Propane boiler malfunction, turning off and re-igniting during heat cycle

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Old 12-24-11, 12:40 PM
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Propane boiler malfunction, turning off and re-igniting during heat cycle

Hello,
New to Do it yourself, Nice forum!

Anyways, I have a propane boiler heat system acting up. A bit of history first, it has a S8610m controller and just had a new pilot assembly installed by service tech last week. This boiler has always had a hard time lighting for the first time if it sits for a while. The system will sometimes go through three failed pilot lighting cycles before successfully lighting the pilot and starting up. It seems that once the furnace lights and the system is warmed up, it re-lights very quickly (almost like it looses it's prime when it sits for a few hours without running).

Anyways, Thats the history and now the newest problem. Now the furnace will be running just fine and all of a sudden when the furnace is nice and warm (about 180 degrees) it quickly shuts off, starts re-igniting cycle and restarts- all within 3 or 4 seconds. This will sometimes happen a dozen or more times and sometimes just once or twice and there is no noticeable time frame of the occurrences. The thermostat is still calling for heat and I'm certain its not breaking the loop to cause the problem because I have jumped the connection at the furnace and it still does it.
Other things I have tried so far: Jumped the flame roll out switch and blocked flue switch.
Any thoughts?

Thanks
 
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Old 12-24-11, 03:29 PM
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had a new pilot assembly installed by service tech last week
How come?

What's the make/model of the boiler?

Was this a propane unit since day one? In other words, it came from the factory set up for propane?

Did the tech check the gas pressure?

What do the flames look like when it's burning?

The possibilities that I can think of are:

1. BAD GROUND CONNECTION.

2. Pilot flame not hitting the flame rod correctly.

3. Problem with the 8610 flame sensing circuit (intermittent).

It sounds as though the control (8610) is thinking that the flame went out... and relights. I would first examine very carefully all the ground connections... they are critical to the operation.
 
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Old 12-25-11, 12:02 AM
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NJ

The service tech replaced the pilot assy because I told him of the problem with the unit not starting very easily. We have been using this same guy to do yearly service and maintenance to our furnace for years and he thought that might be the problem. I noticed that this new pilot assy seems to get a lot of that black soot built up on the fork part where the pilot flame hits it and it knocks right off with a little tap. I remember seeing that soot before but not as much and not as fast. Maybe this starting and stopping has something to do with this new pilot assy. It looks like trying to fix one problem may have caused an additional problem.
BTW, I have checked all the grounds and all checks out. I'm really not sure of the flame placement on the rod so I'm going to have to do some research on that, and after looking into replacing the 8610m, it looks like this is an obsolete unit and there is a newer version (8610u) out with a status indicator light that may help troubleshoot some problems. Its really looking like this unit may be the problem with the stubborn ignition issue and maybe the pilot flame position may be incorrect.

Thanks for the heads up and I'll post back after the holidays when I get some info on that flame position and possibly a new 8610u module installed.
 
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Old 12-25-11, 07:20 AM
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But what about the rest of the questions?

What's the make/model of the boiler?

Was this a propane unit since day one? In other words, it came from the factory set up for propane?

If this was a 'field conversion', it must have been done properly. There are several things that need to be done for a nat to LP conversion.

Did the tech check the gas pressure? IMPORTANT!

What do the flames look like when it's burning?

Describe the color.
seems to get a lot of that black soot built up on the fork part where the pilot flame hits it
That shouldn't happen. There should be no black soot, anywhere! If there is black soot, there is a combustion problem. Black soot also means there is CO ! Check gas pressure and pilot adjustment.

It looks like trying to fix one problem may have caused an additional problem.
When troubleshooting ANYTHING, always start with the last thing that was touched.

BTW, I have checked all the grounds and all checks out.
How did you 'check' the grounds. Sometimes just looking at them isn't enough... that flame rod puts out a very miniscule current which can be disrupted by even the slightest resistance in the ground connection... particularly the one to the burner, which is subject to the heating / cooling. Since the pilot assembly has been changed and things were 'wiggled around' in there, it's all the more reason to suspect a grounding problem.

possibly a new 8610u module installed.
It may come to that, but that part ain't exactly cheap, so have tech do the other checks first, and also have him TEST THE COMBUSTION! with an instrument... you need to know that the flame is burning clean...

AND MAKE SURE YOU HAVE FRESH BATTERIES IN YOUR CO DETECTORS, and IF YOU DON'T HAVE DETECTORS, GET THEM!
 

Last edited by NJT; 12-25-11 at 07:36 AM.
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Old 12-25-11, 07:28 AM
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If you do end up replacing the 8610, pay attention to the wiring. The new module will have some differences between the old. In particular, the notes in the right hand column of "TRANSFORMER SECONDARY" in Table 3 of this PDF:

http://customer.honeywell.com/techli...it/69-0729.pdf

Read and understand the instructions before starting!

Take digital pics of the wiring before starting, and tag each wire where it came off the old control!

Patriot Supply - S8610U3009
 
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Old 12-25-11, 07:41 AM
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The pilot soot problem could be due to the wrong orifice in the pilot. If the pilot looks unusully large the orifice could be for natural instead of LP.
Your initial slow start could be an LP regulator problem or a pilot valve not opening as it should. In both cases it takes someone with instruments to measure the gas pressure.
 
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Old 12-29-11, 09:25 AM
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Well, thanks for all the replies, I got it figured out. After having the service tech come back out, it turns out the pilot was both turned up too high as well as mounted a bit offset where the pilot was not getting a complete burn at the tip of the assembly causing that black ball of soot to quickly build up on the tip. This was interfering with the flame sensing process and causing the controller to think the flame was out. All is well and its been up and running for a couple days with no buildup at all on the pilot.

Thanks a lot
 
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