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cylinder water cooling

  • 07-07-2012 11:05PM
    #1
    Cerbera
    Registered Users, Registered Users 2 Posts: 371 ✭✭


    I'm not sure if this post is in the right section (it is sort of stove related) and if it's not can someone please move it.

    Anyhow I just noticed today that the hot water in my cylinder is cooling down as heat is "leaking" to the boiler in the stove.

    The pipe from the top of the boiler in the stove is really hot and the lower one is warm.

    The water is being heated by solar panels since earlier this year and always held it's temperature until the stove went in.

    Once the solar panels stopped working this evening the temperature at the bottom of the cylinder dropped by about 35*C in about 3 hours.

    There is a U-shape dip in the pipe from the stove to the cylinder (the plumber who piped it said this was to prevent this from happening) but obviously it doesn't work.

    Should there be a non-return valve on this pipe or is there some other solution?


Comments

  • #2
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    Is the pipe stat that switches on the circulating pump for the stove located in the hot press?
    If so, it needs to be moved. The heat is naturally leaking out of the cylinder and switching on the stove pump, dumping the heat from the cylinder to the stove.


  • #3
    Cerbera
    Registered Users, Registered Users 2 Posts: 371 ✭✭Cerbera


    shane0007 wrote: »
    Is the pipe stat that switches on the circulating pump for the stove located in the hot press?
    If so, it needs to be moved. The heat is naturally leaking out of the cylinder and switching on the stove pump, dumping the heat from the cylinder to the stove.

    It is located there.

    It's on the pipe coming from the stove to the cylinder and is set to cut in to bring on the pump at 50*C.

    The problems with moving it are (a) everything is closed up / slabbed now so it would be difficult to move it and (b) the pipe from the stove to the cylinder is only about 1.5m long so it'll be hard to move it far from the cylinder.

    Is this the only option?


  • #4
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    It must be moved. To confirm, heat the cylinder to temperature and turn the pipe stat to its highest setting. You will notice the drop in temperature has been eliminated.

    This is a common mistake solar installers make when installing systems incorporating solid fuel.

    Is the pipe going up into the attic and then down to the stove or is going through a side wall or down through the floor?


  • #5
    Cerbera
    Registered Users, Registered Users 2 Posts: 371 ✭✭Cerbera


    The pipes go through a wall.

    The stove and cylinder are almost back-to-back.

    The stat is as close to the wall as it can be while still in the hot press.

    The only place to move the stat is to is into the living room but then it'll be right at the outlet of the stove.

    If the stat has to be moved then I'll find some way of getting a cable to it but it's just going to be a pain in the hole now that everything is slabbed and skimmed again.


  • #6
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    The flow pipe from the cylinder must drop somewhere to the stove as the stove must be lower than the cylinder coil. If you put the stat on a vertical section of pipe as low as possible it should work ok.

    As a temporary measure turn up the stat to its highest setting and this will stop it dumping heat from the cylinder but just make sure you turn it back to 55 - 60 before you light the stove.


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  • #7
    Cerbera
    Registered Users, Registered Users 2 Posts: 371 ✭✭Cerbera


    shane0007 wrote: »
    The flow pipe from the cylinder must drop somewhere to the stove as the stove must be lower than the cylinder coil. If you put the stat on a vertical section of pipe as low as possible it should work ok.

    The stove is lower but it's a nice gradual rise to the coil in the cylinder with just a very short vertical section and that's where the stat is.

    :(
    shane0007 wrote: »
    As a temporary measure turn up the stat to its highest setting and this will stop it dumping heat from the cylinder but just make sure you turn it back to 55 - 60 before you light the stove.

    Yeah that's what I've done.


    FWIW is a NRV out of the question as an option to stop the flow of water back to the stove?

    I remember that being done in a house I was renting years ago with 2 back-boilers that "stole" the heat from each other rather than jeating the water / rads and it worked perfectly in that situation to solve the problem.


  • #8
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    Cerbera wrote: »
    The stove is lower but it's a nice gradual rise to the coil in the cylinder with just a very short vertical section and that's where the stat is.

    Bring the cylinder to hot, check along the flow pipe from the stove to the cylinder and place the stat on the coldest section of pipework, furthest away from cylinder and closest to the stove.
    Cerbera wrote: »
    FWIW is a NRV out of the question as an option to stop the flow of water back to the stove?

    I remember that being done in a house I was renting years ago with 2 back-boilers that "stole" the heat from each other rather than jeating the water / rads and it worked perfectly in that situation to solve the problem.

    No, you should not install a NRV. You can only put NRV's on the secondary circuit and not on solid fuel primary circuit. Should there be a pump failure or a power cut whilst you have a fire lit to heat the parish, the non-return will restrict the gravity circuit and the system will end up over-heating, banging and pitching.


  • #9
    Cerbera
    Registered Users, Registered Users 2 Posts: 371 ✭✭Cerbera


    I'm still having a problem with this and despite plenty of promises the plumber who installed everything still isn't coming back.

    Anyhow, I've set the stat up high and not lit the stove and a lot of heat is still being lost from the cylinder.

    The pump isn't cutting on but hot water is still flowing slowly from the cylinder to the stove to the point where the top pipe off the stove boiler is hot and I can fel heat in the flue off the stove where obviously the boiler has warmed up as well.

    I wouldn't mind a loss of a couple of degrees but overnight the bottom of the cylinder went from 60*C down to 28*C.

    Surely there has to be some way of improving this.

    Anyone ?????


  • #10
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    Without seeing the installation, we can only suggest various possible causes. Your installer should be the one to resolve this.

    One of two causes will be the issue if the pump is not coming on.

    1. The cylinder is at the same level as the stove and is naturally siphoning the heat out of the cylinder into the stove.
    Solution: Raise the cylinder height.
    2. There is a leak on your domestic hot water pipework.
    Solution: Turn off the cold feed to the cylinder and see if there is no drop in tempertaure, then there is a leak.


  • #11
    Cerbera
    Registered Users, Registered Users 2 Posts: 371 ✭✭Cerbera


    I understand what you asid re the same height and it may just be the case that this is what's happening.

    Also I don't think there is a leak but I'll check that.


    And in the emantime I'll make a few more attempts to get the installer back. :mad:


    Thanks. :)


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  • #12
    Cerbera
    Registered Users, Registered Users 2 Posts: 371 ✭✭Cerbera


    I've asked for this thread to be deleted as I feel it may read like I'm unhappy with the installer but my request was declined.

    I'd like to point out that I'm not unhappy with the installer and if it came across that way it wasn't meant to.

    All seems to be good now.

    :)


  • #13
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    Cerbera wrote: »
    I've asked for this thread to be deleted as I feel it may read like I'm unhappy with the installer but my request was declined.

    I'd like to point out that I'm not unhappy with the installer and if it came across that way it wasn't meant to.

    All seems to be good now.

    :)
    So what was the cause of the issue?


  • #14
    ccsolar
    Registered Users, Registered Users 2 Posts: 423 ✭✭ccsolar


    Hi
    You have what's called thermosiphining going on in your system.
    The stove heats the tank when the fire is lit through gravity, but when the solar is working you have the same affect with the solar heating the stove.
    You need to fit a non return valve with a flap.... Note this is not a normal NRV and must be installed by a good plumber in the correct location.
    Cc


  • #15
    Cerbera
    Registered Users, Registered Users 2 Posts: 371 ✭✭Cerbera


    What was happening was exactly as I suspected and ccsolar confirmed it using the correct terms. :)

    A flap-type non-return valve had to be fitted and all seems to be ok now.

    On the few days we had enough sun to heat the cylinder via solar the heat stayed in in.

    The stove was lit just to check if was working and it too seemed to be doing everything properly.

    Thanks for the help folks.

    :)


  • #16
    johnjoe 123
    Registered Users, Registered Users 2 Posts: 138 ✭✭johnjoe 123


    great thread guys it would be great if they were all like this.. . . i installed solar into a house recently the stat on back boiler is bringing on the pump on a sunny day due to hot water in cylinder i put this down to heat transfer yes???? que 2 its a triple coil indirect clyinder could the domestic hot water heat the coil of back coiler circuit enough to heat rads ???


  • #17
    ccsolar
    Registered Users, Registered Users 2 Posts: 423 ✭✭ccsolar


    johnjoe 123 wrote: »
    great thread guys it would be great if they were all like this.. . . i installed solar into a house recently the stat on back boiler is bringing on the pump on a sunny day due to hot water in cylinder i put this down to heat transfer yes???? que 2 its a triple coil indirect clyinder could the domestic hot water heat the coil of back coiler circuit enough to heat rads ???
    Hi johnjoe
    Is the stat positioned on the or near the back boiler outlet or is it positioned nxt to or on the tank??
    I'm thinking your system is thermosiphining also,
    Note:
    You could use this as a heat dump into the rads and prevent the solar from overheating in summer...
    Question 2.
    Yes you could do this but it doesn't really work as you would be loosing out on the hotwater side ,
    How ever if you had underfloor heating and a bigger system/ tank it would work in winter.
    Note: radiators run at 60 degrees but underfloor runs at 35 degrees

    Cc


  • #18
    keveng
    Registered Users, Registered Users 2 Posts: 5 ✭keveng


    I would advise you to take that NRV out (its dangerous) you must have non restricted 1" flow and return to your cyl with solid fuel.. the problem sounds like its with the pipe work i would advise you get a third party to check it out. If your system is a combined oil or gas and solid fuel be carefull a lot of plumbers dont know how to pipe these systems correctly..


  • #19
    Cerbera
    Registered Users, Registered Users 2 Posts: 371 ✭✭Cerbera


    keveng wrote: »
    I would advise you to take that NRV out (its dangerous) you must have non restricted 1" flow and return to your cyl with solid fuel..

    Dangerous? In what way?

    Is a flap-type NRV considired a restriction?
    keveng wrote: »
    the problem sounds like its with the pipe work

    I don't see how it could be piped any other way.

    The distance from the stove to the cylinder is fairly short (pretty much just the other side of a thick wall) and doesn't allow for any real variation in the route of the pipework.
    keveng wrote: »
    i would advise you get a third party to check it out.

    I might just do that if necessary
    keveng wrote: »
    If your system is a combined oil or gas and solid fuel be carefull a lot of plumbers dont know how to pipe these systems correctly..

    It's a triple-coil cylinder.

    The stove has one coil, the oil has one and the solar has the remaining one.

    Is this what you mean combined?


  • #20
    shane0007
    Closed Accounts Posts: 4,677 ✭✭✭shane0007


    keveng wrote: »
    I would advise you to take that NRV out (its dangerous) you must have non restricted 1" flow and return to your cyl with solid fuel.. the problem sounds like its with the pipe work i would advise you get a third party to check it out. If your system is a combined oil or gas and solid fuel be carefull a lot of plumbers dont know how to pipe these systems correctly..

    Spot on. I totally agree. There are no restrictions allowed on a gravity primary circuit and the NRV is a restriction, flap type or not. The issue is the pipework and should be re-done to suit.


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