Weil Mclane natural gas boiler issues

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Old 10-15-14, 11:33 AM
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Weil Mclane natural gas boiler issues

I've recently become a homeowner, and along with said home came a Weil Mclane CGA-5-PID series 1 boiler that I'm slowly learning about (more accustomed to forced air). It's got three zones in total.

During the summer, I had no problems with it functioning. Around the time we started to need heat for the house, we began to not only have no heat but also no hot water.

On the unit itself, it has the Power, TSTAT/CIRC, and LIMIT light lit at all times (none flashing). It will, at regular intervals, attempt to light and heat. In this process, it properly opens the damper, lights the pilot, and lights the main flame. After the main flame has been lit for a couple seconds, I can hear the gas valve audibly close, and the flame extinguishes and the damper closes again, returning to the initial state. ETA: Circulator pump is functioning properly, water is circulating.

Going through the manual, I checked continuity as instructed in the troubleshooting guide, continuity intact at all sensors etc. The troubleshooting guide advised to replace the control module if such was the case and the limit light was lit . Control module has been replaced. In the midst of this, I also replaced the backflow/autofill valve (Caleffi) because it was evident that it wasn't functioning properly. I replaced both of those yesterday. It was happily working, calls for heat worked properly, I checked the limit switch, it was working properly, although I did notice there was some water coming from the air release valve (so I'll be replacing that as soon as I can procure one). This continued for probably 10 hours, at which point I went to bed. 5 hours later, I got up to check on things, and it was back to its same three light no heat no hot water, low water temp status.

In checking the whole unit over, the release valve on the unit has corrosion, has obviously been weeping some so I plan to replace that, but I have a question on that as well- the pipe on the vent literally goes flush to the linoleum floor. This doesn't seem proper to me, as there is no way (in a blowoff) that the water could freely evacuate the area. Can anybody confirm this? In regard to the valve, I did also check to see if the expansion tank is waterlogged- It has not failed (no water from valve upon checking it) but I haven't gotten a chance to confirm if it is up to pressure, either.
 
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Old 10-15-14, 04:36 PM
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During the summer, I had no problems with it functioning.
Running during the summer would imply that your domestic hot water is produced by the boiler? i.e. it has a 'thankless coil' built in?

the release valve on the unit has corrosion, has obviously been weeping some
It might be weeping because of a pressure issue. What is the reading on the boiler pressure/temperature gauge?

Read this:

http://www.doityourself.com/forum/bo...ure-gauge.html

You probably have a diaphragm type expansion tank, read this if you haven't already:

http://www.doityourself.com/forum/bo...sion-tank.html

I did also check to see if the expansion tank is waterlogged- It has not failed (no water from valve upon checking it) but I haven't gotten a chance to confirm if it is up to pressure, either.
If it's a diaphragm tank, and not been checked in a couple years, it's low on air. Follow the steps in the post linked above EXACTLY.

This test is only valid if the air valve is pointing DOWN. If your tank is 'standing on it's head' it's not usually a good test. Is it pointing down?

the pipe on the vent literally goes flush to the linoleum floor. This doesn't seem proper to me, as there is no way (in a blowoff) that the water could freely evacuate the area. Can anybody confirm this?
Yes, if the valve is corroded, replace it.

The pipe from the relief valve should typically end about 6" from the floor, preferably near a floor drain if one is available. Many people will keep a pan or small bucket under the pipe. It absolutely should NOT be sitting on the floor.
 
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Old 10-15-14, 04:47 PM
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When it's working, do the LEDs light progressively on a call for heat as they should?

First the TSTAT/CIRC, then the LIMIT, then the DAMPER, then the FLAME ?

What happens at this point when it fails?

In other words, referring to figure 24 on page 37 of your manual, what happens after step 5 ?

After the main flame has been lit for a couple seconds, I can hear the gas valve audibly close, and the flame extinguishes and the damper closes again, returning to the initial state.
When you're watching it, this is where I want to know the condition of the LEDs. Does the FLAME LED go OUT?

What do you mean by 'returning to the initial state' ? Do you mean with the TSTAT and the LIMIT lights lit?
 

Last edited by NJT; 10-15-14 at 05:05 PM.
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Old 10-15-14, 04:52 PM
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Yes, boiler produces hot water for the house.

Current reading on pressure is about 28-29 psi @ 70 degrees. I turned off the gas and the power to the unit so that it doesn't aimlessly initiate and stop firing. ETA: The gauge on this reads from 0-160 psi, so it isn't exactly that fine of detail.

Tank is diaphragm, unknown how long since it's been tested as I've only been in the house for a handful of months. It is in the "schrader valve down" position. I've already read your links, only reason I hadn't confirmed and checked the pressure in the tank is I was going to install a faucet to better facilitate maintenance, per your recommendation as well as my air bleeder at the same time. Only issue is that I'm pretty rural and the nearest store is a bit of a drive so I wanted to know if I needed anything else before heading out.

I didn't think the pipe was correct. I'll be cutting that tonight. Will buy faucet/air bleeder tomorrow after work and get back to you after I check my expansion tank pressure.
 
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Old 10-15-14, 05:01 PM
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Yup, behaves normally before failing. You can hear an audible electric buzz and the gas is shut off. At the instant that the gas shuts off, it goes from all of the lights properly lit to only power, TSTAT/CIRC and LIMIT lights on. When the gas gets cut, the main flame is fully ignited, not just the pilot. The damper then closes, the unit sits like that, and some period of time later (I haven't timed it) it repeats the process.

Oddly, I found by accident that if I leave it with the gas/power off for several hours and then attempt to turn it on, it will usually work for a period of time before entering back into this angry circle. I discovered that when I first was trying to troubleshoot it the day after this all began (had turned off the power/gas to prevent it from cycling).

After replacing the control module and the backflow/autofill, I observed it for the majority of the day, with it cycling on and off at proper intervals. Temperature limit switch was functional, I tested it and it behaved as expected and corresponded pretty closely with what the temp gauge read as I was testing it. I observed no temperature/pressure spikes throughout the day. As of now, I'm yet to witness it actually going from behaving to misbehaving, I just keep discovering it cycling with the 3 lights on.
 
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Old 10-15-14, 05:26 PM
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Current reading on pressure is about 28-29 psi @ 70 degrees
Since you've read my rantings, you know how I feel about pressure gauges... but of course if this is real it's certainly the reason that your relief valve is weeping.

Why is the pressure that high I wonder? You said you replaced the pressure reducing valve... you should be at 12-15 PSI with boiler cold.

Back to the burner problem......................

The GROUND wiring is extremely important with this type of system. Make sure that all the ground connections are CLEAN and TIGHT. Systems that use this 'flame rectification' to prove the pilot flame is lit are very sensitive to this. They operate on MICROamps of current, the slightest resistance in the ground wiring can make the control think the flame has gone out and will shut down the burners.

Have you observed the flames? Do they look OK according to the manual?

I'm not sure why the manual doesn't seem to suggest that the FLAME ROD should be cleaned? This could be a possible cause... use a scotch-brite pad and scrub the flame rod.

Is the damper a FIELD CONTROLS? There could be an issue with the 'endswitch' in the damper motor assembly. They tend to develop a high resistance over time and this will 'trick' the control into thinking the damper has closed and if this happens, immediate flame kill. You might want to monitor the voltage at the vent damper plug on the control -- pins 2 and 4 -- to see if this voltage is correct and does not 'go away' while the damper is still in the open position.
 
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Old 10-15-14, 05:31 PM
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I just keep discovering it cycling with the 3 lights on.
So when it 'recycles' have you observed that the DAMPER light lights when the damper opens, and the FLAME light lights when the pilot lights?

And then it runs for a few minutes and shuts down? At this time is when you want to try and observe the lights to see if you can tell which one goes out first.

That control is a 'continuous retry' model and will keep going... and going... like the E-bunny.
 
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Old 10-16-14, 07:01 PM
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Update: Replaced the air bleed valve (big difference in performance there... I can audibly hear it function when I opened the valves back up vs the existing one), cleaned the flame rod (some light buildup but not too bad), cut the vent pipe, topped up pressure on expansion tank to 12 (was around 6psi). FWIW, the water in the vent pipe was under pressure. I think the combination of the vent pipe and the expansion tank combined together to create the problem I was experiencing. There's no way to tell at this point but give it some time. It is behaving normally, will update after a day or so of monitoring. I didn't even get to get a video of the "problem" cycling either... but to clarify, it would have all 5 lights lit, ignite the flame, and then you could hear it shut off, then the DAMPER and FLAME lights would go out simultaneously, and the damper would close and I'd be left with the other 3 lights lit (not flashing). If it goes back to cycling, I'll get a video before shutting it off. Thanks for all the help thus far.
 
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Old 10-16-14, 08:12 PM
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topped up pressure on expansion tank to 12 (was around 6psi)
You followed the step by step instructions, correct? After you pumped it to 12, you drained the boiler back to zero, etc, etc, and repeated the steps until the boiler stayed at zero and the tank stayed at 12, RIGHT? Just checking..............

FWIW, the water in the vent pipe was under pressure.
It was THAT tight against the floor? That could have been disastrous... as in 'Earth shattering KABOOM!"
 
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Old 10-16-14, 08:46 PM
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The setup that I currently have makes it possible to isolate the tank on its own, so I isolated, drained the excess water, and then did the pressure check. It just doesn't have a localized faucet, so I have to use one a few feet away, so not quite as convenient as your suggestion (didn't have the proper faucet in stock today when I went in...).

And yes... I share the horror of that vent pipe. When I first moved in, I knew nothing about boilers, and due to the rigidity of the pipe from the pressure, I actually initially thought the pipe went through the floor.

I've also, as a result of going and checking everything out, fixed the vent on the water heater as well and discovered it wasn't even sweated at the 90 degree elbow. Once I get the right couple (again, out at the local place) I'll be verifying the expansion tank pressure of the tank on that, as well. I've also got a very lightly weeping zone valve that was clearly just sweated poorly and needs to be redone at some point.

On the upside... really glad I've learned to see all these problems instead of...sitting on a time bomb, like when I moved in.
 
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Old 10-17-14, 06:12 AM
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I'll be verifying the expansion tank pressure of the tank on that, as well
FYI, you probably already know this, tanks on potable systems should be pressurized to the nominal pressure of your water system, typically 40-50 PSI.

Keep us updated on the progress!
 
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Old 11-18-14, 06:41 PM
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Success!

So, I'm confident that I can now claim victory on the boiler, as it has been running happily since I fired it back up. Tank on the water heater is at proper pressure now as well. Thanks for the help.
 
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