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Double coil for 3 heat sources (solar, sf, oil).

  • 22-06-2011 3:43pm
    #1
    topazkk
    Registered Users, Registered Users 2 Posts: 169 ✭✭


    Hi folks,

    Just got solar panels and believed I was getting a triple coil cylinder installed for the solar, oil fired and solid fuel. Now as I was disposing of the boxes left after the plumber I noticed that the installed hot water cylinder was a double rather than a triple, with the pipes teed in the hot press, the issue of cost aside should I be worried about any effect on performance from this set up?

    Thanks,

    Brendan.


Comments

  • #2
    DoneDL
    Closed Accounts Posts: 902 ✭✭✭DoneDL


    Change the cylinder to a triple coil, get a good quality cylinder that is sized properly for the solar panels. Any thing else will work short term but will not be efficient or meet building regs.


  • #3
    topazkk
    Registered Users, Registered Users 2 Posts: 169 ✭✭topazkk


    I believe the cylinder to be of good quality (Joule 400 litre) and the solar system is up and running, my issue is the possible performance implications later in the year when the other systems are back in use. I'm wondering if anyone else has a similar set up working? :(


  • #4
    quentingargan
    Registered Users, Registered Users 2 Posts: 1,627 ✭✭✭quentingargan


    Whatever way you look at it, sharing coils is a compromise, but it is hard to tell what has been compromised without looking at the system. But people don't opt for three coils just to spend more money.

    What two systems have been Teed together? Solid fuel and oil on the top coil? or solar and oil on the bottom coil?

    If you lets know what two are teed and where, then someone can let you know (possibly) what the compromises are.


  • #5
    topazkk
    Registered Users, Registered Users 2 Posts: 169 ✭✭topazkk


    Thank's for the reply.The feeds from back boiler and the oil fired boiler seem to be teed, I don't imagine that it would be possible to tee the solar feed to either of the others with it circulating glycol rather than water.


  • #6
    quentingargan
    Registered Users, Registered Users 2 Posts: 1,627 ✭✭✭quentingargan


    topazkk wrote: »
    I don't imagine that it would be possible to tee the solar feed to either of the others with it circulating glycol rather than water.
    I've seen it done....

    It is usually best practice to give the solid fuel a dedicated coil, and this coil should be 1". This is in case of a power cut to ensure that the cylinder can be heated by gravity in the event of a power cut. I assume that the cylinder itself is vented.

    It is hard to know how the system might work without seeing it. But for example, when the central heating is heating the cylinder, does heat from that system travel down to the solid fuel boiler? If it does, that's a bit of a waste.

    Likewise, if the solid fuels is circulating heat into the oil circuit.

    If you have a roaring fire and you shut off the electricity to all pumps, do you get water boiling in the pipes after a while?

    Those are the first things that spring to mind. The main one is that twin coil cylinders usually only have a 3/4" coil in the top, not the 1" required for solid fuel.


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  • #7
    topazkk
    Registered Users, Registered Users 2 Posts: 169 ✭✭topazkk


    1 inch feed from back boiler to hot press where reduced to what looks like 3/4 inch then it's teed to hot feed from oil burner and connected to upper coil in cylinder. The cylinder is vented and if the pump for the back boiler was switched before the installation (when we had a roaring fire) then we did get water boiling and gunning from the adjacent pipes.


  • #8
    quentingargan
    Registered Users, Registered Users 2 Posts: 1,627 ✭✭✭quentingargan


    topazkk wrote: »
    ...if the pump for the back boiler was switched before the installation (when we had a roaring fire) then we did get water boiling and gunning from the adjacent pipes.

    This may well be because the 3/4 coil cannot dissipate the heat from the stove. I have seen lots of systems that boil like this - ultimately if you leave a solid fuel fire roaring after a power cut, the water in the system will have to boil, but if it does so at a time when there is relatively cool water in the hot water cylinder, that's not great.

    If sufficient hot water boils into a plastic header tank, that can also be bad news - there have been incidents of these melting with disasterous consequences (here).

    I also wonder though if heat is travelling from one system into another. This isn't the weather to be testing all this, but at any time, pipes that are not in use should not be hot. So if the solid fuel is on, the OFCH pipes shouldn't be hot and vice-versa.

    But if you were quoted for a triple coil system, and you didn't get it, I would kick up a bit of a stink.


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