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I have a crazy boiler. It keeps on and off every 30 secs

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shandian28
shandian28 Member Posts: 10
in Gas Heating
Hi guys. I have a weil mclain wm97+ 155 boiler for my house. It is running crazy these days. It fires up for may be 10 seconds then gas stopped, and the fan keeps running for another 10 seconds then the fan stops. Right after that the system starts again and repeat everything just happend. I checked close with the temp reading on the display, the supply temp never reaches the target temp, so I don't think that is because the boiler is lack of water flow and the system shut off when it hit the target temp for supply. Thus it is not the circulation pump. What goes wrong here? Any thoughts? Thanks in advance!

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  • Zman
    Zman Member Posts: 7,569
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    That boiler has a ton of on board diagnostics and error fault logging.
    Read the manual and let the boiler tell you what is wrong.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • shandian28
    shandian28 Member Posts: 10
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    Zman said:

    That boiler has a ton of on board diagnostics and error fault logging.
    Read the manual and let the boiler tell you what is wrong.

    The problem is there is no error msg or so showed up on the display. Nothing. It just keeps on and off with a noise running.
  • Zman
    Zman Member Posts: 7,569
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    Try jumpering the tstat terminals. You may have flaky call for heat.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • shandian28
    shandian28 Member Posts: 10
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    OK I just checked the output for diagnose. For boiler circulator it shows "off". I guess it should be some voltage numbers when it is running. I may have a fail circulator then. How do I know if the circulator is failed? And what can be the causations?
  • Zman
    Zman Member Posts: 7,569
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    I don't work with that boiler but would be surprised if it knew whether the circ was running.
    It is very likely that it looks at the supply and return temps compared to the firing rate and knows that there is flow issue.
    Check voltage and amperage to circ if you have the means. Pay attention to the delta between supply and return temps when boiler is running. No delta, no flow...
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • shandian28
    shandian28 Member Posts: 10
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    Zman said:

    I don't work with that boiler but would be surprised if it knew whether the circ was running.
    It is very likely that it looks at the supply and return temps compared to the firing rate and knows that there is flow issue.
    Check voltage and amperage to circ if you have the means. Pay attention to the delta between supply and return temps when boiler is running. No delta, no flow...

    Based on the manual, it should give me the reading of voltages applied to the pump. It is reading off right now so I guess the voltage is 0 and I don't know why
  • Zman
    Zman Member Posts: 7,569
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    I suspect the boiler circ was somehow turned off. Check out page 79 of the install manual. There are quite a few ways to configure a system. Is the circ wired to the boiler circ terminals?
    If you wait until morning, one of the east coast guys probably works on these all the time and will have better answers.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • shandian28
    shandian28 Member Posts: 10
    edited April 2017
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    Zman said:

    I suspect the boiler circ was somehow turned off. Check out page 79 of the install manual. There are quite a few ways to configure a system. Is the circ wired to the boiler circ terminals?
    If you wait until morning, one of the east coast guys probably works on these all the time and will have better answers.

    Actually, my circulator is good.i checked my settings for dhw mode, the circulator is off (I have an indirect water heater connected). I turned on the circulator to high speed and the circulator worked as expected, but the boiler kept on and off. So it is not because of the circulator so it is not because of low Water flow. On the display, no errors at all so no breaking sensors. What else can that be?
  • rick in Alaska
    rick in Alaska Member Posts: 1,457
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    As Zmzn says, jumper the stat terminal, especially if you have a Nest thermostat. I just had a furnace that was cycling like that because of a bad stat. Jumpering it would prove if it was the boiler or not.
    Rick
  • lchmb
    lchmb Member Posts: 2,997
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    If your reading 0 volts to the circulator it is not a bad circ. It could be you have a bad module...
  • newagedawn
    newagedawn Member Posts: 586
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    i agree, sounds like a shorted t stat or low voltage wire somewhere
    "The bitter taste of a poor install lasts far longer than the JOY of the lowest price"
  • shandian28
    shandian28 Member Posts: 10
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    rick in Alaska said:

    As Zmzn says, jumper the stat terminal, especially if you have a Nest thermostat. I just had a furnace that was cycling like that because of a bad stat. Jumpering it would prove if it was the boiler or not.
    Rick

    I am not quite following here. Why a bad thermostat can cause the boiler cycling like that?

    In addition, currently, it is not floor heating system (that is, not the stat) calling for heat, it is my indirect water heater, so I think the stat can be ruled out? However, no matter which system is calling for heat, heating floor or water tank, the boiler runs in the same manner.
  • shandian28
    shandian28 Member Posts: 10
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    lchmb said:

    If your reading 0 volts to the circulator it is not a bad circ. It could be you have a bad module...

    My bad, the circulator works just fine. It was disabled for DHW mode in the setting by default.
  • Zman
    Zman Member Posts: 7,569
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    I know a guy that did that, a bunch of times.... :*
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • shandian28
    shandian28 Member Posts: 10
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    Ok guys, following your thoughts on the thermostat i come up with a new theory. But I have question first, does the indirect water heater has a thermostat in it? If it does, it may cause my problem? Let's say my supply target is 170 F, and within the heater, the stat is set to 140 F. Thus, the boiler keeps trying to heat up the water yet the stat within the heater says no. I noticed that the pump for the indirect water heater is connected to the boiler directly. So, it may be the case that the heater keeps trying to shut off the boiler because it cannot shut off the pump?
  • Zman
    Zman Member Posts: 7,569
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    By default indirects usually come with an aquastat. Most boilers have an option to install a tank temp sensor.
    An aquastat making a flaky connection would cause a problem like yours. Jumper that connection temporarily to eliminate the possibility.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • shandian28
    shandian28 Member Posts: 10
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    Zman said:

    By default indirects usually come with an aquastat. Most boilers have an option to install a tank temp sensor.
    An aquastat making a flaky connection would cause a problem like yours. Jumper that connection temporarily to eliminate the possibility.

    Update: I ruled out the faulty thermostat on my indirect. When I was home, I turned on the heating for my basement. After turning it on, the boiler start to run under the same pattern: on and off every 30 seconds or so. Im sure my thermostat is OK since I tried with 2 different ones. Even it is the heating floor calling for heat, the boiler will burn gas for about 5 seconds before it gives up.
  • shandian28
    shandian28 Member Posts: 10
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    OK, I figured out. Conclusion first: I may have a faulty flame sensor/igniter.
    Previously, I thought the problem is purely related to my indirect water tank, but I was wrong. No matter what cycle it was running on, the boiler turns off and on all the time. Then I read the manual again. Under the maintenance section I found that my boiler require a minimum 150 reading from the flame sensor, or it will shut off and start again and try to hit the reading. Then I went to read the readings: below 80. Boom, that's the problem. The boiler keeps restarting to hit the 150 reading. Even though it couldn't hit it, the boiler does not bother to sent an error msg. I took out the igniter and cleaned it, fire the boiler up, no changes. Then I guess it may be broken. However, there is another possibility. Based on the manual, a low flow of gas may cause the same issue. Since the previous owner of the house never performs any kind of maintenance for the last three years, I guess the burner may be dirty. I will try to clean it first. If the problem remains, I will replace a new igniter.

    Thanks for all your helps, i appreciate it.
  • Zman
    Zman Member Posts: 7,569
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    It is pretty lame if the boiler does not log an error code for that.It is a very common and often intermittent problem.
    A faulty flame sensor is the most probable cause.
    You at at point where the right thing to do is perform a combustion analysis. It will tell you exactly what is going on with your flame. Getting the combustion correct in your boiler will increase efficiency and longevity.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein

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