Please help mystery troubleshoot - boiler not getting up to temperature

IsaacT

Hi,

Installed a new thermostat after having house rewired. Noticed roll off and the boiler desperately needed a cleaning so hired a pro to clean it out. It is now running seemingly well, burning normally, but ran it from yesterday morning through the night and it never got up to temp. The thermostat was set to 70, and the highest it got was to 62 before dropping in the night as it got colder outside.

3 things to note-
All radiators (nesbitt heating convectors) warmed up and were bled with little air released, aside from one which is broken
the excess pressure valve is trickling water so that probably needs replacing but that should be irrelevant to the issue (according to the pros)
The PSI pressue on the gauge is shifting but the temp has remained at about 115. Can the temperature portion somehow be broken but not the psi on the gauge? Tapped on it but it is not loose enough to see if it is stuck.

Any clue as to why it is not getting hotter? How long should it take for the first heating of the season. I'm not sure how to account for this, as heating potentially dozens of gallons from a very cold temperature would take a long while, but it dropped as the night got colder, which I would guess means there must be some issue because it should heat sufficiently to overcome the drop in temperature?

It is an old home and last year was our first winter but it worked without any issue and warmed up very quickly. We have an old brick home which is of course not very efficient but we have many radiators (about 15 in total.)

In the near future, would love to install more insulation and better windows or at least small patches and hacks to make it better sealed. At the moment, just needing it to heat our home so the home and us can survive the philly winter.

Thanks so much! My partner is exhausted with the old house problems (renovating slowly so it's been never ending) and we'll be so grateful to have this sorted out.

JUGHNE

Did the fire run constantly for all that time or was the pump what you could hear?

IsaacT

JUGHNE said:

Did the fire run constantly for all that time or was the pump what you could hear?

Fire seems to run constantly. Pump also seems to be working.

https://archive.org/details/ModernHeatingWithNesbittConvectors/page/n5
these are my radiators also btw. Very cool original guide that I found online.

JUGHNE

If the fire was running constantly without full flow of water the burner would cycle on and off on high limit. And the boiler and close pipes would be very hot.
The high limit could have been inadvertently turned down to 115 and the fire is cycling but pump stays on.

Pictures of the boiler piping and the controls on it.....might be under panels......could help.

IsaacT

JUGHNE said:

If the fire was running constantly without full flow of water the burner would cycle on and off on high limit. And the boiler and close pipes would be very hot.
The high limit could have been inadvertently turned down to 115 and the fire is cycling but pump stays on.

Pictures of the boiler piping and the controls on it.....might be under panels......could help.

Okay, I'll get some photos. thank you. pipes directly above outgoing from the boiler, and coming back are warm but feel about 115 not anywhere near 140-180 which the shut off has been set at. We put it down to 140 to see if it would get up to temp but I haven't witnessed this yet.

Thank you very much for the help. Excited to figure it out.

JUGHNE

You said new Thermostat.....it needs to be set for 1CPH...cycle per hour. Most come set for forced air...maybe 5 CPH.

Check that first. Installer set up program directions.

IsaacT

We are now thinking it must be sediment build up blocking heat transfer on the exchanger. What's the best way to clean it or confirm this? My hvac guy is very old school and said he would simply flush the system and then put in a couple of galloons of vinegar and then run the system for 10 hours or so to hopefully flush it all out.

IsaacT

JUGHNE said:

You said new Thermostat.....it needs to be set for 1CPH...cycle per hour. Most come set for forced air...maybe 5 CPH.

Check that first. Installer set up program directions.

It is a nest e thermostat. It gave me an option to select radiant heating, but I don't have any other insight on this. suspecting this is probably not the issue but I'm happy to call nest and troubleshoot this for the process of elimination.

what do you think about the theory of the exchanger having too much sediment build up blocking heat transfer?

Btw is a very old weil mclain boiler. Should have more than enough btus for the home according to my guy. Thanks again for your input.

mattmia2

If you can figure out which are the thermostat terminals on the boiler, usually labeled TT, put a jumper across them and see if the boiler gets up to temp. Nest t-stats can have a lot of problems especially if they don't have a separate power feed from the transformer.

Jamie Hall

The two really critical questions are -- does the burner fire continuously and is the circulator pump really running? Most of the rest is gravy. If the burner fires continuously, but the outlet pipe stays as cool as you suggest, something is amiss in the burner -- it just isn't putting out the heat it should. It could, I suppose, be that the boiler is incredibly dirty, but your technician should have noted that as a very high exhaust gas temperature (his vinegar trick, by the way, certainly won't hurt anything -- but may not help much, either). On the other hand, if the burner is shutting off before pipes out in the circulation get hot, there may be a problem with circulation or with the setting of the aquastat -- which should be at 180 for older systems like this.

And if both the burner and the circulator shut off -- then you need to look cross-eyed at the Nest. They can work with your system, but aren't really all that compatible. If you still have the old thermostat, you could reinstall that an see what happens.

IsaacT

Jamie Hall said:

The two really critical questions are -- does the burner fire continuously and is the circulator pump really running? Most of the rest is gravy. If the burner fires continuously, but the outlet pipe stays as cool as you suggest, something is amiss in the burner -- it just isn't putting out the heat it should. It could, I suppose, be that the boiler is incredibly dirty, but your technician should have noted that as a very high exhaust gas temperature (his vinegar trick, by the way, certainly won't hurt anything -- but may not help much, either). On the other hand, if the burner is shutting off before pipes out in the circulation get hot, there may be a problem with circulation or with the setting of the aquastat -- which should be at 180 for older systems like this.

And if both the burner and the circulator shut off -- then you need to look cross-eyed at the Nest. They can work with your system, but aren't really all that compatible. If you still have the old thermostat, you could reinstall that an see what happens.

Thanks. Yes, it is firing continuously (from what i can see) and the pump must be working as the radiators throughout the house are warm, just not enough to do any heating.

Going to look and see if I can find the old thermostat to see if that is somehow the issue. Doesn't seem likely or to make much sense as I can see the boiler is on, etc.

Something must be amiss with the burner as you said I guess

IsaacT

mattmia2 said:

If you can figure out which are the thermostat terminals on the boiler, usually labeled TT, put a jumper across them and see if the boiler gets up to temp. Nest t-stats can have a lot of problems especially if they don't have a separate power feed from the transformer.

Hmm interesting. Why would it matter if it doesn't have a separate power feed? Thanks!

JUGHNE

The Nest needs power to work. The standard R and W connection might be all the wires going to the tstat location.
To get its power it may shut down the system and rob power.
I'm not sure, never had one nor want anything to do with them.

If you remove the Nest and find the R and W wires, typically red and white. Power boiler down, Just tie them together. If any other wires connected leave them be and don not touch any wires together other than R and W.
Boiler should run non stop and shut off on high limit.

There is a search function, enter "nest" and there are many pages discussing (and cussing) the nest.

mattmia2

You can also clock the gas meter if it is natural gas, time how long it takes for one revolution of the foot or quarter/half foot dial on the gas meter with the boiler firing and you can multiply that time to figure out the firing rate of the boiler and compare it to the ratings plate of the boiler (assuming the gas regulator at the meter is providing the correct pressure)