2 Pipe pumped return. New to steam. Lots of issues

Kinburnfields

Hello,

I have what I would consider a two pipe steam system with pumped return in an old building. There are several issues here, which I'm trying to wrap my head around. Our boiler has failed inspection and the powers at be want me to replace an old Taylor Forbes (previous coal and converted to natural gas) with a new/used steam boiler. That is an issue in itself but I want to resolve the system issues before attempting to install a new boiler while trying to mitigate issues that may arise with that.

Issue 1 - The vent off the condensate pumps is spewing water vapor.. I measured the temperature on the outside of the pipe for the condensate return and it was slightly over 200F. I think the condensate is flashing inside of the condensate pumps. Here's the vent from outside:




Issue 2 - There's overheating and no heating throughout 3 floors. I'm guessing its a mixture of TRV/and radiator steam traps failing. There's also 4 main F&Ts at end of the supply runs between the returns. Most likely these have also failed. See F&T below (not to mention uninsulated supply main):





Issue 3 - I noticed the pressuretrol set at around 3psi with a subtractive diff of 2.25, but I noticed a second pressuretrol set at around 7 psi with a subtractive diff of 2 psi. They looked to be daisy chain wired together... The pressure gauge for the system was at 7psi when not firing.. after firing it would go up to 9psi... much too high I think, but also doesn't correspond to the pressure control? Could the one be wired backwards? then adding 2 psi to the 7 psi set point?

Here's the beautiful boiler.. which is much older than me:





Ultimately what I'm trying to get at is... will this be a disaster waiting to happen trying to install a more modern style steam boiler (with lower water content) on this system? I already know the new waterline would be lower than this massive older boiler and that the condensate pumps should probably be feedwater with new boiler controlling it.

My thought process:
1 - rectify the existing issues with the distribution system
2 - have new steam boiler design properly to tie into the existing distribution system

We only need to get two years out of it.... I simply said we should bite the bullet and convert this to a new condensing hydronic system with new convectors/piping throughout, but probably 0.5 million... trying to fix the system might be under $100,000.

Jamie Hall

The steam coming out of the vent outside... oy. You have at least one, and most likely several failed traps. Your very first (well, no -- see below) concern should be to find ALL the traps (radiator and F&T) and make sure they are actually working. If not, fix them. That will probably work wonders on evening out the heat in the building all by itself -- and should not be expensive.

The pressuretrols. The high one -- set at 7and 5 -- is the safety backup pressuretrol. It's fine just as it is -- particularly since it seems to be functioning (I wouldn't trust the reading on a 0 to 30 psi gauge to be any closer than 2 psi). However -- it should never function. The two pressuretrols should, as you note, be wired in series -- and while the lower one might be set lower, it is clear that it isn't doing anything. If it were, the pressure would never rise to 7, never mind 9. Find out why. Blocked pigtail is the first and easiest culprit, but it could be itself not functioning, or it could be wired wrong.

The system should be fine -- once it is fixed up -- with a new boiler, and since you already have a condensate receiver tank you don't have to worry much about the water line. You will want to control the tank and pump as a boiler feed tank, not as a condensate return tank. That is to say, the boiler feed pump should be. No. Make that must be controlled by the water level in the boiler, regardless of the water level in the condensate return tank. In turn, the level in the condensate return tank must be controlled either by a float valve or a float switch or probe activating a feed valve. You will need to have a check valve between the boiler and the tank -- obviously -- but perhaps less obviously you will need to have an overflow pipe going to a drain (with an air gap); the overflow level should be above the boiler water line.

ChicagoCooperator

You'll need to replace the traps no matter what you do - and before going to a new boiler. There may be rebates in your area to do that (from the gas/energy company) and is far cheaper than a new boiler. You'll need to make sure that there are no hidden traps missed though - people have a tendency to bury them in walls or if a heating unit is removed...

109A_5

Hello, @Kinburnfields,

Kinburnfields said:

Our boiler has failed inspection and the powers at be want me to replace an old Taylor Forbes (previous coal and converted to natural gas) with a new/used steam boiler.

Why did it fail inspection ?
Just the boiler or the whole system ?

Kinburnfields said:

We only need to get two years out of it.... I simply said we should bite the bullet and convert this to a new condensing hydronic system with new convectors/piping throughout,

Why replace the steam boiler then change out the whole system two years later ?

Kinburnfields

@109A_5 just the boiler failed. Pin holes around the supply/return. Flames shoot out the combustion damper, etc.

The funding is complicated. Currently a rental unit. May be annexed in the future to another occupancy, which means different funding. I know seems ridiculous, but if the replacement is successful and we can keep maintenance up maybe we keep the steam going. I was just worried it’s beyond the point of trying to save… but may be my only option at this point.

thanks everyone else for the comments. Had a feeling the traps are the main cause of everything. Will have to look at cleaning the pigtails as well after heating season.

109A_5

Hello, @Kinburnfields,
The pressuretrols are wired in series, so if either one trips it shuts the burner down. One for working pressure (typically lower pressure) and one for backup (typically higher pressure setting) if the working pressure unit fails. The higher pressure unit may be a manual reset type.

pedmec

Replacing an old steam boiler before fixing the steam traps is the worse thing you can do. you need to get the system right before you put in a new boiler. all the oxygen loaded water going into that boiler to replace the water leaving the building thru the tank vent as steam will eat up a new cast iron boiler in no time. Not to mention all that steam is killing the condensate pump seals. not only the f&t's but the thermostatic traps on the radiators if thats what you have.

retiredguy

I do not know where you are located but a good commercial boiler company that can replace the boiler tubes, has a certified welder licensed for pressure vessels and has people that service old burners is what you need to find. The company I worked for could do all that. If you are anywhere near Pennsylvania, they could do anything that was needed. To get rid of the steam coming from the condensate tank you need to test all the radiator traps replace those that have failed, and rebuild the main line F&T traps As far as the boiler/burner goes, call someone. I worked on and serviced these boilers every day for 35 years. Sure it is old and can it be fixed , yes. You need to call someone today and have the problems fixed and plan for what you need to do next.

Sylvain

Kinburnfields said:

Will have to look at cleaning the pigtails as well after heating season.

Why not now? It shouldn't take long unless something breaks. Be sure to have spare parts and tools on hand.