.
Took the aquastat sensor out, fits in a thermowell/dry, and used non hardening thermal conductive paste already.

So! I can basically set the low just like I did the HIGH, great! Just going by the guage TEMP reading. I would think I do this as the boiler is cooling off after a heat call? Watching the boiler
TEMP and when it is 150F, adjust my LOW to have it refire regardless what the dial on the aquastat says? Want to set these at LOW/160F and DIFF/15.

Greg
 
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Old 02-08-15, 03:20 PM
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Yep, that's the drill. Once set you shouldn't have to fiddle with them.
 
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Old 02-08-15, 03:26 PM
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But! I like fiddling! Lol

I just had a heat call so i turned the thermostat up a bit to make sure it got back up, AND stopped firing at 180F.. It did so i reset the thermostat back to normal..
Cooling down now so I'll kep an eye now to do my LOW

Appreciated!
 
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Old 02-08-15, 03:27 PM
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Remember Greg, set the LOW as low as possible consistent with adequate hot water supply to the home. The lower you set it, the more fuel you'll save.
 
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Old 02-08-15, 03:49 PM
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Hey!!! Nice to have you drop in Troop!

Now is as good a time to pose another ? then

My intent was to have my HIGH at 180F, but til now was 170F, so when I just made the LOW
adjustment I reset the HIGH to 180F... and as you prob read, now waiting for it to cool to do the LOW/DIFF. However, after setting the HIGH to stop firing at 180F, and I went back down to check on it, The Pressure relief valve had released water! YIKES! And the psi was back to 12...Still getting rid of air maybe?
It hasn't popped the relief since back up and running at HIGH/170F

As soon as I think I'm making headway... SURPRISE!

 
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Old 02-08-15, 04:05 PM
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The Pressure relief valve had released water!
Good Grief Greg... WTH is going on there?
 
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Old 02-08-15, 04:06 PM
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I hope y'all don't mind, but I removed the OT posts... sorry. Nuthin personal, but da rulz iz da rulz.
 
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Old 02-08-15, 04:10 PM
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Good Grief Greg... WTH is going on there?
You're asking me??? IDK, it's been great so far until I increased the HIGH to 180F, although the TEMP HAS been approaching 30psi without popping, then usually decreases back to 12psi when cool... hmmm

New tridicator but...
 

Last edited by Tyannt; 02-08-15 at 04:15 PM. Reason: remove OT
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Old 02-08-15, 04:32 PM
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Yeah, I started out by fiddling with controls and worked my way up to designing them.

I have to apologize though when I stated you didn't have to fiddle with your controls once set. The only time you need to have the ability to raise the temperature of your heating water to 180 degrees would be the dead of winter and even then it may not be necessary. Any other time you could probably save some money by lowering that high limit to only the temperature needed to maintain the desired temperature in the house. You do, of course, need to maintain a certain minimum temperature for the domestic hot water and to minimize flue gas corrosion in/on the firesides of the boiler. This is what an outdoor temperature reset control does automatically but you can effect some savings by doing it manually.

Another thing is if your burner is set up to only fire when the circulator is running then you can run a significantly wider differential, say as much as 40 degrees, leaving the high limit set at 180 degrees and achieve almost the same benefits as indoor reset. What will happen is the room thermostat calls for heat, the circulator starts and if the burner previously went off on high limit it won't start until the boiler temperature drops to 140 degrees. Meanwhile the intermediate temperature (say, 150 degrees) circulates, releases its heat, satisfies the thermostat and the circulator stops, all without firing the burner. Of course the next time the temperature will likely drop to the cut-in point but it may not reach the high limit and this cycling will save fuel and each cycle will probably end with a little lower water temperature which will translate to a little longer burn time in the next cycle which is good for the burner efficiency. The room temperature iwll be maintained to the differential of the thermostat. The only real downside is that recovery from a deep setback may be slower. this scheme also works best with a system that has a high mass due to large water content but it will work on any system.
 
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Old 02-08-15, 04:35 PM
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Wide pressure excursions that follow wide temperature excursions are almost always due to insufficient expansion tank volume. But Trooper already knows that.
 
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Old 02-08-15, 04:42 PM
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Yeah... I thought I did! (know that)...

Greg... so that I don't have to go back and refresh my memory, let's start back at square one as if you are new poster.

What type of heat emitters in the home? Fin-tube baseboard? Cast Iron radiators?

What size expansion tank on the system? (you replaced it, right?)
 
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Old 02-08-15, 04:56 PM
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Baseboard/Fin-tube heaters in a ranch style, 2nd zone in half the basement, finished.
Had an HTX-30 Exp-tank which I replaced with the same size, new boiler guage and auto air vent.
Original issue was popping the Pressure Relief Valve...

Might remember right after I put the boiler back into operation I had innacurate tank psi... I corrected that and since starting back up has been at HIGH/170...and haven't really adjusted the LOW/DIFF, just set the LOW 20 below the HIGH.

All has been great, no further leaking, have been hearing the air vents hissing occasionally, but, psi over a few days has been inching up to 30 BUT, never popping the Relief, until a while ago when I changed the HIGH to 180F
Funny thing I've been noticing...when the boiler cools down it returns to 12psi.

There ya have it!!
 

Last edited by Tyannt; 02-08-15 at 04:58 PM. Reason: add info
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Old 02-08-15, 05:06 PM
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when the boiler cools down it returns to 12psi.
Expected... IF you have the manual water feed valve open.

When the relief valve ejects water, the boiler cools and the fill valve puts that water back in again.

You MIGHT still have issue with fill valve.

When boiler is cool and at 12 PSI, CLOSE the manual feed valve and monitor closely.

I think you ruled out the 'thankless coil' ?

Either that... or somehow you still don't have the correct air charge in the tank... that 30 should be large enough for a fin-tube system.
 
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Old 02-08-15, 05:16 PM
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You MIGHT still have issue with fill valve.
I tested the fill valve by leaving the boiler water feed on, after charging the tank with a digital guage that states an accuracy of +/- 1% + o.5psi... I figured that accuracy was adequate. So I let the system sit at least 20 hours like that to see if the psi changed, IT DID NOT.

As far as the tankless coil goes, i can't say I've noticed any difference since opening it back up but, I could certainly turn it back off for a while just to be doubly sure!

I have NOT closed the manual feed off and ran the system, monitoring it... If that would answer "unanswered" questions I can do that now..

Odd, when the boiler has finished firing, then cooling down, guessing about 135/130psi it appears that that is when the psi drops dramatically from whatever it was; 20, 25, 28, to the original 12psi.
 

Last edited by Tyannt; 02-08-15 at 05:20 PM. Reason: add info
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Old 02-08-15, 05:23 PM
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guessing about 135/130psi it appears that that is when the psi drops dramatically from whatever it was; 20, 25, 28, to the original 12psi.
A 'dramatic' drop in pressure could mean that there's a bit too much air in the tank.

When the boiler is heating from cold, do you see the pressure RISE QUICKLY to some value, and then SLOWLY after that?
 
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Old 02-08-15, 05:28 PM
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When the boiler is heating from cold, do you see the pressure RISE QUICKLY to some value, and then SLOWLY after that?
YES... as a matter of fact! "I might add a correction also! I had put 12.5 lbs psi in the tank... given the accuracy, That could mean near 1lb psi either way? Just figured 12.5 was close enough.
maybe I shouldn't have "figured" Lol
 
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Old 02-08-15, 05:32 PM
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Furd... I actually DON'T need to have the HIGH/180F 170 was quite adequate so perhaps I'll reset it back to 170! and thanks for the added info on "Outdoor temp reset controls"!
 
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Old 02-08-15, 05:35 PM
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Trooper,
My system is currently off, and has cooled to 140F at 12psi according to the NEW boiler tridicator, a BII/Brand from Home Depot.

I checked the tank psi...reads 27.5 psi ???
 

Last edited by Tyannt; 02-08-15 at 05:39 PM. Reason: Add info
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Old 02-08-15, 06:08 PM
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I checked the tank psi...reads 27.5 psi ???
Yeah... how that happen?

You need to follow the step by step again.

Although... you might just be able to let some air out... if the tank is at 27.5 and the boiler is at 12... there should be no water in the tank to deal with... so first try letting air out.

CLOSE the manual feed.

If you see the boiler gauge start to drop while you are letting air out, STOP THERE!
 
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Old 02-08-15, 06:21 PM
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Yeah... how that happen?
Can't be a bad tank can it? Geesh, now I'm thinking my old tank was fine Lol
Should be no water in it? I removed this new tank once since getting it and my boiler was cold/90F
and was thinking of exchanging it because it had 2.5 gallons of water in it!
I have that ball valve between the tank and air scoop too, remember!

Ok, will close boiler manual feed, reduce the tank air to 12psi, but STOP if i see the boiler psi start to drop. Will report results
 
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Old 02-08-15, 06:28 PM
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I've lowered the tank psi to 10.5... thought I seen the boiler guage JUST twitch! Stopped there!

I HOPE i wasn't supposed to stop at 12psi regardless! Thinking I should have stopped at 12, then increased with fill valve Although, If i look VERY close, they are a match now!
 

Last edited by Tyannt; 02-08-15 at 06:40 PM. Reason: edit
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Old 02-09-15, 01:35 PM
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You MIGHT still have issue with fill valve.

When boiler is cool and at 12 PSI, CLOSE the manual feed valve and monitor closely.
I may in fact still have a fill valve issue, the boiler is right back up approaching 30psi after running for 12+ hours... " first few hours seems steady about 15psi, next few hours steady about 19-20psi, then 25psi, and eventually hovering on 30psi...
I thought the concensus was, fill valve is ok if NO RISE in boiler psi after hours of being off left to sit..Maybe that's not definitive enough so i'll shut the feed off and monitor...

The only other possibility, to my limited knowledge, is the HWC leaking into the boiler due to a higher psi.

Can anyone explain how water comes through to the taps in dribbles when the feed to the HWC is off? Same, even after replacing the shutoff. I even entertained the thought that cold is designed to flow through the hot within the faucet body, for whatever reason! Is that a silly hypothesis? Lol I had to ask, ya never know!
 

Last edited by Tyannt; 02-09-15 at 03:06 PM.
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Old 02-09-15, 06:37 PM
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Boiler's been off since 4pm, waiting to zero out and adjust tank psi and run with the manual feed closed to test fill valve...

Boiler 90F @ 12psi ... Exp-tank @ 21.5psi

Does this make any sense at all?
 
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Old 02-09-15, 06:54 PM
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T,
Please read this. It may help

www.comfort-calc.net/expansion_tank_info.html
 
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Old 02-09-15, 07:36 PM
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spott,

I read the article and understand the tank's purpose and how it functions as a cushion...

I'm having a hard time getting past seeing the system read 12psi, and the tank 21psi type thing...
I'm obviously failing to understand "the how" of it. Yes, I've been told reading it while there is system pressure means little..

I get impatient I know, but I realize I'll be confused until I at least understand the basics...Trying!

System is cold now, going to zero etc etc
 

Last edited by Tyannt; 02-09-15 at 08:00 PM. Reason: recant
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Old 02-09-15, 08:17 PM
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Didn't you put a ball valve between the system and the tank.
Close the valve, remove the tank and see what it says.
 
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Old 02-09-15, 08:28 PM
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Yes I did put a valve between.. last time I removed the tank it was 1/2 full of water!

I just finished tryint to zero the boiler but can only get it down to 7psi @ 90F, have only let out about 1 quart of water...should I have to let more out, or assume the guage is off! Lol

Water feed, and air vents closed of course!
 
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Old 02-09-15, 08:44 PM
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Are you pulling a vacuum. Why is air vent closed, no need.
Hot or cold if you empty boiler 0psi will appear if gauge correct.
Didn't you say you put a drain on tank also. Did you drain water before testing it.
 
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Old 02-09-15, 08:54 PM
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There is only a ball valve between the tank and the air scoop, didn't have time to wait on ordering a 3 way. The new tank WAS installed and i was having these same problems so I removed it, had to dain it, recharge it and put back on. I didn't measure psi when it was off, I had a crap guage anyway then but bought a digital one since

Closed the air vents according to...
When zero'ing the boiler, close boiler water feed, close any auto air vents, let water out until it drops to "0" etc etc etc as the "sticky" on Exp tanks & relief valves says to do. When the tank is 12psi and boiler still holding 0, open water feed and air vents.

Tried letting more water out with the air vents open, still won't go below 7psi on boiler guage. I
tried at both the pressure relief valve AND the boiler drain. Do not feel a vacuum, flows freely.
 
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Old 02-09-15, 09:03 PM
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So you're getting 21 or whatever with the valve off but water still in the tank. Remove drain and check.
With tank off at some point get a 1/2" nipple, tee, drain.
 
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Old 02-09-15, 09:10 PM
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When I checked the tank psi, the ball valve between it and the air scoop was open!
21psi on the air side, 12psi on boiler.. But, that tells me next to nothing! right, Lol

Anyway, don't know why the boiler guage still reads 7psi when there is obviously no pressure so I'm going to assume the guage is crap even though it's new...Home Depot eh!

Gonna fire this thing up, fill valve has never leaked water in over the 12psi I've set it for, even after 24 hrs... I know it can take longer but, I haven't had the thing running without popping the relief for any longer than that! ONLY thing i haven't done is run the boiler with the water feed off, and keep an eye on, don't want to be up all night worrying cause I don't have a Low Water cutoff..

Maybe tomorrow!
 
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Old 02-09-15, 09:15 PM
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Am I causing you guys mental anguish yet? Lol
 
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Old 02-09-15, 09:21 PM
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How do know its empty. Did you at least open relief valve to see what happens.
If its really empty you can take gauge out and it should say 7psi if crap.
 
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Old 02-09-15, 09:34 PM
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Yup, Used the relief valve AND the boiler drain to try to zero it.
NO i didn't EMPTY the boiler !
Only about 2 quarts of water
Too late to take guage out now..I pressurized the system already, Boiler guage & Tank read 12psi.
 
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Old 02-09-15, 09:49 PM
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Average 3section boiler holds holds about 13 gal. of water. No wonder you still had pressure.
 
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Old 02-09-15, 10:13 PM
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Sooo, I probably did not release enough water out to bring it to "0" ?
I even googled to try and find out how much i may have to let out!

You must have missed me asking that. Maybe I need to start another thread
more on topic Lol

Well, I fired the boiler up.. only reached 18psi by the time it got to 175F.
I am sure by morning it will have popped the relief valve!

Another day of fun..
 
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Old 02-09-15, 10:18 PM
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I would start by draining and checking the tank and go from there.
It wouldn't be the first time for a bad tank.
 
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Old 02-09-15, 10:43 PM
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I hear ya..
I think I'll take the Tank & the guage back... maybe a new fill valve since it's the original from 2005...
Time I got sleep...catch ya, same time, same channel haha!
 
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