Wits End With Single Pipe Steam Problem - No Heat in Multiple Risers

GiantPineapple

Hello all! Having an issue with single pipe steam in my Brooklyn brownstone. Please see photos for the non-performing main, as well as a crude overall diagram. Note that the diagram does not show every fitting/turn/etc. It's just an overview.

My main splits off in three directions from the boiler. Two of the branches work fine. The remaining branch leads to four risers and none of them heat up. The main will be too hot to touch, and the riser, twelve inches from the tee, will be room temperature.

I have read two of Mr. Holohan's books, and they were indispensable in getting as far as I have, but I am now stumped. Do I need to flush the lines? Or is there anything else I can try? Any help is much appreciated!

Background:

I got no tenant complaints last winter. That's not *proof* the risers used to work, but it's suggestive. This year I got complaints from both tenants, within a couple weeks of heating season starting. Things I have tried, in chronological order:

1) I changed the vent on the underperforming main from a C to a Groton #2. This dramatically improved the uptake on the main, but did not help the risers.

2) I insulated most of my mains. This helped mains uptake a little, but did nothing for the risers

3) I added a riser vent (a Groton #2) to one of the risers. This pulled heat maybe 10' up the riser, but *only the first couple of times I cycled it*. I also got mild-to-moderate water hammer on or near that riser for 1-2 days and then that stopped as well.

4) I increased the pitch on the 16' segment (see photos) - it is now about 1" over 16'. This drained a *lot* of water out of what must have been a low spot. Sent my gauge glass from half-full (which is normal) to full. I drained that water out of the boiler.


Other information:

1) The low spot was probably my fault. I replaced a rusted segment of the drain line in the summer, and probably (though I can't be 100% sure) mucked up the pitch in the process.

2) In the off season I (through a sub) added a backup LWC, and a backup Pressuretrol. One interesting thing about the LWC, it never worked. It consistently went into nuisance trip, and after five failed callbacks I bypassed it electrically, and then left it alone. (I never wanted it - it was a local requirement that got spontaneously enforced because of a permit for separate issues. The boiler tech is pissed off at me for cutting them off at five tries and won't come back to remove it).

3) I removed a couple of radiators on the first floor during the last off season as part of a remodel (we got a heat pump for the first floor. I capped their supply lines and left the pre-existing vents in the caps. There were radiators removed from both working risers and non-working risers. All risers' behavior seems unchanged by any of this.

4) My Pressuretrol is set to 2PSI, but the system is controlled by a thermostat - so I thiiiink (?) the Pressuretrol just acts as a safety cutoff.

5) The water in my gauge glass is clear (well, pink from chemical treatment, but not cloudy). The water that came down from the low spot also seems like it was clean. When I drained it, there was some rust in the water, but no more than you'd get opening the drain on any given day.

EBEBRATT-Ed

I am thinking that the section you show as a low spot is still a low spot.

Look there is only a few things that can stp the steam

1. Low spot in the main. You will usually get water hammer with this
2. lack of venting
3. not a long enough boiler run time
4. blockage in the piping
5. plugged return letting water back up in the main/

It would be hard to believe a blockage in the pipe with more than one riser affected.


Shut the boiler down and remove the vent at at the end of the main. Start the boiler and see what you get. If you get water either you have a sg in the main or the return is blocked or partially blocked.

If that doesn't point to the problem remove the riser vents and install stem petcocks or ball valve on them and check them while the boiler is steaming.

Clock the gas meter to see if the boiler is running at it's capacity

How is the water level when the boiler is steaming. It should be steady and not bounce more than an inch or so. any bouncing should be gentle. Violent bouncing means dirty water and the boiler needs skimming

GiantPineapple

Thanks so much for your feedback, this is extremely helpful. FWIW yeah, my instinct was some kind of water blockage. Didn't occur to me that I could look for a blockage in the return, or how I would do that, but these are great ideas. Same for putting a valve on the riser vent. I have lots of stuff to try now. Thanks so much!

GP

EBEBRATT-Ed

@GiantPineapple good luck hope u track it down easily.

STEAM DOCTOR

In addition to above, clock the gas meter to ensure your burning proper amounts of gas. And of course check the radiator air vents.

exqheat

If the thermostat is satisfied before the last radiator is satisfied, move the thermostat closer to the end of the system. You could reduce the size of the vents near the thermostat, and enlarge the far distant rads. If relocation is difficult use a Honeywell 8000 thermostat with remote FR sensor (I love them for my work)

GiantPineapple

Hey exqheat, I didn't know you could get remote sensors for Honeywells, that's very handy to know if that turns out to be part of the issue. Thanks!

clammy

That low water cut off is mounted in the wrong location this is why it trips ,it gets mounted with the probe in the boilers block you can look in the boiler installation and operation manual . Think you’re lucky the contractor isn’t coming back espically if he can’t get a low water cut out installed in the correct location .
Peace and good luck clammy

STEAM DOCTOR

That is a secondary low water cutoff. I think

TonKa

Have you checked for pipe pitch problems in any horizontal segments of the risers? If you fixed the main's slope, it may have affected the takeoffs.

exqheat

another way to check vents is to feel if they are hot.

SteamingatMohawk

It would be helpful if you could provide the pipe sizes and lengths for the mains and risers. The numbers can be estimates. That way, proper vent sizes can be figured out.