Towel Warmer - Steam Valves Question

Mike_Sheppard

Good evening!

One of the very large buildings I do work for in DC is having some issues with steam coming back on the returns. It is not a ton but enough that it is causing issues.

System info:
- 2 pipe steam
- All radiators are trapped
- Steam mains run around the basement and all the drips are trapped
- I worked with the maintenance engineer last winter to check traps. He got a thermal imager and checks all radiator traps and also disconnects the outlets of F&T traps to check for steam blowing by.

Despite repairing all of the bad traps and not being able to find any others leaking by, there is still steam making it's way back to the vacuum pumps.

He found this a few weeks ago. There are some towel warmers in various bathrooms. Steam towel warmers are new to me, I haven't seem them before. Here are two pictures, one is the return valve and the other is the supply valve. They both appear to be normal valves with no traps. I did tell him to disconnect the valves and look for orifices. We suspect these towel warmers may be allowing steam to pass.

If they are in fact allowing steam to pass, could we add orifice plates to the supply valve union to solve the problem? We have the system operating at 1 - 1.5 psi and just installed a brand new vacuum tank system.

Steamhead

Change the return-side valve to a trap. If they're 3/4", the Hoffman #8C is a good choice since it doesn't vent air that quickly, so should not let steam get in so fast that it bangs.

EdTheHeaterMan

Towel warmer = radiator. Just because it has a different name, does not make the steam and condensate inside the TW work any differently. If "ALL THE RADIATORS" have traps, and the TW is a radiator, then your "ALL THE RADIATORS" statement is incorrect. Do what @Steamhead suggested, Treat it like a radiator

JohnNY

I feel like this heat emitter is a good candidate for a supply valve orifice.

Jamie Hall

I agree with all three of thes gentlemen. Eh? Well, those things, like it or not, are radiators. Radiators have to have some way of allowing air to get out and not steam. In this case, they are two pipe. Hence -- either traps or orifices.

The orifices are in some ways simpler -- but they are going to be very small openings, since the towel warmer radiators have a very small EDR. On the other hand, since they are likely all alike, once you get one of them figured out you have the rest. I'd be a bit concerned that that small an orifice might have an audible whistle...

EdTheHeaterMan

Jamie Hall said:

I agree with all three of thes gentlemen. Eh? Well, those things, like it or not, are radiators. Radiators have to have some way of allowing air to get out and not steam. In this case, they are two pipe. Hence -- either traps or orifices.

The orifices are in some ways simpler -- but they are going to be very small openings, since the towel warmer radiators have a very small EDR. On the other hand, since they are likely all alike, once you get one of them figured out you have the rest. I'd be a bit concerned that that small an orifice might have an audible whistle...

Then if I needed to diagnose that sound on a service call, I would suggest that the towel warmer just forgot the words, if you place the sheet music in plain view of the TW then that radiator could just sing along with the rest of the system. These new radiators take longer to learn the songs! but give it time

Mad Dog_2

Whichever route you choose, you need a "Gatekeeper" from the Steam to Return side.  Mad Dog 🐕 

EBEBRATT-Ed

I would use traps to keep things consistent. Everything else in the building has traps.

And, I never herd of a vacuum pump being used with an orifice system.

Jamie Hall

EBEBRATT-Ed said:

I would use traps to keep things consistent. Everything else in the building has traps.

And, I never herd of a vacuum pump being used with an orifice system.

true. The bit people miss when talking about a vacuum system is that the differential pressure -- which is what drives flow across the orifices -- can be quite high (relatively speaking) and variable. Traps are the better approach.