TRV's On 2 pipe system......Does the Radiator Need a Trap?

JUGHNE

Working on "Principal Amy's" school that has steam blowing out of the cond pump vent pipes.
If all TRV's have convectors shut down to where they barley heat across, would a functional trap be needed?
Wouldn't this be like an orifice inlet system on an emitter without traps?

This school has 28 convectors, all of which have TRV on steam inlet.

If the TRV's have all convectors shut down and steam is still passing thru the dry returns would that would narrow the failed traps to the 4 EOM F&T's and the 1/2" traps used for down feed steam pipes drip traps.

From what I was able to see the convector and drip traps are 1/2" 17C's.

I believe the TRV's have been installed for at least 10 years or more so the outlet traps may not have seen much steam.

Just thinking about the availability and cost of trap elements.

Jamie Hall

If all the TRVs are shut and you are still getting steam, it has to be one or more of the other traps -- all of which are needed on a system with a vented condensate receiver (every single line which has or can have steam has to be trapped).

That said, the radiators with TRVs also need traps and they have to work -- when the TRVs are open, it's no different from any other two pipe system.

EBEBRATT-Ed

I think you have to do all the traps to make it work right. Usually with a real bad trap you can hear it.

JUGHNE

Jamie Hall said:

If all the TRVs are shut and you are still getting steam, it has to be one or more of the other traps

EBEBRATT-Ed said:

I think you have to do all the traps to make it work right.

Thanks for the replies. I actually know this but just thought to throw out the question.

Others could use this process of elimination for finding bad traps.

As far as ID the actual culprit(s), if the job were close I would do the isolation method.
Or maybe limiting inlet orifices on the valve in addition to the TRV's, but having found the boiler set up to run 8 PSI and the chance of busy fingers on the pressuretrol, that may not be a good idea.

And have read and heard of bad old trap elements killing new elements that get added if the system is not completely done in one shot.

So it looks to be a complete change out done non stop.

mattmia2

You could perhaps add orifice plates so that even if the trv is open the amount of steam that can enter is limited to what the convector can condense, but the conventional way would be to have working steam traps. You could probably open the TRVs one at a time and test the traps individually, although you may need to fix the other traps first so steam in the returns doesn't close the trap you are trying to test.

Also look for water line issues, make sure there isn't anything that should be under water that isn't with a boiler change(or the addition of the condensate pump) or isn't far enough under water.

jumper

Makes one wonder if in long run may be more practical for each terminal to have own return to boiler room?

JUGHNE

I have used orifice plates when I knew that the operating pressure was going to stay within the design range used for the orifice sizing.
But this is a school house 150 miles away.

The last repairs done here was to replace the condensate pump hoping it would not let the steam escape from the condensate receiver......that didn't fix the problem.....so that is the level of understanding of steam in the area.

These could be the guys that would crank up the pressure to "fix" things the next time there is a problem of any sort.

EBEBRATT-Ed

Probably only have 40 or so traps. That will go pretty quick when you get set up right.

If you don't do all of them you will always be wondering...........................

EBEBRATT-Ed

Others messing with it afterward there isn't much you can do about....hang a sign on the p trol LOL

JUGHNE

Yes, change them all.
The right socket and impact driver will get most of them open.

I believe the 4 or 5 F&T's are the 3/4" 4 bolt Hoffman's that you can just change the front plate on and be done.

Maybe a return trip on Saturday to get exact info.

JohnNY

Wait. @JUGHNE is asking a very good question here. Forget about standard installations and think like steam. If the TRV is going to modulate and interrupt the flow of steam, what would be the job of a trap?

I look at 2-pipe steam as a system divided into two main sections: the pressurized section and the non-pressurized section. The dividing line is at the traps. If you move the dividing line from the trap at the outlets of the radiators to the TRV at the inlet of the radiators, there wouldn't be much difference in functionality. The hot radiator would close the TRV instead of closing the traps. Baboom. Same thing. sort of.

JUGHNE

If the TRV truly modulates and IF there was a way to set a permanent "stop" in the mechanism for max temp.
It seems the trap may never see steam.

However, in a schoolhouse or other public places, we have all found all things defeated by numerous tampering:

1 pipe steam valves partially closed
Programable tstats set on "Permanent Hold"
TRV control heads completely twisted off
Huge TV (running) parked by tstat
Window AC running when heat on
And of course leaving windows open

Then in the boiler room setting steam pressure up to 8-10 PSI,
This would blow thru any orifice control and maybe TRV and trap damage.

So I can see the traps being the best insurance.
You could do all of the above and not blow steam into the dry return.

Jamie Hall

I'm with @JUGHNE on this -- sorry, @JohnNY ! There are residences with conscientious and knowledgeable owners... there are a few bigger buildings with a super or warden who is likewise conscientious and knowledgeable. And then there are all the rest... and, as in so many things, it is almost impossible to think of all the ways that a heating system can be defeated.

mattmia2

I agree that you won't prevent all tampering, but maybe tuck a 3rd pressuretrol on the piping somewhere so even if someone decides to crank up the one on the boiler the pressure still stays at a reasonable level?

JUGHNE

I like JohnNY's thoughts on this.
A never tampered with TRV may be like a fixed orifice insert or a fixed vapor steam inlet valve.
As long as the room temp is within reason. But someone leaves a window open and 10 degree air hits the TRV bulb it would perhaps fully open to catch up with what it perceives to be tremendous heat loss.
Then full steam could go to the trap.....but maybe the CI rad is also at 10 degrees so condensation would take place.....now my theory is becoming clouded.

But wait...in this install the TRV has remote bulbs under the convectors so that would be something different.

But fixed orifices or orificed valves are not going to open more than their preset permanent passage.
They can only be overcome with high pressure...which happens all too often.

All of the orifices I have installed are on systems not capable of more than 2 PSI or in a home where no one will mess with the vapor stat....which only goes up to 1 PSI.

This is a 30HP boiler that can do an easy 8 plus PSI all day long on this system.

So back to the traps.....for this case.

EBEBRATT-Ed

Add an additional pressure control and make it the operating control and leave all the others in place. Mount the "new pressure control" on the wall and build a armored box around it with access only by a lock & key. Run 3/8 soft copper between the boiler and the new pressure control.

You need to adjust the new pressure control to allow for the water in the tubing.

This was done all the time in the past whith huge HRT boilers where you would need a 10' ladder to reach the pressure controls they would mount the operator on the wall for easy access .........or in this case to lock it up.

retiredguy

I worked for school districts servicing their boilers for 40 years and the one thing that I have found is that you always have to prepare for the worst case scenario. Will the next service tech fiddle with the pressure settings, of course they will. Also, most school systems have a night building temperature set back. The boilers shut off, an 8-10 degree lower temp is in force. On univents that are mounted on the outside walls they have fresh air dampers that are "supposed" to close tightly but usually do not, and in the morning when the building temp is reset to the day temp, steam is produced and the steam coils go to full heat to raise the building temps. So to answer questions about steam traps, yes steam traps are necessary. Not to insult Principal Amy but, Private Catholic Schools are almost always underfunded and they are always trying to save a buck. Their funding is always at a minimum, that is just the way it is. So they have to get by on much less than the areas public schools. We handled the Pittsburgh Catholic Dioceses and others across Pennsylvania so I had history with them.

I mentioned that I serviced almost all of Pennsylvania. So, a 300 mile one way trip to Philly was not out of the question for me. I always carried a change of clothes and toiletries and a company credit card for overnight stays. The customer always picked up the tab and yes I got paid to travel in my F350 pickup.