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    • marks87
    • By marks87 6th Oct 16, 12:06 PM
    • 146Posts
    • 28Thanks
    marks87
    Help me understand our central heating!
    • #1
    • 6th Oct 16, 12:06 PM
    Help me understand our central heating! 6th Oct 16 at 12:06 PM
    We had a brand new central heating system installed at the start of the week, and it's the first time we've had CH (old house + lack of funds =ed costly electric ).

    Anyway, the plumber explained the basics of how the system works and how you control the temperature. But we're still not entirely sure how to get the optimal settings for the whole house, so I was hoping someone on here could explain in reasonably simple terms!

    We have radiators throughout the house with TRVs, except in the living room where the thermostat is - I believe this is normal, yes? We can then set or programme a temperature for the boiler to then kick in and start heating the house. The TRVs can then be used to control the temperature in the other rooms. That's straightforward enough.

    What's confusing is is what happens if, say, we have visitors and the living room gets warm enough to cut the boiler based on the temperature detected by the thermostat? Does that mean the rest of the house will be cold because the living room is too hot? If so, what's the solution? Or have I completely misunderstood.

    My gut feeling is that the system must work to heat the whole house somehow, including hotter and colder rooms - otherwise, nobody would ever want it. But being CH n00bs, we don't quite yet understand it!

    The thermostat we have is a Worcester Wave, if that makes a difference to how things work.
Page 3
    • lstar337
    • By lstar337 12th Oct 16, 9:20 AM
    • 2,873 Posts
    • 1,470 Thanks
    lstar337
    Should i be setting this temperature lower then to make my boiler more efficient providing it is enough to still heat the house of course.
    Originally posted by hawkwind
    As CashStrapped says, yes. A lower temperature for longer heating period will be more efficient for a condensing boiler. Note: This is not an advocation of the "heating on all day is better than using timers" theory. It is never good to heat when you are not in.

    What would be the lowest temperature you would recommend setting it to.
    Originally posted by hawkwind
    Quite simply as low as you can go. Just make sure the output is enough to keep up with your house losses.

    Your aim is to have the return temperature at 55c or below. I stuck a thermometer on the return pipe to check mine.

    I have a well insulated house so it doesn't take much output to keep it warm all day. In winter I have a 1 hour heating period in the morning, and a 1 hour heating period at 6:30. My boiler temp is set a 50c, which means it is always condensing because the return will always be lower than that.

    I have turned the boiler down to 60C so i will see how everyone feels later tonight once the heating is back on.
    Originally posted by hawkwind
    That's a good start, but you may find you can go lower than that. I adjusted mine very slowly over a number of weeks and found I could go much lower than I thought.

    Give it a try.
    • hawkwind
    • By hawkwind 12th Oct 16, 10:34 AM
    • 199 Posts
    • 69 Thanks
    hawkwind
    Thank you, i will try lowering the boiler temperature then until i strike a happy balance.
    Our house is not a very warm house, end of the row with with 3ft thick walls, the loft is well insulated and earlier this year we had the central heating system installed along with new windows and doors fitted which should go a long way to help keep the heat in compared to previous years gone by.
    • qsk
    • By qsk 12th Oct 16, 11:31 AM
    • 131 Posts
    • 81 Thanks
    qsk
    I designed the system to handle radiators and underfloor heating, plus two hot water cylinders, so it has four zone valves, with a 230V Honeywell two channel programmer, AND a zero volt Glowworm Climastat programmer. Way beyond the Gas Safe engineer's comfort zone, so he called Glowworm. They actually sent an engineer. He didn't understand it, but at least he didn't say no.
    Originally posted by Pincher

    What output temperature do you set your boiler to?
    I have a Worcester CDi Combi to service heating as well as an unvented cylinder through a Y-plan. The Combi's Eco temperature is about 40. However this is not sufficient to heat my cylinder which has temperature set to 60. So I increase the boiler's output temperature to 70 (nearly maximum). But based on discussion in this thread, this is apparently not optimal. Is there any way I can improve it?
    • Cardew
    • By Cardew 12th Oct 16, 11:55 AM
    • 26,077 Posts
    • 12,538 Thanks
    Cardew
    What output temperature do you set your boiler to?
    I have a Worcester CDi Combi to service heating as well as an unvented cylinder through a Y-plan. The Combi's Eco temperature is about 40. However this is not sufficient to heat my cylinder which has temperature set to 60. So I increase the boiler's output temperature to 70 (nearly maximum). But based on discussion in this thread, this is apparently not optimal. Is there any way I can improve it?
    Originally posted by qsk
    I don't understand what you mean by an unvented cylinder which 'has the temperature set to 60'

    unless you mean the immersion heater is switched on and set to 60C.

    An unvented cylinder - like any other hot water cylinder - will simply heat up to the output temperature of the gas boiler. e.g my boiler is set to provide hot water to my unvented cylinder at 50C and that is the maximum temperature it will reach. If I turned the boiler down to 40C, or up to 60C, that is the temp the cylinder will reach. Naturally the immersion heater is switched off.
    • qsk
    • By qsk 12th Oct 16, 2:26 PM
    • 131 Posts
    • 81 Thanks
    qsk
    Many thanks Cardex for your response.


    Unless I misunderstood, my cylinder (Santon Premier Plus 210L) has two thermostats: one for direct/immersion and one for indirect/boiler. Both are set at 60 degrees (manufacture recommended temperature). Like you I normally use indirect/boiler to heat the cylinder. The indirect thermostat will turn on the boiler on demand and turn it off when the water reaches 60. I used to rely on it to start/stop boiler, which seemed to have worked fine (the cylinder has good insulation). My old boiler has the output set to 80 so it can bring the cylinder to 60. But if the output of boiler is 40, it can never take the cylinder to 60, which means that boiler will be on all the time. Because of this, I have to add a timer to control the cylinder's demand for indirect/boiler. I am still not sure what's the recommended way to control the cylinder's demand though, thermostat as I had before or timer as I'm having now? Do you use a timer for your cylinder?
    • Pincher
    • By Pincher 12th Oct 16, 3:14 PM
    • 5,860 Posts
    • 2,143 Thanks
    Pincher
    What output temperature do you set your boiler to?
    I have a Worcester CDi Combi to service heating as well as an unvented cylinder through a Y-plan. The Combi's Eco temperature is about 40. However this is not sufficient to heat my cylinder which has temperature set to 60. So I increase the boiler's output temperature to 70 (nearly maximum). But based on discussion in this thread, this is apparently not optimal. Is there any way I can improve it?
    Originally posted by qsk
    The Glowworm has a free hand to optimise for condensation as much as possible, forcibly fixing a boiler output temperature is unnecessary.

    Obviously, to maintain a room temperature of 20 degrees, the boiler needs to vary output to match heat loss.

    For domestic hot water, its amazing! In order to heat the cylinder water, the boiler output needs to be higher, but it doesn't need to be 85 degrees if the cylinder water is at 18 degrees. So the Glowworm outputs at say 55 degrees to begin with, so it can still condense, but increase to 85 degrees near the end. I assume it measures the return flow from the cylinder so it can work out how hot the cylinder water is.

    The cylinder stat is an electrical contact relay.
    When the cylinder water temperature is below the set point, in your case 60 degrees, the relay closes, and makes contact. In a normal setup, this means a "demand for heat" to the boiler.

    Obviously, for heating a cylinder, you will need very hot output, whereas you want nice and low output for central heating, to encourage condensation.

    For really ancient no-condensing boilers, it is possible you had just one boiler output, which is used for both, but these days, you need to tell the boiler it's working on heating a cylinder, or keep it low for central heating.

    With a combi, the default set up is NO CYLINDER, so I suspect it will only do condensation friendly low temperature output, UNLESS you went to the manufacturer's training course, and know the "other" way to wire it.

    Having a cylinder and a combi is a non-standard set up.
    Maybe you had a one trick pony plumber who cobbled together a system based on partial knowledge. Just ask: "How does the boiler know it's heating hot water, and not central heating?"
    What happens if you push this button?
    • qsk
    • By qsk 12th Oct 16, 3:45 PM
    • 131 Posts
    • 81 Thanks
    qsk
    Thank you very much Pincher for the indepth explanation. Much appreciated.

    When I first had the heating system installed many years ago, I was aware that Combi + Unvented Cylinder is not a standard setup. I wanted a bit flexibility that I would still have hot water even if one of them fails (HW from Combi services ground floor taps plus a shower) but missed the point that the two circuits need different output temperature:-(

    Seems I have no choice but set the boiler output to be high (70) in order to service both heating and cylinder. Hopefully that will not shorten the boiler's life.
    • lstar337
    • By lstar337 12th Oct 16, 4:55 PM
    • 2,873 Posts
    • 1,470 Thanks
    lstar337
    Seems I have no choice but set the boiler output to be high (70) in order to service both heating and cylinder. Hopefully that will not shorten the boiler's life.
    Originally posted by qsk
    Or have cooler water at the taps. Do you really need 60c at the taps?

    I would think 45-50 would easily suffice.
    • Pincher
    • By Pincher 12th Oct 16, 7:40 PM
    • 5,860 Posts
    • 2,143 Thanks
    Pincher
    Seems I have no choice but set the boiler output to be high (70) in order to service both heating and cylinder. Hopefully that will not shorten the boiler's life.
    Originally posted by qsk
    Or find a Gas Safe engineer who knows how to do it the correct way.

    Maybe it just needs a re-wire.
    What happens if you push this button?
    • qsk
    • By qsk 13th Oct 16, 8:20 AM
    • 131 Posts
    • 81 Thanks
    qsk
    Or have cooler water at the taps. Do you really need 60c at the taps?

    I would think 45-50 would easily suffice.
    Originally posted by lstar337
    60C is for HW in cylinder which supplies HW for two bathrooms (showers etc).
    HW from my boiler itself is set for about 40C.
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