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How to measure radiator height

straubtm Member Posts: 2
Hi all -

I'm trying to calculate the EDR of my radiators so I can better balance my steam system. I'm using the charts from The Lost Art of Steam Heating and I have a question on measure the height of the radiators. Should I be measure from the floor (thus including the legs) or should I be measuring an internal (no legs) section.


DIYer / homeowner in PA


    EBEBRATT-Ed Member Posts: 15,513
    Yes from the floor. It's common for radiators to differ from the charts a little an inch or so one way or the other doesn't matter
  • straubtm
    straubtm Member Posts: 2
    Thanks Ed! I figured a little variation won't hurt as long as I am consistent throughout the home.
    DIYer / homeowner in PA
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,817
    I was going to be a Smart A** and say "with a tape measure' but I won't.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • straubtm
    straubtm Member Posts: 2
    "With a tape measure" is right up there with "you better go catch it" in regards to your refrigerator running ;)
    DIYer / homeowner in PA
  • Hap_Hazzard
    Hap_Hazzard Member Posts: 2,846
    Speaking of phone pranks, who remembers this one?

    Just another DIYer | King of Prussia, PA
    1983(?) Peerless G-561-W-S | 3" drop header, CG400-1090, VXT-24
  • SteamingatMohawk
    SteamingatMohawk Member Posts: 1,003
    All I see is Prince Albert in the can, but I was a youngster when it was said decades ago.
  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    Don't forget that, along with the tape measure, a low pressure (0-3 psi) gauge will help you get the steam to each radiator at the same time.
    Under 2 ounces is the magic number for measuring your main venting. then start with slow vents on the radiators, and then tweak from there.
    Disregard the Gorton website advice, as while they make excellent main vents, they don't seem to understand their application.--NBC
  • neilc
    neilc Member Posts: 2,702
    someone better let the prince out
    known to beat dead horses
  • straubtm
    straubtm Member Posts: 2
    Hey @Hap_Hazzard, I'm in Ardmore. I use to live in KOP. Small world.
    DIYer / homeowner in PA
  • bburd
    bburd Member Posts: 912
    I lived in Ardmore for 11 years. 😎

  • straubtm
    straubtm Member Posts: 2
    @nicholas bonham-carter thanks for the info. I previously installed a Vaporstat and 3psi gauge. Vaporstat set to cut out at 8oz, and diff at 6oz (so cut-in at 2oz if I understand it correctly. Gauge typically shows between 1/8 and 1/4lb....so 2-4oz. It's not steady...the needle jumps around between these bounds. I'm not sure if this is to be expected or not.

    On each side of the main (~83 and 58ft long respectively), I've added a Gorton #2 in addition to the existing Hoffman #75. This decreased the time needed to bring steam to these vents by a couple minutes. Not surprisingly, the longer side is still a couple minutes longer that the shorter side. I am thinking of adding a 3rd vent to this main but instead of adding to the manifold at the end, I was thinking of adding it about 45' into the run. I radiator was previously removed and there is a 1.5" line capped. Was thinking of adding a Barnes & Jones Big Mouth here. Thoughts?

    As far as radiator venting, in general I have slower vents Hoffman 40 (0.067 @ 2oz) on most of the 1st floor. Some vary based on radiator size. Vents tend to get larger on 2nd and 3rd floor respectively. These are a mix of Ventrite #11 (0.1 @ 2oz) and Heat Timer Varivalve (0.158 to 0.850 @ 2oz). Again some variation based on size of radiator and room.

    I would say most of the room are within a degree or two of the thermostat (1st floor). I do have one 2nd floor room giving me a bit of trouble. It can be as much as 6-8* behind the thermostat. This is ~53ft down the long main line. Passes through 1st floor in an exterior wall with R13 insulation on the exterior side of the riser. Riser was converted to copper from cast when the riser was moved into the wall as part of a kitchen reno. 1st floor is 9.5ft tall. The riser splits and supplies a 2 column 38" x 7 section radiator (28 EDR) in a bedroom and a wall mount (13x24x2 7/8" single section, ~8 EDR) in a powder room. I have a Heat Timer Varivalve wide open on the bedroom radiator (0.850 @ 2oz) and the radiator still seems to lag...meaning when others are hot 3/4 across, this one may be 1/2 or 1/3. Further down this main at @ ~68 feet I have riser going up to the 3rd floor (so an additional 9 vertical feet of second floor space to pass through) to get to a 2c 26" x 14sec (37.2 EDR) radiator. This one is fully inside the house and heats very well with a Heat Timer Varivalve wide open.

    So couple of thoughts/questions.
    1. Regarding furnace pressure...is it common to see the needle bounce around a bit?
    2. Regarding the main, what are people's opinion about adding a vent midway vs adding at the manifold at the end?
    3. Regarding the 2nd floor slow radiator, the system wasn't well balanced prior to the kitchen reno as I didn't address it as a personal project until afterwards. So I can't say if the if moving the riser and changing to copper made a direct impact. Thoughts?
    4. Could some sort of vacuum be going on between the two radiators on the single riser?
    5. If I slow down other radiators on this main run, could it help this one particular radiator? Does it matter of the other radiators I slow down are before or after this riser at 53'?
    Thoughts??? Anything else you want to know to better understand the system?

    Thanks all. I'm a analytical geek by nature and this forum/site if steam heaven:)

    DIYer / homeowner in PA
  • SteamingatMohawk
    SteamingatMohawk Member Posts: 1,003
    In the event you didn't know, the 30 psig gauge is required by the code.

    If you intend to keep a lower range gauge permanently installed, it should either be installed with a shutoff valve so it can be isolated when not in use or get a gauge like a Magnehelic 2203 that is good for more than 15psig (that's the relief valve setpoint).


    A few weeks ago in another discussion several of us talked about using lower pressure gauges to better monitor the system pressure. As a result, I contacted two manufacturers of low pressure gauges. Both said their gauges are designed for only 30% over pressure (3psig * 1.3 = 3.9psig). If your system has pressure above that amount, the gauge could be damaged and if pressure is high enough leak or fail.

  • straubtm
    straubtm Member Posts: 2
    Thanks for the info @SteamingatMohawk. I did not know any of that.

    So the 30psi gauge is still there...it's just not shown in the picture.

    Regarding the 3psi gauge, is having the Vaporstat installed and set to cut out at 8oz not enough? I should still either have a shutoff valve or a more robust gauge like you suggested?
    DIYer / homeowner in PA
  • SteamingatMohawk
    SteamingatMohawk Member Posts: 1,003
    The theory is that something goes wrong somewhere for whatever reason and the pressure goes up. The relief valve provides an upper limit on how high the pressure could go. Therefore, installing something that cannot handle that pressure is not a great idea, even if there are multiple protective devices.

    There are lots of comments in discussions about the unfortunate-ness of the 30 psig gauge, because for a properly working system the operating pressure is a lot lower than 15psig. In The Lost Art book there is a discussion about the 2 psig standard that was established in the beginning of the 1900s. There are also stories in the book about the early days and the problems that existed, which led to the standard.

    The Magnehelic meets the criterion, but it is a bit more expensive as you could see on the web page I referenced.

    JUGHNE Member Posts: 11,060
    I had a system running on ounces and the gauge and the HG vaporstat both were in jiggle mode. I put another pigtail on top of the original one and that smoothed things out. Double water loops.
  • ethicalpaul
    ethicalpaul Member Posts: 5,701
    SteamingatMohawk said:

    The Magnehelic meets the criterion, but it is a bit more expensive as you could see on the web page I referenced.
    ebay is your friend
    NJ Steam Homeowner. See my sight glass boiler videos: https://bit.ly/3sZW1el