F&T traps in a weird place.

sig

I was recently called in to figure out why there are some radiators are not heating after a new boiler was installed.  The owner claims everyting worked fine with the oil boiler (yeah right). It is a 2 pipe system and the B dimension is adaquate and according to the contractor the water line is exactly the same as the old boiler (he made the point that he made sure of it).  The main vent on the return was replaced with the boiler.  In additon to some radiators not heating, the boiler short cycles (it reaches limit of approximately 1 psi and the pressure immediately drops to zero when the boiler shuts off) and the water level starts at about 3/4 of the guage glass when the boiler fires but it drops very quickly  and empties the sight glass when the boiler is firing and comes back pretty quickly when the boiler off.

The first thing I noticed was the end of the mains were dropped low and run back to the boiler as a wet return and there were new F&T traps installed at the very bottom of the leg where the piping goes from vertical to horizontal, which puts them below the water line. When I tracked down the plumber who intalled them (who was not the guy who replaced the boiler) I was told that he didn't replace them but added them.  I investigated further and found a steam vent laying in the dirt near the F&T trap and saw where it had been in removed from the end of the main.  I called the plumber back and he swears that he didn't remove the vents, they were not there when he got there.  The homewoner does not recall anyone removing them and the system has always heated evenly before the new boiler (yeah right).  The returns from the raditors go a seperate dry return and each radiator has a termostatic trap.

It looks to me like the original design used the steam vents at the end of the mains and the wet return in lieu of F&T traps. Looking at the 90 layers of paint on the radiator traps and the customer having no knowledge of ever servicing them it is my assumption the vent removal and F&T installations were done to fix a problem caused by bad radiator traps.

It seems cut and dry to me...I have to restore the system to it's original design and replace the radiator traps...BUT...there are 3 main branches of steam supply and only 2 had the vents at the end, the 3rd has had an electrical panel installed consealing the end of the main and the drip leg a many many years ago and it is clear it either never had a vent or the vent was removed a long time ago.....it appears it has always vented through the radiators.  SOOO...do I now attempt to install a vent there? as it is no easy (or cheap) task given the wiring obstical.

Lastly, other than keeping the wet return wet, is there anything I should worry about regarding to my water line?

Jamie Hall

Sounds like fun...

In my humble building super's opinion, if you have trips going into wet returns you don't need any traps there at all.  Nice of the boiler installer to take the trouble to verify the water lines -- that's one thing you don't have to worry about!



Also it is likely, as you say, that the F&Ts and maybe some other things were done to correct bad radiator traps.  Not that big a deal to fix those.



However, it is always worthwhile verifying the system pressures; you say it shuts off at 1 psi, so the pressure is probably OK.



That main near the electrical box.  It would be nice to get a vent at the end of it, but it may not be too practical.  I would be inclined to go as close to the end as I could reasonably get, and install a vent there (I have this thing about potentiial moisture sources and electrical panels... maybe it's just me).  The other possibility is that if there is a riser really close to the end of that main, can you put a good big vent on the top of that instead?  Or does it come up in the master bedroom... ?



I'm not really keen on the boiler water level dropping that much or that quickly when it fires.  It makes me wonder if the equalizer is right... or if you have a really seriously slow return somewhere (but that, I think, would be slower).  Worth standing there and contemplating for a while, though.

JStar

Steam

How can the air get out? It can't!



You are on the right track. Ditch the traps. Reinstall main venting. Is there any type of crossover trap on the difficult main?

sig

F&T traps in a weird place.

Thanks Jamie.  The equalizer looks correct and the Hartford loop ties in at the proper level but the wet return turn is less than 2" above my low water cut off point.  Do you think the water could be backing into the wet return and if so would dropping the return down (making a trap)  or installing a false water line (flooding more of the wet retun) would solve that,

JStar

Return

The return is only 2" below the equalizer connection?

sig

F&T traps in a weird place.

I'm with you..but with the compounding screw ups of the other guys means I'm only going to get one crack at it so I need to be right.

sig

F&T traps in a weird place.

No its about 6" below the equalizer but it is only a couple of inched below my low water cut off point at the boiler and pretty near my low water cut off point at the furthest point from the boiler.

Steamhead

Some Vapor systems

especially Webster "Type R" systems, did use F&T traps (or sometimes large thermostatic traps) on wet-return drips. Apparently the idea was to keep the steam pressure out of the returns, so if they broke they wouldn't lose so much water. This setup was called a "non-pressurized return".



A system using this configuration would have needed to run the condensate from the steam mains thru a Return Trap to make sure the water could return to the boiler if the pressure got too high. Nowadays we handle this with a Vaporstat.



Don't confuse this with thermostatic traps piped between the steam main and the dry return. These simply vent air from the steam mains into the dry returns.



Have you been able to find any of the system's original hardware (valves, traps etc) and get the manufacturer's name off of it? This would help us tell you what to look for.



Where is this system located?