Cycling Off Before Radiator is Full and Hot & Hissing Vents

FJL

I might have posted this question before, but I can't recall.



I am noticing that my system will cycle off due to pressure before a certain radiator in my apartment is full and hot. From what I read on this board, that should not happen, is that correct?



The radiator is in my bedroom and is fed by a horizontal feed pipe that is connected to the riser at the end of the main in the basement, about 50 feet from the boiler.



Another problem I have with this radiator is that air vent hisses after pressure builds to about 1 ounce or so (an estimate) at the radiator. This is a wet hiss (if that makes sense). This hiss occurs regardless of whether I change the air vent and put on a new one or clean the one on now.



A radiator in my bathroom also has an air vent that hisses in the same way, when pressure in the radiator reaches an ounce or so. This air vent hisses less and stops and starts, which is what you would expect, I think, as steam condenses. This one I can tap hard a few times and get it to temporarily stop hissing.



Any ideas would help. The hissing wake me up at night, as it did last night, when the heat turned on three times during the night.



Thanks.

nicholas bonham-carter

hissing vent

are you certain that the hissing occurs on only 1 ounce of pressure, verified by a good low-pressure gauge?

what make of vents are these? is your main venting functioning properly? if the main vents are not letting all the air out, then that puts added pressure on the radiator vents, and in this case, the radiator vent has to handle the 50 foot riser.--nbc

FJL

Hissing Vent

I have a low pressure gauge attached to my bathroom radiator.  The two rads start to hiss when the needle gets up to one ounce.  The rads are close to each other in the room but the steam has to travel through much more pipe to get to the bedroom rad.



I am using Gorton air vents for these rads. 



I have vents on the main and on the five risers that feed the upstairs apartments, and steam hits the risers and travels up the risers before the rads get hot, so I take that to mean that the main and risers are well vented.



I've set my vapor stat to run at 12oz/4oz.  My vapor stat has a slider to set the cut out, so I can't set it precisely and I've never gotten around to installing a low pressure gauge on the boiler.  Maybe I should set the cut out to 8oz and the cut in to 2oz? 

Big-Al_2

Bimetal

Vents with bimetal actuators like Gortons and Maid-O-Mist close very gradually, and when they are closing, they can make a sizzling noise from the condensate that forms in the vent itself.  Is that what you're hearing?  I find that the Gortons are the noisier of the two brands . . . and that even among supposedly identical vents, one can sound different than another.  I found one Maid-O-Mist  vent that was really quiet, even when I put a  big "D" sized orifice on it. . . out of a batch of about six that I bought . . . and that one is installed in the master bedroom.  The others are installed further away. 



You might find that the snap-action alcohol filled vents, like Hoffman 40's, will not hiss as much . . . but they make a clinking noise when they open and close.  No free lunch. 



I'm convinced that the folks who say that the vents should be silent are just propagating some kind of a cruel hoax to torment us light sleepers. 

FJL

Sizzling Sound

Your description is pretty close and explains why a very small amount of water collects on the tiny lip right outside the hole in the vent.  Never enough that water spits or spills on to the floor, but just enough to make the air hole and the area outside it moist.  I guess I'll try a Hoffman and see if I get a different result.  

FJL

One Problem ...

with a Hoffman 40 vent is that it does not vent fast enough.  I've throttled the rads in the room with the t-stat with Gorton 4s, and need to vent the bedroom rad quickly in order for it to fill with steam before the t-stat is satisfied.  

Big-Al_2

Maid-O-Mist

That sounds exactly like my situation.  I started out with a VariValve, but it would gurgle and spit sometimes.   I then tried a Gorton D in the bedroom and it was loud enough to wake me up.  What I have in there stairted out as a Maid-O-Mist #6, but I kept drilling it out bigger, figuring that if it got too noisy, I could always swap the orifice with a different one.  It's at a size D now and it's still quiet, but fast , , , no spitting either.  Maybe it's because the opening is on top . . . or maybe I just got as good one.

FJL

Drilling it Out?

What do you mean by drilling it out? Are MOM vents adjustable? Or do they come in different sizes that must be purchased separately?

FJL

I Lowered the Pressure ...

I lowered the pressure on the v-stat to 8oz/2oz. I still get hissing with my Gorton air vents.



Not sure how lowering the pressure from 12oz/4oz is better for the system. Now the boiler just cycles off due to pressure more often than it did before because the cut out i now 8 oz instead of 12 oz. I thought that less cycling off due to pressure was better for the system.



Am I missing something?