Mysterious radiator issue

Gene_2

Thank you for the detailed reply Brad! My knowledge of these sort of systems is quite limited, but let me see if I can answer your questions and help get closer to a solution.

When I vented the one radiator that has a visible "key" access point (both last year and today) I immediately got water, so it doesn't appear to be a lack of water in the radiator itself.

Regarding the water pressure, the gauge appears to show a decent amount of pressure, though I think perhaps they use something other than psi here, because the scale on this gauge is quite different from what you described. I've attached a photo of the two visible gauges (pressure and temp), as well as the boiler and one of the radiators, to perhaps help compensate for my lack of knowledge and descriptive ability. :-)

I think both radiators have a valve like you described, but both valves are "locked" in place (see photo for a close-up), so I don't think it's very likely that either of them was closed manually. Besides, wouldn't that have prevented them from randomly heating up a month or so ago, when they did get very hot on at least one occasion?

House calls? I'm a renter so any payment would go through the landlord, but I'd be happy to compensate anyone who wanted to make the trek with fine Belgian beer and chocolate! ;-)

Gene_2

Odd radiator problem

I am living in a third floor apartment in Brussels, Belgium with a rather old gas-powered radiator heating system. We moved in last fall and by wintertime quickly realized that the two radiators in the two front rooms of the apartment were not working. You could feel some heat in the pipes leading to them but neither one of them would ever get more than just slightly warm. We tried bleeding them at our landlord's suggestion but that didn't help, so we just dealt with it last winter since we didn't expect to remain in the place.
We've found ourselves staying an additional year, and in early October I was surprised to notice one semi-chilly day that both radiators got quite hot! Hooray, or so I thought. Suddenly, come November and colder weather it's back to the original problem, with absolutely nothing different having been done on my part. A few additional bits of information: our heating system appears to be independent from the other apartments, because we have our own boiler and thermostat. It is located in the center of the apartment, so the non-functioning radiators are no further away from the boiler than the functioning ones.
Does anyone have an idea of what could possibly be causing this?

Brad White_202

Some thoughts

Do you know the water pressure in your system? I at first suspected that if pressure was low, (i.e.: a leak somewhere), the water level might drop and not fill the radiators. Then again, if much of a leak, you have people living below who would tell you....

When you do vent the radiators, do you get air at all? Or water? Or... nothing? If nothing, I suspect that the water is below the radiator vent point and no automatic valve to fill it. Then again, this would likely lock out your boiler (as I strongly would hope!).

Now, naturally if low water pressure, this would affect all radiators. But on the other hand, if just low enough to get heat at all, the colder rooms (the ones with the greater heat loss) would be the sentinel spaces which would feel cold when all radiators get the same water temperature, whatever it is. The ones with less heat loss would not care as much and may be getting by. Just one thought. Does that make sense?

Normally the pressure in most same-floor systems wants to be about 5 PSI (0.33 Bar) at the very minimum just to fill the system, but then the boiler probably wants to have a higher pressure as a safety function to make sure it cannot fire dry. My French-made boiler requires 1.0 BAR (about 15 PSI) to even start. This is enough pressure for a two-story house.

Might you also have thermostatic valves on the radiators? How are they adjusted? Might they have been closed manually and so forgotten? I have to ask. The valves may not be so obvious (meaning internal to the radiators) so you may have to look.

Another thought is that outdoor reset is probably used so the hottest water coincides with the coldest weather. Your tepid feeling may just indicate that it is mild outside.

If this is the case and the space temperature still feels too cool to you, your heating curve (the ratio of water supply temperature to outdoor air temperature) may need to be adjusted.

I do not think a lot of the folks here make house calls, but some might be persuaded.

nicholas bonham-carter

chilly muscles in brussels!

maybe those radiator valves are more for balancing the system flow rather than shutting it off.perhaps the pump is failing, and therefore not able to handle the whole system all valves open without favoring some radiators.
luckily one of the frequent contributers to this site is at present only 2 hrs. away from you by TGV! maybe he will take you up on your offer[better include some mussels]!--nbc

Brad White_203

Ahhh Chocolat Belgique....

What my wife would not do for Belgian Chocolate... our address is....

As Nicholas said, may be a circulator (pump)/water delivery issue. The boiler control is set at 50C and the thermometer reads in range of that, a bit more.

If those valves are fully open or at least partially so, you should have plenty of heat it would seam. (No fooling! Politicians' answer...

The pressure seems reasonable, I assume that those readings are in meters of water (roughly 1.42 PSI per meter) and the red indicator is usually to indicate the initial fill elevation in meters (3 meters or about ten feet = ~4.3 PSI). If on the same floor, even though it is less than peak pressure, the system must be full.

Too bad you are across the pond. A half-hour on-site would tell so much more.

Do this: Turn up your thermostat and see what happens: Does the boiler fire right up or does the circulator turn on first? Sometimes the boiler fires until it reaches temperature, then the circulator starts. Some systems have the circulator run 24/7 in the heating season and fire the boiler of the thermostat.

What I want you to look for is when the circulator starts. Feel the pipe (carefully) and see if you can feel the hot water migrating along the pipe. If it stops at some juncture, (fitting, valve, tee), make note of that. Note which radiators get hot and which do not. Sort of a detective thing, radiator by radiator. My point is one of gathering information from which some dots might be connected. Others I am sure will have more suggestions. Nothing clicks with me yet but it might.

By the way, maybe only the obscure heating folks here would notice, but see the hemp wicking used to seal those pipes? The Old World stuff works.

Gene_2

Oui, le chocolat Belgique est magnifique!

Thanks again for the reply Brad, and Nicholas as well. You might have earned your wife some Belgian chocolate by the time this is through!

The boiler does fire right up when I turn up the thermostat, but I will have to listen for the circulator as I've never really noticed the sound of it before. I will also have to do a bit more detective work in the morning to try and figure out where the heat stops flowing through the pipe that leads to these radiators. It definitely stops, or at least slows at some point, because by the time it reaches the radiators this pipe is nowhere near as hot as the ones in the other part of the apartment - I'd say it's medium-warm at best. The pipe runs across the top of a 10 foot ceiling so it's going to take a ladder to do the "heat feel test". I have one though, so I'll give it a try tomorrow and get back to you!

Thanks again!

Brad White_202

Another thought...

Might it be that your radiators are piped in series? Like pearls on a string? The first radiator gets hottest water and every one downstream gets the "used" water until the last radiator, poor thing, gets bupkes. It weeps, silently ignored by it's older siblings. All it wants is love, I tell you. And hotter water...

Can you map out the flow pattern as a diagram? Does each radiator get fed by a branch off a main or does each radiator have a supply pipe then exiting to supply a downstream radiator? It has been an inexpensive way to pipe radiators sometimes.

Anyway, just a thought.

Chris Kuzila

Pressure Gauge

Could the gauge be reading in Bar? Two and a half Bar=thirty-five PSI?

Brad White_202

No, I do not think so

The gauge says, Mw (meters if water). I thought BAR too at first and before I looked more closely. But BAR for a one-floor system that did not make sense. If it were BAR it would say so.

I also figured that Mw was not "Megawatts" and did not look like an electric meter

World Plumber

Are there caps on the els that go into the radiators? If so there is a valve to close the line if removing the radiator built into the el. They use a hex key to open them someone may have worked on the system and forgotten to reopen it.

tim smith

I am thinking that there is an air trap in piping overhead

She mentions that the mains run up at 10ft off floor. This could mean that she has full radiators but air locked mains. Maybe there is an air vent up at ceiling that is blocked or maybe just a manual vent on main up high. Take some pics of ceiling piping above boiler and maybe several around room. PS: too bad you can't wait till next June, I think my bus. partner and I will be going to our favorite boiler mfr in Brussels then. Any way, further pics a help. Just took 2nd look at gauge and if in Mw, then appx 3.5 psi, not enough to get to top of mains if at 10ft off floor I think. Tim
PS: that copper pipe in the gauge photo might be the fill line for the boiler. Need pics of where that line goes and maybe we could walk her further through this. Tim

Gene_2

Making progress?

Okay thanks to all of your comments, questions and suggestions I think I did discover something significant; the main pipe that runs to the front of the apartment and the two radiators in question remains hot, right up until the point where it "splits" into two pipes that in turn lead to each of the non-functioning radiators. Beyond that point both pipes feel significantly cooler; the difference is striking. It's a 90 degree "tee" split in the pipe that occurs at the top of the wall dividing two rooms (at ~10ft), which I have photographed.

Does this support the possibility that Tim Smith raised, of an air block of some sort? If so, is there anything more I can do about it, or is it then to the point where I need to contact my landlord and get a heating professional in here to evaluate it?

Even if this is as far as anyone is able to get me, I truly appreciate all of your input and good humor! Given the language barrier (I'm still trying to learn French - not an easy language!), it will be infinitely easier to explain the problem to anyone who comes here if I can point them directly to it...so thank you all!

Gene_2

\"Emotionally rejected\" radiators...love it!

I just re-read your first paragraph Brad, and I'm still laughing!!! :-)

tim smith

There is probably a purge valve somewhere up on that pipe

at the ceiling. Follow it around room and look to see if you can find it. It will tee off of that horizontal pipe at ceiling somewhere. Also still need to figure where that smaller copper pipe by gauge goes as that I think is probably the fill line to add water to system. Take pics of both above items and this will help. Tim

Gene_2

More pictures

Thanks Tim, I followed the small copper pipe like you said, and it snakes through the apartment and ultimately ends up connecting to the tankless water heater in the kitchen? That was a surprise to me, and maybe now is a good time to mention that we've had trouble with the pilot light going out on both our kitchen and bath water heaters. The kitchen heater often shuts off after use and the bathroom one recently started shutting off whenever it feels the urge. I never perceived those issues to be related to this one, but perhaps I was wrong.

Anyway, regarding the purge valve, I didn't see anything like that along the section of that pipe that I can see (part of it isn't visible in the hallway, where the ceiling is lower). I poked around more in the utility room and took several additional photos of stuff in there. There's a few shots of what I'm pretty sure is the circulator, which is a good 8-10 ft up in the air, so sorry if a couple of those are blurry - I took them while hanging one-armed off a roof-access ladder! I also took a shot that shows a few knobs/valves in the vicinity of the boiler that could be what I'm looking for, but I'm really not sure. Please let me know if you need a different angle or zoom on any of these shots too.

World Plumber

Might the gauge be stuck and the pressure really much lower than it reads?

tim smith

I think in pic 009 is the fill valve to the right of the flue

pipe. I cannot be 100% sure as I can't see what it ties to coming at me. I think the tank up high on the wall, the silver one is the reserve tank that is probably empty due to lack of water in heating system. I really think you ought to have the owner call in a heating person as if we steer you here without all info, you could flood your flat and that would not be so good. Sorry I can't help you much further but I really don't want you to be living in a bathtub. Tim

Gene_2

Time to call the landlord...

Yeah, it sounds like it's reached the point where I'm not going to get any further with this on my own. Still, I'm glad I at least tried and hopefully ruled out any extremely simple fixes or "user error" issues.

Thank you to all who took the time to read and contribute!

Brad White_203

Wrap Up

I was out of town yesterday (Maine, not Belgium, darn it.) But Tim has a point, re: potential air binding. But that point about a sudden cooling has me thinking a combination of air binding and poor circulation, that gravity circulation sometimes works, sometimes not...

Rather than give conjecture from 6,000 miles (9650 kM) away, we admit defeat and let your landlord try.

Please let us know how it turns out!