Weil-McLain oil boiler locking out once per day. Please help.


  #1  
Old 12-03-05, 12:17 PM
bgauch
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Weil-McLain oil boiler locking out once per day. Please help.

The specs:

Forced hot water, Oil heat, Weil-McLain P-368-WT, Beckett Model AFG burner, set up in an induced draft side power vent configuration, about 13 years old.

My burner has been locking out aperiodically for the past 2 years that I have owned this house. At times it is worse than others. Right now, it is locking out once every day or two. It almost always restarts on the first reset. I have had the annual service done both years (Dec 03 and Oct 04). In addition, they came out again this past April to try to resolve this issue. Each time they tested and proved all the safety controls and said they were working perfectly. Each time they have replaced the nozzle and the eye (which was covered with soot) as well as the filter on the tank. They tested the transformer and said it was fine. At the last service, it tested at 85 1/2 % efficiency. There is someone comming out on Monday, but I am guessing all they will do is replace the nozzle and eye and tell me to call them back if it happens again. My main problem with that is that when I call them back I get a machine and they never call me back.

It seems to always lock out at night while I am asleep. Last night, I happened to be lying in bed awake at 3:30 when I heard the burner kick on for 10-15 seconds, off 3-5, on for 10-15, off for 3-5, then on for 10-15, then off. At that point I knewfor it was locked out. After about 15 minutes I went down and sure enough, the thermostat was reading 20 degrees colder than the minimum setting on the aquastat. I hit the reset and it started right up. At that point, I started searching for answers to this problem. I have pretty much reached the "replace it all" state, but I calmed back down adn am prepared to hunt this problem to its correct solution. I am good with my hands and could probably do this myself, but I mostly want to know what I should insist on having done on Monday. Please help. Thanks.
 
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Old 12-03-05, 12:59 PM
U
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I like to put a second screw on type filter by the burner. It looks like an oil filter from a car, but made for an oil burner. change the filter at the tank. the pump strainer. check the oil pressure at the pump, and the cutoff pressure. when the unit stops, the pressure should drop about 15 to 20 % and hold for at least 5 min. do a vacuum check. securely install a vacuum gauge in an unused intake port. you should get 1" for every 1 foot of lift- 1" for every 10 feet of horizontal run and 1" for a clean filter. If there is substantially more vacuum present, there is a restriction in the oil supply. check under the primary control that all wire conections are tight. Turn off the power first. a compleat combustion test should be done. Make sure they do a smoke test and get NO smoke. that is what causes soot build-up. they can NOT tell how the flame is doing by eye.
Mike
 
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Old 12-03-05, 05:24 PM
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Lockout

In addition to Mike's comments, with which I would agree, I would like to see the addition of a pre & post purge primary control. You could use either a Honeywell R7184P or R7184U. Either one would require the installation of an electric oil solenoid valve if there is not one already. If your service company uses Carlin controls, Carlin also makes similar devices but I don't know the numbers. The power venter should be set for at least a 5 minute post purge.
 
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Old 12-04-05, 04:16 PM
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Do notg rule out the draft prover onthe powerventer. I have had some trouble with pressure switches on powerventers. If yours is connected to the safety circuit the burner should not have started and stopped but if yours is tied into the burner power circuit, it may be the source of the trouble. An onwatch data logger would be helpful if your service company can hang that on for a few days. We use the current sensor input on the powerventer so that we can determine if the motor is intermittent. Delayed oil valves can drive you nuts too.

Ken
 
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Old 12-04-05, 04:50 PM
bgauch
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I'm not sure exactly what the fan is wired to, as I am not familiar with the wiring of boilers. Based on the two possible connections that you refer to, I am betting that the PV is wired to the burner power circuit. The tech that came out in '03 said, off hand, that it was wired wrong. He followed it up with, "Don't worry, its completely safe. There is just a right way and a wrong way to wire it." Any time there is a call for heat, the PV is turned on. Even when the burner locks out, the fan is still running. That's actually how I tell that the system is locked out. If the PV is running without the burner firing for more than 10 minutes or so, I go and check the temp. I think I might insist that they rewire the PV properly and/or replace it.
 
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Old 12-04-05, 05:03 PM
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The way it is probably wired what will happen is
1. There is a call for heat
2. Safety control is activated and voltage is sent to draft prover switch instead of burner. That is one main difference on powervented units.
3. Powerventer starts.
4. Draft prover (pressure switch) senses draft and allows voltage to pass through and go to burner motor.
5. Burner starts and runs through cycle.

If the draft is low or the pressure switch fails, the burner motor never gets voltage never lights and the safety control is counting seconds for lockout. After 45 seconds of no flame, the safety control locks out. It sounded like the pressure switch was intermittent when you said you heard the burner for a few seconds and then it stopped and started again. Please let us know what is found.

Ken
 
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Old 12-05-05, 05:37 PM
bgauch
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Well, the guy just left. He decided that the problem was with the primary control unit. It was an old Honeywell 8184G that he replaced with a brand new 8184G. It did something he didn't expect when he was troubleshooting it. That caused him to very lightly tap the box with back of the screwdriver which caused the burner to shutoff and then turn back on again. When he replaced it, that didn't happen. He tested the eye and it tested out fine. When he opened it up, I saw part of what the problem was with the PV wiring. It looked like the cad cell is wired to the vacuum switch and then back down to the controls. So the PV has power whenever the system wants heat. The vacuum switch proves after the burner fires. It kind of defeats the purpose of the switch, but I guess it works well enough. Its running fine now. I only wish I knew what to do before I called the guy. That way it would have saved me 2 years of aperiodic aggravation. Thanks for all your help people.
 
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Old 12-05-05, 05:53 PM
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Primary control

Ah yes, the old tap it with the screwdriver handle trick. Not exactly the most scientific way to test for a weak relay but it certainly works. I can't tell you how many I've found by exactly the same method. That ventor should be wired to operate as KField said.
 
 

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