Boiler cycling constantly without thermostat request

tmeric7

Hello,

First post, but thanks for everything I've learned for these boards! I bought a 1 pipe steam heat house a few years back and have been working to improve it, but this question isn't about my house at all.

I was walking by an elderly neighbors house today and said hello. She said that she hears sounds in here basement. I only had a few minutes, so here's what I learned. Her boiler is cycling constantly in this manor: damper opens, boiler tries to light and fails, damper closes, repeat. The thermostat is set way below ambient temperature (it's summer). I honestly don't know if it's a steam or hot water system, but I suspect steam like my house... I was in a hurry. The boiler looks fairly new. I told her I'd come back in the morning to look at it for more than 2 minutes. What can I look for? My first thought is to disconnect the thermostat wires and see what happens. Wish I had done that today, but I was in a hurry to get my son from daycare. Thanks.

nicholas bonham-carter

Take some pictures of the boiler and piping when you go back, and then we will be sure of the nature of the beast.
By all means, temporarily disconnect one wire of the thermostat and see if the attempted firing behaves.
Check and see if the boiler is making hot water, as there may be a problem there.--NBC

tmeric7

Here's what I learned this AM:

It's a hot water system, Utica boiler about 2 years old. Pics attached.

My neighbor said that she heard the boiler doing its business off and on throughout the night (sometimes silent, sometimes active).

Here's my experience today:
- Found the unit quietly doing nothing in standby mode, just like it should on a summer day (i.e. not behaving like I saw yesterday).
- I turned on the thermostat and the boiler fired up just like it should. I waited several minutes to confirm that the pipes were getting warm (they were).
- I turned the thermostat off and *thought* I heard it click, but when I went to the basement the boiler was still running. I waited a few minutes... still running.
- I disconnected a thermostat wire and the boiler stopped immediately.
- I reconnected the wire and it started up like normal (thermostat still set well below ambient).

Finally, I disconnected the thermostat wire so it would shut down. I told my neighbor that she shouldn't hear anything now and that I'd come back to put on another thermostat I have sitting around. She has the standard manual Honeywell, same as I have (replaced to go programmable). Am I on the right track? Anything else to consider? Thanks!

JUGHNE

With the tstat removed from the wall, I would inspect the wires where they come out of the wall. There could be an intermittent short in those wires. If enough extra cable pull it out of the wall and look at the first foot or so. Clearly separate the individual wires in the cable. If the boiler cycles during the night with wires apart then the other end of the tstat cable or the cable itself may be the suspect.
If that end looks good then the cable itself could be pinched and with old failed internal wire insulation could be the intermittent short.

MilanD

You are a good neighbor. I have some rental properties and have seen weird things with boiler/furnaces just because of a faulty t-stats, esp. the round Honeywell. Replace the t-stat and monitor. If that doesn't fix it look for shorted wires as @JUGHNE suggested, or the control board might have issues with the transformer or just a loose wire connection from the t-stat on the boiler side.

HVACNUT

I'm not familiar with that ICM, so like the OP says, the damper opens and closes on each pre ignition attempt.
That would mean just what you guys have suggested.
If the problem was after the thermostat portion of the circuit, (as far as R,W on the boiler) the damper would stay open, recognizing a constant heat call.
The fact that the boiler never actually fires is suspect.
The control wiring or thermostat ALWAYS opens the circuit before just before ignition?
Bad anticipator or bulb in the T87F?

tmeric7

All, thanks for the comments. HVACNUT, the boiler was firing up the second time I was over (my second post), but even with the thermostat off.

I just went over and installed my old Honeywell. Same behavior. I tried to check the thermostat wire for a short, but it's over 100 years old. I actually don't think it's the problem becaus with the wire disconnected at the boiler I get open circuit when the thermostat is turned down, closed when turned up.

So to summarize the symptoms, now the boiler wants to run (burn and make heat like its winter) whenever the thermostat is connected. Even though I get an open circuit from the thermostat at the boiler when disconnected and turned down. Now it's voodoo to me. Control board? That's beyond my pay grade (free, haha).

Fred

There should be a water temp control that controls the temp of the water flowing through the system. I would think that control, or the wiring to/from it could be suspect also. There may be contacts in that control that are sticking closed, calling for a flame to bring the water up to some minimum temp but since the Tstat is not calling for heat, the circuit isn't being completed to fire the boiler. Just a guess.

HVACNUT

It's a cold start boiler. It does not maintain temp.
@tmeric7 , at the boiler, the thermostat wires connect to 2 wires from P5-1 and P5-3. If you remove the thermostat wires from those splices, and keeping the P5 wires separate (not touching each other), there's no way that boiler should fire.
Is there a number code on the display? If so, the back of the manual has a troubleshooting section with numbers corresponding to a particular fault.
As above, if the boiler fires, or does ANYTHING with the wires from P5-1 and P5-3 disconnected, it's a faulty ICM, and would recommend turning the emergency switch off until the ICM is replaced. (Possibly under warranty)

BobC

As an experiment try disconnecting the thermostat at the boiler so it and the wiring are out of the picture. Connect another thermostat and some new wire to the boiler and hang it in the basement somewhere. Make sure the boiler will still start when you increase the thermostat setting and reduce the setting to stop it. Let it stay that way for a day or so and monitor it to make sure it's not acting up

If all is well with the new tstat and wiring that old tstat wiring is shot. If it's still acting up the control on the boiler is bad or there are loose wires somewhere.

Bob

tmeric7

Thanks for the comments guys. Bob, I like your suggested experiment. I'll give that a try here soon. HVACNUT, no the boiler does not do anything with wires disconnected. There is a status code that I've been paying attention to, but it has only reported normal operation steps. It just wants to run when I connect the thermostat which reads "open circuit" on my multimeter before I hook it up. Hopefully our new experiment will give some valuable information.

HVACNUT

If there's absolutely no activity with the tstat wires removed from the ICM, then I'd say it's the wiring between the boiler and the tstat, since you already replaced the tstat.

j a_2

It's P.F.M.

rick in Alaska

We are assuming that there is not an indirect water heater hooked to the boiler? If not, it sure sounds like a shorted stat wire or a problem with the control.
Rick

Zman

I agree it sounds like a bad wire.
You might look at something like this for a solution.
http://www.supplyhouse.com/Honeywell-YTH5320R1000-Wireless-FocusPro-Non-Programmable-Thermostat-Kit-11471000-p

HVACNUT

> @rick in Alaska said:
> We are assuming that there is not an indirect water heater hooked to the boiler? If not, it sure sounds like a shorted stat wire or a problem with the control.
> Rick
>
>
>> In the pics it shows a gas fired water heater.

tmeric7

Thanks for your comments everyone. Two days ago I conducted Bob's experiment and the system behaved properly. Today I went back and replaced the t-stat wire in the wall. Everything seems fine. I'm surprised I didn't detect this with continuity checks, but perhaps it was an intermittent problem.

Cheers,
Tristan

ratio

I found a similar problem with one of these. Our service guys couldn't figure out why a mini split kept blowing fuses on the feed to the indoor head. It rang clear with a multimeter, but the megger showed one conductor had about ¼ the resistance to ground as the others. Solved, and got an attaboy from the service manager!

BobC

Meggers can be a great troubleshooting tool.

Bob