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A handful of steam questions


I've been lurking around the site now for almost a year - I bought my first home in November 2009 and with it came a glorious steam heating system that had been neglected and maintained by knuckleheads (the oil guy!) over the years.

I've finally had a bit of money (and a Merry Christmas as well) which means I've been doing some work on the heating system.

- First out was the pressuretrol that couldn't seem to keep the pressure under 3PSI. It's now been replaced with a very nice honeywell vaporstat (about a week ago). I'm currently operating with 12 ounces and a 6oz differential. That may still need tweaking.

- Next up was a set of new radiator vents. Last year when I bought the house my dad stumbled across a heat-timer varivalve at a local plumbing supply shop to replace a bad vent on the steam baseboard in the dining room (room with the thermostat). It performed so well there that for Christmas (this year) I received a set of them for the whole house.

- The slow/clogged main vent has been replaced with a varivalve as well.

- Spent most of today insulating that near boiler piping and as much of the main as I could. The basement is finished and it's nearly impossible to get to large sections of the steam main, but I've installed at least 30' of insulation along the main and many of the steam take-offs and risers as well.

I also have a programmable thermostat which sets back approx 4-6 degrees (4 at night, 6 on weekdays when I'm at work and nobody is home).

So, on to the questions:

1) Vents making noise: my new vents - only the ones on the second floor - like to make noise. More noise than I'm happy to hear in the wee hours of the morning when the house is warming up. They sound like they have water in them (though no vents are spitting and there's no water to be seen anywhere). They kind of gurgle. It's usually the worst during system start-up, after they've closed the first time and after they cycle once or twice to remove any leftover air in the radiator. I suspect the previous owners had the pressure cranked up so they'd just slam shut and never open again to solve this problem.

(disclaimer: I believe my near boiler piping isn't excellent. It's probably not awful, but could stand some fixing). Is it likely that I've got wet steam?

I've also raised the pressure a little, I was running 10oz with an 8oz diff - which in hindsight 2oz is probably too low, I've increased to 12/6 today.

2) Gas conversion. I think I want to at least explore this option. My oil fired hot water heater gave up the ghost this past September and I replaced it with gas. Doing the same with my boiler is definitely something on my mind.

3) Hot water zone: I'd like to add one. That basement needs heat, and not via uninsulated steam mains either. I'm also open to other creative ideas that may cost less. The kitchen is also a candidate for remodel and I like the idea of a radiant floor.

4) A good steam guy in the East Northport, NY area. Anybody have a favorite? I'd like to have someone come in and at least give me an opinion on the questions I have here along with what some of my options might be.

5) balancing. Especially when coming back from set-back, it seems I choke in my bedroom in the morning. I've adjusted the t-stat today to come back slower (64 instead of 66) but it seems I can't get the system balanced. The baseboard in the room with the thermostat has the vent wide open. The bedroom has the vent mostly closed. I'm still struggling.



  • David Nadle
    David Nadle Member Posts: 624

    A couple of things you wrote stand out. The first is that you replaced the main vent with a varivalve. Those are fast but probably not adequate to vent your mains quickly. Hopefully the tapping is larger than 1/8" and you can put a real main vent there soon.

    The second thing is that you raised the pressure---no you didn't. You raised the pressure limit. If your system operates at less than 10 ounces before all the vents close then there's no reason to set your vaporstat cut-out higher than 10 ounces. The reason for a vaporstat is to save fuel by cutting out as early as possible. It won't change your operating pressure or make a bad system work better. This may seem an obvious point but I think a lot of people have this misconception about what they're doing when they adjust the pressure limit. In 2011 Wallies should all resolve to always refer to adjusting the pressure limit, not the actual pressure.

    In order for any pressure limit device to cut out and save you money, you have to build some pressure. If your vents don't close---and it sure sounds like your vents are not closing---you may be able to run forever without cutting out. The reason your vents are not closing is wet steam. That could be dirty or oily water, or it could be an installation defect. 

    I think the first thing you should try to improve your system is stop setting back, for now. Make sure the system heats quickly and quietly. See if the bedroom still overheats. A thermostatic radiator vent would help that situation.  
  • BobC
    BobC Member Posts: 5,473
    noisey vents.

    A couple of things come tp mind. Do you know what pressure your at just before the heating cycle ends? Does the system ever cycle off on pressure or does it just shut down when the thermostat is satisfied? You might want to add an auxiliary low pressure gauge so you can see exactly what pressure your running at.

    Is the water in the sight glass bouncing around a lot? Do you see any water droplets above the waterline in that glass?

    The heat Timer is a very aggressive vent, if some rooms are heating too much try turning the valve as low as you can; at that setting it still vents 0.156 CFM at 2oz of pressure. Venting radiators very fast can cause problems like your experiencing with hissing and spitting.

    How long are your steam mains and what diameter is the pipe (circumference will do), with that information we can tell what volume of air your trying to vent in that main. the one fault a heat timer has is it does not have a float so it can't close if water gets into it and it may spit like mad. It sounds like you have a pretty sizable main and you may well need more venting in your main(s).

    Post some pictures of your boiler and the pipes that come and go from it - take them from a couple of different angles so we get a good idea of what your dealing with.,
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • thefloyd
    thefloyd Member Posts: 6
    RE: ideas

    David - a few points:

    - main line venting: I'm not sure whether or not I have enough, but I'm inclined to disagree that the varivalve doesn't provide enough venting capacity when compared to another vent. It's rated (when fully open) at faster than even a gorton #2. (Hard to tell from the graph, but looks like it vents > 0.8 cfm). Agreed that still might not even be enough for my system, in which case I'd need multiple main line vents no matter which vendor I choose. The main vent was on a 3/4 opening of a tee where the steam main connects to the condensate return. From Dan's books, ideally it should be moved back a few inches on the main but that's not practical at the moment. I did raise it a solid 8" up on that tee though.

    - pressure: This is a toss up. All the vents on the 1st floor close properly, make no noise, and function as they should. The 2nd floor is hit or miss. I was in my office last night which is a 2nd floor room at the end of the steam main and the vent definitely never closed. On a whim I decided to swap the vent just in case I was chasing a defective vent problem. I (extremely carefully) swapped the vent while the system was running. As soon as I pulled the old vent the radiator quickly filled with steam and when I got the new vent on it shut quickly and quietly. I suspect my rads aren't ever getting enough steam for the vents to properly close. I also noticed the steam coming from the open vent hole *appeared* to be somewhat dry (the first few inches from the vent hole I saw nothing - it cold have been plain old air if I didn't know better, which according to Dan's books should be dry steam).
  • thefloyd
    thefloyd Member Posts: 6
    re: noisy vents


    The system does cycle based on pressure. It runs for a while until the air is out of the system. Once all the radiators heat up (I've walked around the house and done some quick "feel" tests) the pressure does slowly build. The vaporstat cuts the burner off for a short time (usually a minute or less) and then the system fires for a while (several minutes or more) and the cycle continues to repeat until the thermostat is satisfied. I do need to add a low pressure gauge and that's on the to-buy list.

    The sight glass does not seem to bounce around too much, but I'll pay particular attention to it the next time my boiler cycles. It is dry above the waterline in the glass.

    As for my piping, I have about 80' of 2" main. (Rough measurements came to 72, but they're not exact. 80' is a safe number). The pipe off the boiler is a 3" pipe, which the installer nearly immediately (within the first 6") reduced to 2" copper (!). The 2" copper then rises 41" off the boiler, makes a 90 degree turn to horizontal, another 90 degree turn to change direction and is then connected to the main (which is not copper). The take-off to the house is not connected in the middle of an inverted "U" like the diagrams in Dan's book all suggest, instead it comes straight off the boiler, hits a couple of 90 degree elbows and it's off to the races. See the attached pic.

    My spring time to-do (may do this sooner depending on how bold I'm feeling) is to rip out all of that copper and re-pipe the near boiler piping properly. I suspect I need 3" off the top of the boiler pretty much the whole way to the top, and then reduce to 2" when I take-off for the main. I've been reading up on the velocity of steam leaving the boiler and I'm not entirely convinced my system is ideal. I do suspect the fact that there are 41" between the top of the boiler and the first 90 degree elbow helps my situation, though. The guy who installed this system was a complete knucklehead.
  • BobC
    BobC Member Posts: 5,473
    Venting and piping

    The VariValve has a maximum venting rate of 0.85CFM while a Gorton #2 is 1,75CFM - both at 2oz of pressure. Your 80ft 2" main has 1.74 cu ft of air that has to be vented, the faster the better. Whatever vent you decide to use you can pull of that nipple you installed and replace it with a short nipple and an elbow, then a 15" nipple back along the pipe and another elbow to mount one or two vents onto.

    Your right about that boiler not being installed correctly. You should no reducer on the boiler output port, the piping should stay at full size (at least) untill it mates up with the steam main. That reducer is increasing the steam velocity and may be contributing to water carryover and wet steam. The real problem is getting everything apart without cracking something.

    If you don't have the installation manual for that boiler see if you can download one, if you can't find it post the boiler model here and maybe someone has a copy.

    I also noticed the gas hot water heater is feeding a T at the top of the boiler exaust stack (boiler is oil fired?), that is not good. The gas water heater should have it's own port into the chimney above that of the oil fired boiler.
    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • thefloyd
    thefloyd Member Posts: 6
    re: venting and piping

    Bob, thanks for the vent specs. I'll re-work the main vent stack as you recommended (I was actually considering doing something similar with the elbows and a long nipple but didn't do it that way).

    I'll try boiling the vent that was there in vinegar for the short term - it vents, but extremely slowly. Perhaps there's some life left in it until I can rework the main vent stack.

    You're correct about the exhaust piping. The gas water heater replaced a standalone oil fired water heater and is connected the way the old one was.
  • Charlie from wmass
    Charlie from wmass Member Posts: 4,314
    Do any thing you like to that vent short

    of cutting off the top it will be slow. You need proper vents. Vari valves are not them. I would bet in a month you have a question about water spurting out of vents next. Gorton for fixed vents or Vent rite or Hoffman 1 A's for variable vents.
    Cost is what you spend , value is what you get.

    cell # 413-841-6726
  • thefloyd
    thefloyd Member Posts: 6

    I've put up 4 videos (2 of my sight glass and two of the noisy vent). They should be web-streamable for anyone with a broadband connection. They're at:

This discussion has been closed.