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Existing Woodburning Stove to Thermal Store, How to add Combi?

Discussion in 'Plumbing and Central Heating' started by Nabbers, 4 Jun 2016.

  1. Nabbers

    Nabbers

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    Hullo chaps first post, looks like some good knowledge here; some advice please.

    In the deepest wilds of the back of beyond where plumbers fear to tread I have a house with the following set up:

    16KW woodburner sends 12kw of heat on a good day via gravity fed open vented 28mm pipes to a 300L Gledhill SOL thermal store(TS). Controls are simple, when the store gets to 70deg, the tank overheat stat turns on the CH pump and the CK kicks in. Got to be burning some decent fuel for that to ever happen! DHW is off a heat exchanger on the TS and I'm happy with that, except for having to always light a fire if I want a decent amount of DHW.

    Anyway, a game changer is that I was given a Worcester Greenstar Heatslave, Oil fired combi external and a decent tank etc, so as they are for free and I have no money, I decided to use them. I have a OFTEC chap who is going to commission the boiler and sign it off, but I am plumbing it in, I've done a lot of plumbing so can do the hands on stuff competently, but don't have the other knowledge....

    A systems boiler would have been better for my needs, but I have it and need to use it so here is my plan.....I thought I would utilise the Solar Coil at the bottom of the TS and run a pressurised flow and return to and from the boiler. The alternative is to use the boiler ports direct to the TS and be vented, but I'm not sure the boiler is going to be compatible with that....comments please?

    In summer I might not want to light a fire for DHW so the combi function will be good, but in winter I would have 2 DHW sources, combi and heat exchanger. With only 1 kitchen sink and 1 bathroom, it's a dilemma..could I..?

    a) Have a switch over valve so I can choose between the heating source, I know this means when using TS heat exchanger the boiler is wasting fuel keeping DHW ready for delivery, but my woodburner is saving fuel which compensates.

    b) Use the DHW from the store to pr-heat the DHW cold inlet to the boiler, or (radical) use the boiler to pre-heat the thermal store heat exchanger cold inlet?

    Then there is the issue of controls, I like simple, I thought keep the tank stat that kicks the CH in when the store is 70 degrees but have a stat on the tank that kills the boiler as a failsafe. Utilise normal programmer to boiler so I can dictate when it is heating the store. Any cause for worry there?
     
  2. Nabbers

    Nabbers

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    Anyone?
     
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  4. Just because it's called a combi doesn't mean it has to be one ;)

    Use it as a system boiler maybe install one hot tap kitchen/utility etc off the combi?

    You need to make sure you've got all your Saftey devices in place though.
    Interlocks etc what if the boiler has got the TS up to temp and then you light the fire too? Is there a heat dump for the log burner?
     
  5. Nabbers

    Nabbers

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    My worry was that the Combi would waste oil keeping the heat exchanger ready to supply DHW...and Gledhill the TS manufacturer issued doom laden warnings that running two sources of hot in one property could cause problems back flowing through mixers...I'm thinking of having lever valves, low tech, but be able to kill either DHW source, go boiler in summer when fire not lit and TS in winter when it is.

    There is a heat sink rad for the Woodburner, and as long as the electric is on, all the radiators act as a pumped heat sink as the tank overheat stat turns on the CH pump and cannot be overridden by time clocks etc. Was going to have another tank overheat stat signalling the boiler to turn itself off.

    Basically living this way is a bit of hassle, but not the end of the world, gonna appreciate the heat next winter !

    Am I going to have problems using the solar coil for the boiler to heat the TS and not having an additional heating circuit straight of the boiler, all 7 rads coming off the store?
     
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  7. Tipper

    Tipper

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    Have a look at Heating Innovations Limited's H2 panel (I think) or one of their other systems.

    http://www.h2panel.co.uk/
     
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