Where's my steam traps??...and other questions

It's quite possible that the system was built without traps. You can do that if, as @JUGHNE says, there are orifices either at the inlet or the outlet of the radiators -- and the pressure is kept low enough. On the other hand, there may be more than meets the eye in those innocent looking outlet elbows. Either way, a close up of both a typical valve and a typical outlet elbow would be helpful.

Also, as he said, where do the outlets go? If this was built without vents and traps, it's almost a given that they go into dry return pipes in the basement, which in turn go back to the boiler and drop into it. If this is the case, there should be a vent or vents on the dry return(s) just before they drop to go into the boiler.

So -- his questions need answers!

And I agree -- I don't think much of the existing insulation -- but replacing it, while it will be a bit messy, is very much a do it yourself proposition.

You may find the duct tape is covering asbestos. It encapsulates it so it doesn't become airborne.

Better pictures of the piping above that boiler would help too. Is this a counter flow system? Aside from that one, fairly small pipe, that drops into the bottom of the boiler, I don't see and other returns or an equalizer or Hartford loop. I don't even see a water supply to add water to the boiler. A lot missing in the current set of pictures.

Some of my radiators are piped like this. Looks like they don’t have traps until you look in the basement. The traps are on the radiator return just before they join the main dry return. Not sure why this was done. Might be worth checking your basement for traps.

You definitely need more main venting. Measure the length and diameter (outside diameter of the insulation is fine, don't disturb it) and post the results here. We can tell you what you need.

For the vent on the dry return, use a Gorton #2, or two if need be. It has a float which will close against rising water whereas the Big Mouth does not. In this type of system, if the boiler pressure gets too high, water can back up into the dry return and will flow out of a vent that has no float to stop it.

So you got 2" pipe for the mains. You have some type of orifice system. If you vent it right, keep the pressure low you won't need steam traps.

Keep in mind this system was originally designed for a coal boiler=constant firing and =low pressure. To make it work well on oil or gas may take a little work and a few modifications....like adding venting but it can be made to work well

If your replacing boiler, and if you can get to all the radiators. Switch it over to hot water run pex tubing to each radiator.
This way each radiator can be zone, have multi temp threw out the house. System would be quiet, efficient and comfortable.

Never mind the ridiculous expense of the conversion...

trivetman said:

And does the low pressure gauge replace the existing gauge or need to be installed alongside it?

Needs to go alongside it -- a T, couple of nipples, couple of elbows -- 10 minutes.

25 min is a little long but the fact that the pressure doesn't build quickly is a good sign. I would add more venting. You wan't to move the steam in the mains as quickly as possible. 2 1/2 psi isn't awful but you might lower that a little.

Short cycling is frowned upon, but an occasional short cycle like 2 /hour isn't objectional

I don't recall your mentioning it, but it is an important question: are there crossover traps from the ends of the steam mains to the corresponding dry returns? They would look like radiator traps, but be piped up from the steam main, then over to the trap and down to the dry return.

If you have crossover traps, then you do not need -- not want -- vents on the steam mains themselves. That's what the crossover traps are for. If you do not have them, then you do need vents on the mains.

In either case, you must have adequate venting on the dry returns at the point where they drop down -- usually right near the boiler. That Hoffman 75 is almost certainly not adequate -- you should add a Gorton #2, unless your system is very very large.

Now. That Gorton #75 on the dry return should, in general, never close. There are certain types of vapour system (notably Hoffman Equipped) where, under certain circumstances, it will close -- but in general it should never close. The most likely cause for it closing is that somewhere in the system there is a steam trap which has failed open. This needs to be found and fixed. Both of the major exceptions to that have to do with the pressure being much too high; if the system still has the vapour steam equipment, then you need to run a cutoff pressure of no more than 8 to 12 ounces per square inch -- possibly less -- with a cutin of no more than 3 to 4 ounces. In any case, your cutout pressure for a system of that type should certainly be less than 1.5 psi and better around 1 psi -- which means a vapourstat.

You mention that the system runs at about 0.5 psi for about 25 minutes. Good, but a little high; the extra dry return vent may help that. That plateau, though, also indicates where the system is balanced to run -- and all the more reason to set the cutoff at less than 1 psi (but perhaps more than 0.5 -- say around 12 ounces).

When you reach cutoff, start timing the cycle -- so many seconds before it cuts back in, then so many seconds until it cuts out again. Do this after you get the vapourstat. The ratio of off time to total cycle time is a very good indication of how much too big, if at all, your boiler is in relation to the system demand.

OK. Probably orifices -- and with any kind of luck, they are still there. All the more reason to keep that pressure down. Orifice systems are dismayingly sensitive to pressure. It is quite possible that your thought about the trap closing when steam makes it past the radiators is quite correct.

Now. Suppose that the orifices have been removed from some -- or even a large number -- of the radiators. Is there a solution? Yes there is, and it may well help those two radiators which don't heat all the way. But it will require some patience. You can use the inlet valves on the radiators as throttles. What you want to do is to close the valve on each radiator to the point where each one gets hot almost all the way across and down to the outlet. Almost. But not quite. Mark that location on the valve; you can go below that, if some room or other is overenthusiastic -- but not above it. That point is the point at which exactly the same amount of steam is getting into the radiator as it can condense. If there are no orifices in some of the radiators, you may find that the valve will be quite nearly closed -- particularly on smaller radiators -- but if the radiator is hot across and almost down to the bottom, that's all it will ever put out anyway.

This is very pressure sensitive! Given your system pressure -- and put in that Gorton #2 on the dry return before you start playing; the vents on the mains will speed things up, but not change the plateau pressure which is where you want to be working -- and then make sure that the boiler doesn't go over twice that plateau pressure, and preferably not over 1.5 times the plateau.

Have fun!

How long are the mains, and what pipe size?