Do you need to have a trap before a Boiler feed tank with wet returns

Heating_401

We installed a W/M 380 series boiler to replace a W/M 868 series boiler and are having problems with the condensate return time in the building. It is a 1 pipe system with 2 wet returns. We are experiencing a 1 hour delay in getting the condensate to return. We then had the W/M rep come out and he recommended installing a Boiler Feed Tank with a F&T trap. While I agree with the boiler feed tank, I question what purpose the F&T trap will serve. From everything I have read on this website and in the Lost Art of Steam Heating, we shouldn't need a F&T trap unless we use a Condensate pump or have dry returns. Can anyone offer any advice? And if we do need a F&T trap, what would be the best way to pipe it in? Thank you in advance for your help.

EBEBRATT-Ed

Trap

If the returns are wet you don't want a trap on them. That will make the problem worse. If the condensate came back by gravity before and doesn't now what changed?

Did someone install zone valves? Is the boiler water line higher or lower than the old boiler? You may or may not need the boiler feed tank........It cant bring condensate back that's not their. Are the wet returns plugged?

Jamie Hall

How big is this system

overall?  A one hour delay in getting condensate back to the boiler is -- at least in my humble opinion -- outrageous unless you are looking at a huge college campus or something like that.  And even then it is a bit long, to put it mildly.



First thing I would do before I started messing around with feed tanks and pump and traps and all that is to find out why the condensate takes so long to come back and fix that problem.



Then if you still have problems, figure out where to go from there.

Heating_401

RE: Trap

Q:) If the condensate came back by gravity before and doesn't now what changed?

A:) The only thing that changed is the boiler. The water line is higher because of the boiler, but the amount of water is less ( new 3 section commercial boiler compared to old 8 section residential boiler).

Q:) Did someone install zone valves?

A:) No

Q:) Are the wet returns plugged?

A:) No, we pulled apart the returns and they do not appear to be plugged

Thank You

Heating_401

RE: How big is the system

The system is 828 sq. ft of steam-- 16 radiators and 20 feet of 6" main piping, 30 feet of 4" piping, 100 ft. of 2" main piping. The building is a church from the 1800 era.

The church used to take 3 days(literally) to raise the temperature 8 degrees. With insulation on the pipes and installing venting stations, we are able to raise the building 10 degrees in 6 hours. The problem is that the boiler will go off on Low water and then start to short cycle, eventually leading to the boiler shutting off on the manual reset Low water cut-off. I timed the return and it take 47 min from cycle start to the return comes back.

Thank You

Jamie Hall

You've made progress!

At least you've gotten the time to get the building warm down to something reasonable... and it sounds as though you've done all the right sorts of things to do it.



Still, the condensate return times are way out of whack.



I neglected to ask before: what pressure are you running at?  It shouldn't be over 2 psi. 



Your system is actually smaller than the one I care for here and, although this is a two pipe system, there is essentially no delay -- at least no significant delay -- in getting condensate back.



The stuff must be getting trapped somewhere.  It just has to be.  You need to really examine the whole system, and figure out what is happening here.  You certainly don't need fancy gadgetry here!

nicholas bonham-carter

Slow returns

Could there be some old vacuum vents on the radiators which let the air out, but don't let it back I in, thus being a finger on the end of the straw? If one of the rad vents is unscrewed 5 minutes after a long steam, then that would let the air back in, and let the condensate out.

Could all the inlet valves have dropped their disks, letting the steam in, but being like check valves and trapping the water?

Any obstruction would have to be on the end of the dry return to effect all the rads on that line. An hour for the return is most unusual, so there must be some reason for that.--NBC

Gordo

Long Ago When Your System Was New

The condensate returned via gravity only. 



That WM rep is giving you VERY unsound advice.  



Is there water hammer? Gurgling at the radiators? Spitting air vents?  None of these things should be tolerated.  Something killed that old boiler.  It may now being trying to kill your new one.

 





 

Heating_401

RE:You've made progress!

Thank you and I agree in 17 years I have never seen returns take that long to come back. The boiler is running at 1 psi with a .5 psi diff. The only reason I thought a boiler feed tank would be a good idea is that the older boiler held a larger volume of water, which must have masked the slow return problem.

Heating_401

RE: Slow returns

Q:) Could there be some old vacuum vents on the radiators which let the air out, but don't let it back I in, thus being a finger on the end of the straw? If one of the rad vents is unscrewed 5 minutes after a long steam, then that would let the air back in, and let the condensate out.

A:) All the vents have been changed and are working, in fact we added 4 main vents to balance off the steam supply. I had the same idea and pulled vents off to see if I could get the return back quicker, but all I accomplished was getting steam to fill the radiators quicker, the returns didn't speed up at all

Q:) Could all the inlet valves have dropped their disks, letting the steam in, but being like check valves and trapping the water?

A:) Thats a thought.. I didn't pull apart every radiator valve. I think I will try that on Monday

SWEI

Couple questions

Can you post a picture of the boiler and nearby piping, perhaps with a pointer to the waterline when the old boiler was installed?



Any idea how long it took for condensate to return to the old boiler?

Heating_401

RE: Long Ago When Your System Was New

Q:) Did he say the boiler was installed correctly? Pictures would be helpful.

A:) Yes it is piped correctly and the rep did confirm that as well

Q:) Is there water hammer? Gurgling at the radiators? Spitting air vents? None of these things should be tolerated. Something killed your old boiler. It may now being trying to kill your new one.

A:) No water hammer, no gurgling and no spitting vents. What killed the old boiler was a faulty (un maintained) LWCO. The church is unoccupied for 5 days a week and no-one checked the water level, tested the LWCO or cleaned the boiler for that matter.

Q:) Do you have working main vents? Are they big enough? Are they old vacuum type vents?

A:) There were 2 main vents originally. I added 2) venting stations with 3) Gorton #1vent manifolds. We also installed vari-valve angle vents on each of the radiators

Q:) Check to see if all of the radiator valves are fully open. Steam could be getting in to the radiators passing through the mostly closed valves, but the condensate can't get out until the boiler shuts off. That is something you should be able to check right away.

A:) The one thing we didn't check was all of the steam radiator valves. I ASSumed that they were open. I should have thought of that. Thanks for the reminder

nicholas bonham-carter

Checking valves

Just unscrewing the bonnet of the valve will be a lot easier than disconnecting the rads.--NBC

PS, if there are any loop seals on the dry returns, which have never been flushed, they can fill with debris over the centuries, and provide a barrier to the flow.

A thermal IR camera would probably find the points of restriction in a few minutes.

Heating_401

RE: Couple questions

Q:) Can you post a picture of the boiler and nearby piping, perhaps with a pointer to the waterline when the old boiler was installed?

A:) I don't have any pictures of the old boiler as it was cracked and burnt when we first saw it. I will post pictures of the new boiler and piping on Monday when I return to the church

Q:) Any idea how long it took for condensate to return to the old boiler?

A:) I have no idea as the old boiler was not able to run when I came to the seen.

Thank You

Gordo

Oh Boy

It sounds like you are doing all the right things.  My apologies to you if I sounded churlish. 



You may try and flush the wet returns.  If you can, run a hose to each end, remove the main vents and put on a hose fitting.  If you can, open the wet returns at the boiler end and verify they are indeed flowing clear.



I can't see what you see, so I don't know if that is possible.  It may not be due to piping or clearance issues.



Just a weird theory I've got...maybe when the old boiler dry fired, it somehow caused a chunk of sludge to be baked hard inside the temporally-no-longer-wet returns.

EBEBRATT-Ed

Water line

You said that the water line was raised when the new boiler was installed. What is the approx. difference in the water lines?? Was the old boiler in a pit?/ is the new one ? Raising the water line may cause this system not to work

That is probably why they are recommending a boiler feed or condensate pump.