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Limit switch

  • 28-11-2014 11:15am
    #1
    The Buster
    Registered Users, Registered Users 2 Posts: 218 ✭✭


    The upstairs radiators not working in my house. There are 3 zones of the boiler, upstairs rads, downstairs rads and hot water. The 3 zones split under the bolier and are controlled by limit switches (is that the correct name).

    In trying to figure out what the problem is I noticed that the 3 pipes going into the limit switches are hot but coming out of the limit switch the upstairs one is cold. I'm guessing my problem is with the switch and it needs replacing. Does that make sense or should I be checking for something else?


Comments

  • #2
    nmacc
    Registered Users, Registered Users 2 Posts: 459 ✭✭nmacc


    They are not limit switches, but motorised valves, although each does contain a microswitch which triggers the boiler.

    There should be a thermostat controlling the valve, check that it's turned up and, if it has a neon indicator, that it comes on.

    Each of the valves will have a lever or a knurled wheel on the side. If you move the lever when the system is off you will be pushing against the spring. If the system is on and the thermostat is calling for heat, then the lever should move freely. If it doesn't then the motor has probably failed.

    There will be a slot or notch into which you can hook the lever which will hold the valve open manually and allow heat to the radiators. Similarly if there is a knurled plastic wheel instead of a lever, you need to turn it until you find a flat on the wheel as this is the Open position.


  • #3
    The Buster
    Registered Users, Registered Users 2 Posts: 218 ✭✭The Buster


    nmacc wrote: »
    They are not limit switches, but motorised valves, although each does contain a microswitch which triggers the boiler.

    There should be a thermostat controlling the valve, check that it's turned up and, if it has a neon indicator, that it comes on.

    Each of the valves will have a lever or a knurled wheel on the side. If you move the lever when the system is off you will be pushing against the spring. If the system is on and the thermostat is calling for heat, then the lever should move freely. If it doesn't then the motor has probably failed.

    There will be a slot or notch into which you can hook the lever which will hold the valve open manually and allow heat to the radiators. Similarly if there is a knurled plastic wheel instead of a lever, you need to turn it until you find a flat on the wheel as this is the Open position.

    Thanks Nmacc - thats the name of it alright. I couldnt think of it

    Yes I have opened the valve manually but no luck. However the hook looked to have had better days so I'm guessing its not working. Sounds like i need to replcae it

    The fact that the pipe is hot before the valve and cold after it, I can be fairly sure the valve is the problem and I need to replace it


  • #4
    nmacc
    Registered Users, Registered Users 2 Posts: 459 ✭✭nmacc


    Probably, but check it by opening the valve when the system is on. If the pipe beyond the valve gets hot then the valve motor has probably failed. In many but not all cases, the head of the valve can be changed without removing the valve, which makes life a bit easier.

    An elastic band may help with the lever.


  • #5
    The Buster
    Registered Users, Registered Users 2 Posts: 218 ✭✭The Buster


    nmacc wrote: »
    Probably, but check it by opening the valve when the system is on. If the pipe beyond the valve gets hot then the valve motor has probably failed. In many but not all cases, the head of the valve can be changed without removing the valve, which makes life a bit easier.

    An elastic band may help with the lever.

    Thanks nmacc. I'll give that a try


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