Steam radiators heating intermittently

tylerjgardner

So I was called out to this house and did some piping repair on the steam boiler. It had pin hole leaks in several different places in the basement on the dry return which was pouring water out of it through tiny holes. 1st question why would this happen in so many different places and seem to occur within the same time frame? Also, why is it water and not steam? Now that im typing this out that seems like a significant issue. Another issue the homeowner had me check out was that two of the radiators weren't heating all the way across. I understand they'll not always heat all the way across depending on how long the boiler runs, but she said sometimes they dont even heat. Its two pipe. The supply has a Danfoss thermostatic radiator valve, set as high as it can go. Also, what I find odd is that there are no steam traps. The steam just flys through. Ill attach some pictures. I have pictures of the piping in the basement if needed. The air vents at the end of the steam main are working for sure. I found a 3/4" plug at one fitting that I removed to see if that helped but it didnt do much. Also, the boiler was over filled I drained it and corrected the issue by telling the WFE-24 water feeder to wait longer before filling to allow the condensate to return. When I was there today the radiators were heating fine, but upon a previous visit I can atest that at one point they werent working.

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bburd

That thermostatic radiator valve is installed with its sensing head in the wrong position. It should be horizontal to sense the room temperature. Installed vertically like that, when the steam comes up the rising warm air around the supply pipe will heat the sensor and tend to make it shut off the steam flow before the radiator gets hot.

Jamie Hall

Those return elbows may not be as innocent as they look. Either that, or there may have been calibrated vapour valves on the radiator inlets, or orifices.

In any case, steam blowing through the radiators is lethal. One radiator may heat gloriously, but the steam from that radiator in the dry return will pressurize the dry return — and other radiators may not heat at all, or at best very poorly.

Whether this has fancy elbows or originally had either inlet orifices or calibrated vapour valves, you are going to have to get the pressure down for starters. Absolutely no more than 0.5 psig cutout (that's 8 OUNCES) — and that means a Vaporstat for control. If those are fancy elbows, that alone may solve a lot of problems. If not, you are going to need orifices on the inlets to the radiators to control the steam flow to what the radiator can condense and no more. (that radiator with the TRV will almost certainly need an orifice — TRVs are OK on two pipe systems with radiator traps, but are a menace on other types).

Now. Pinhole leaks in a dry return — or what is supposed to be a dry return — suggest again verry strongly that water is being backed into the dry returns — which again suggests excess pressure.

So — step one is to get the pressure under control. Then see what else needs to be attended to.

tylerjgardner

Thanks for the input. Would you mind elaborating on adding an oriface? Is that on the supply or return side? I'm not sure what you're referring to because I dont think I've ever seen one.

Jamie Hall

Usually the easiest place to place an orifice is on the supply side. Several ways to do it. The trick is to size them so that they allow enough steam in to heat the radiator — but no more than that.

They are also pressure differential sensitive — so the first step is to get that under control.

IF you still have vapor style valves, they can be used instead of orifices (in fact, that's why they are used) and adjusted with the control handle to allow the right amount of steam through. Newer conventional globe valves can also be used this way, but are much less precise and harder to get right.

delcrossv

FYI

https://maconcontrols.com/steam-radiator-inlet-orifice-plates/