Boiler turns off before thermostat reached, but starts again if turned off & on?

MaybeFrustrated

I have a 7 year old Lennox steam boiler that has a new problem. When turned on, it runs for about 20-30 minutes then shuts down, regardless of whether it has reached the thermostat temperature. If I switch the boiler off using the switch on the boiler, then turn it back on again, the boiler starts up and gives me another 20-30 minutes. Have called two companies to take a look and of course the boiler stopped this behavior right before they showed up and they couldn't see the problem because it appeared the boiler was working correctly. But now it's been another week of stopping after 20-30 min. If I go to sleep with the temp on the thermostat saying 70, I wake up to the house being 64 because I haven't flipped the switch in 7 hours.

Any thoughts on what this could be? I thought maybe thermostat but the fact that it starts up immediately when power is shut off and then on makes me think the boiler is getting the right info from the thermostat.

Thanks for any thoughts/advice.

JUGHNE

Do you have a "Nest" thermostat?

Is your low water cut off (LWCO) control a "Cycleguard"?

When the boiler shuts down are there any lite up lights on the LWCO?

I would have the LWCO probe cleaned and also the pigtail loop under the pressure control.
Would have thought your service people would have at least checked those items.....but then maybe they didn't charge you.

Jamie Hall

It is necessary to figure out what control is turning off. Since it resets when you cycle the power, it's not a manual safety (some boilers have those) -- but something. @JUGHNE mentioned the more obvious ones.

You have discounted the thermostat, but I wouldn't do that just yet. I seem to remember that some of the so-called smart thermostats take it into their heads to limit run times...

EdTheHeaterMan

MaybeFrustrated said:

I have a 7 year old Lennox steam boiler that has a new problem. When turned on, it runs for about 20-30 minutes then shuts down, regardless of whether it has reached the thermostat temperature. If I switch the boiler off using the switch on the boiler, then turn it back on again, the boiler starts up and gives me another 20-30 minutes.

Thanks for any thoughts/advice.

Has anything changed on the boiler or control system between the time when the problem did not exist to now? New thermostat?, maintenance service? repair?

Some digital thermostats have a "cycle per hour" setting in the programming (or on micro switches on the back) Older thermostats have a Heat Anticipator for this purpose. It is designed to reduce overheating of steam and "large mass" water boiler systems. This might be a case where you just need a new thermostat An electric meter with a little understanding of electricity can determine the cause.

Are you Handy that way? If not, then you need a service technician there when the problem is actually occurring so they can do the proper test to see where the open electrical circuit is.

Another thing occurs to me... the pressure control has a cut in and cut out setting that may be improperly set. Has anyone adjusted the pressure for any reason?

MaybeFrustrated

Thanks for the replies. The thermostat is a Carrier programmable, not a Nest or anything like that.

The Low Water Cut Off has not been a problem as far as I can tell. It is indeed a CycleGuard. The system is not shutting down based on getting to low water as far as i can tell, the lights are not on and plenty of water in the sight glass. I have been in the room when it shuts down and never low water.

The only thing I can think of that has changed recently is that the pipes running the length of my basement (which I believe are the return pipes if I understand my system correctly) have had some holes that I've patched up. I'm now getting those pipes replaced altogether in a few days, but I did not think they were the problem because they are not currently leaking and I'm not getting the low water cut off. I'm hoping that they might be the source of the problem, but not sure why they would be since I don't see water loss.

Jamie Hall

How is it that you have a Carrier thermostat trying to operate your steam system?

That said, I notice that at least some Carrier thermostats have a nifty (?) feature called Smart Recovery which "begins working in advance, turning the system on and off as needed to slowly adjust the indoor temperature. During these transition periods, you may notice that the actual temperature and your temperature setting don't match. "

Which is right up there with a box of rocks on the genius scale.

I would be very much inclined to try a stupider thermostat for a while and see if the problem persists...

MaybeFrustrated

Thermostat was put in by the installer of the boiler, not sure why that thermostat in particular.

The reason I can't see the thermostat being the problem is that the boiler is never activated again once it shuts down. If it was a degree or two between the setting and the actual temperature, that would make sense, but when it's set to 70 and still doesn't kick on at 64, that feels like the problem is elsewhere. But obviously I don't know or I wouldn't be asking in the first place, so everything I know is clues without a solution

Jamie Hall

It's a control problem, as I suggested above. In order to fix it, it will be necessary to figure out which control -- starting with the thermostat and right on through to the burner control box itself -- is telling it to stop, and then not resetting unless the power is switched off.

If you are handy with a multi-meter, you may be able to do some troubleshooting yourself. The overall basic principle is that for the boiler to run, it must see T-T on the burner control box as a closed circuit -- Zero voltage between T and T. All the other safeties are the same -- as is the thermostat. But it may not be easy to get the villain to misbehave...

HVACNUT

It seems as if after 20 to 30 minutes of run time, the burner circuit opens on pressure, but a possible blockage in the pigtail is preventing the switch from closing again. Neither company checked? 
Also what make and model pressuretrol? If a Honeywell PA404A or equivalent, then then .5 psi cut in, 1 psi differential. 

neilc

HVACNUT said:

It seems as if after 20 to 30 minutes of run time, the burner circuit opens on pressure, but a possible blockage in the pigtail is preventing the switch from closing again. Neither company checked? 
Also what make and model pressuretrol? If a Honeywell PA404A or equivalent, then then .5 psi cut in, 1 psi differential. 

I was thinking the same thing,
but,
how would cycling power, or stat, then allow for refire?
I go pigtails all the time, but maybe not here

Big Ed_4

Normal CycleGuard has a built in cycle to shut off for a few minutes without going off on low water. The thought behind it was to let the condensate time to return though any old partly plugged returns .

I know ..Just as the mains start to fill it goes off and you can reset with a flip of a switch .. If I was King , the off cycle should start on low water , before turning on the feeder or give us some adjustment on the cycle.. Normal annoyance with CycleGuard ..

JUGHNE

Just a WAG that the Cycleguard is doing it's thing of shut down to check water level. Could it not be resetting as it should (lost part of it's mind) for restart of burner until a power recycle is done?

neilc

the psycogard and the carrier thermostat Jamie called out, not playing well together?
wonder what would happen with a simple on/off t87

JUGHNE

Or at the tstat just tie R and W together and wait....do not leave unattended.

MaybeFrustrated

I don't know a whole lot about boilers beyond the very basics, so I'm a little lost on some of these answers but I do appreciate them and will print out all these answers so I can challenge the next repair person I call if they can't figure it out! Thanks for the input!

MaybeFrustrated

One other thing. Even when boiler is working, it doesn't seem to get the heat upstairs much, and sometimes when I turn it on, it fires for only 30-40 seconds before shutting down for 30 seconds and then doing that again. Is that what is meant by short cycling?

Anyway, when it is on, even with me consistently resetting it through off/on switch, the heat doesn't seem to be dispersing correctly through the house, but it eventually works well enough to satisfy the first floor thermostat while upstairs is clearly colder.

Zman

You need to find an experienced steam heating contractor, not just a typical plumber or HVAC tech. You might try the find a contractor tab above or post your location and ask for recommendations.
The book "We got steam heat" available in the bookstore on this site will help you understand your system.

kenlmad

Your initial post is describing normal operation of the Low Water Cutoff (LWCO) "Cyclegard" model. You are defeating the "Test Mode" when you manually cycle (ON-OFF-ON) the main power.
For the boiler not firing back up for the next call for heat after some period of time, are you sure you aren't leaving the boiler main switch OFF when you walk away?

What is the model # for the Cyclegard LWCO? If it's a "CGxxx-1560" that means every 15 minutes it shuts off for 60 seconds; a -1090 model, then every 10 minutes it shuts down for 90 seconds. There's also some -2060 and -2090 models. While in this "test mode" the Green LED is on for the 60 or 90 seconds. The boiler burners should fire right up after the test mode is finished. Can you verify that the Cyclegard performs at least one successful "test mode" cycle during a call for heat; ie. burner on-off-on?

With an actual low water condition or a failed/dirty LWCO probe the Cyclegard's yellow LED is on. The Yellow LED turns off when the low water condition no longer exists. The probe should be removed and cleaned periodically, every year or 2.

BTW - A Cyclegard will do it's scheduled test cycle regardless of when the call for heat occurs. I've had my boiler go "off" in test mode (Green LED on) within 10 seconds after the damper opens and the boiler initially fires up. Very annoying.....

What is the model of the thermostat? Next time you have no heat and the boiler should be on, give the thermostat a quick finger flick to see if a stuck mini relay inside the thermostats circuit board is the culprit.

What is the status of the Ignition Module's diagnostic LEDs after the failed restart and prior to your power-cycle?

In what position is the vent damper (open or closed) after the failed restart and prior to your power-cycle?

After the failed restart and prior to your manual power-cycle, is the transformer making a normal characteristic 60 hertz electrical hum? Or is it silently unpowered?

ethicalpaul

Great post by @kenlmad. It has a Smartcycle mode where it will synchronize its test timer to the firing of the burner but I haven’t tried setting mine up that way yet

MaybeFrustrated

I think I diagnosed the problem, though don't have it solved yet. The boiler has a Cycleguard LWCO right next to the boiler by the sight glass. There also is a secondary/backup Safgard LWCO mounted by the wet return/Hartford Loop piping.

When the boiler is turned on, it fires for about 8-10 minutes. Then, even though there is plenty of water in the boiler according to the sight glass (and no alerts from the Cycleguard LWCO), the yellow light on the Safgard kicks on and the boiler is shut down. The rest of the cycle is Safgard light on for 40 seconds then it goes off, boiler fires again but then Safgard light comes on in 30-40 seconds, then light goes off and boiler fires again until finally Safgard light stays on for a longer period and the whole system shuts down at about the 25-minute mark for the whole cycle. Then it's all over unless I restart things.

I discovered that I can re-start the cycle not just by turning boiler off and on, but also by hitting the manual reset button on the Safgard LWCO.

So this all leads me to believe it's that Safgard LWCO that is the problem. Does that sound right? I've seen elsewhere that there is a probe or float or something inside that could need help, but that's not something I want to tackle. Unfortunately just got our first winter storm so I'm not first in line to get a pro out to help me.

Does that all make sense, though?

kenlmad

It sounds like the Safgard is the system's secondary LWCO. The Safgard probe should be mounted lower than the Cyclegard's probe.

If the Cyclegard isn't reporting low water and the sight glass appears sufficiently full, then I agree with your suspicions. (Unless BOTH the Cyclegard is failed AND the Sight glass ports are clogged.) Occam's razor ===> its the Safgard LWCO.

My guess - The Safgard probe seems to be going open circuit when it gets hot (fitting expands enough to create a poor connection with the probes threads. System cools and the probe works again, sort of ... anyway please read this manual that may be for your Safgard probe, particularly the bottom of page 3.

https://s3.amazonaws.com/s3.supplyhouse.com/product_files/Hydrolevel-45-550-Install-Instructions.pdf

ethicalpaul

Can we see pictures of this situation? I'm pretty sure no one had any idea of a second, manually-reset lwco on the near boiler piping

If your pictures can be of the boiler and near piping, from floor to ceiling that would be best. Maybe also with some closer (but not extreme closeup) shots of the controls.

EdTheHeaterMan

Is this in an apartment house or commercial building? There is no requirement for a manual reset control on a residential system. Not saying you should remove it, just odd that someone would put a manual reset control on a single-family residential boiler.

The location of the manual reset control is important. You may need to have the probes cleaned or there may be blockages in the wet return piping. Steam condensate does have a way of clogging up old pipes.

MaybeFrustrated

Got someone to come out and it appears to be fixed. Seems like a combination of the probe in the backup LWCO and a return valve that wasn't fully open. Hard to understand the half-open valve, almost wondering if a different repair person inadvertently did it while trying to diagnose the problem. Can't think why I would have touched it really.

Anyway, thanks for all the input. I'm really getting to know and love my steam boiler after 18 years with it.

mattmia2

That was my first thought after hearing of a second LWCO was that someone closed a valve that was isolating that LWCO.

Actually, it was my second thought, having no idea that there was a second LWCO I was wondering if something intermittent with whatever the combustion controls used to prove flame.