Boiler Steam heat short cycles

coolfx35

Hello,

Do you know what the issue is with this?

https://youtube.com/shorts/_BdPycuxvc4

This only happens in the morning time, I kind of think it's hitting the pressure max, then it cycles .

night time i set temp to 65, but in the morning I set it to 68, and it could never go there.. and this problem occurs.

Thanks for you advice.

Jamie Hall

Well that's kind of short on information. It's more likely to be the pressuretrol limiting -- but if it is, it's badly out of proper adjustment. Could use some pictures of the boiler and its piping, and the controls...

mattmia2

Looks like it is having trouble proving flame. Dirty flame rod, clean it with something like a piece of paper. Bad ground path between the ignition control and the burner. Sense wire chaffed and shorting to the frame of the boiler somewhere. Bad or corroded connections on the sense wire.

coolfx35

don't think it's the flame because when the system is cold, I can run it without an issues. it's only when the system is already warm.

I think Jamie saying the pressuretrol limiting might be more like it. the system was put in 3 years ago. and can't remember this was an issue until this year. could it be the pigtail is stuffed?

coolfx35

Also any problem if I increase the pressuretrol setting a little bit?

Jamie Hall

Pressuretrol is already set as high as you want it. More likely you have inadequate venting or, even more likely, if the problem is mostly once the system is well warmed up -- say coming out of a setback or something like that -- the boiler is simply too big for the system. Not much fix to that.

coolfx35

Yes, I think you are on point, the boiler might be too big for the house.

before the replacement of my boiler, I remember the old unit had it set to 2.5 What's the downside to do something like that? So that the boiler can run a little longer to avoid cycling.

I have been playing with the temperature settings. So if I set it to 68 all day and all night, the problem just go away? I will try it this week.

this could be my solution?

coolfx35

Hi Jamie, do I need to bother with cleaning the pigtail at all? could that contribute to my issues as well, I haven't cleaned it for 3 years.

mattmia2

In that 5 seconds the flame is on it isnt changing the pressure appreciably.

mattmia2

@Jamie Hall watch the video.

Jamie Hall

Yes, sir. Right away, sir.

mattmia2

The only thing other than the ignition control that could react that fast is if there is a bad connection or a bad contact somewhere. I guess an electronic low water cutout that is fouled could do this. You could jumper the safety chain for 30 seconds or so while it is happening to see if it stays lit continuously to rule out things other than the ignition control.

Do not leave it like that, and only do it while you are watching it.

coolfx35

@mattmia2 interesting observation, please note i don't have any issues during day time to evening. only morning.

ethicalpaul

> before the replacement of my boiler, I remember the old unit had it set to 2.5 What's the downside to do something like that? So that the boiler can run a little longer to avoid cycling.

Don't do it, don't even think it. Ask yourself: Why do you want your boiler to be running when the system has as much steam as it can consume?

The pigtail is good to check annually, but if it's blocked, it will let the boiler run too long building up too much pressure, it won't cut out early from that. I doubt the pigtail is your main concern here. I like MattMia's suggestions.

coolfx35

PSEG replaced this.. hopefully that solves my issue.

ethicalpaul

It's one possible cause! Did it work after they replaced it?

retiredguy

Did you check to see if the water line is bouncing when steam production starts and are you sure that the returns aren't blocked or restricted. Remember, a cold system needs a lot of steam for the pick-up load.

By the way, could you show us a picture or 2 of the near boiler piping?

ethicalpaul

> Remember, a cold system needs a lot of steam for the pick-up load.

Regardless of how much it needs, the boiler isn't aware of that...how would that make his fire shut down?

retiredguy

@ ethicalpaul; I guess that I didn't write that very well. Let me re-phrase, A cold system that comes on in the morning after a night setback will need a lot more steam supply and a longer run time than a hot system that is cycling just to maintain building temperature. If, the near boiler piping is wrong, the boiler is being overfired, or the boiler's water is dirty and needs skimmed, you could be making wet steam causing the boiler to rapidly cycle on the low water cut-off control.

ethicalpaul

Gotcha. Yeah this case seems to be connected to the morning recovery, and yet that speedy repeated cut out and cut in doesn't seem like it could be due to pressure or water level--it's too fast. But maybe the long runtime is causing some heat-related failure like mattmia said

pedmec

I would look at the water line in the boiler. The cold start takes a while for the boiler to try and produce steam which would allow it to run longer. Eventually its making steam and now the water line is all over the place. You also said it was a 3 year old boiler and maybe its wasn't skimmed properly. Water in boiler could be bad

ethicalpaul

@coolfx35 lives real near me so I went over and had a look. The water is good, the piping is reasonable, it's not surging.

The pigtail was dirty but I don't think it was fully blocked, maybe hindered.

I watched it produce steam for over an hour before it started to finally fill the radiators and started cycling on pressure, so it's not unreasonably oversized.

Cycling on pressure is not what we see in the video here.

What I did see was the newly-installed control module blinking lights indicated that the flame sensor was only getting 1 microvolt (it started at two when it first fired then went down to 1 after some minutes).

We cleaned the electrode with paper and it was then displaying 4 microvolts but after a few minutes it went down to two. It later went down to 1 again and this behavior seemed to return in later mornings (I think the time of day is irrelevant...it's just what we see after a long cycle).

My thinking is replace the sensor and wire (I noticed the wire jacket looked like it had been strained at one point near where it connects to the module). What do folks think?

mattmia2

Did you look at the ground path from the pilot burner to the ignition control? You can add a separate jumper directly between the 2.

pedmec

I would probably check the gas pressure. One hour to heat up the radiators is a long time. Could be that they don't have the capacity out in the street. I have that issue with some of the properties we handle. Only rears its ugly head when it gets around 10 degrees. Then you can barely make steam. Maybe it happens when everybody is getting up in the morning and turning there heat on.

ethicalpaul

No I didn't look at that. Does it normally use the pilot gas tube to provide that?

pedmec

Flame sense is only as strong as the path. Reduction in pilot size can effect flame signal.

mattmia2

I don't think there is a specific planned path but the area where the ionized part of the flame contacts the pilot burner has to have a low impedance path back to the electronic control, that is where the current that flows thorough the flame flows back to the control. It could be through the pilot tube and the gas valve body to the chassis or through the burners and back to the chassis of the boiler.

ethicalpaul

Thanks. The OP had the gas company out again to look at it again, or their contractor rather, and they seemed unaware of the concept of the strength of the flame sense signal (not that I'm any expert but even I can read blinking lights)

@pedmec the pilot looked good and was hitting the electrode which was glowing orange/red

bburd

Have you clocked the gas meter to determine the actual firing rate when the boiler is firing and other gas appliances in the building are shut off?

ethicalpaul

No but the flame looked reasonable and the boiler is heating all the radiators and it eventually cycles on pressure as expected. Do you think it may be that the firing rate is low and that is making the pilot be low and that is making the proving voltage be low?

bburd

If it’s heating all the radiators and eventually cycling on pressure, it’s not a firing rate problem.

mattmia2

Does the size of the pilot flame shrink as the current falls?

ethicalpaul

It's kind of hard to see and I didn't lay down there the whole time to see if it changed size. I looked at it when it was registering 1 microvolt and it looked OK but I don't look at these for a living so my opinion may not be worth much!

Chris_L

ethicalpaul said:

It's kind of hard to see and I didn't lay down there the whole time to see if it changed size. I looked at it when it was registering 1 microvolt and it looked OK but I don't look at these for a living so my opinion may not be worth much!

microvolts? I thought you were supposed to measure current--microamps--to see if the rectification is occurring. See:
(yes, it is not steam, but same principle applies)

mattmia2

Wait, are you measuring microvolts or microamps? Current is what the control is measuring. A bigger flame will reduce the voltage drop over the junction so it makes sense that the voltage decreases over time but that doesn't tell you what is happening with the current.

ethicalpaul

I wasn't measuring anything. The control module measures it and reports it as a number of blinks of the status LED. I believe it said "uV" (microvolts) but I can't swear on it.

ethicalpaul

The pilot-related stuff I recall seeing was a heavily insulated conductor which I think is to generate the spark to light the pilot, and the pilot gas tube, and that's it (I think it's the same as mine has).

It didn't have this additional sense line that is in the video (that I remember)

mattmia2

Some have separate electrodes for spark and sense, others use a single combined electrode.

Regardless, the problem is probably something corroded between the pilot burner and the ground connection of the ignition control.