A little more help needed with the Tudor two pipe system

Jim Bergmann_6

I have a two pipe vapor system that I am working with no traps (Tudor system) The boiler was replaced about 3 years ago by another contractor and had not heated since. The customer was experiencing very high gas bills. The system has no main air vent. I have searched from one end of the system to the other. About 80% of the radiators had 1A's or 40's on them.

I have adjusted the pressure down to about 8 oz from 8# cut in is 3 oz and replaced or added 1A's on every radiator to vent air from the system. I am now getting heat at every radiator, and in this cold weather, the system is making about 2.5 oz of steam and cannot make pressure, but it does cycle off on temperature at the stat. I have checked the input, and it is correct.

After the system makes temperature and shuts off it hammers at the next start up. My question is, on a two pipe vapor system is it the same as a single pipe in the manner that the supply valve must be fully open or closed?

Should the air vents be used to regulate how fast the steam enters the radiator versus the hand valve to control overheating of individual areas of the home?

I have some of the radiators that had no air vent at all, and still heated very well. If you cannot throttle the inlet, how can the heat be controlled into the radiator?

All of the radiators are two pipe, both entering at the bottom. The radiators are almost dead level. With this configuration is it necessary to pitch them?

Three of the radiators were replaced at some time and a standard ball valve has now replaced the orifice equipped valve that controls the flow of steam into the radiator. Any suggestions on what to do with this? ( I have them shut off right now because I am sure that they were contributing to water hammer and equalizing the supply and return sides of the system causing it to lock.

The short of it is now that I have heat, I need to control the water hammer.

Jamie Hall

I'm sure Steamhead or MadDog

or one of the other real experts will chime in, but to start...

There should be a main vent, somewhere right near where the returns actually drop to the boiler. Otherwise, air can't get out of the returns, which may be a problem.

Radiators should pitch at least slightly towards the outlets, and the returns should either pitch towards the boiler or towards a drip and a wet return -- otherwise condensate can't get back where it belongs; this may be part of the water hammer problem.

The feed lines should pitch back towards the boiler, or again to a drip to a wet return. If there is anywhere that doesn't, that will hammer, pretty near guaranteed.

My understanding of the Tudor system is that if there is adequate main venting, the individual radiators don't need vents -- and, if you can control the heat in a radiator with a vent at the radiator, it's a sure sign there isn't adequate main venting!

Most vapour systems can be throttled quite happily with the inlet valve; in fact, one way or another, most systems were throttled! Either with an orifice on the inlet or on the outlet, or by controlling (e.g. Hoffman) how far the valve could open. If there is enough pitch, this won't cause a problem (unlike a one pipe system, where the only control was the vent on the radiator and the valve had to be either open or closed).

Jim Bergmann_6

I figured that there was not enough main venting, and from what I read, the main premise of the design was that it reduced costs by not requiring radiator vents, and the fact that good radiator vents were not available at the time of installation. The problem is I cannot easily add a main vent in without breaking into the main piping. I figured that venting the radiators would help out for now (which it has as far as getting heat to the house) and I could add main vents later and get the system working even faster.

All of the returns are dry and both supply and returns pitch back toward the boiler. The valves are only on the inlets (when equipped) Some of the radiators have pipe in and out, and some have what looks like a metered fitting (orifice type).

The question in my mind is if the system is not making pressure to begin with, will adding main vents improve the operation. I was thinking if I could not get the air out of the system, it would shut off on pressure because the system would be air locked and the steam would not be condensing in the radiators. This is what I think is happening since the system will no longer make pressure, and it was before I added the vents. Simply now that the steam is getting to the radiators, it is condensing as it gives up its heat. Now I am wondering if the water is getting back in the off cycles. It appears to do so since the sight glass drops about 1.5-2 inches during operation and then comes back in the off cycle and the electronic feeder is not adding any water.

I have also started to add insulation to all of the steam lines that were bare, but I have not finished that either.

The piping is pitched up to the radiators and all of the returns are dry. What I was wondering is if the system could be draining back both directions in the off cycle.

There have been so many hands and so many changes to the system, it is hard to know where to start.

Jamie Hall

know what you mean

when you have umpteen years of knuckleheads, it can get hard to figure out where to start!

Sounds like your on the right track, though...

Get back to you on this tomorrow.

Steamhead (in transit)

Jim

just drill and tap as many 1/2" pipe-thread holes as you need to add vents. That's what we do, and we rarely if ever have any trouble. One on each steam main, and one on the dry return should do it.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Mad Dog_2

JIm......................

Have you or can you post some pics..on many old vapor systems I see BAD boiler piping...sometimes its just real dirty too. All great advice from the guys. Mad Dog

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Jamie Hall

Where was I?

Steamhead beat me to it. To install the main vents, as he says, you should be able to drill and tap 1/2" on the dry return just near the boiler, and also one near the end of each steam main. Gorton #2s should do it; it's almost impossible to over vent a main or return. This really isn't that hard to do, but if you don't have the right tools find someone who does!

The radiator vents can be left as is; they won't hurt anything.

You will probably find, once you have main vents, that the radiators with just pipe out need to be throttled down; use the valve on the inlet for this. It may take some experimentation to get it right, but the objective of the exercise is to get the radiator to heat, but not allow so much steam in as to get steam into the outlet. Trust me -- it can be done, but it can also be a little fussy. Worth the effort.

The main venting may help the condensate return to the boiler faster -- but you're basically OK on that. It probably is draining back in both directions during the off cycle, but that's OK too. However, the condensate in the steam mains must be really free to drain (and minimized in amount). Double check the pitches on the steam mains; I'm not doubting you, but even a slight sag can let a slug of condensate build up, which will bang. Insulating all the mains will help a lot, too.

You're fine on the pressure. Vapour systems weren't and aren't meant to build pressure; an ideally balanced system would condense the steam just as fast as the boiler made it. What happens in real life is that on a very long run (such as might be recovering from a setback, or a cold day) the boiler should eventually produce more steam than the system can condense, as mains and things heat up, and then it will shut off on the vapourstat until the condensation catches up. This would be at the very end of the run, and would typically be a minute or so off, and then a run of a couple of minutes, and so on until the thermostat is happy. This is NOT short cycling, and not to be worried about.

Carry on, and keep us posted! Sounds like you're doing fine so far.