Simple question

Scott Brink_2

I know this may be a simple question, but here it goes.

How can I tell if the hissing from the radiator vents is air or steam? From what I understand, you shouldn't be able to see the steam. I was wondering because I think I have a couple of faulty vents.

Tom_42

Similar problem

I have a similar problem. I don't think its the vents that are at fault. I think what might be happening in my case is that my burner is overfired thereby trying to deliver more steam to the radiators than they can actually radiate. If you take the vents off (when the system is cool) and blow in them and air comes out then they are probably working ok.

John Ruhnke1

Steam is visable, air isn't

Steam is visable, air isn't

The vents should vent with a very low nonvisable hiss. When you see a foggy mist that is steam. If you have steam coming from the vent, replace it because it is bad.

JR

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Mad Dog

Very Dry (optimal ) steam is nearly invisible

But you knowyou've got a bad vent when the rad is hot all the way across and at the vent, and its still!!!!! hissing and tell tale - spitting. Mad dog

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scrook_2

true, but...

You can see the hot condensed fog formed from the steam, which most people will call "steam". Technically, dry steam is not visible, "wet steam" is actually both steam (gas) and water droplets/fog (liquid) mixed; you see the liquid part.

Once the rad is hot the vent should close and not make any hissing sounds. Leaking steam will rapidly fog a mirror or a glass sheet or a spoon, etc., held over the vent.

Mike T., Swampeast MO

From Mr. Wizard as a kid

Dry steam (the "invisible" kind) will ignite a wooden match. Wet steam (the visible kind that is really not steam but air and hot water) won't.

Tom_42

If all the vents are closed

and the rads hot all the way across then the pressuretrol should sense that and shut the furnace down, correct? This lets air back in so that the cycle could start all over again. But if the pressuretrol does not shut the furnace down then will the steam eventually force its way out through whatever cracks/holes it can find?

Scott Brink_2

Thanks

That was what I was thinking. I replaced a couple of the vents and now there is no more noise and I can hear a "click" when the vent shuts. What a difference when you can compare a brand new vent to an old one. The difference is clearly obvious to me now.

John Ruhnke1

The steam condenses

As the steam cools it condenses and turns back to water. The water or condensate returns to the boiler to get reheated and turned back to steam. A undersized boiler will run and run and never shut off. A properly sized boiler will run a long time before it has to shut off on pressure. In the spring and fall it could shut off on temperature before it shuts off on pressure.

John Ruhnke

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John Ruhnke1

If pressuretrol is broke..................

I think your questions was about what happens if the pressuretrol is broken and the boiler keeps making steam. The steam compress's. Pressure in the system keeps building up, and finally at 15psi the relief valve blows. If the relief valve is stuck, then the pressure keeps building UNTIL SOMETHING BLOWS UP. In the 1800's before relief valves, steam boilers killed a lot of people.

JR

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