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Thread: New biomass boiler - not sure about controlling it

  1. #1

    Default New biomass boiler - not sure about controlling it

    Hello!

    This my first post here and I need to ask for advice on heating control for a new biomass system that has just been installed. We have a wood pellet boiler " retrofitted" to an existing radiator system. The boiler is installed in our garage with a buffer tank in place of the old boiler in a utility room. Our supplier has removed the original control thermostat and we are left with just a timer controlled pump feeding the rads from the buffer tank. All rads in the house bar one in a small ensuite room are fitted with mechanical trv's.

    Is this the correct way to control the heating? The buffer tank heat is controlled via two sensors wired to the boiler control system but the rad side is as described above.

    I'm not certain that this is a efficient way to control the heating and have considered fitting wireless controlled trv's on all rads and an additional control to the circulating pump. Is this worth doing?

    Any advice on this would be appreciated

    B.

  2. #2
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    You really need to consult a Renewables specialist here as what you have described doesn't sound right.

    You can use an Evohome on your system, using the boiler relay to open a valve/pump from the buffer, you can then radiator zone as you like.
    I work for Resideo, posts are personal and my own views.

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    Quote Originally Posted by macborders View Post
    Hello!

    This my first post here and I need to ask for advice on heating control for a new biomass system that has just been installed. We have a wood pellet boiler " retrofitted" to an existing radiator system. The boiler is installed in our garage with a buffer tank in place of the old boiler in a utility room. Our supplier has removed the original control thermostat and we are left with just a timer controlled pump feeding the rads from the buffer tank. All rads in the house bar one in a small ensuite room are fitted with mechanical trv's.

    Is this the correct way to control the heating? The buffer tank heat is controlled via two sensors wired to the boiler control system but the rad side is as described above.

    I'm not certain that this is a efficient way to control the heating and have considered fitting wireless controlled trv's on all rads and an additional control to the circulating pump. Is this worth doing?

    Any advice on this would be appreciated

    B.
    What your installer has done is left the biomass system in control the buffer cylinder with its own control system and then a timer to turn your radiator circuit on and off. This is acceptable, but not the best level of comfort control you can achieve.

    My Ground Source Heat Pump runs exactly the same as your Biomass boiler does, however my central heating system is evohome controlled.

    If you need more info, give me a call but it would be very easy to fit evohome to your installation with all the advantages that come with it.

    Obviously you get paid RHI at a 'deemed' rate so if you can save on buying woodchip etc, you will make more money.

  4. #4
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    I too have a new okofen biomass boiler. It is far too clever for itself and so I believe it cannot be controlled by other AI. As the importers have no manual for it and it has about 29 different control screens I can only pay with the timer. With HG I'm assuming we will have it on 6:00 til 23:00 but have all radiators controlled by HG valves. With 2 daughters at home still there are no set times when everyone agrees to have heating on, electric heaters to up at all times and we two work from home and just rattle around the big old house.
    Should save us money though the initial cost us eye watering!

  5. #5
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    I have a similar arrangement with a Windhager boiler. It controls the loop between the buffer tank and itself and the Evohome system is the other side of the buffer. It works well and doesn't need a bypass or uncontrolled radiator as needed when the system is connected to the boiler.

  6. #6
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    I have a hot water tank but don't know enough to know if that is what you are calling a buffer tank! Do you leave yours on semi permanently and just call on it with your Evohome?

  7. #7
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    I've had an Okofen Pellematic for about a year now and its a fantastic piece of kit. In terms of control, there is a 12v relay contact you can 'call for heat' using. I don't have a buffer tank - the boiler has a 60l jacket that provides enough of a buffer for my needs. I use Heatmiser, with 3 underfloor zones, 2 radiator zones and one hot water zone. The heatmiser (via UH1's) thus manage the valves for each zone and the pump for the UFH manifold. It 'calls for heat' from the Okofen via a relay to the 12v interface, and I'm running the main system circulation pump via the Okofen directly. Thus this means the Okofen runs the main pump (and thus doesn't circulate cold water when its heating up etc)...
    This gives a good level of control; in fact most of the 'control' is actually from Cytech Comfort as I use the UCM/Heatmiser and actually control the system from there... e.g. on/off schedule, setting back when leaving home etc.
    I would have thought you could use a similar arrangement if you had a buffer tank. E.g. run the system circulation pump straight from the 'call for heat' from the UH1, and us a separate DHW zone with a dedicated call for heat for the boiler to run the buffer tank? Just a thought...

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    Quote Originally Posted by jnorris235 View Post
    I have a hot water tank but don't know enough to know if that is what you are calling a buffer tank! Do you leave yours on semi permanently and just call on it with your Evohome?
    We leave ours on 24/7 in Winter and Summer. The Evohome calls upon it whenever the radiators call for heat.

    A buffer tank, or thermal store, is a large cylinder with multiple tappings that allow the hot water to be layered. Typically, the bottom half of the tank will be used for heating radiators and the top half for hot water.

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