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  • FIRST POST
    • 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 2
    • Pincher
    • By Pincher 10th Oct 16, 12:12 AM
    • 5,846 Posts
    • 2,133 Thanks
    Pincher
    I've been looking at the different bits of the Wave app and I was wondering what weather compensation does?
    Originally posted by marks87
    My Glowworm just gives me Profile modes 1,2,3 and maybe 4 to choose from.

    About twenty years ago, I was with a German, trying to figure out the boiler controller for his apartment building, about four flats are supplied from the basement boiler. It was a PID ( Proportional Integral Differential ) controller! The Differential is really wild! It reacts exponentially to RAPID change in external temperature.

    Well, the neighbours can open the windows if it gets boiling hot.

    this system doesn't have its own external sensor but instead uses several online weather sources to determine the temperature.
    Originally posted by marks87
    That is so clever: so is it actually connected to the internet?
    Or does it have its own GSM connection?

    This is what an outdoor sensor looks like:

    https://www.plumbnation.co.uk/search.php?search=outdoor+sensor

    Supposed to be out of sunlight to avoid false readings.

    I bought my own, then the Gas Safe engineer wired it wrong anyway, so the boiler never enabled weather compensation, until I ended up redesigning the whole thing. He also fried the first Programmer by wiring it like a three wire thermostat into 230v AC.
    What happens if you push this button?
    • marks87
    • By marks87 10th Oct 16, 12:40 AM
    • 146 Posts
    • 28 Thanks
    marks87
    All boilers these days are condensing boilers. It is important to understand that they operate most efficiently when they are in condensing mode. There are thousands of websites that explain the principle of a condensing boiler but this is sufficient:



    To get the water temperature returning to the boiler as low as possible, the output temperature should be as low as possible; and that essentially is the purpose of weather compensation. It senses the outside ambient temperature and adjusts the boiler water temperature.
    Originally posted by Cardew
    So basically, using weather compensation is good because it should allow the boiler to be more efficient? That's good to know.

    That is so clever: so is it actually connected to the internet?
    Or does it have its own GSM connection?
    Originally posted by Pincher
    It's internet-connected via WiFi. Nearly all settings are via an app that works from anywhere (so for instance the timer setting can be adjusted if we're going to be home earlier or later than expected, to avoid the house being cold/the heating being on unnecessarily).
    • Pincher
    • By Pincher 10th Oct 16, 3:56 AM
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    Pincher
    So basically, using weather compensation is good because it should allow the boiler to be more efficient? That's good to know.
    Originally posted by marks87
    In its true form, weather compensation is about temperature stability, used on the industrial scale, to avoid spoiling the product in reaction chambers. By anticipating heat loss, you add heat to maintain a set point (temperature) within a precise range.

    I have a 30kW boiler, which is great for heating up hot water quickly, but I could probably run the central heating on a 10kW boiler, which will condense more.

    You can run a simple boiler manually at 50 degrees just by turning a knob, or dialing the output down, and still have lots of condensation.
    What happens if you push this button?
    • matelodave
    • By matelodave 10th Oct 16, 8:37 AM
    • 2,584 Posts
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    matelodave
    My heating system has weather compensation which adjusts the central heating flow temperature in accordance with the outside temperature - so when it's cold, say 0 degrees then the flow temperature is about 40 degrees. When it's a not so cold say 10 degrees then the flow temperature is reduced to around 30 degrees. This balances the difference in heat loss from the house.

    We've got a heat pump which feeds underfloor heating so the flow temperatures are a lot lower than a system with radiators. It does mean however that the house is a lot slower to react to rapid temperature changes and takes a long time to heat up.

    The system is running virtually continuously but at a low level and as we are at home all day this suits us. The room temperatures are only reduced by about 3 degrees overnight.

    Each room has it's own programmable thermostat so their temperatures are adjusted to suit their useage. ie bedrooms & bathroom is only turned up during the mornings and bed time, whereas the study and living room are on all day.

    Hot water is only heated to 45 degrees to maximise the efficiency of the heatpump
    Love makes the world go round - beer make it go round even faster
    • stevegrass777
    • By stevegrass777 10th Oct 16, 10:15 AM
    • 50 Posts
    • 19 Thanks
    stevegrass777
    If you want the rest of the house a bit warmer leave the living room door open a bit,that door is your control over the temperature of the rest of the house,if you are happy to have the rest of the house a bit cooler to save money keep the door shut,if you are needing the rest of the house a bit warmer just open the door a bit,if you want it warm throughout the house open it wide.
    It's that simple.
    • Pincher
    • By Pincher 10th Oct 16, 10:32 AM
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    Pincher
    Hot water is only heated to 45 degrees to maximise the efficiency of the heatpump
    Originally posted by matelodave
    Legionella?
    What happens if you push this button?
    • matelodave
    • By matelodave 10th Oct 16, 11:09 AM
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    matelodave
    No because it automatically heats it up to 60 degrees for half an hour every Saturday to avoid it and as the tank is well insulated it doesn't need to be reheated on Sunday so it really doesn't cost us any more.

    However I don't really understand how I can get legionella into the system as it's fed directly from the cold water mains which is well chlorinated and the system is sealed & pressurised. It doesn't have any open tanks for it to get in.

    Is there any evidence of legionella in the water systems of domestic premises? or is it another H&S bandwagon
    Last edited by matelodave; 10-10-2016 at 3:18 PM.
    Love makes the world go round - beer make it go round even faster
    • Pincher
    • By Pincher 10th Oct 16, 7:25 PM
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    • 2,133 Thanks
    Pincher
    Is there any evidence of legionella in the water systems of domestic premises? or is it another H&S bandwagon
    Originally posted by matelodave
    Forty years ago, I found a pigeon in the loft cold tank.
    It had a lid, total mystery to me how it got in there.

    Why do they bother with the oxygen mask above my seat?
    Will it really save my life if something happened?

    It's when you are sitting in a third world bread van, packed full of backpackers, driving on the edge of a precipice, that you really appreciate the insistence on MOTs and that brakes should work.
    What happens if you push this button?
    • marks87
    • By marks87 11th Oct 16, 10:25 AM
    • 146 Posts
    • 28 Thanks
    marks87
    The morning and evening temperatures have been colder these past couple of days and with weather compensation enabled the system seems to be doing what we kind of expected central heating to be like.

    The timer kicks in at 7am then 5pm, heats all rooms (up to the TRV setting, except the Living room natch) then keeps a small heat flowing to maintain it for the rest of the morning/evening.

    On the first night the living room got a bit too hot while the other rooms were comfortable, but with none of the TRVs fully-open. So I set the room influence to "medium", and yesterday it was much more balanced.

    The only thing now is that the boiler seems to be always "on" (electrically) whereas previously it would only come "on" intermittently. But I guess the electrical consumption is minimal, and the efficiency savings for using weather compensation (and thus better condensing) offset it?

    The issue we now have is that our energy plan is ending and we need to find a new one. But we have no idea how much gas and electric we're going to use I guess, though, using the Ofgem "estimated" figures will work because even if we don't know the absolute energy use, having a rough idea of the balance between gas and electric will produce the best deal in terms of unit price, even if the headline figure isn't quite right.
    • Pincher
    • By Pincher 11th Oct 16, 1:41 PM
    • 5,846 Posts
    • 2,133 Thanks
    Pincher
    The traditional central heating was based on a clicking thermostat, which has a relay contact switch, which is either ON or OFF. This meant the boiler (non-condensing) was either on or off.

    This meant the room temperature was up and down, and the plot of the temperature was a saw tooth wave form. ON the thermostat clicks, the boiler heats up to 20 degrees, then OFF it clicks, and the house cools down to 18 degrees, then ON it clicks, and so on.

    In a weather compensation set up, you are accepting the fact that the house is losing heat at a rate of 5kW (or whatever, depending on your insulation), so the boiler simply supplies heat at 5kW, ALL the time. The extra refinement is, when the outside is 2 degrees, the controller decides to output at 6kW, in anticipation of greater heat loss.

    The Wave app should allow you to configure how sensitive the reaction to temperature change is.

    By being on a continuous simmer, the boiler is condensing all the time.

    I was horrified to find that the Gas Safe engineer tried to install the Glowworm based on a clicking on/off thermostat, because that was all he knows!

    Died in his sleep about three years ago. Rest in Peace, and be happy in an analogue heaven, none of this fandangled digital non-sense.
    What happens if you push this button?
    • lstar337
    • By lstar337 11th Oct 16, 3:34 PM
    • 2,866 Posts
    • 1,469 Thanks
    lstar337
    I was horrified to find that the Gas Safe engineer tried to install the Glowworm based on a clicking on/off thermostat, because that was all he knows!
    Originally posted by Pincher
    We have a gas safety inspection every year because we rent. The guy that does it doesn't seem to understand our boiler either. I have set it up on a very low output which is perfect for us because the house is A rated so it doesn't need a lot of heat, and it keeps the boiler condensing because of the low return temperature.

    Every time he gets his hands on it he writes a note at the bottom of his report saying "returned boiler to optimal settings". These "opimal settings" are nothing more than cranking the output temperature to the absolute max and setting it to always on so it ignores my timers!

    Now not only do his "optimal settings" stop the boiler from ever having a chance at condensing, but is also results in radiators that burn to the touch, and a house that is like a sauna!

    Now I'm pretty sure he looks at my boiler settings and thinks "Idiots been messing with the boiler again", but to me it is he that is the idiot! He clearly has no idea how the boiler should be set.

    Next time I will leave a note telling him the boiler settings are to be returned to how I had them prior to his tests!
    • matelodave
    • By matelodave 11th Oct 16, 3:44 PM
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    matelodave
    I don't know how the Worcester set up works, but ours is different insofar as it anticipates that if I want, say 20 degrees in the lounge and it's 0 degrees outside then it supplies water at around 40 degrees to compensate for the 20 degrees temperature difference between inside and outside.

    If however the outside temperature is only 10 degrees, then the difference is less so the room loses less heat so the system reduces the water temperature to around 30 degrees to maintain the same temperature so it's not flogging away at it's rated output but reducing it to balance the heat loss.

    I'd guess that a modern boiler with a modulating burner and weather compensation would do somewhat similar, just supplying enough heat to balance the heat loss.

    It took me a while to tweak the weather compensation slope (outside temp/water temp) to balance the heat loss but it works pretty well as I can continuously record the power consumed by out heating system and see the difference.

    It's a bit frightening when it's below freezing outside and we get through 40-50 kwh of leccy a day in say December to February but our annual energy consumption averages out at around 18kwh a day overall.
    Love makes the world go round - beer make it go round even faster
    • weddingringman
    • By weddingringman 11th Oct 16, 3:48 PM
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    weddingringman
    (Sorry for hijacking your thread!)

    We have an ideal logic combi, which has a temp dial for the heating and one for the hot water. We have TRVs on all radiators.... but no thermostat!

    When our heating is 'on', does this mean our boiler runs periodically to ensure the temperature of the water in the radiators meets that set on the boiler dial..... or is our boiler running flat out while the heating is 'on', screaming "help... theres no thermostat!!! What do I do!!!? Arghghgh!!!".

    The installer said a thermostat wasnt essential....
    • CashStrapped
    • By CashStrapped 11th Oct 16, 3:56 PM
    • 857 Posts
    • 477 Thanks
    CashStrapped
    When our heating is 'on', does this mean our boiler runs periodically to ensure the temperature of the water in the radiators meets that set on the boiler dial..... or is our boiler running flat out while the heating is 'on', screaming "help... theres no thermostat!!! What do I do!!!? Arghghgh!!!".

    The installer said a thermostat wasnt essential....
    Originally posted by weddingringman
    It is not essential, just an automated labour saving device that can have efficiency savings if you no not use the boiler controls effectively in a manual fashion...

    The thermostat just turns the boiler on and off at a specific set temperature.

    See this thread posted today asking the exact same question....

    http://forums.moneysavingexpert.com/showthread.php?t=5539304
    • hawkwind
    • By hawkwind 11th Oct 16, 4:39 PM
    • 199 Posts
    • 69 Thanks
    hawkwind

    Combi boilers side note: Modern combi (or any modern condensing boiler) boilers work more efficiently when the system is used at the lowest temperature (controls on the boiler) possible to keep the house warm. Therefore there is an incentive to run the central heating system at a warm temperature for longer rather than very hot for a short period(s). This is because it allows the condensing part of the boiler to recover more waste heat. This will improve boiler efficiency. This only happens at a lower temperature.

    I hope that helps!
    Originally posted by CashStrapped
    With regards to this part, i have a Glow-Worm Easicom 28w combi with the heating set to 70 degrees C on the boiler.
    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.
    What would be the lowest temperature you would recommend setting it to.

    All radiators have TMV`s apart from the bathroom and we have a wireless Myson plus MPRT RF wireless room thermostat that can be placed in any room we like.
    Last edited by hawkwind; 11-10-2016 at 4:49 PM.
    • CashStrapped
    • By CashStrapped 11th Oct 16, 5:17 PM
    • 857 Posts
    • 477 Thanks
    CashStrapped
    With regards to this part, i have a Glow-Worm Easicom 28w combi with the heating set to 70 degrees C on the boiler.
    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.
    What would be the lowest temperature you would recommend setting it to.

    All radiators have TMV`s apart from the bathroom and we have a wireless Myson plus MPRT RF wireless room thermostat that can be placed in any room we like.
    Originally posted by hawkwind
    Yes, in theory.... yes.

    Running your boiler at a lower temperature for longer, rather than very hot (and therefore very hot radiators) for short periods should be more efficient.

    Basically you are trying to maintain a temperature at the same rate heat is lost from the house. This should, in theory, be the most efficient way to heat a house. So the minimum temperature required to do this, should be the most efficient. The more insulated the house, the easier this is to achieve.

    What many people do is have the boiler on very high under the impression it heats the house quicker and faster and is not on for long. This means the radiators are red hot for short periods. The boiler cycles (turns on and off more often), which wastes heat and gas. Furthermore the return temperature of the water to the boiler is so high that condensing never actually takes place much. This makes a condensing boiler pointless as it is not doing what it is designed to do.

    That's the idea basically. In practice there can be a lot more variables. Every house and person is different. Some people like a very warm house which can make this approach more difficult if the set-up is not well designed. For example, undersized radiators may need to be much hotter to maintain a rooms temperature.
    Last edited by CashStrapped; 11-10-2016 at 5:28 PM.
    • hawkwind
    • By hawkwind 11th Oct 16, 5:40 PM
    • 199 Posts
    • 69 Thanks
    hawkwind
    Thank you for the reply
    I have turned the boiler down to 60C so i will see how everyone feels later tonight once the heating is back on.
    • Cardew
    • By Cardew 11th Oct 16, 7:17 PM
    • 26,059 Posts
    • 12,529 Thanks
    Cardew
    Thank you for the reply
    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 will make no difference to the temperature in your room/house; provided you have left the TRVs at the same setting.

    Turning the water temperature down from 70C to 60C will mean the room will take a little longer to reach the required room temperature. However as stated above it should mean the boiler is operating in a slightly more efficient mode.
    • hawkwind
    • By hawkwind 11th Oct 16, 7:56 PM
    • 199 Posts
    • 69 Thanks
    hawkwind
    Yes thanks TRV`s are at the same setting as before, no complaints from anyone so everyone happy especially me if i am saving money
    • Pincher
    • By Pincher 11th Oct 16, 10:40 PM
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    • 2,133 Thanks
    Pincher
    Next time I will leave a note telling him the boiler settings are to be returned to how I had them prior to his tests!
    Originally posted by lstar337
    Good luck.

    I realised long ago that passing exams doesn't mean they understand anything. They learn to do Y-Plan and S-Plan, without really understanding why and that is what they live on for years. It's only when things go wrong and a Third Dan Guru Plumber passes on his wisdom, then they realise why they do what they do.

    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.

    The problem is, nobody understands how it works except me, so if anything goes wrong, I'll have problems getting an engineer willing to touch it.
    What happens if you push this button?
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