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Timer switch on thermostat heat call circuit?

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Zipper13
Zipper13 Member Posts: 229
edited October 2021 in Strictly Steam
All 10 of my steam traps are failed open on my 2 pipe system.

Sure, I could replace the cages...but I tried to replace one this summer I'm pretty sure I'm the first on in 100 years to try to do this and I'm positive that for the amount of force I need to pop the trap covers, I either don't have the right tools or I'll break something more expensive if I get more force on them!

I've thought about cheating by adding a timer switch to the call for heat in conjunction with my adjustable Hoffman balancing valves. I don't know, maybe after 45? 60? minutes of firing on a particularly cold day when it wants to run long, I'll have it shut down for 10 minutes or something like that before it can burn again for up to another 45 min if needed.

My thought process is that I'd be tripping the system off when it should otherwise be tripping off on pressure if the traps were good.

I suspect that the parts to do this timer switch would be far cheaper than the cost to do it right by replacing 10 trap cages while breaking who knows what in the process! But I wonder if I'm way off base with this Idea.

I think I recall @ethicalpaul mentioning last year that he integrated something similar to his boiler but I cant find the thread - and if so, I'd be interested to hear if he feels had any benefit from it.
New owner of a 1920s home with steam heat north of Boston.
Just trying to learn what I can do myself and what I just shouldn't touch

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,616
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    I would replace the trap internals.

    Put a good size wrench on for a back up.

    The trap MFGs have wrenches that fit the trap caps

    or buy a socket.

    Best way is an impact driver with a socket


    The other alternative is to remove the traps, put them in a vise so you can get the cap off.


    When I used to bid buildings for trap rebuilding we could do them in 15 min or less if you had the tools.

    And yes if you did 30 traps or so you may find one where you have to replace the trap

  • Jamie Hall
    Jamie Hall Member Posts: 23,433
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    As @EBEBRATT-Ed says, my first thought would be to replace the trap internals -- use a 6 point socket to fit, a cheater bar, a helper and a backup wrench -- or better, a good impact driver.

    If that didn't work, I'd do two things together: first, invest in -- if you don't already have it -- a vapourstat and set it for 7 ounces cutout, 4 ounce differential. Absolutely no higher. Then having done that, I'd go around and use those Hoffman radiator valves for what they are intended (and it's not balancing): set each one so that the radiator gets hot on a long run across 80 to 90 percent of the width and no more. Then figure out how to keep people from fiddling with them.

    (a side note -- if your main venting on the returns is inadequate, you may have cycling problems. And, worse, if among the failed trap elements are the crossover traps, you will either have to replace those internals or plug the connection on the dry return and put main vents on the mains. This fix is not optional).

    Set up this way, the system will run just fine without traps. In fact, that is the way a system with the Hoffman valves was intended to run, and the traps were sort an additional safeguard, but not really needed, unless the boiler got carried away (coal boilers did...).

    Or you could go the timer route. It's a kludge, but it does work.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,616
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    @Zipper13

    Anything you do will be more expensive than repairing the traps
  • JUGHNE
    JUGHNE Member Posts: 11,075
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    I have had great success with 6 point socket and 18 volt 1/2" impact.

    Grind the end of the socket to remove the bevel to get better contact on the cap if needed.

    I do use a back up wrench to just be safe. After a few you get the feel of how willing the caps will be to be removed and may not need the back up.

    You could just eliminate the trap guts and install orifices in the union of the supply valve union.
    This is for about only 20% of the cost of new trap parts and you never have another issue of repairs.

    I have done this on a few jobs.

    You must determine the pressure typical of the system and calculate the orifices' size to heat only 80% of the rad capacity. I get the orifices predrilled to 1/8" and enlarge as needed based on charts that I have.

    If you start small on sizes you can increase as needed.

    It seems you are a "hands on" HO and would be able to master this.
  • pecmsg
    pecmsg Member Posts: 4,883
    edited October 2021
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    And a lot of never seize reassembling. 
    mattmia2
  • PMJ
    PMJ Member Posts: 1,265
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    @Zipper13, your thought process is the right direction to go. As you have seen already there won't be much support for it here, but I endorse it. No you really are not way off base. It is the least expensive thing to do by far.

    Think about how the system would have run with the original coal boiler. The radiators could never have been full (or close) because the steam supply was continuous and full radiators would have roasted the occupants. So there is never an actual need to fill a radiator and therefore no fundamental need for a trap.

    With the change to intermittent fire some sort of burn time limiting mechanism (definitely not pressure) is needed to control the firings such that radiators can never fill. I have done it for more than two decades now. You couldn't pay me to go back to the standard control. The heat this way is dramatically more even. Once over this logical hump size of boiler and devices at each radiator in a two pipe system become unimportant. I have 23 radiators and haven't fussed with a device on one of them for years and years.

    Start simple and go from there. Happy to help if you like.



    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control
  • Zipper13
    Zipper13 Member Posts: 229
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    Thanks, all, for the comments!

    Considering cost of replacement internals (and the risk of me breaking something in the process), a timer relay really is significantly cheaper (like probably 20% of the cost!). I get that the benefit of the timer may not pan out perfectly, but I'm encouraged to take away that my logic at is reasonably sound and that testing it out is not likely to break anything at least!

    I did try an impact driver and had nothing to show for it. I used a cheater too, but the radiator itself was moving around more than this DIYer was comfortable seeing so I decided that I wasn't going to touch them myself and maybe if/when the boiler gets replaced (13 years old), we'll have the traps dealt with by a pro with a better feel for them then.

    I took a look back and was able to find @ethicalpaul's comment that I referenced. He suggested a timer triggered by a pressure switch so that the relay timer only counted once steam was actually being made, which makes sense since time to steam could vary.
    New owner of a 1920s home with steam heat north of Boston.
    Just trying to learn what I can do myself and what I just shouldn't touch
    BobC
  • PMJ
    PMJ Member Posts: 1,265
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    Good show @Zipper13. Stick to your guns. You are on the right trail with sound logic. You are also one of the lucky ones to have a 2 pipe system.

    Consider a control strategy that skips pressure altogether. By the time you are getting anywhere close to measurable pressure you already have too much steam out there. Your timer should be a delay off from a temp switch on a radiator inlet after steam actually arrives to adjust a fill level, not a delay to next on from a pressure stop already reached. Much more even heat can be achieved this way.

    1926 1000EDR Mouat 2 pipe vapor system,1957 Bryant Boiler 463,000 BTU input, Natural vacuum operation with single solenoid vent, Custom PLC control