Boiler Firing - But Why ?!

GuidonTheBee

Apologies if this is waffly but I dont really know what I'm talking about (Nothing changes ...:o ) I'm experimenting with my heating/hot water settings to find the minimum necessary 'on' time to meet my requirements.

So far I've discovered that I cant have the heating on without the hot water on too (I've got a thermal store thingy & the instructions do say this, but it seems frustrating as at this time of year I dont need any hot water after early evening, but occasionally its still cool enough to want a tad of heating later in the evening)

So - I have the CH on in the evenings, but with the thermostat set lower than the room temp (as the last few evenings have been quite warm). I dont want heating (unless the thermostat triggers) & I dont want any hot water - so is there a reason why the boiler is firing constantly ?!

I seem to be burning a load of gas just because I want my CH on in case the temperature drops low enough to trip the thermostat. Surely if I program HW off & CH on but the room temp is higher than the thermostat I shouldn't have to be using expensive gas ??

Stormy

Hi,

My system is very similar to yours and I am too looking for ways to save gas, it seems the system is not very versatile (Thermal Store) because the boiler will always be heating the water tank upto 75c (or whatever your tank is set to - There should be a Thermostat on your tank to allow you to adjust it)

My tank at the moment is at 55c as I am not using the heating, and not actually in the house alot at the moment. Once I moved in full time I am going to have a play with the thermostat on the tank to see what the best setting is when I am only using small amounts of hot water, and not much heating.

Like you I would like to heat my tank just when I need hot water, and not all day long but with a Thermal Store the tank is always heated by the boiler whether you want it or not. I don't think there is a way to stop this, I thought about some timer or something but am not sure how it would work.

The room thermostat for your central heating doesn’t control the boiler; it controls the central heating circulation pump, which is attached to your Thermal Store Tank. So when the temperature in the house drops, the room stat triggers and this circulation pump dishes water out to the radiators.

The hot water is basically your cold rising main, fed through the tank in a heat exchanger to heat the cold water, the benefit of this is mains pressure hot water.

Your boiler will constantly be topping up the temperature in the tank when it drops, but it should only do it occasionally, or when you run the heating or use hot water. How often is it firing?

Does your tank have pre-factory installed foam coating? If not get a tank jacket for it, also lag all the pipes in your airing cupboard (or where you tank is) with the standard foam pipe lagging you can buy from B&Q (15mm or 22mm etc)

Hope some of this helps,

Mike

GuidonTheBee

Thanks for that Stormy - I'll be studying your response in depth :beer:

The boiler seems to be firing pretty much constantly - whenever the HW is on or whenever the CH (& therefore the HW as well !) is on. It goes for a few minutes then stops briefly (maybe half a second) before it starts up again. Surely the 'store' cant be loosing heat rapidly enough to require a constant top up ??

However - you're right to flag the lagging. Its a new build & the tank is just a massive copper cylinder. I'm surprised as my previous house was a new build (but with a regular tank) and it was one of the pre-insulated ones. I added an extra jacket & for 2 adults & a tiny I only needed to have the HW on for 15 mins every morning. Lagging is definately on my 'to do soon' list.

Have tried turning cylinder thermostat down (mostly as HW is too hot out of the taps & with a toddler around I'd prefer it down a bit) but then shower doesn't get hot enough. I hate not understanding how my own house works !!

I'm beginning to wish the builders had just put 'normal' heating in ...

gavinp

A lot of showers have an adjustable upper temperature limiter so you may find that you need to increase this if you want to reduce the cylinder stat.

Another thing worth considering if you don't have one (in addition to lagging the cylinder) is swapping a manual thermostat with a digital one. We have a "normal" system but the boiler fires far less now the thermostat was changed to a digital one although I suppose it is possible that our old manual one was faulty (although it certainly didn't seem to be).

Thanks

Gavin

Stormy

Hi again,

Is your tank in the airing cupboard? There should be a Thermostatic Blender Valve for the hot water, a plastic cap may be covering it but you should be able to unscrew it (It may say something like HOT / COLD / MIX on the various pipes inlets.

The Thermostatic Blender Valve allows you to control the temp of your hot water, basically it lets you feed an amount of cold water to mix with your hot feed from the tank. Mine actually doesnt work as the valve is broken but with it just being me in the house and no little ones its not a problem. (I will replace the valve at some time but they seem quite expensive and mine seems no standard in its layout )

What temp did you lower your tank to when the shower was not hot enough?

Your boiler does seem to be firing up too much, even discounting the jacket.

Mine usually fires up a) when I am running the central heating (it fires up usually when I run the heating, as the hot water from the tank gets circulated in the rads, it will then top up the heat while the central heating is running. b) After I have ran off some hot water (for maybe 5 minutes). c) to top up the tank temperature when the temperature in the tank drops naturally.

It doesnt seem to come on then go off only to come on a second later, the whole benefit of Thermal Stores is supposidly the "long" burn times of the boiler not needing to cycle constantly. Yours seems a bit strange but I am no expert, I only learnt about my system a few months back. I have not started using it in anger.

Mike

Andy_Davies

GuidonTheBee wrote:

I'm beginning to wish the builders had just put 'normal' heating in ...

But then you'd have really crappy shower pressure...

We've got a thermal store and it's great - Given the choice I wouldn't have anything else now.

Does appear like there's something wrong with yours as the boiler shouldn't be firing all the time, if it's a new house any chance of getting the builders to get the plumber back in?