Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.

Wiring

Nycwrenchturn
Nycwrenchturn Member Posts: 19
How do you wire 67 McDonnell miller manual reset on steam boiler . 24 volts and primary lwco is prone type 400

Comments

  • Nycwrenchturn
    Nycwrenchturn Member Posts: 19
    Can I just bring power to terminal 1 and 2 and then terminal 4 breaks my Tstat?
  • Jamie Hall
    Jamie Hall Member Posts: 17,049
    It doesn't require power. The terminals are plain switches, and it is wired in series will all your other safeties.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Zman
  • Mike_Sheppard
    Mike_Sheppard Member Posts: 680
    It depends on how it’s wired with your boiler. And if it’s controlling a feeder or not.

    It would be best to consult the manual.
    Never stop learning.
  • Nycwrenchturn
    Nycwrenchturn Member Posts: 19
    Manual stinks it only shows reg 67 not manual reset . Primary is controlling feeder I just need it to turn burner off
  • Nycwrenchturn
    Nycwrenchturn Member Posts: 19
    So which terminals do I run the limits through ?
  • Nycwrenchturn
    Nycwrenchturn Member Posts: 19
    Terminal 3 is the manual reset button . Then there is terminal 1 2 and 4

    Do I just run a limit through 1 and 2 and call it a day
  • Nycwrenchturn
    Nycwrenchturn Member Posts: 19
    ?? Anybody ??
  • DanHolohan
    DanHolohan Member, Moderator, Administrator Posts: 15,425
    I don't think you can do manual reset with the 67.
    Retired and loving it.
  • JUGHNE
    JUGHNE Member Posts: 8,941
    The 2013 M&M catalog shows a 67-M part number 149700, 67w/manual reset.

    I don't think the wiring would be any different with manual reset unless you want to connect an alarm to notify of boiler hard lock out.....not a bad idea sometimes.
  • Nycwrenchturn
    Nycwrenchturn Member Posts: 19
    I have a 67 that’s manual reset . Normal terminal 3 isn’t there anymore it’s where reset button pushes in . Can I just run my Tstat for boiler through terminals 1 and 2 ?
  • Jamie Hall
    Jamie Hall Member Posts: 17,049
    There is no wiring diagram in the manual? Odd. Well, if not, the principle is this: 1 and 2 are the terminals for the float switch. Normally closed. You want to wire it in series with your pressuretrol(s) and the other LWCO you mentioned. Sometimes -- but not always -- the thermostat is in this loop. More commonly, the thermostat goes to T-T on the burner control, and the safeties (of which this is one) are on another loop -- but there are a variety of ways to hook things up.

    The important point is that this is a safety control, and must be in series with all the other safeties on the boiler -- however that is done on your setup.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Zman
    Zman Member Posts: 6,980
    It is a simple double pole, single throw switch.
    1-2 and 3-4 will make or break simultaneously.
    If you are trying to disable the t-stat, what you are proposing will work fine. Most boilers have a string of safeties wired in series. typically your safety switch would be tied into that.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • JUGHNE
    JUGHNE Member Posts: 8,941
    I was taught years ago that a switch is determined to be labeled as NO or NC when it is on the shelf or still in the box without any outside influence applied.
    So I would say you are looking for normally open contacts and when the float is up in the water the switch would be closed for "normal operation". Loss of water would put the switch in the dry mode, as if still in the box or on the shelf, and the contacts would open shutting down the burner.

    The main thing is that during water loss or blow down the LWCO will shut down the burner. And even if the water returns to normal the burner will NOT restart until you manually push the reset button. It should be tested with the burner running.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 10,268
    Yes you can have a manual reset #67. It just has a manual reset switch instead of the normal switch a #11 switch or a #11m I believe.

    With either switch you wire terminals 1 & 2 in series with you thermostat, operating controls and other safeties, those are the low water cutoff terminals

    MAKE SURE ALL YOUR SAFETY'S WORK AFTER MAKING WIRING CHANGES.

    Terminals 3 & 4 are use for operating a feeder or for an alarm. You can't use a feeder with a manual reset so that is why terminal 3 is missing