Most efficient boiler settings

Bendy_House

The visible steam is generally a good sign. This is the 'plume' referred to with condensing boilers, and is condensed water vapour formed from the combustion process. 
The fact you can see it immediately from the flue does suggest that 'condensing' has taken place, tho' it's hard to know how much. For example, in very cold weather, you'd likely see a plume even from non-condensing boilers simply because the freezing air condenses the steam ('steam' is invisible) as soon as it hits it.
Can you ID the flow and return pipes under your boiler? If so, a wee check can be to touch them both! The flow should be 'ouch', whereas you may be able to leave your fingertips on the 'return'. (I don't mean 'literally' leave your 'tips behind ..).
How would you describe the flow and return pipes?
Anyhoo, I have to say that your existing system must be using more gas than it should as it doesn't really appear to be controllable.
I picked up a 6-month old Hive +receiver for £50 a few weeks back. These, or a similar wireless stat, would need some knowledge to install on your boiler since you don't have an existing wall stat, but it ain't rocket science. And a sparky should be able to do this in under an hour - the receiver goes next to the boiler, and the stat in the main living area.
Mind you, if your bedroom TRVs ain't working, then...

Norman_Castle

Bendy_House said:

The visible steam is generally a good sign. This is the 'plume' referred to with condensing boilers, and is condensed water vapour formed from the combustion process. 

https://www.theheatinghub.co.uk/why-our-condensing-boilers-do-not-condense

How can I tell if my boiler is condensing?

Unfortunately your boiler cannot tell you how efficient it actually is. One of our recommendations to the UK Government via our Close The Gap campaign is for the efficiency of boilers to be digitally displayed on the boiler. Alternatively, you can fit thermostatic pipe clips to the flow and return to monitor the temperatures.

In the meantime you can look at the flue emissions. Contrary to popular belief, a sign that your boiler is condensing is an invisible discharge from the flue. A boiler is NOT condensing when white plumes are exiting the flue. This is a sign that the energy is not being recovered as the heat is lost to outside.

theoretica

When the boiler is condensing at its best most water goes down the condensate drain pipe, so the plume is much less visible. It needs to condense into liquid in the boiler to have the heat extracted and recycled.

OP, now you have turned the boiler down do the radiators feel less hot to the touch?  That is the simple test that that particular control is working.  Does the radiator stop getting warm when you screw the TRV all the way to off? To check the valve is working and not stuck.

Bendy_House

Good points, NC and Theo.

In an ideal setup - ie a boiler connected to oversized rads or UFH, I would expect much less of a plume. For many retro-fitted condensing boilers, which need to run at quite a high flow temp in order to heat the old rads as effectively as the old non-cond boiler did, there will be more visible plume, but this does not mean it isn't condensing to a fair degree. (Mine is in this ballpark - plenty plume, but also plenty liquid condensate).

You can make water vapour condense out on even a pretty hot surface, provided there is enough vapour being produced - ie the flue gases are saturated, and that is often the case.

If you compare the visible flue emissions between a cond and non-cond boiler, the non-cond would typically have an invisible emission - 'steam' - exiting the flue terminal, and - depending on the air temp - this would either become visible as it subsequently condensed in the cold air, or else got blown away, still 'invisible'.

A condensing boiler will almost always manage some condensing of the flue products before it's chucked out; this will show as a visible plume immediately exiting the terminal (and placing your hand in it would find it fairly cool).

It's quite funny, then; a non-condensing boiler will likely have an invisible flue emission. A partially condensing boiler will have visible f-es. A fully condensing boiler might revert back to invisible emisisons!

I suspect quite strongly that for any condensing boiler fitted to a retro system in the average home, a 'lack' of plume would not be a good sign; it'll be because it's running too hot.

User_Name_1

blagoslovljena said:

I have a Worcester Greenstar 30Si boiler circa 2008 that has recently had most of its innards replaced on my BG homecare contract due to a crack in the heat exchanger. I’m assuming it’s running more efficiently as a result anyway, but I heard the guy in charge of Octopus Energy on the radio the other day saying that people could save 20-30% on their heating costs just by adjusting the boiler settings.

Does anyone know what settings are most efficient for my boiler? Because it’s ancient by boiler standards it doesn’t have any digital controls, literally a dial for heating and another for hot water. Heating dial runs from 1-6, then ‘max’, and hot water the same but with a ‘min’ setting before the 1 and 5 is replaced with ‘e’. I’ve had a look around online to no avail, and the manual’s no help.

 https://www.worcester-bosch.co.uk/support/literature/download/release/8716115165/12685

"3.1.5 DOMESTIC HOT WATER PRE-HEAT The hot water heat exchanger is kept “pre-heated” to reduce the time taken to deliver hot water at the tap. Pre-heat is enabled by default, during the initial boiler start up and the ECO button is not illuminated. Eco mode is an energy saving function allowing hot water to be heated only as and when required, by running a hot tap, this OFF by default. 1. Press and hold the Eco button for at least four seconds to enter the energy saving Eco mode, when Eco mode is active the Eco button will be illuminated. "

CENTRAL HEATING SYSTEMS WITH ROOM THERMOSTAT/THERMOSTATIC RADIATOR VALVES With modern heating systems set around a 20 °C heat loss, the optimum setting for a condensing boiler will be approximately between one and two on the central heating temperature control. The system must be balanced correctly and the radiators may need upgrading. This allows the boiler to condense as much as possible for the central heating system. The temperature of each room can be set individually (except primary room with the room thermostat) using the thermostatic radiator valves.

BUFF

Bendy_House said:

If you compare the visible flue emissions between a cond and non-cond boiler, the non-cond would typically have an invisible emission - 'steam' - exiting the flue terminal, and - depending on the air temp - this would either become visible as it subsequently condensed in the cold air, or else got blown away, still 'invisible'.

A condensing boiler will almost always manage some condensing of the flue products before it's chucked out; this will show as a visible plume immediately exiting the terminal (and placing your hand in it would find it fairly cool).

It's quite funny, then; a non-condensing boiler will likely have an invisible flue emission. A partially condensing boiler will have visible f-es. A fully condensing boiler might revert back to invisible emisisons!

I suspect quite strongly that for any condensing boiler fitted to a retro system in the average home, a 'lack' of plume would not be a good sign; it'll be because it's running too hot.

I have a 13 year old Worcester condensing combi, my neighbours (in a row of terraces so nigh on identical) has a 2 year old Worcester condensing combi which in theory should be a good few % more efficient than mine. They are nice people but not the sort, I feel, to get involved in the nitty gritty of how to most efficiently run their system so I strongly suspect running higher flow/return.  My "plume" is 1/3 the size of theirs. 

User_Name_1

Looking at this booklet from viesmann it shows the big differance a well insulated house makes, it says the best insulated property can run the boiler at below 30  flow temp ,if its minus 20 outside .

https://cdn0.scrvt.com/2828ebc457efab95be01dd36047e3b52/213c10bd1531de9e/3e490822d36e/Weather-Compensation.pdf

blagoslovljena

Thanks everyone. 👍

 I’ve turned the two bedroom TRVs off and there’s still a bit of residual warmth, so I guess they’re shot (or at the very least stuck), so I’ll probably need to get in touch with BG Homecare yet again (3rd time in 5 months 😫). But on the plus side, turning them to the off position reduced the temperature in the rooms to 21C, so at least no-one’s cooking in there in the meantime.

 I contacted Worcester Bosch directly for their take on things specific to my boiler (probably should have done that in the first place tbh 🤦‍♀️), and this morning they emailed me the following:

“Thank you for your enquiry.

The below shows the approximate target temperatures set using the heating and hot water control dials.

The hot water should be set to the comfort level required for water coming out if the tap. A setting above E will mean the boiler provides hotter water but the burner will most likely be running at maximum burn for the duration of a hot water demand to achieve this.

The central heating flow temperature setting would be dependent on the temperature required to effectively heat the radiators to ensure the property reaches the desired comfort temperature. Condensing boilers are at their most efficient when the flow temperature is set to approximately 55 degrees. This would only be suitable however if the radiators have been sized to heat at a lower flow temperature. Typically radiators on older systems were sized to heat with a 70-75 degree flow temperature and so the set to the lowest flow temperature that can effectively heat your property during a heating demand.”

So on that back of this info, I’ve set my CH to 2 (it was originally on 4 before I received advice from you lovely people on this thread!), and my HW is on 2.5, which is still warming up nicely. Eco button is on, so I no longer get any pre-heat to HW, and temperature in the house with TRVs (apart from the dodgy ones) set to 2 is absolutely no different from before when boiler CH setting was higher.

I’m assuming then that I’m actually going to be saving a little bit of money compared with this time last week!

So thanks everyone for all your help, and I’ll seriously consider the room thermostat suggestion as it wasn’t something I had thought would make such a difference. 🤗

Bendy_House

Great stuff, Blag!
It does seem to suggest that your house is quite well insulated? If you can keep the house warm, and heated up quickly, with such a low flow temp, then that's really good.
If you want to check your TRVs, then we can guide you through this. It's either that the 'valve' part has seized, or the 'head' part is kaput. Heads are dead easy to swap, and the valves usually respond well to being eased.
Just ask. You know you want to... :-)

BikingBud

TimSynths said:

"Off".                           .

Whilst this is clearly true and perhaps not the advice the OP was wanting I do wonder how serious people really are about saving energy when they have 21/22 deg during the day and only roll back to 20 deg at night. 

No need to go to extremes but setting 18/19 and possibly 15 at night might make a massive difference to bills with very little real discomfort.