Boiler cycling madness

gwsieg

I recently bought a 30 yr old home with hydronic radiant floor heating where all heat comes from a boiler. It's all very foreign to me as I've only ever had a house/appt with a furnace and separate water heater - so I barely understand what a boiler is.
However, I do think the behavior shown in the linked video is bad.
https://photos.app.goo.gl/dNH4WHR7kJno57uL9

It is the original boiler in the house so I'm wondering if it's repairable or needs replaced.

I have a person coming out in the next day or two being supplied by the home warranty that came with our house, any ideas on what questions I should have or what I should be expecting from the service technician?
Thanks.

Prevch

Are you on propane? Could be your gas pressure. The cold snap across the country has caused a lot of regulators to have ice build up in them which can cause gas pressure fluctuations. You may have just enough gas pressure to fire the spark, but not enough to amp up to high heat. If the regulator is not frozen, you may have a bad regulator on the house or on the propane tank (obviously if you are on city natural gas this this does not apply) The other thing it could be is a flame sensor. If your flame sensor is covered in soot, sometimes you can just sand them off with some emery cloth or an oscillating tool, wipe them off and reinstall and they work fine. If I had to guess, it is one of those two things. I guess the other possibility would be a faulty gas valve. The igniter seems fine since the boiler is actually lighting. Personally, based on what I see in this video, you probably do not need a new boiler. I am guessing you will be able to get this fixed. If it is a gas pressure issue, a new boiler would not help anyways. Honestly, I prefer the old boilers. Yeah, they are not as energy efficient, but they barely ever break. Keep us updated.

gwsieg

Thanks for the good writeup Prevch. It is a natural gas boiler so your info about propane wasn't relevant to me, but still useful. I could see the flame sensor as the issue as it seems like it's been getting worse over the last month or two which would be caused by just getting more dirty. My appt with warranty provider is Wednesday, so I'll keep you up to date.
Any other help on what to ask technician would be appreciated.

Prevch

gwsieg said:

Thanks for the good writeup Prevch. It is a natural gas boiler so your info about propane wasn't relevant to me, but still useful. I could see the flame sensor as the issue as it seems like it's been getting worse over the last month or two which would be caused by just getting more dirty. My appt with warranty provider is Wednesday, so I'll keep you up to date.
Any other help on what to ask technician would be appreciated.

Ok. So I guess I would ask him to check the following:

1. Flame Sensor (most likely)
2. Use a CO sniffer to check for leaks
3. Check gas pressure
4. Check gas valve

Good luck, Let us know

pecmsg

Forget the home warranty there beyond worthless

Ask family, friends who they use and recommend.

Where is this located there might be a member nearby. Thats a lot of BTU's how big is this house.

Pic of the piping will help

Prevch

gwsieg said:

Thanks for the good writeup Prevch. It is a natural gas boiler so your info about propane wasn't relevant to me, but still useful. I could see the flame sensor as the issue as it seems like it's been getting worse over the last month or two which would be caused by just getting more dirty. My appt with warranty provider is Wednesday, so I'll keep you up to date.
Any other help on what to ask technician would be appreciated.

Ok. So I guess I would ask him to check the following:

1. Flame Sensor (most likely)
2. Use a CO sniffer to check for leaks
3. Check gas pressure
4. Check gas valve

Good luck, Let us know

mattmia2

Some good, clear pictures of the gas valve and the pipes and wires coming off of it as well as a the control board if t has one would also help, also the schematic inside the cover of the boiler. With it starting up again as quickly as it does it is almost like it is something loose in the control wiring. I suppose it could be some weird issue with one of the gas regulators as well.

FrankB101

Also don't overlook the thermostat. I have seen where an old mercury type Honeywell round has an improperly set or defective anticipator.

gwsieg

Here are a couple more pictures as @mattmia2 requested.
This is the only schematic I see and there's no cover for me to pull up. The gas valve and other wiring box attached to the boiler. And one final picture of the entire area for reference.

The technician was supposed to arrive yesterday, but no showed on us and called around 7PM to let us know they weren't going to make the noon-4 window. We'll see today, supposed to come first thing this morning. Fun.

JUGHNE

If I got this call, I would first jumper the Tstat wires and see if this still short cycled.

Not affecting this problem, but as a point of interest, has anyone else seen the 12 VDC rating on the gas valve??

mattmia2

Or put a voltmeter on the gas valve and see if it loses 24vac there (or if it spikes up) or if it is a constant ~24 vac when it is and isn't firing to figure out if it is a control problem or some sort of valve or regulator problem.

It is a 24 v standing pilot system.

Bronxtech

Shut the switch after you lower T-Stat.
Check all the wiring connections ,on sensors ,blocked vent switch. Also check chimney n boiler for being plugged.
Seems like it goes off very soon after firing.
Good luck, as mentioned earlier ,ck flame sensor and other items mentioned.
Let us know, John

bio_guy

I would not ask the tech anything right off the bat. Just describe the behavior and let-em have at it. Maybe use your knowledge to ask follow-ups later.

Nobody said it, but lots of the propane comments are good for nat gas as well, low pressure, icing regulator,.....

EBEBRATT-Ed

The blue low voltage wire going to B1 looks like its pinched under the red wire on the limit terminal

Prevch

Any updates?

gwsieg

Yes, thanks for all the comments, sorry it took me a while to circle back.
The technician did a few checks and checked for leaks, but went right to the idea that it needed service. Turns out, after hanging out with him for 45 minutes, this cycling of the flame only happens after it's been running 10-15 minutes.
His point that it needed service was that the high temperature sensor was kicking off the flame and then when the flame shutoff, it wasn't really hot so it turned the flame back on.

I wasn't super keen on his diagnosis, as I would think a high temperature flame shutoff would keep the flame off a longer period, but then it was somewhat backed up by the fact that it works fine for 10-15 minutes and then it starts cycling the flame. Also, by it only happening after the boiler has been running for some time limits feasibility of some of the other comments above. Though, I didn't know that it was only after some running when I posted this.

All of your comments were great, I did cycle a few of them through the tech, but he was not moving off his diagnosis. I'll post again if we are able to get it serviced under the home warranty we got with the house when we bought it in August.
Thanks.

mattmia2

If the boiler is very oversized or some parts of the system is not heating either because water is getting trapped somewhere or some venting isn't opening when it doesn't need steam or is missing altogether, the cycles may be very short once the system heats up and fills with steam.