Single Upstairs Radiator No Heat

[kolinl79]

Hello, first timer to the forum.

My system is a Triangle Tube HE, put in 15 months ago, two zone system.

I live in MN, so it's damn cold. I noticed one of the upstairs radiators wasn't getting heat. I attempted to bleed, however all that produced was a short fizzle of air. I attempted bleeding the remaining radiators upstairs, each had some air to give, but not much. The system I have is supposed to remove air in the lines which it appears it failed to do so. The flow upstairs is good, 3 of 4 radiators are getting heat, etc. except the radiator furthest from the boiler which is my cold radiator.

In reading the forum I attempted to turn off the valves to all other radiators and attempt to force the radiator to take heat. That did not make a difference. I did notice in the basement where the boiler sits, at the manifold where the outtake hose is connected, it's not getting heat where all other hoses on the manifold are. I attempted to turn off the flow to the cold radiator and adjust the flow by turning the knobs, still no change.

This boiler was working fine a few weeks ago, I fear a sudden drop in the weather (no heat in open basement either) caused an issue.

Any suggestions or advice as to what else to try would be much appreciated. I dread dropping another $450 as they were just out for another problem (replacing a valve on another radiator)

[BadgerBoilerMN]

It could be a frozen line serving the one radiator. Are all the radiators plumbed from a single manifold with PEX tubing. Air elimination in an old cast iron radiator heating system is done by the radiators, no matter what your plans. Do you set back the heat at night?

[kolinl79]

It's possible, however I should feel heat on the line soon after the manifold and while it's not cold, it's not even close to the heat generated on the other lines in that zone. I attempted to set the heat high directed at this single radiator for 30+ minutes with no change.

I have a two zone system, 4 manifolds, 2 cold, 2 hot. The heat is set back, it doesn't run much at night since most heat is fed from the 1st floor zone.

If I had a frozen line, what can I do to unfreeze it? I tried heat at where I thought the line was frozen without change to the operation of the radiator.

[Tom Sawyer]

It's frozen.

[cacher_chick]

You will need to warm the inside of the wall cavities where the piping is routed. IMO, this piping should never be routed through an exterior wall. If it is a new install, you should ask the installer to resolve the issue.

[kolinl79]

It's a new install, however the pipes have been there since 1925. The two zone system is new, and since it's not heating the upstairs radiators as often as the 1st floor, I suspect the -30 degree weather here froze the pipes is what is already a cold wall.

I started downstairs attempting to heat the tubing and existing metal lines and work my way up.

Another question, could I potentially have an issue with a burst pipe if not resolved?

[jadnashua]

Anytime you get a hard freeze, yes, you could have a split pipe or fitting. Not necessarily, though...it depends on lots of factors. If you have an autofill valve, I'd shut it off if it isn't already. Then, if there is a split or cracked section, you won't be pouring makeup water into the walls. It will shut the boiler down, but then hopefully, someone will be home to notice. IMHO, it's not a great idea to setback much when the long-term weather is so cold.

[kolinl79]

I put heat on the lines in the basement and in the wall cavity. I also adjusted the thermostat 2 degrees warmer. Eventually, the flow started. I will keep an eye on that radiator over the next few days to make sure.

Thanks everyone for the help!

[BadgerBoilerMN]

Setback thermostats were designed for inherently inefficient force air furnaces and occupants whom, for the most part, don't know what winter time comfort is.

The Triangle Tube, like all condensing boilers sold today, has a built-in out door reset that will reset delivered water temperature according to outdoor ambient temperatures. This feature saves fuel and creates the ultimate in comfort all without the need for night set-back. In the coldest weather--a few days a year--thermostats should not be set back as they let the system idle in a no-flow condition, often just long enough to freeze up plumbing and heating lines set too close the perimeter.

Here in Minneapolis there are many old homes with cast iron radiators fed with steel pipe set at the rim joist and beyond. A hundred years without a problem and then the gas company comes along and tells folks; you can save big with one of these little gadgets. Next cold spell and all those saving go to re-piping the new radiator line.

There are a few condensing boilers, e.g. IBC and Viessmann, that reset water temperature for a predetermined period of time allowing more flow and comfort at reduced water temperature and slightly reduced indoor air temperature. This is the proper way to set back a radiant floor or old cast iron hydronic heating system.

When we replace a gravity boiler in an old house, we often re-pipe the cast iron radiators with PEX using outside wall when necessary but PEX can suffer many freeze cycles without damage.

[Tom Sawyer]

I told you so.