Not getting any heat in risers

George80

Hey everyone I have a 27 unit building with a HB Smith gas boiler - 1 pipe system. Since the start of the heating season Ive been experiencing a problem with a riser that goes from the 1st floor all the way up to the 5th floor. The riser in the "C Line apartments - 2c,3c,4c,5c) haven't been getting warm or hot at all. I changed the air vent at the top of the line in apartment 5C and replaced it with a no.40 air vent and still nothing. This riser is located in the bathrooms in the C line. All of the other radiators in the C line are working fine. I haven't received any complaints or calls in regards to the other line apartments, just the "C" line.



Any help or advice is appreciated.

nicholas bonham-carter

Rising to the occasion

If you have a helper, then have him at the boiler, ready to turn it on and off.

Remove the vent in the top radiator . Have him fire the boiler, and ready to kill when you see steam come out the tapping. Listen for any noise of panting as the steam is building pressure.

If no steam will come up, then look for some horizontal runout from the main in the basement, which feeds this riser. Has it sagged, creating a watery pocket, through which no air or steam can pass?

Have you owned the building long enough to know what has changed? It must have worked at some time.

The Hoffman 40 is fine for venting 1 radiator, but pretty small for 5 floors length of pipe. If steam arrives at the empty tapping, then I would try a bigger vent on that radiator, such as a Gorton D. You may find the system more responsive to larger vents on all the top floor radiators. How is your main venting? If you have a good low-pressure gauge, you can see when you have enough main venting. My 55 rad system gets the air out with 2 ounces of pressure.--NBC

BobC

Vent or slope?

Is this vent on the riser itself or is it on the radiator the riser feeds? If it's on the riser it probably wants to be a faster vent, what kind of vent was on there before? Has any work been done that might have caused a pipe to move? Make sure the pipe that feeds that riser has not dropped for some reason, if that pipe did move steam might not be able to gt up there and it might have seemed to work at the very start of the season and then stopped working. That could occur because condensing steam would eventually fill and low spot in the pipe and stop the flow of steam..



The 40 vents at 0.04cfm, you might try getting a Maid O Mist #5 (0.11cfm) because you can unscrew the orifice and turn it into a 0.33cfm vent. If that were too fast you can drill out the #5 orifice to get something in between. Once you know what size vent you might need you can use the right size Gorton vent if you don't like the maid o mist vent for some reason.



Assuming the piping slopes are all good you want to vent the mains and any long risers fast and the radiators relatively slowly.



Bob

George80

NBC AND BOB

NBC and BOB

Thanks for the reply. I will have someone stay downstairs and I will go upstairs to the 5th floor and remove the vent to see what happens. I may try a D vent as well. Also I will be inspecting the line in the basement to check for any sags.  I purchased the property in Aug 2012 and the riser was working last year. Something had to have happened over the summer.



Silly question but do you guys think something in the basement might have fallen and sorta either knocked or sagged the pipe? I have a few things in front of it and it may have caused it? 



Thanks !!

George80

bob

Bob- the vent is on the riser itself on the top in the 5th floor.

BobC

String

as Nicholas suggested I'd try removing that vent and see if you get steam out of it, just have someone ready to kill the boiler if steam comes pouring out of the tapping. If you still get nothing there must be a pocket of water somewhere down below that is blocking the air and the steam.



Try stretching a string along the horizontal pipe in the basement so you can spot any dips in the piping. Then you can use a level to make sure it has pitch so water can find it's way back to the boiler through the main or a return pipe (if it has one).



Bob

steamedchicago

maid o'mist kit

Maid o' mist sell a kit that's a vent body and the whole set of orifices (4 through D); it's only a couple of bucks more than a valve with a single orifice.  It's not stocked everywhere, but it might be worth tracking them down.  It's much easier to switch the orifice than it is it to drill it out.  And once you know the required size, you can switch to another brand, if you prefer that. 



Also, if you're new to the building, don't overlook something like a valve or a totally disconnected riser. 

George80

Follow up

Earlier today I removed the vent from the 5th floor bathroom riser and replaced with a #6 air vent. The hardware store was closed and I only had a brand new #6. I first tested the riser as per the suggestions above and removed the old vent and some stream did come out. I screwed in the #6 vent and the pipe still isn't getting hot. The #6 vent was venting as I heard air coming out of it and it was making noise, but still no heat.

BobC

Is this a new problem

or was it problematic last season as well? What pressure is your boiler running at? Steam systems run best at low pressure, it should not be more than 2PSI in most cases.



If it's new then something has changed, if a horizontal pipe somewhere developed a sag it could be pooling water collapsing steam as it travels along. The steam might eventually get to this branch during very long steaming cycles in deep winter cold, but at milder times it doesn't get there before the boiler shuts down.



If this branch has always been slow to heat it could be a matter of balance between this branch and the other branches. Is all the piping in the basement insulated? You could try a D vent which is twice as fast as the #6 vent and see how that works out. What kinds of vents do all the other radiators and risers have on them?



Bob

Dave in QCA

What Changed?

You indicate that nothing has changed since last year. Are absolutely sure it was working last year during MILD weather? Mild weather with short steam cycles really can make an issue with areas that are slow to receive steam. When it gets colder you don't notice it. Also, while you said nothing changed, how about the tenants. Do you have new tenants who are paying closer attention?



Since you got steam to the vent hole with no problem when the vent was removed, I would put a fast vent on the riser and see where that gets you.