Over-running high temperature limit control!

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Old 01-13-07, 02:29 PM
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Over-running high temperature limit control!

I started snooping around my boiler (CAC/BPD) because my heating bills have been very high. I noticed the following.

- An auquastat ( 6" X 8" box attached to the control side of the boiler. It is set at 180 deg.

- Honeywell L6006C Auquastat strapped to the return, set at 200 deg. (inside the offset dial is set at 5)

In observing several cycles I noticed that when the thermostat calls for heat the burner lights and stays on until the temperature is about 215 deg. (Bringing the pressure to 28 psi against a 30 psi emergency relief valve!). After the burner shuts off, it does't come on again until about 130.

Questions:
1. Why do I have 2 aquastats? (burner and pump control? which is which?)
2. What is causing the temperature to rise above the setting on either aquastat?
3. Does this sound like the cause of high heat bills (it seems to take forever (20-30) minutes for the temp to get from 180 to 215).
4. What controls the temperature that the burner fires. It seems like it should be higher than 130 deg.
5. Is the "Strap on" design of the L6006C reliable?

Thanks in advance for you help.

Steve
 
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Old 01-13-07, 04:15 PM
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GAS or OIL ?

Without seeing how it's wired, I would guess the 6006 to be a secondary high limit control, which would act in case the primary high limit in the other aquastat box failed.

If it's a high limit, it's probably set correctly.

If instead however, it's a low limit control, then it's not set correctly, but don't change anything yet!

I don't think your circulator pump is running, and you may have a marginal condition with the expansion tank. If the secondary high limit is what's shutting down the burner (temp going high... 215 is too high IMHO, should be 180-ish) then you probably also have some problem with the primary aquastat (the 6x8 box) ... WHAT MODEL is that primary ?

just my amateur guesses... what thinks others?

You might oughta get a tech to look it over especially if it hasn't been serviced regularly!

Snoop around with the search feature on this forum also, you'll find all kinda good info ...
 
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Old 01-13-07, 04:27 PM
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Gas

Thanks for the reply.

Thanks for the confirmation about the settings being correct. Any idea why the burner is ignoring the settings and continuing to run.

You're probably right about getting a tech but I'm a little gun shy from my last experience with a local tech. 1 week after a "routine cleaning" the furnace failed to light (after many years of perfect operation before the "service". Since this house is seldom used in the winter, the result was frozen pipes, demolished house, requiring complete renovation. Needless to say, I'm a little queezy about my heating system.
 
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Old 01-13-07, 05:06 PM
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I don't know what you mean by the control being "6" X 8" box attached to the control side of the boiler". If it has a model number that would help a whole lot. If it has a bulb that goes in a well on the boiler, we need to know that too. If it is a triple aquastat (which we could tell by the model number) we can figure out why it is acting up. The control strapped on the return sounds like it should be a reverse aquastat. There to stop the circulator if the return water is too cool. It won't function quite right if it is installed that way, but without seeing it, I can;t see any other reason to have a control on the return pipe. Give us more info and pictures if possible and we can unravel this mystery.

Ken
 
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Old 01-13-07, 05:15 PM
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L8148e1257

According to the boiler manual it is a L8148E1257. Unfortunatly, I'm not at that house right now so I don't think I can answer the other questions.

thanks,

Steve
 
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Old 01-13-07, 05:38 PM
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xxxxxxxxxx
 
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Old 01-13-07, 05:41 PM
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Originally Posted by KField View Post
... The control strapped on the return ...
Ooops... Ken thanks for saying that again, cuz I missed it when I read the first post! That's a whole 'nuther ball game, not a high limit.
 
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Old 01-13-07, 05:46 PM
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Question Why it might be over shooting.

I've seen aquastats fail, and found that It was off by a margin of upto 60 degrees. Why is uncertain. I have customers who's aquastats high limits are set at 120 degree's, but the boiler runs till it gets upto 180 degree's. If I were to turn it up to 180 degree's it would boil and blow off the relief valve. After explaining what I found, they all opted to keep the aquastat at the lower setting instead of replacing it (spending a couple hundred bucks). I could only assume that one of a few things might have happened. The well that the probe is in could have mineral buildup or something else that is acting as an insulator, causing the temp to overshoot due to the delay. Another possibility is that the aquastat just failed to be accurate anymore. I wonder if perhaps the L6006C on the return might be a circulator control that is just set wrong. I've seen applications where a strap-on on the return was used to keep the circulator running after the control & thermostat stopped calling to help dump the heat into the living space instead of having standby loss. Pictures would help. Is (CAC/BPD) an abreviation for something? This is oil, right? Is there a model # on the aquastat (6x8)?
 
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Old 01-13-07, 05:51 PM
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Cool tools/knowlege?

Do you have and know how to use a multimeter? Do you understand electricity/circuitry? If worse comes to worse, you may need to call a tech in. I reccomend asking for someone who is good at troubleshooting or perhaps use a company that doesn't sell oil. Where are you located?
 
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Old 01-13-07, 05:54 PM
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HVAC, if that is a circ control as you describe, with it set at 200 would the circ always run or NEVER run... I'm thinking never ???

Where are the wires on that control going to ?

pics, we need pics...
 
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Old 01-13-07, 06:15 PM
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Originally Posted by HVAC-EMT View Post
I've seen aquastats fail, and found that It was off by a margin of upto 60 degrees. Why is uncertain. I have customers who's aquastats high limits are set at 120 degree's, but the boiler runs till it gets upto 180 degree's. If I were to turn it up to 180 degree's it would boil and blow off the relief valve. After explaining what I found, they all opted to keep the aquastat at the lower setting instead of replacing it (spending a couple hundred bucks).

I would agree!
So what do I do...figure out which one of the 2 aquastats controls the burner and just keep turning it down. the whole system is only about 3 years old. Do you think it might be covered in a warranty?

I could only assume that one of a few things might have happened. The well that the probe is in could have mineral buildup or something else that is acting as an insulator, causing the temp to overshoot due to the delay.

It seems to be just strapped on to the pipe. Honeywells website seems to indicate that the C designation does not go in a well. I wondered if it doesn't have good contact with the pipe and that is causing the error.

Another possibility is that the aquastat just failed to be accurate anymore. I wonder if perhaps the L6006C on the return might be a circulator control that is just set wrong.

What would indicate that it is set wrong?

I've seen applications where a strap-on on the return was used to keep the circulator running after the control & thermostat stopped calling to help dump the heat into the living space instead of having standby loss. Pictures would help.

Unfortunatly I'm not at that house.

Is (CAC/BPD) an abreviation for something?

It's the only designation I could see in the manual (searching the web, I thought it might be the manufacturer.

This is oil, right?

Gas

Is there a model # on the aquastat (6x8)?
According to the boiler manual it is a L8148E1257.
 
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Old 01-13-07, 06:17 PM
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Yes I have a multimeter and come knowledge of circuitry

Yes I have a multimeter and come knowledge of circuitry
 
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Old 01-13-07, 06:21 PM
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Talking if wired in parallel

NJ, I believe the boiler aquastat is a cold start control, and if L1 was wired to the strap on and it was utilized as a close-on-temp-rise aquastat with the other side wired into C1, with that terminal also wired to the hot side of the circulator, then if the thermostat called for heat, the boiler aquastat would send power to C1 making the circulator run. If the strap on aquastat was set at 120 degree's, then as soon as the temp of the return pipe reached 120+, it would also send power to C1. Next, after the thermostat satisfies, the boiler aquastat stops sending power to C1, but since the return pipe is still over 120 degree's, the circ. will still run. As the system temp drops below 120, the strap-on opens, causing the circulator to stop running till the thermostat calls again. This would only really work if you either had one zone or if each zone had it's own circulator and strap-on.
 
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Old 01-13-07, 06:21 PM
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Circ

Originally Posted by NJ Trooper View Post
HVAC, if that is a circ control as you describe, with it set at 200 would the circ always run or NEVER run... I'm thinking never ???

if the system gets to 215 deg. and the thermostat is still calling for heat, the circ stays on until the stat is satisfied


Where are the wires on that control going to ?

pics, we need pics...
Uhhh...I forget...I sure wish I had some pix.
 
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Old 01-13-07, 06:29 PM
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parallel

[QUOTE=HVAC-EMT;1107054]NJ, I believe the boiler aquastat is a cold start control, and if L1 was wired to the strap on and it was utilized as a close-on-temp-rise aquastat with the other side wired into C1, with that terminal also wired to the hot side of the circulator, then if the thermostat called for heat, the boiler aquastat would send power to C1 making the circulator run. If the strap on aquastat was set at 120 degree's,

The strap on was set at 200 deg.
 
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Old 01-13-07, 06:38 PM
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Question aquastats

The strap-on aquastat doesn't have a well. The bigger one does, and it most certainly controls the burner (unless you had a "creative" installer). The question is, does the strap-on close on temperature rise, or open on temperature rise? I believe these controls have 3 terminals making so you can use them as either. Where does the wire from it go to? I would suggest turning down the temp on the boiler aquastat (6"x8" box) to a temp 35 degree's below what it is set at and see what happens. Why does it drop down to 130? More info might help. Is this a gas gun, burner rack, sealed combustion, ceramic burner, etc... does it have a standing pilot, spark ignition, hot surface ignitor, etc... is there an automatic damper? Any other info?
 
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Old 01-13-07, 06:44 PM
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Unhappy 200 degree's

My thought is that maybe the installer had installed it and set it at 120 +/-, but perhaps for some reason, someone turned it up to prevent the circulator from coming on to troubleshoot or service something, but then forgot to turn it down. I'm making lot's of assumptions since I don't know how it is wired, and what it goes to. I could be way off on my theory. If I was there in person, I could tell you one way or the other for sure, but I'm not.
 
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Old 01-13-07, 06:48 PM
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So if it _is_ a circ control, set up to STOP the circ if the return temp is below setpoint, then with it set at 200* the circ will almost NEVER run ???? or should the standard A'stat run the circ since the switch in the 6006 is wired across the contacts ? I think I'm confused...
 
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Old 01-13-07, 06:54 PM
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And if it were setup as Ken thought, it would be wired in series with the circ, and set up to break on temp fall... is that right ?
 
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Old 01-13-07, 06:56 PM
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Lightbulb parrellel/series

Originally Posted by NJ Trooper View Post
So if it _is_ a circ control, set up to STOP the circ if the return temp is below setpoint, then with it set at 200* the circ will almost NEVER run ???? or should the standard A'stat run the circ since the switch in the 6006 is wired across the contacts ? I think I'm confused...
If several switches are wired in series to a light, then all of them would have to be on for the light to work, but if they were all in parrallel, then if just one of them was on, then the light would work. What I am referring to in this application is that if either switch (the boiler aquastat or the strap on aquastat) were to close, then the circulator would come on. The only way for it to shut off is if both of them were off. So, if the thermostat calls, the circ would come on, or if the strap on were to call, the circ would come on. If they both called it would come on too. Hopefully I didn't over simplify it.
 
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Old 01-13-07, 07:01 PM
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thanks, you are very helpful

[QUOTE=HVAC-EMT;1107062]The strap-on aquastat doesn't have a well. The bigger one does, and it most certainly controls the burner (unless you had a "creative" installer). The question is, does the strap-on close on temperature rise, or open on temperature rise? I believe these controls have 3 terminals making so you can use them as either. Where does the wire from it go to?

If I recall, it goes to the L848E, I'm stretching a bit but I think one lead goes to the TV point?
 
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Old 01-13-07, 07:02 PM
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continued

I would suggest turning down the temp on the boiler aquastat (6"x8" box) to a temp 35 degree's below what it is set at and see what happens. Why does it drop down to 130?

what controls the minimum temperature of the system, that is, what tells the burner to fire? It drops down to 130 if the stat is satisfied.

More info might help. Is this a gas gun, burner rack,

There are 3 manifolds (cylinder in shape) in the burner, it has intermittent ignition, the model is BW1 according to the manual. I have looked but can't find a manufacturer name...which seems odd. there is an automatic damper. the whole system was replace about 3 years ago.

sealed combustion, ceramic burner, etc... does it have a standing pilot, spark ignition, hot surface ignitor, etc... is there an automatic damper? Any other info?[/QUOTE]
 
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Old 01-13-07, 07:09 PM
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Question Other possibilities???

If the strap on were wired in series, then what would it go to? If it was used as a high limit safety, then I would think that it would be strapped to the supply and wired in series to the burner, but being set at 200, and on the return, I can't think of any sane reason to have it that way. The temp on the return should never ever be 200 degrees. Maybe it should be turned down too. Why else would you put a strap-on on the return? Is there a hydrocoil piped into the system? I think the answer to our mystery is in the wiring. If it were wired in series with the circ and setup to break on temperature fall, then the return would need to be 200 degrees before the circ kicked in, but how could that work?
 
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Old 01-13-07, 07:17 PM
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...If several switches are wired in series to a light, then all of them would have to be on for the light to work, but if they were all in parrallel, then if just one of them was on, then the light would work...

right, that's the difference between an AND or an OR gate. I got that part ok, just wanted to understand the difference between your idea and Ken's idea. They are subtly different I think.

If wired in series, the circ would stop if the 6006 were set up for break on temp fall (or make on rise, same thing, ain't it?) and the temp fell below the setpoint +/-diff . I think this is what Ken sed.

If wired across the K1 contacts in the 8148, as you suggest, then the primary would always be in control of the circ, but the 6006 would over-ride the 8148 and run the circ after the heat call, until the return falls below setpoint +/-diff ...

Now, keepit thinks there might be a wire on the TV terminal... hmmm.

Keepit, are there zone valves on the system ? or circs ?

need I say again... did someone say something about ... naaahhhh
 
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Old 01-13-07, 07:17 PM
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Cool Burner operation

With a cold start control (boiler aquastat), the only thing that tells the burner to fire is the thermostat. If you were to turn the thermostat all the way down or off, I think you will find that the boiler will drop to room temp. The setting on the control acts as a high limit for the burner. What is that set at, by the way? If it is turned all the way up, then I can understand why it is reaching 215 degree's. The burner will fire as long as the thermostat is calling, and the aquastat hasn't reached it's high limit setting. Has anyone worked on it since last winter? I've seen guys turn up the limits for testing purposes, but then forget to turn them down. Who else has access to the boiler?
 
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Old 01-13-07, 07:23 PM
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2 zone valves, 1 recirc pump

2 zone valves, 1 recirc pump
 
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Old 01-13-07, 07:24 PM
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...If it were wired in series with the circ and setup to break on temperature fall, then the return would need to be 200 degrees before the circ kicked in, but how could that work?...

It couldn't. That's kinda what I'm trying to figure out. The way his system is reacting, it's as though the circ isn't running, and possibly the high limit in the 8148 is shot ... I mean, even if the circ wasn't running, the burner should shut down somewhere around 180* , right ? Maybe it IS shutting down at 180, but since the circ might not be running, it's overshooting up over 200 ... isn't that the title ?

If it were wired as Ken suggests, with the 6006 set at 200* the circ would never run until the system was WAY over setpoint. With only gravity flow to heat the house. And high bills.
 
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Old 01-13-07, 07:25 PM
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What is that set at, by the way?

It is set at 180 deg

Has anyone worked on it since last winter? I've seen guys turn up the limits for testing purposes, but then forget to turn them down. Who else has access to the boiler?[/QUOTE]

no one else has access
 
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Old 01-13-07, 07:27 PM
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...If the strap on were wired in series, then what would it go to? ...

C1 to R on the 6006, but NOT the circ.

either W or B (whichever is make on rise) on the 6006 going to the circ.


I would think this setup has the potential to thermally shock the boiler.
 
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Old 01-13-07, 07:30 PM
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I say, when you get back over there to take the pi.... ahh, never mind.

I would take the setting on the 6006 down to 130 and see what happens.
 
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Old 01-13-07, 07:37 PM
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I think the manf might be Carrier/Bryant ...
 

Last edited by NJT; 01-13-07 at 07:48 PM.
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Old 01-13-07, 07:45 PM
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I'll try that

I guess one of them has to be the high limit. If I turn each of them down to 130 (one at a time) I should able to tell which one it is.

thanks for your help
 
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Old 01-13-07, 07:49 PM
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Red face Hmmm, Good Luck!!

Originally Posted by keepitrunning View Post
I guess one of them has to be the high limit. If I turn each of them down to 130 (one at a time) I should able to tell which one it is.

thanks for your help
Otherwise, you may need to pull out yer multi-meter and trace out wires.
 
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Old 01-13-07, 07:50 PM
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The high limit is definitely the one in the 8148. The 180* setting on that is more or less correct. I would first turn the 6006 down to 130-140 and see what happens.
 
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