TRV's--Steam in return--slow cond return

JUGHNE

Have school with 2 pipe system, TRV's on most CI rads, traps only 1 year old. Cond pump return.
After changing control system (T-stat) and lowering PSI as low as possible, the boiler will be flooded on some mornings.
There was some discussion concerning TRV and failed traps. I believe this was trapping water in rads and causing slow return which would activate fill valve.......of course this was only noticed after I was there tinkering with things.

One other item is that custodian said if the boiler is over filled it will not fire unless he drains the level down to normal.....I said that is a good thing as it would hammer like hell if it fired with water well above the sight glass.
But what keeps it from firing?? (not that I want it to). Boiler has a MM #63 and a #47, each with a #2 switch. Is it possible that having water on the top of the float of the 63 (LWCO only) would push it down keeping the switch off??
But he says boiler will fire when he gets the water level corrected.

I did the broken union test on the water fill and those valves all hold their water.

When the boiler did fire on a normal cycle, with maybe 1/2 PSI on the system as pressure came up, suddenly cool/cold condensate started returning to the pump?? This was the phantom water?? It came from the return that later was passing steam to the cond pump.

This has attic mains with downfeeds to rads.

Jamie Hall

You're beyond my pay grade on this one, @JUGHNE ! But I will bang one of my favourite drums -- can you rewire that condensate pump so that it is a boiler feed pump instead? That is, activated by #47? That might help with the over filling.

You need to find the trap(s) which are letting steam into the main -- but you know that.

I have only one thought on the overfill/won't fire: is the overfill enough, and does it cover the inlet to the pressuretrol pigtail, to keep the pressuretrol off? I wouldn't have thought so -- that's pretty high after all -- but it just occurs to me...

Keep us all posted! I like to learn!

nicholas bonham-carter

overfilling could certainly activate the pressuretrol, and prevent firing, and some vacuum must be holding up the condensate in the pipes.
Are there vacuum breakers on the TRV's?--NBC

JUGHNE

On a 1 pipe system I have had the 1 pipe type TRV (air vents) without vac bkrs hold up condensate 2 1/2 floors. On that job you could hear cond come down like a toilet flushing.

These are 2 pipe TRV on the inlet pipe. Don't know about if they have a vac bkr.

I am now thinking that with steam in the return, closing some traps, that water is trapped in rads.
It may have been a coincident that the water came back after just a small of pressure was applied to the system.

I can not get back to this until after the first of the year.
So what I did was set the CPH to 2, added temp drops during the day on programmable T-stat. Thinking that more cycling of boiler would perhaps allow more drain back.

This has Warren-Webster rad traps that were supposed to have had new elements last year. The steam main drips have (I believe) Warren-Webster F&T's, some of which have been rebuilt.

Steamhead

Either bad traps or vacuum.

We like to replace those Webster F&T traps with Sarco-type traps that have 6-bolt covers. This makes future maintenance a lot easier.

JUGHNE

The bad traps are an obvious.

The vacuum you refer to, do you mean a vacuum on the entire system or just for each radiator as the TRVs would close tight?
The boiler only has a 0-60 gauge for now....will be changed.

Would the WW F&T repair kits have been available or could they have just opened them and maybe cleaned out sludge??

One unique item on this particular return line is a 1/4" pipe teed into the line before it connected to cond pump. It is set up to drain into the sump pit. The 1/4" line appears to be part of the original installation. Either meant to be an air vent or steam passing indicator. It will pass steam towards the end of the cycle.

Another return has a 1/2 indicator type pipe with a valve usually closed. (no steam in this return).

jumper

Does water level in receiver control condensate pump? Ideally condensate pump fills another receiver above B dimension. That way boiler level can be controlled independently from condensate flow.

JUGHNE

We just have a plain vanilla condensate pump. The inlet of it is below all returns. It fills up, the float in the pump turns on the motor and pumps water into the return of the boiler.....whether it wants it or not. Not a feeder pump.

The boiler is a good sized 1,800,000 Btu input, a hefty American Standard CI from 1973 or earlier. So I think there is enough water capacity to handle the connected EDR and piping.

Problem is what is holding condensate back while steaming?
The main return under floor has just been replaced. There was some replacement of smaller return piping which is above the floor in the rooms. When I get back I will do more of a site survey.
Could be some dry returns without slope working on a syphon action that gets moved with a little nudge of steam pressure??

This is an attic express Mills down-feed system.
Only the boiler room is down in a half depth basement.

Jamie Hall

I still think that it wouldn't be that hard to rewire that pump so it was controlled by the LWCO on the boiler, and reroute any fresh water feed to the condensate tank -- control it with a float valve.

JUGHNE

Yes, that would be possible. But a condensate pump has a limited storage capacity, it is met to get rid of its water after a short time. I fear it would fill to overflow, blocking the air venting capabilities of the dry return it is connected to.

I am coming to the conclusion, as I talk this out, that the problem is not slow return but delayed return. The water flow coming back after light off was cool which to me meant that it was sitting in some dry return or cold radiator.

As much as I regret it I am being drug off to some tropical island for a week and will miss out on the possible first coldest bit of weather we are going to get...-15 tomorrow night. And to get dramatic tomorrow -35 to -45 wind chill. It always seemed warmer before they discovered wind chill charts.