Venting risers

JUGHNE

Would this work? I have 20' of 2 " risers to 1 pipe rads.  They have 30 year old Danfoss RAV 1PS TRV controls that still function but lack a vac breaker for off cycle air to return to main.  I'm thinking to add Gorton D vents to the "wrong" (valve end) of the rads to vent the risers and then to allow air to re-enter on off cycle.  Would venting the "wrong" end of the rad vent air from the riser accomplish this:  the Gorton D would close when steam arrived up the riser--then the TRV would then control the rad venting on the "correct" end (opposite of valve end) to desired room temp--then when boiler cycles off and the Gortons allow air to re-enter draining condensate. (I'm assuming the D would open as a vac breaker when the pressure drops off like any other rad vent.)  The TRV have new straight vents installed.  The pressure is 2 PSI max.  Oversized Boiler cycles quite often.  Condensate now gets trapped in rads/riser and will suddenly return as a toilet flushing.  Hopefully fix 2 issues with minimal repairs. 

Then which and how much tapping oil or lubricant could be applied without causing boiler water woes??  Thank you for any advice and help.

Unknown

why??

Why at high pressure of 2psi for this small system?

JUGHNE

2 psi

This 1 pipe section is part of about 1886 EDR combo 1 pipe/2 pipe school house.  1954 Boiler is NG 1,008,000 BTUH.  only about 1/4 of the original (1922) 1 pipe is still connected.  This system ran at 5 PSI for at least 35 years because someone from the city said so and who would question an expert.  It seems to be a Hoffman vapor system from coal days.  Orifices in the 2 pipe valves plus Hoffman traps. The pressuretrol is set as low as possible.  Budget is always a concern.  So I'm trying to improve things as possible.  Just going from 5 to 2 psi has improved things a lot.  Changed traps (original) and down sized orifices in 2 pipe part.  Yes pressure is high but boiler might only run 6 minutes now to hit 2psi on a mild day.  4" zone valves operate each section. So would a vaporstat improve things??   Room for lots of improvement such as a smaller boiler.  This will hit 83% gross efficiency for the 6 minutes it runs.  1329 EDR of 2 pipe and 557 of 1 pipe connected.

JohnNY

If..

If you have reason to believe that condensate is truly being trapped in the rads/risers due to vacuum, then I think your idea is a valid way of dealing with it, however unorthodox.

You'll sometimes get a little heat to some of the rads whose TRVs may be closed, but I suspect that won't be much of an issue.



Since you're adding so much venting, I'd go for the vaporstat at that point.

nicholas bonham-carter

Ancient TRV's

Why not find out how the rads function without those old TRV's? When the system was running at over pressure, they may have been installed to throttle down the heat. At lower pressure (6ounces), the radiator output may be fine, unless over-sized.. More main venting may help as well as an accurate 0-3psi gauge.--NBC

Dave in QCA

zone valves

Zone valves always add a great deal of complexity to often problems to a steam system. I wonder if the zone valves in combination with 5 psi operating pressure created the phenomena where condensate came rushing (flushing) back to the boiler. Does this system have a boiler feed tank or condensate tank or is it gravity return to the boiler. If it is gravity return, 5 psi would hold back condensate in the return piping or dry return 11 feet or more above the normal water line of the boiler when the valve was closed. Then, when the valve opens, the "B" dimension becomes and "A" dimension of about 28" and a whole bunch of water that was pushed up into the dry return would come rushing back to the boiler.



One things for sure, condensate does not just hang in a pipe in defiance of the laws of gravity. There has to be something pushing there. Vacuum does not change gravity unless there is a measurable flow of air because of vacuum in a portion of the system.

Thank of a vacuum cleaner, where the vacuum hose can pickup objects, there is a large flow of air. Flow always goes from high pressure to low pressure. Inside the vacuum canister, (think of a shop vac), there is a pretty strong vacuum, but that does not cause the objects inside to float around.

JUGHNE

Risers

Thanks for all comments.  More info; there is 165' of main from boiler to cond pump.  All 414 EDR (correction--not 557) are connected within the first 70' of steam main line.  So is the remaining 95' considered dry return?  Would moving the 2 existing Hoffman 75 vents from the 165' point to the 70' point be best?  Also there is a working 1" F & T at the cond pump (the 165' point).  The zone valves do not seal 100% and when the other larger (1329 EDR) 2 pipe zone calls for heat some steam will get into the 1 pipe side.

Moving the 75's and the drill/tap rad Gorton D's seems to be an easy (read cheapest) fix maybe and easy to change back if things don't work out.  Thanks again