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Need larger throughput from just one steam radiator vent - see pix

davevargadavevarga Posts: 29Member
edited January 2 in Strictly Steam
Hi, I have a 100 year old house with one pipe steam system. All is well and is balanced except for one particular radiator that needs a vent with a larger throughput, hope you can help me locate one, let me explain. I'm using Maid O Mist 1/8" right angle vents.

On the second floor there is one radiator that I have placed the largest opening insert (size D), however it is not sufficient. Well in the morning when the temp goes from 66 to 70 in the house it is sufficient as the entire length of the large radiator heats and the vent closes at that point, but the room heats nicely. However, on all the incremental maintenance heat cycles throughout the day, this radiator heats but not enough when the boiler shuts off from the sensor on the first floor that says it is 70.

The problem could be solved if the radiator vent had a slightly larger throughput. The point of restriction is the 1/8" hole built into the vent, where the float moves up to seal when it gets hot. If the hole could be a little larger, then during the incremental heating during the day the radiator would get hotter. Any ideas? See pix, you can see the 1/8 " hold inside (and the screw in insert)



  • neilcneilc Posts: 661Member
    what if you slow all the others down by one size ?
    or just a couple that "Heat" a little too well?
    like that one by the thermometer?
    This will push more heat to that cooler rad.
  • FredFred Posts: 7,853Member
    That "D" orifice vents at .341 CFM at 1 ounce of pressure. That's about as fast as any radiator vent available except for the Varivalve and they are problematic because they vent too fast. Do you have good main venting on your Mains? The problem may be it takes to much of the heating cycle to push air out of the mains to get to that radiator or as @neilc says, you have the other radiators venting so fast that they have become the path of least resistance for the steam and it doesn't get to this radiator until all those other ones are full. We always warn people that the goal for a properly balanced system is not that all the radiators get hot all the way across but that the room temp is comfortable. Either slow the other radiators down a bit (especially the one nearest the thermostat/sensor) or move the sensor to a more appropriate location or make sure you have adequate main venting.
  • davevargadavevarga Posts: 29Member
    Hi NeilC,

    The sensor is in the 1st flr living room and the radiator in it has recently been changed to the smallest aperture insert. I also made the insert on the closest radiator to the living room two insert sizes smaller. It helped in that the entire house heated up a little, but I still need this one radiator to radiate more heat during the maintenance heating cycles.

    BTW there are three floors that are heated, all are balanced except for this last radiator. What complicates this is that this multi-family house is singly heated, so I would end up going in and out of apartments a lot with the tenants in them if I rebalance the entire system.

  • neilcneilc Posts: 661Member
    So try Fred's varivalve there, and see if that works for you.
    If not, we can all get further into the weeds with main vents, boiler pressures, boiler EDR and connected EDR in the house.
  • davevargadavevarga Posts: 29Member
    OK I am going to order an adjustable VariValve and hope I can arrange for a quick fix. If not, will explore replacing the mains or at least the one in the section that feeds those particular radiators. I have had this house for 15 years and have not switched out the mains. I do not know how to determine if they are functional or not functional and need to be replaced. I can explore around this great forum, I know how to determine this is here somewhere, I have seen it before. BTW, I was surprised to see this 2600 sq ft house has two large Gorton mains and one small one.
  • FredFred Posts: 7,853Member
    You should use one Gorton #2 for each 20 to 25 ft. of 2" main. Each main needs to be vented that way. For the same money, you can order a Barnes and Jones Big Mouth and get 2.5 time the venting capacity of a Gorton #2 so one Big Mouth will do about 50 ft. of 2" Main. You should always properly vent the mains first and then balance the radiators as proper main venting will get steam to the radiators a lot faster and save fuel cost because the boiler is not running as long to push the air out of the system.
  • gfrbrooklinegfrbrookline Posts: 369Member
    Ditto @Fred. Once you figure out your main venting your radiators should have plenty of steam to heat them. You will likely need to slow some radiators down but you will save money in your fuel bill.

    I would not order a varivalve as this will just band aid a system wide problem and cause a problem somewhere else.
  • nicholas bonham-carternicholas bonham-carter Posts: 7,825Member
    I second the advice to improve/fix the main venting, before changing the radiator vents. Your fuel company will hate this because your fuel consumption, with proper main venting will result in 15-25% less purchase from them.
    However, don’t worry about them, but just do the upgrade, as they have plenty of money from others who have not taken this step!—NBC
  • neilcneilc Posts: 661Member
    well as long as we're talking main vents,
    what boiler pressure are you set for?
    and what do you see on the boiler gage when she's been running a while?
    has the pigtail for the pressuretrol been checked for clean and clear?
  • mikeg2015mikeg2015 Posts: 785Member
    I had some luck with adding a vent on a elbow on the riser feeding that radiator. Adds some venting for short cycles.

    Sounds like your limited on balancing. But U found that once I slowed everything down at the radiators, it was much easier to balance. I had trouble controlling it all with Gorton or MoM, 6, C , D’s. But not i have 4’s a n5’s everywhere or Hoffman 40’s or Ventrites, which are now my absolute favorite.
  • mikeg2015mikeg2015 Posts: 785Member
    .... just a reminder tha most balancing issues start with main vents. These old system utilized coal which modulated, so slow venting all around was OK. Fire heated up slowly and then peaked after the system was already mostly hot and was turned down to match load. The ON/OFF nature of gas is challenging for venting.
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