L8148E Aquastat problem

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Old 11-08-12, 04:37 PM
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Buderus Logano G234 will not light

Prior to the recent storm in the northeast I disconnected the Logamatic controller and turned off the power and gas from my burner.
I got lucky and was not flooded.
I've now reconnected the Logamatic and restored power and gas to the boiler, but it will not fire up.
The controller powers up, there are no error messages, but, although the readout shows that the burner is on, the gas does not ignite.
I've determined that the aquastat relay is not getting power through terminals 8 and 12, and assume this means that the gas valve is not being energized.
Not sure where to go from here.
I made careful notes when I disconnected the controller, and am confident that I've reconnected it correctly.
Any input gratefully received.
 
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Old 11-08-12, 04:43 PM
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Sorry - that's terminals 4 and 12 on the aquastat.....not 8 and 12
 
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Old 11-09-12, 07:15 PM
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L8148E Aquastat problem

Further to my problems with my Buderus gas fired boiler. I initially posted an issue with the Logamatic 2107 control - now apparently resolved. However, the boiler still will not fire.
I now suspect the Honeywell L8148E aquastat.
When I turn on the system the Aquastat is energized, the relay pulls in - but I'm not getting 24 volts across B1 and B2. My aquastat has the vent damper option installed, and that circuit does not seem to be getting 24 volts either - the damper is in the half open position. Jumping out the thermostat - TV & T - does not change the situation.
Before I condemn the Aquastat, what else can I do to test it?
Thanks for any input.
 
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Old 11-09-12, 11:05 PM
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Hi Shang, I've merged your two questions into one thread, there's no problem asking another question in the same thread on the same problem. Makes easier for us to answer as we know a bit of 'history'.

Does the relay in the aquastat 'click' when a thermostat calls for heat?

If your damper is stuck in the middle, the system won't fire up. You need to repair that first. Don't try to turn that damper shaft by hand, you will damage the motor and/or gears for certain.

How did you determine that the damper isn't getting 24V ?
 
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Old 11-10-12, 05:06 AM
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Hi NJ Trooper
Thanks for your input.
Yes, when I switch the control on the Logamatic to manua,l the relay on the aquastat clicks in, and the line voltage circulator turns on. I am not getting 24 volts at terminals B1 and B2 - but I understand that the damper circuit may be preventing the B1/B2 circuit. I'm looking for a wiring diagram for the Effikal vent damper now. The plug on the aquastat end has 5 wires - on the plug end at the damper, 4. When I research that Effikal product on the internet I find references to a recall, and it doesn't seem to be generally available now. I did find a product which appears to be a replacement. Made by Field controls.
GVD-7PL - Field Controls GVD-7PL - 7" Automatic GVD Vent Damper
The wiring color codes appear to be the same.
I'm going to try to test the aquastat plug now to see if I'm getting 24volts.
More later.
 
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Old 11-10-12, 05:40 AM
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Update:
According to the wiring diagrams I can find, at the damper, the black and brown wires - terminals 1 & 4 should receive 24V constantly when the boiler calls for heat. I'm not getting anything there.
Although I can't find a reference to terminals T1 and T2 in the literature for the Aquastat, it looks to me as if these terminals are the 24V output from the transformer. I'm not getting anything there, either.
I have a Buderus room sensor wired in to the Logamatic. Another odd and disturbing thing is that the indicator lights are flashing between day/night & automatic when I turn on the boiler. I suspect that this may also have to do with the lack of 24V at the aquastat.
 
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Old 11-10-12, 07:00 AM
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Sorry to make this such a treatise.......but I think I've gone as far as I can go.
This is what I've got:
I was wrong about T1 & T2. With the terminals from the transformer plugged in to the circuit board I have 24V ac at the terminals when I turn on the boiler.
I have 24V ac at the brown and black wires for the damper - I believe they should be energized when the boiler is turned on.
I disconnected the damper motor from its circuit board and supplied 24V to the motor, it rotates and the damper appears to be fully open.
I've tried jumping out the room sensor (thermostat) on TV & T.....I believe both the thermostat and damper switches must be made to energize the gas valve.
Still nothing.
The Logamatic tells me the burner is firing - but the gas valve circuit never energizes.
To me its looking more and more like the circuit board of the aquastat, but I'm eager to be told I'm wrong!
Thanks
 
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Old 11-10-12, 09:02 AM
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I'm unable still to get at my reference materials... my network router took a dump and all that stuff is on another machine... let me see what I can figure out from what you've written. Standby please.

By the way, I'm not at all familiar with the Logamatic operation, but I don't think the problem is there from what you've checked out so far.
 
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Old 11-10-12, 09:13 AM
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With one meter probe on the aquastat TV terminal and the other on either or both of the terminals on the top of the high limit switch in the aquastat ( OR terminal #5 of the damper plug in the aquastat) you should see 24VAC on a call for heat.

When the damper is fully open and the 'endswitch' in the damper motor assembly 'makes', you should see 24VAC on terminal #2 of the damper plug in the aquastat.

If you have voltage at terminal 5, but NOT at 2, it means that the damper assembly endswitch is not 'proving' that the damper is fully open.
 
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Old 11-10-12, 09:17 AM
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Terminals 1 and 4 in the aquastat damper plug should be always 24VAC. This is the power to the damper motor assembly.

When the aquastat calls for heat AND the high limit has not been met (cool boiler), you should see 24VAC at terminal 5.

When the damper endswitch proves, that 24VAC on pin 5 is passed through the endswitch in the damper assembly and back to terminal 2 and from there to terminal B1 to the gas valve.
 
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Old 11-10-12, 11:05 AM
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Boy, what a trooper you are!
From TV to the top of the high limit switch, I have 24VAC
On terminals 1 & 4 of the damper cable assembly I have constant 24VAC
I don't immediately see how to test for 24VAC at terminal 2.......but I'm definitely not getting 24VAC at B1 & B2
 
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Old 11-10-12, 11:09 AM
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While the aquastat end of the damper cable has five conductors (Yellow, Brown, Orange, and two Blacks), the cable plug at the damper end of the cable only has four conductors. The Black & Brown (conductors 1 & 4) are constantly energized when the boiler is on. I'm confused about the precise function of of the orange (2), and the yellow (3).
 
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Old 11-10-12, 11:18 AM
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I neglected to mention that I bit the bullet this morning and purchased a new aquastat (the supply houses were closing for the weekend, and I'm supposed to fly out of the country early tomorrow).
The new aquastat made no difference. Still no juice at B1 & B2
It came with a plug for use with those who have a damperless system. There is a jumper across the yellow and one of the black conductors.
From the logic you laid out in your earlier post, I would have thought that a jumper should have been between a black and the ORANGE wire (terminal 2) - but perhaps I'm confused. Anyway, with the jumper plug in place I still do not have 24V at B1 & B2.
 
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Old 11-10-12, 12:34 PM
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Mr Trooper - I owe you a huge debt of gratitude!
Your analysis has apparently led me to the solution.....problem does, indeed, appear to be the damper endswitch.
I was thrown by the little jumper plug that was supplied with the new aquastat.
The jumper was between the orange wire terminal (from the thermostat), and the 24V hot line. That didn't seem right to me. I changed the jumper to provide power to the terminal for the yellow line......feeding B1, plugged it in, and bingo!
I don't want to be too triumphal......danger of hubris!, but the boiler is currently running. I have the damper in the fully open position. Thank you so much.
 
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Old 11-10-12, 04:22 PM
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PLEASE! MAKE ABSOLUTELY CERTAIN THAT THERE IS NO WAY IN HELL THAT THE DAMPER CAN BE ACCIDENTALLY CLOSED!

If that damper is allowed to close while the boiler is running people can be killed from Carbon Monoxide poisoning!

Make ABSOLUTELY CERTAIN that it is CLAMPED in an OPEN position and there is NO WAY for it to close!

Replace it AS SOON AS POSSIBLE!
 
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Old 11-10-12, 04:27 PM
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I understand.
I'll have it replaced next week.
It is unplugged from the wiring harness, and I will put a couple of screws through the duct as an extra precaution.
Thank you again.
 
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