Honeywell 8182D Aquastat Cycling Fast Cycling On/Off

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Old 03-04-13, 01:58 AM
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Honeywell 8182D Aquastat Cycling Fast Cycling On/Off

Hi all. First post.
I have a Crane 70 series oil fired boiler that supplies domestic hot water through a tankless coil. It has a Beckett burner and is controlled by a Honeywell 8182D triple aquastat set at 180/160/15 diff.

The problem Im having is when the burner is called for, the burner relay on the 8182 cycles on and off at about a one second interval (one second on, one second off). Each time the relay closes, the burner fires up fine. And if I manually hold the relay closed, the burner continues to run fine.

Does this sound like a bad relay? I have a parts 8182D unit from the last time I replaced it -- two years ago. If it is the relay, is there any reason I cant replace it with the circulation relay from the old unit? (Im perfectly comfortable removing and soldering components to circuit boards)

BTW: I just replaced the nozzle, checked/set electrode gap, cleaned strainer/screen, and replace the filter.

Thanks in advance.
 
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Old 03-04-13, 06:00 AM
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Before doing that, make sure that it's not a thermostat problem.

Change batteries in t'stat first.

If that doesn't help:

Place a jumper across the " T T " terminals in the aquastat to see if the relay holds.

No, it probably is NOT the relay itself. I believe that would be a mistake to change the relay.
 
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Old 03-04-13, 06:53 AM
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Hi NJ Trooper. Thanks for your response. Your posts have been very informative as I've searched the forum archives.

Per your suggestion, I changed the battery. That did not solve the problem.

I then jumpered across TT. That also did not solve the problem. Jumping across TT is just bypassing the thermostat, right? This problem occurs whether there's a call for heat, or if the boiler is just maintaining it's low setting. That would rule out the thermostat, wouldn't it?

Thanks in advance.

jp
 
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Old 03-04-13, 07:06 AM
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This problem occurs whether there's a call for heat, or if the boiler is just maintaining it's low setting. That would rule out the thermostat, wouldn't it?
Yes it would.

Two relays in the 8182, correct?

Are BOTH cycling?

And you say it's like a 1 second period... is this very regular? or is the timing somewhat random?

Just asking to try and figure out what could be causing this... strange one!
 
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Old 03-04-13, 10:03 AM
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Regarding 8182: yes, two relays. The circulator side is functioning fine.

It started out somewhat random: at the beginning, it would drop out momentarily on occasion. I would go down to the basement to check it out, and it would be running fine. Over the next couple of weeks, it would happen more frequently, and the cycling would last longer. Now it happens every time the burner kicks on.

I noticed something that confuses me, but maybe you have an explanation. I was observing the relay cycling and decided to hold it closed to see what would happen as the temperature rose. When it reached 170 (+/-), the burner shut off... while I was still holding the relay closed. So I propped the relay so it stayed closed, and went up and turned up the thermostat so it would call for heat. The burner came on and successfully went through a heating cycle -- providing heat to the radiators, then shutting off when there was no longer a call for heat. I observed it through a few more cycles, and the system seems to be functioning properly with the burner relay propped closed. It heats the living space and provides hot water without over heating. What do you make of that?

Again, thanks in advance.

(EDIT to add: Yes the cycling/rhythm is now very regular: one for one second, off for one second.)
 
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Old 03-04-13, 11:34 AM
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I noticed something that confuses me, but maybe you have an explanation
I'll try...

The relay that is called the 'circulator relay' in the Honeywell docs ALSO DOES control the burner, this is the one that is labeled as " 1K " in the schematic diagram. This is the one that is located to the 'outside' of the control.

Relay 1K is controlled by the thermostat.

The contact set ' 1K1 ' operates the circulator and the set ' 1K2 ' operates the burner.

The other relay, called " 2K " is located in the 'center' of the control and is the 'safety lockout relay' which in the event of a call for heat and a 'no flame' condition (the CAD CELL senses no flame) will lock out the burner.

The relay 2K is only controlled by the safety circuit.

I presume that the relay you are propping closed is the 2K relay?

If so, what you are observing makes sense.

Your 8182 control is a 'combination' control. It actually consists of the boiler aquastat AND the oil burner primary control combined into one package.

The 1K relay is the aquastat relay, and the 2K relay is the oil primary safety relay.

I have to caution you that you are bypassing a very important safety control by propping that relay closed! If there is a call for heat and your burner does not fire, or the flame fails, your burner will continue to run and spray fuel into the combustion chamber. NOT GOOD! Could be DANGEROUS!

I do believe that the aquastat is defective. Swapping a relay from the old one won't fix it. The problem is in the safety circuit. Possibly a defective triac component... but can't say for sure without testing it...

So it sounds as if you need to replace that, but it is remotely possible that the CAD CELL in the burner is either dirty, or defective.
 
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Old 03-04-13, 12:24 PM
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Hi again NJ Trooper.

Thanks for your detailed explanation of the layout/operation of the 8182. That info along with one of your posts in another thread have really helped my understanding of the system.

You're correct: the center/K2 relay is the one that's cycling, and is the one I've been operating manually. Good to know that I'm currently operating without a safety net... indeed, not a good thing. I will definitely remedy that right away.

I did clean the CAD when I did the other maintenance (filters, nozzle, electrodes). For diagnosis of a bad CAD, can I simply short the two yellow wires together?

What are the other components that comprise the safety circuit?

Thanks again!
 
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Old 03-04-13, 01:02 PM
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For diagnosis of a bad CAD, can I simply short the two yellow wires together?
Yes and no...

You won't be able to START the burner with the CAD shorted, it will fault and lock out... or it SHOULD.

You can short them AFTER the burner starts though.

Do you have a multimeter and know how to measure ohms?

Since you are already proficient in bypassing the safety circuit, prop the 2K relay closed, remove the cad cell wires from the control, start the burner and measure the resistance of the CAD cell... Anything over say 1500 ohms is a problem. A 'typical good' resistance would be around 400 ohms or so...

Thing is though... if the cad is bad, the control should simply lock out.

That is another test you can do, while the thing is running, disconnect the cad and see if it does in fact lock out.


Safety circuit in yellow highlight:

Name:  pierce100_8182D.jpg
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The HIGH LIMIT is ALSO a safety circuit, but not part of the flame sensing safety.
 

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Old 03-04-13, 01:49 PM
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Yes, I have a multimeter and can measure ohms. Will test as you describe:

I'll start the burner, disconnect the CAD wires (see if that initiates lockout) then measure resistance through the CAD.

I also have another CAD from a "parts" burner that I can swap in if necessary.

I'll let you know what I find.

Thanks!
 
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Old 03-04-13, 04:50 PM
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Tested the resistance on the CAD: 400 - 450 ohms with the burner running.

With the safety circuit intact (not propping the relay closed) and the CAD disconnected, the "breaker" would trip and lock out.

If I'm understanding this correctly, that's telling us the CAD is functioning properly, correct?

jp
 
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Old 03-04-13, 07:11 PM
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Yeah, that all sounds just fine...

Honestly, I don't know what else to tellya. I suppose that one of the electronic components could be 'leaky'... but it still doesn't explain why it would 'cycle' on/off/on/off ... one would think it would just simply lock out and that would be that.
 
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Old 03-05-13, 12:12 PM
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Hi again NJ.

It looks like its time for a new aquastat.

From the info I gained from searching on this forum (most of the info coming from your posts) it appears I can ditch the 8182, in favor of a simpler aquastat and separate primary. That would save me $150 in new parts. But as it turns out, I have those parts at home already (they were given to me as spares from a friend). I'll check the part numbers to ensure exactly what I have.

Does that seem like a reasonable strategy?

Again, thanks!

jp
 
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Old 03-05-13, 06:23 PM
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So the parts I have on hand are:

L8124C 1102 Aquastat

8184G 1427 Primary.

Any reason I can't use these in place of the 8182? Anything I'd need to watch out for?
 
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Old 03-05-13, 06:31 PM
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Any reason I can't use these in place of the 8182? Anything I'd need to watch out for?
They will work.

The challenge for you is going to be mounting and wiring.

Of course the 8124 will mount on the same immersion well as the 8182, but you will need to mount the 8184 on a utility box and wire it to the burner.

Are you comfortable with this?
 
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Old 03-05-13, 07:13 PM
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You'll wire like this:

Name:  pierce100_8184G.jpg
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If looking at the PDF for the 8184, your AQUASTAT is the " LIMIT " that is referred to in the diagrams.

Note also the JUMPER on the T T terminals of the 8184.
 
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Old 03-05-13, 07:32 PM
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Thanks for the schematic.

Yes, I'm comfortable mounting the 8184. I was thinking I'd mount it behind the primary coil -- I have one of the Carlin half-size coils, so thought it might fit nicely there.
 
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