Thermostatic angle traps airbound?

bigpete638

When starting up a system, we’ve had to bleed through the union on the individual angle traps off the heating element.  We have heat throughout the system but the elements go cold again and need to be rebled.  This is usually only for the start up of the system.  I know that some of the traps are relatively new(about two years), so I’m not sure if they all just failed in the closed position.  Condensate and air are not be pushed through on this two pipe system.  Do all the traps need to be replaced or is something else going on?
Again, any and all information is greatly appreciated.

Jamie Hall

Picture of a trap? But a very real possibility is that somewhere else on the return to which they are attached there is a trap which is failed open and pressurizing the return. Either that or the return isn't pitched properly to drain.

bigpete638

This is similar if not the same trap as the ones in question.

bigpete638

The return lines from these elements end up in a crawl space about three feet high that runs maybe about 100 yards.  The whole line is covered in asbestos down there and at least two substantial leaks.  Probably more.

There are least a few spots where the condensate lines actually jump up in some cases a couple feet.  The engineers actually were telling me the vacuum pumps were needed to bring the condensate back.

Thank you for your input and quick response.  It makes sense.

JUGHNE

Without the vacuum pumps the return would sit full of water filled up to the first jump up of piping. No air would get thru that water trap.

Could be one of those times when the engineers are right.

bigpete638

I remember reading that vacuum pumps are only designed to remove air from the system.  Wasn’t sure how much condensate they were able to move and what the possible consequences of too much sitting water under vacuum would be.  I’m pretty sure no lift fittings were installed.  The engineers made it sound as if removing condensate was the purpose of the vacuum system.  You’re saying that is true in some cases?  

JUGHNE

I don't know. The Pump Guy who replied to your other posting would most certainly know. If you change your header and include the word "pump" he might pick up on it.

To me it seems that with a 2' water trap that air and water would get back quicker with some assistance.

bigpete638

It makes sense and I know it does, but not sure at what capacity.  Also not sure if any vacuum pumps are installed for that sole purpose.

EBEBRATT-Ed

@bigpete638

@jughne is correct without the vac pump you may not be able to move condensate.

While we always want condensate to flow out by gravity it isn't always possible. In fact many vacuum systems were designed with lift fittings for the purpose of lifting water to where it can flow back to the condensate tank by gravity.

Without a vacuum pump you may (I hate to say this) bump the steam pressure a little to move the water

bigpete638

They certainly have been doing that.  They have 7lbs in one building.  

bigpete638

For a temporary fix, can I install radiator vents?  The returns are hot so there are most definitely traps failed in the open position.  I would like to get heat to the building while waiting for asbestos abatement.  This would save me from having to bleed the elements everyday.  Constantly getting pulled from one job to start another.

EBEBRATT-Ed

I suppose you could put vents on but finding vents that work at higher pressure can be an issue. probably won't work well

bigpete638

I think it’s only 4 or 5 lbs of steam.  On the higher side of what it should be, but too high for a radiator vent?

bigpete638

I just checked the specs on an air vent.  Should be good up to 6lbs operating pressure