Hissing vents help!

Tasha123

So I have a two year old  boiler that works really well. I had it skimmed multiple times last year and twice this year. I have an issue with hissing vents. During the end of the cycle the vents don’t stop hissing till the thermostat is satisfied and sometimes I see a small bubbles of water but nothing major. It just hisses a lot. Is this normal the tech that came out says it is. I also have used 4 gallons of water since October. He also says its normal. I changed my vents on a couple of radiators to expensive 5 Groton ones on two rads suggested by supply house. The hissing has stopped there but continues on the other rads. Should I live with this? I have three Groton vents on the mains. And the pressure is set to 1.5. The pigtail was cleaned last month. I don’t have a huge surge.  I’m not sure if I should be fixing anything or just live with the loud hissing. 

Fred

It is not normal. That is an indication that the system pressure is too high. What is the Pressuretrol set at? Also, make sure the pigtail (looped pipe that the Pressuretrol is mounted on) that the Pressuretrol isn't clogged. If it is clogged, the Pressuretrol can't manage the system pressure.

Tasha123

The pressure is set to 1.5 I think and the pigtail was cleaned when serviced last month when the skin was done. Here’s a picture. 

Tasha123

I have 8 rads. 3 upstairs and 5 downstairs the one in the bathroom downstairs and the dining room are small. The ones in the living room and kitchen are 3 larger ones. My house isn’t that big and the rads are a no more than a 5 feet from each other. 

Fred

Tasha123 said:

The pressure is set to 1.5 I think and the pigtail was cleaned when serviced last month when the skin was done. Here’s a picture. 

That setting on the Pressuretrol is set to "Cut-In" at 1.5 or 2PSI. That scale should be set at .5PSI. Inside that box (Remove the one screw at the middle bottom and lift the cover off) there is a white dial that should be set at "1" facing out towards the front of the box. What you have now is the 1.5 (Cut-in, plus whatever the white wheel is set at, which is higher than you want.

Tasha123

Thanks so much Fred!! I’m going to ask the tech coming tomorrow to do it as I want them to check the pigtail again! 

Tasha123

 I appreciate all your help. 

dabrakeman

Hissing is obviously air moving out of the radiator through the vent as steam moves in or if it is after the boiler has shutoff then air moving back in as the steam collapses and creates vacuum. Is your hissing occurring while the boiler is still running or soon after it has shut off?

Assuming they are hissing during the cycle the amount of hiss for a given vent would be a function of the rate that air is being forced out of the radiator through that vent which is a function of a few things: 1) the venting rate of that air valve. A slower vent/smaller orifice will vent less air and possibly reduce your hiss, 2) Pressure. Higher pressure will force air out faster creating more hiss. Higher pressure though is bad for a number of reasons including efficiency of the steam so you don't want the pressure really ever going over the 1.5psi if even that high (get a 3 or 5 psi gage and make sure you are staying under ~0.5psi) 3) Rate of steam production vs capacity of the radiators attached to the boiler. This is most easily understood as EDR of the boiler (often on the tag on the boiler) vs EDR of the radiators (charts are available for you to total up the EDR of all your radiators). If the boiler is too big relative to the attached total radiator load then it will have the tendency to fill the radiators quickly causing the vents or some of the vents to close off and then start building pressure. What are your EDR's? If your main venting is not adequate then hissing may ensue early in the cycle as the air from them mains gets pushed out through the radiator vents instead of the main vents.

In my experience some hissing associated with low pressure air (<0.5psi) being expunged rather quickly from the radiators from an oversized boiler situation is normal but it is usually not very loud or annoying at all. When it becomes loud is when the cycle is long and the radiators are filling nearly completely and as individual radiator valves close as steam reaches them the rate through the others increases as the boiler is still making the same amount of steam but it has less places to go. How to avoid this is avoiding the long cycles. If you have an oversized boiler situation there are others threads ongoing discussing that matter. If you don't and your main venting is good then try venting more slowly or try different models of vents (sounds like the Gortons you used on a few of the radiators helped. Minimizing your recoveries from setbacks will also help.

If you are mainly noticing hissing after the boiler has shutoff that is the air returning into the system after steam collapse. The degree again seems to relate to how filled your radiators end up per cycle. IF you are able to heat your home comfortably while not requiring the radiators to ever fill more than 50% or so then most of both issues tend to go away. More shorter cycles.

Tasha123

The hissing stops when the cycle ends. It starts when the radiator fills up but towards the end go into over drive. Then the vacuum noises are barely noticeable. Sometimes the hissing is loud towards the end and ceases only when the cycle has ended. Sometimes the rads are hot but it’s still going. The issue is that many techs don’t know how to deal with steam and I have been reading these forums for months tried to figure out my issue. I had three people here and not one person mentioned the pressure. I definitely think the cycles are too long and there is excessive steam because the vents rattle when they get too much steam even after they are hot. I’m not sure how to calculate the edr but ask the tech tomorrow. I’m nervous about touching the boiler the most I have done is learnt to skim it. I appreciate all the help here and I’m going to try Fred’s suggestions on the pressuretrol. See what happens 

ethicalpaul

The cycles are only long because the thermostat hasn't yet been satisfied, right? Are these long cycles after raising the thermostat?

When the vents are hissing, are they letting steam out, or air out?

Tasha123

Yes you’re right ! There’s droplets of water and sometimes steam on the upstairs rads. Others just start sounding like an airplane is taking off. The others are quiet. The two that hiss  violently are downstairs. I’m just a lady who was crazy enough to buy a old house 😂. Should I change the pressure or not? I even switched vents and they still hissed the same. 

Tasha123

I might try to upload a video. 

Tasha123

Then new valves put on. I’m still in the same boat. 

ethicalpaul

It's hard, but possible to troubleshoot such things from afar like this.

What was I right about? The long run cycle happening after raising the thermostat? Or the steam coming out of the vents?

Things that would be good to know:
- Does your system have working main vent(s)?
- What model and manufacturer are these new vents that you have put on your radiators?

A video and/or photos would be good.

Your tech makes me nervous. Yes, your pressure on the pressuretrol should be as low as possible (about .5 as others mentioned)

Tasha123

You are right about both. The long cycle happens when raising the thermostat and the steam does come out of only one vent. The rest of them clank violently. The two offending vents rattle on every cycle. Doesn’t matter if it’s long or short. On longer cycles it’s worse. I have three vents seem to be working fine all Groton . I have Groton 5 on the new rads. But they still seem to be feeling the pressure. The upstairs ones rattle on and off but recently spewing droplets or I just noticed. 

neilc

what pressure do you see on the gage when the boiler is firing and the vents are hissing?

you should be able to adjust that Ptrol down yourself,
turn the screw on top counter clockwise gently, it will turn easily, as soon as you feel a resistance stop,
try to bottom out the scale on front,
there's one caveat,
if we go too low the boiler may not fire back up,
and in this case you would turn the screw clockwise one turn, or another, just to raise the scale back up a hair,

the lower you run that pressure the less hiss you should experience,

post a picture of your boiler showing from the floor to the ceiling, let us have a look.

danitheplumber

Sounds like you need to replace steam vents if water or steam coming out... As Dan says "why do they keep making steam vents if they break? Cause people keeping buying them!"

Tasha123

Thanks guys the tweaks on the pressure seem to have stopped the excessive hissing/ vent spitting. So far so good. Thank you to all who responded. 

danitheplumber

Also make sure the steam radiator valve are fully open otherwise condensation won't be able get out as easily and steam coming in will slam against it and shoot it out the vent.

Fred

Tasha123 said:

Thanks guys the tweaks on the pressure seem to have stopped the excessive hissing/ vent spitting. So far so good. Thank you to all who responded. 

Glad we could help. Often times it just takes a little patience and the process of elimination. Merry Christmas!

Tasha123

Merry Christmas 🎄 thanks again