First Start up, hissing radiators

Fmassarotto_9

Greetings to all. 
I just turned my boiler on for the first time this season. Before doing so i cleaned out the pig tail, ensured there were no clogs by blowing into the tail and pushing out the water and cleaned out the sight glass. At the very end of the heating cycle, when the thermostat was at the programmed temperature, one of the radiators began hissing, but did not spit out any water. For context i have 5 radiators on the first floor. 4 of which contain maid-o-mist #4 vents, 1 contains a vari vent since its too close to a wall and i can’t get a new one on. then i have 2 radiators on the second floor which have Maid o Mist C vents. What could this possibly be? I’ve done some troubleshooting and found out if the thermostat would i shut off a few minutes earlier, the hissing wouldn’t happen.

bburd

Do you have adequate main vents, and do they work?

What pressure does the boiler reach before it shuts off? Has the pressure setting been disturbed, or have any other changes been made to the system since last season?

Fmassarotto_9

bburd said:

Do you have adequate main vents, and do they work?

What pressure does the boiler reach before it shuts off? Has the pressure setting been disturbed, or have any other changes been made to the system since last season?

I actually don’t have main vents, the guy who services it for me every year has never mentioned anything about needing them. he told me my system and house is relatively small that the radiator vents are sufficient, and i haven’t experienced an issue since replacing the valves last season. The boiler shuts off just before .5 PSI

Jamie Hall

Just to be certain, that is 0.5 psi? Not 5 psi? What make and model is the vapourstat?

Fmassarotto_9

Jamie Hall said:

Just to be certain, that is 0.5 psi? Not 5 psi? What make and model is the vapourstat?

Yes it is 0.5 PSI. L404F1060

dabrakeman

What size and model boiler do you have?

I really doubt any system is better off without main vents but show some pictures of your system and we can see. Track the main/s to their end/s so we can see if there would be a good place to put main vents.

When your vent is hissing is the boiler still running or had it shut off? If still running check with a mirror over the vent whether steam is escaping the vent (does it fog the mirror?). If so the vent is shot. Main vents (and low pressure) typically make life easier on radiator vents...

Fmassarotto_9

dabrakeman said:

What size and model boiler do you have? I really doubt any system is better off without main vents but show some pictures of your system and we can see. Track the main/s to their end/s so we can see if there would be a good place to put main vents. When your vent is hissing is the boiler still running or had it shut off? If still running check with a mirror over the vent whether steam is escaping the vent (does it fog the mirror?). If so the vent is shot. Main vents (and low pressure) typically make life easier on radiator vents..

I sent these photos to may different guys who work on steam and they all said that my system doesn’t need main venting since it’s small. So i’m torn here. I’ve never had issues with noisy vents until last year, i replaced the vents and then it  solved things. But this one isn’t kicking out steam using the mirror method. But the boiler is still running as the vents begin hissing, as i said the vents hiss at the end before the boiler stops. If the boiler would shut off as soon as the thermostat hits the designed temperature they wouldn’t hiss. So it’s the thermostat that keeps the boiler running even after the thermostat is at temp 

pedmec

if that is the correct model number for your pressutrol then you have a 2 psi to 15 psi range. you would be locking up your air vents and when the pressure drops past the drop away pressure rating its allowing air to escape.

Fmassarotto_9

pedmec said:

if that is the correct model number for your pressutrol then you have a 2 psi to 15 psi range. you would be locking up your air vents and when the pressure drops past the drop away pressure rating its allowing air to escape.

can you elaborate by that? i posted a photo of the oressuretrol, is it a good setting or should i replace it with a vaporstst

neilc

pedmec said:

if that is the correct model number for your pressutrol then you have a 2 psi to 15 psi range. you would be locking up your air vents and when the pressure drops past the drop away pressure rating its allowing air to escape.

uh, not quite right,

the scale on the right, set just under 2, is the cut out,
the scale on the left, is the differential, and it's subtractive, so as it's set at about 1, the cut in should be just under 1,

Where is the main venting?
and what changed since last season?

Fmassarotto_9

neilc said:

if that is the correct model number for your pressutrol then you have a 2 psi to 15 psi range. you would be locking up your air vents and when the pressure drops past the drop away pressure rating its allowing air to escape.

uh, not quite right, the scale on the right, set just under 2, is the cut out, the scale on the left, is the differential, and it's subtractive, so as it's set at about 1, the cut in should be just under 1, Where is the main venting? and what changed since last season?

I apparently don’t have main venting, which i just learned last week. I had a guy come out to clean it out and check the combustion and the usual annual maintenance. He told me my system/ the runs/ the house in general is small/short enough to not require main venting. Which took me by surprise. Nothing changed since last season. 

neilc

how many feet of pipe is there between the boiler, and the farthest rad?
post a general wide shot picture where that last rad leaves your main(s)
you want, need a main vent

AdmiralYoda

I have a similar sized system as yours. Mine isn't piped quite right but I'll share my experience.

When I moved in the radiator vents would hiss and slam shut as the boiler began to make pressure. I later learned my pressure was too high. I set it to 1.5psi with a 1psi differential. My boiler is oversized so it builds pressure faster than it needs to and will hit 1.5psi when it is cold out. I did not have main vents.

The radiators hissed less, but still hissed. I thought this was normal....but it isn't. A few years ago I installed some large main vents and guess what?!?!?!? No more radiator hissing!

The reason the radiators hiss is the steam has to push all the air out of the entire system before it reaches the radiators. If the radiator vents have to do 100% of that work they will hiss. Think of all that air in all the pipes that has to pass through those little vent holes on the radiators.

I also installed a Vaporstat and a low pressure gauge. My system now cuts out at about 12oz and is completely silent. Sometimes I don't even know its on unless I open the basement door to listen if the boiler is firing. That is how steam is supposed to work...silent.

I also get heat to the radiators much faster than before I installed my main vents. Instead of waiting for all that air to get pushed out the pipes through the tiny radiator vents...the main vents blast all that air out and allow the steam to reach the radiators much quicker.

Your plumbing guys are wrong. Will it work without main vents? Yes. But you will have hissing vents and it will take longer for your radiators to get hot which means your boiler is running longer just to push the air out...costing more $$$.

One last note....after my radiators are hot and the boiler shuts off I will occasionally hear a vent "hiss". By nature of steam when it cools down it will begin to pull a vacuum. One of my vents will usually "hiss" for a few seconds to equalize the pressure but it isn't blowing out steam...it is actually sucking in air to equalize the pressure.

This is a sign that I could probably use more main venting. The main vents are usually the ones to break the vacuum and will suck air in much quicker than a radiator vent. And with the main vents in the basement I wouldn't hear it.

ethicalpaul

You should have a main vent, I'm sorry to report your contractors are now highly questionable.

I also see written on your boiler "drain 1 gallon each week". This is faulty advice and will accelerate the failure of your boiler due to corrosion. I would say drain 1 gallon every other year, and add enough boiler treatment to keep the boiler water ph at 11 to further reduce corrosion.

dabrakeman

I'm sure you got a lot of rationalization about not needing a main vent because nobody wanted to go through the trouble of locating where it might have originally been (or still is??). Can't see the end of the main in your pictures. Only one main, right? Is the end of the main accessible?

Fmassarotto_9

dabrakeman said:

I'm sure you got a lot of rationalization about not needing a main vent because nobody wanted to go through the trouble of locating where it might have originally been (or still is??). Can't see the end of the main in your pictures. Only one main, right? Is the end of the main accessible?

I just posted another thread, can you check it out. If it’s ok