Short cycling boiler. I'm stumped.
I have a pretty simple set up. New Yorker low pressure boiler supplies the base board heat and hot water for this 2 floor house. The Beckett burner just started short cycling. Flame for about 5 seconds. Cuts off. Comes back on for 5 seconds. Repeat. Eventually it shuts off and the gage on the boiler goes to zero. I'll reset it and it will fire up and Keeps going until around 170 - 180 degrees. Even though I have the aquastat set to 190? And then it starts short cycling again shortly after! I notice it's even worse if it its calling for heat. Right now without a call for heat, it's run to 170 degrees and hasn't short cycled since I've been sitting here. I'm waiting to see if it kicks back on at 160 per aquastat settings.
I've changed the oil filter, changed the strainer and gasket to the oil pump, and changed the nozzle. The expansion tank doesnt sound full of water. And air did come out when I checked the valve.
Does this sound like an aquastat issue? Its getting cold and any suggestions would be very much appreciated.
Comments
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There is something electrical going on there. When the Aquastat gets to 170°, is when the low limit switches to allow the circulator pump to start. Check to see if there is a dead short on the circulator pump wiring by removing the wire from the C1 terminal on the L8124. If the burner continues to operate all the way up th 190° (or higher), then the problem is in the circulator circuit. Perhaps the circulator wire is pinched and shorting out. perhaps the circulator pump has a bad winding. Depending on how that second zone pump is connected, the relay for that zone may have a problem.
Open the covers and take pictures of the wire connections. See if there are wires on ZC and ZR in the L8124. also how are the wires connected on the other zone switching relay. Pictures of that also.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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What are you resetting? If your resetting the burner control than you you have a problem with the burner. Sounds like the burner is recycling and trying to prove the flame safety if your control is set up for that.
Dirty cad cell maybe. When was it serviced last?
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@EBEBRATT-Ed, The burner seems to operate properly until the water temperature gets to 170°. The problem starts at that temperature. What do you think about that? I believe if the low is set at 160 with a 20° Diff setting, then the power that is operating the burner switches from "the low limit thru the high limit thru the burner" to the "low limit thru to the circulator". if there is a call for heat at that time, the burner get's its power thru the 1K1 relay contacts and the pump gets power thru the 1K2 contacts.
If I walked on that service call I would look at the circuit that operates the circulators and see what is going on there. sometimes a Tech that does not understand how the Zc and Zr terminals on the L8124. work, can make a short circuit mistake or a wire that is not properly protected with anti-short insulators at the end of BX or MC cable can get shorted easily. That should be easy to find with black marks near the trouble spot.
What do you thing one Ed to anther Ed?
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Are these the same boiler? This looks like it is older with newer control
Looks like this one is newer with an older control.
Or do you only work on NewYorker boilers ?????
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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@EdTheHeaterMan The OP said"
"Eventually it shuts off and the gage on the boiler goes to zero. I'll reset it and it will fire up and"
I don't know that is why I asked what is he resetting. Need more info.
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Good Point @EBEBRATT-Ed
Perhaps After short cycling every 5 seconds due to an electrical problem, the safety heater on the primary (like a R8184G) would over heat and trip on safety. It might take 20 minutes at that rate. I'm not sure how the L7124 control in that picture would react. Then there would not only be no heat, but no DHW also. Cold boiler at 0 PSI. Reset the primary and it operates fine until it gets to 170° then starts to do that 5 second thing until the safety trips again.
That poor primary control is being put to the ultimate test if that's the case.
Agree needs more info. Hope they get back with the pictures I asked for.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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"Flame for about 5 seconds. Cuts off. Comes back on for 5 seconds. Repeat."
So the flame cuts out but the fan still runs, then flame again for 5 seconds? If the burner is wired correctly, then that's recycle as @EBEBRATT-Ed mentioned. And as you've seen, it'll recycle 3x then go into safety. Time for an oil tech.
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Im sorry for taking so long to reply. I was taking pictures and didn't realize my phone was about to die.
Ok. I took pics of the schematics inside the covers as well just for my own reference. The two circ pumps, the aquastat and the switching relay on the side of the boiler.
Everything you've said in the comments are accurate to whats going on. It seems like once it's down for good and I reset the burner emergency switch in the morning, it goes until around 170. And then anything after that, any call for heat, or if someone uses hot water, it short cycles for 5 secs. Off and on many times. I actually stopped counting how many times it short cycles.
I also have a power vent that comes on and stays on for the whole process.
Anyway, as for right now, I woke up to the thermostat calling for heat showing the "flame" signal but the boiler isn't running. I turned the thermostat off and came down to the boiler. Here's a picture of the gauge as well.
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I'm resetting the oil burner on off emergency switch. Looks like a new cad cell was put in toward the end of 2018 per records. It looks pretty clean. I've been servicing it since I moved in in 2020. My only knowledge is from 11 months of night HVAC classes
at NTI. Def not a pro like you guys.
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Yeah that one looks a lot like mine.
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Follow Ed's advice above.
Shut off power to the boiler.
Remove the wire from the C1 terminal in the L8124.
Start the boiler again and observe if it runs up to 190F before shutting down.
Additionally, the gauge reading zero is a serious concern. The boiler does not appear to be automatically filling itself to maintain 15 psi. At this point, you need to manually fill it to 15 psi when it is cold.
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Ok. A couple questions, should I wait till the gauge temp is all the way to 0 first? It's almost there.
Also, can I leave the power on while removing wire from C1 terminal?
I've wondered about the regulator valve. The handle on top doesn't seem to want to do anything
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- No, you do not need to wait until the boiler temperature is zero.
If you are a surgeon, you can leave it on. But, why take the risk? There is power on other terminals in that box and you can short it if you touch the screwdriver to the powered terminals and the case.
Lift that tab on the top of the valve so it is vertical. See if the valve feeds water to the boiler. Watch the pressure gauge. You want 15 psi…………not more. Be ready to move the tab back to the current position. WORK ON THE VALVE BEFORE WORKING ON THE L8124.
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Change feed/backflow combo then purge
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Okay. I'm assuming I'm reading from the upper half, from 0 to 20.
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You need to get your auto-fill valve "unstuck". It's not letting the normal 12-15 psi. amount of water at pressure into the system. Or you could replace the fill valve/pressure reducer altogether. In order to do this you'll need the system pressure at 0 psi. and have the house water system supply ball valve shut off.
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Correct.
I have an easier and safer way to perform the electrical test as Ed stated above:
The house has two zones.
Go the the first zone thermostat and turn it all the way down………….as low as it will go………..it needs to be LOWER than the current room temperature. If the current room temperature is below the lowest thermostat setting, this will not work.
Leave the second zone thermostat at 70F. I am assuming the room temperature is below 70F.
When the boiler starts and reaches low limit, ONLY the second zone will call. We will see if there is an electrical issue with the first zone without the need to remove the C1 wire inside the L8124.
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Just wondering, shut these two valves off ONLY to change the fill valve out?
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Boy, I can't even get the tab to go vertical. Wont budge. Must be pretty crusty inside. Does this mean a trip to home cheapo?
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Sadly, it does mean that it needs replacement.
However, today is not the day to do it. Since you have no isolation valve between that valve and the system, you'll have to drain all the water out down to the level of that valve. The zones may have isolation valves to prevent them from feeding back to that point.
Also, you must shut the water to the valve to accomplish that change.
Then, once you are done, you now must purge the zones to eliminate all the air that you introduced.
It's a bit of a job.
Since the boiler does show some pressure, you can run it to determine where the electrical problem lies.
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I have a quick and dirty way out of the fact that the fill valve is non-functional and you certainly do not want to replace it today:
Follow carefully:
There are two blue handled faucet valves above the circulators.
Connect a garden hose to one of those valves..
https://www.homedepot.com/p/Melnor-Metal-Double-Female-Adapter-59Z-FB-HD/206480253
Turn on the water.
Turn the blue handle BARELY counterclockwise………maybe 3/4"………….and watch the pressure gauge. When you get to 15 psi………………..STOP.
Be careful with the procedure. You can easily overfill the boiler if you open the valve quickly and too far.
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So the PRV is making the burner go into recycle, then safety? Weird.
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I'd love to learn all of that. I know its getting brutal cold but if i had a walk through on how to do it all, I'd try it. Or a good detailed video. A lot of stuff on YT doesn't seem to be step by step.
I'm gonna head down and see what's up with that C1. I'll report what happens here in a min.
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Just fill the boiler with the garden hose as I mentioned above. Take you 10 minutes.
Use the thermostats instead of C1 as I mentioned above.
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I don't think so.
Two completely separate issues. That boiler cannot know it's low on pressure.
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By "Turn on the water" you mean the blue handled valve?
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No, the supply from the house. The blue handled valve will allow water into the boiler. Turn it very carefully counter-clockwise…………..slightly………..to allow water in slowly.
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Ahh i see the link to the hose. Alright I get it.
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Man. Now it's just short cycling right from start.. gage at 0. ****!
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What change did you make?
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i just turned my burner off on switch back on at top of stairs and on the boiler.
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I didn't make any changes at all yet
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Do you have an electrical test meter and can you use it?
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Yes I'll go grab it. For the record this burner is just short cycling over and over. Not sure how many times it will do it until safety cut off. Maybe like ED said, when the primary gets hot
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This thing is short cycling almost up to 160 now.
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Go into the L8124 and carefully put the probes on "B1" and "B2". Have someone start the burner and you observe the meter. Does the voltage disappear when the burner stops?
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There is absolutely no benefit to sit there and watch it short cycle. Please just follow the testing procedure as stated.
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Ive got the probes ready, just currently trying to get the burner to start. Burner stopped short cycling at 160 and now temp has slowly decreased. I flip the burner switch on to get the burner to come on and it won't start. Just the fan comes on for a moment. As far as my thermostats, my 1st floor is now set pretty low. 2nd floor is set high so it's currently calling for heat. I'll keep u posted.
I did* hear my circulator pump closest to the boiler come on for a bit. Pipe coming down to it got cold.
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Just the fan comes on for a moment.
What fan? You don't have a "fan".
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What is the model number and the brand of the power vent system you have? That is where your short cycling problem is located.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
1
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