New central heating installation running advice

meat_n2_reg

Hello
Recently had a Worcester Bosch 4000 combi boiler and new rads fitted to my 3 bed semi 
Boiler came with central heating flow control set to 65c have adjusted to 60c at 65c boiler runs for approx 40 mins to get to required temp (19c) , at 60c runs for 1hr to get to same temperature, so extra 20 mins
Heating schedule is on for 2.5 hours morning and night as at work during day and after initial heat the boiler does not kick in again to call for heat for rest of schedule
I have no issue with slower heat up time at 60c , just unsure if boiler running for extra 20 mins compared with 65c is actually going to cost more for my usage pattern

Any help appreciated

Reed_Richards

I'm surprised that your installer was allowed to install a system intended to run at 65 C, they should be aiming for 55 C or less with the radiators sized appropriately.  However, to answer the question, the boiler will use more energy heating the water to 65 C and maintaining it at that temperature than it will do heating the water to 60 C.  It will also run more efficiently at the lower temperature.  So in principle the lower temperature setting is better.  But you don't have to take my word for this, simply read your gas meter before the boiler turns on then after it has turned off again and you can see for yourself.   

FreeBear

meat_n2_reg said: I have no issue with slower heat up time at 60c , just unsure if boiler running for extra 20 mins compared with 65c is actually going to cost more for my usage pattern

The lower the flow (actually, the return temperature), the greater the efficiency of the boiler. Assuming you are getting a 10°C drop in the return temperature, at 65°C flow, you'll be around 88% efficient. At 60°C flow, efficiency will be ~90%. Not a huge amount, but if you can get the return temperature down to 30°C, efficiency increases to some 97%. But to use low flow temperatures and still maintain a reasonable level of comfort requires larger radiators (and a decent level of insulation helps) - Who ever fitted the new boiler & radiators should have done a proper heat loss calculation and sized the radiators appropriately. Were larger radiators fitted ?

A 2% increase in boiler efficiency isn't going to save you anything by running the system for an additional 20 minutes (it will probably cost you more) - You can confirm this by taking gas meter readings before/after each run.

Scot_39

IIRC Some firms were suggesting even lower last winter - seem to remember reading Octopus advice last winter was to turn the radiators down to 50C and the hot water - combi not tank to 55.

Mentioned here 
https://www.moneysavingexpert.com/utilities/energy-saving-tips/


The govt was suggesting many boilers were set as high as 75 to justify savings at it's recommended 60 iirc.


And hopefully a modern install would cope fine - as you could end up ideally want to maybe be running even lower when that gas boiler replaced by ashp  - to help boost its COP rating - depending on design.

And their may be ways to get that heat at lower temperatures into your rooms quicker anc still save - e.g. by using bespoke radiator fans - according to some posts here.

FreeBear

Scot_39 said: IIRC Some firms were suggesting even lower last winter - seem to remember reading Octopus advice last winter was to turn the radiators down to 50C and the hot water - combi not tank to 55.

Currently running my CH system at 50°C and DHW at 45°C, but it is early days with the new boiler, and I'm still tuning the controls. Will have a better idea of how efficient the heating is once the weather turns cold.

meat_n2_reg

Thanks for your replies, British Gas speced the boiler and radiators so hopefully should be fit for purpose
House is a 60s semi , just replaced all double glazing with new , need to get cavity walls insulated and loft is insulated but probably could do with more 
Will check usage figures and see how it goes 

Scot_39

45C seems perhaps a bit too low for hot water - especialky if not using all taps regularly (*).

Cannot remember last time run bath tap for instance.

Iirc 50C at the tap is a normal min recommended for hot water distribution for issues like legionella.

And that I suspect is where boilers at 55C come from.

(*) Our office / factory services team had to flush some pipes after long shutdowns under govt regs / HSE advice - cannot remember exact period - but 1 week with no flow springs to mind - ensuring each ran hot. (Edit after week summer and 10-12 datpy Christmas shutdowns for factory and Xmas for offices)

Certainly know they did the showers - not sure about all taps - but in theory ...

I'm more worried given have an open (to loft tank) vented cylinder   - than I would be with a combi or even pressurised closed tank. 

Paranoid perhaps - but ....

meat_n2_reg

FreeBear said:

meat_n2_reg said: I have no issue with slower heat up time at 60c , just unsure if boiler running for extra 20 mins compared with 65c is actually going to cost more for my usage pattern

The lower the flow (actually, the return temperature), the greater the efficiency of the boiler. Assuming you are getting a 10°C drop in the return temperature, at 65°C flow, you'll be around 88% efficient. At 60°C flow, efficiency will be ~90%. Not a huge amount, but if you can get the return temperature down to 30°C, efficiency increases to some 97%. But to use low flow temperatures and still maintain a reasonable level of comfort requires larger radiators (and a decent level of insulation helps) - Who ever fitted the new boiler & radiators should have done a proper heat loss calculation and sized the radiators appropriately. Were larger radiators fitted ?

A 2% increase in boiler efficiency isn't going to save you anything by running the system for an additional 20 minutes (it will probably cost you more) - You can confirm this by taking gas meter readings before/after each run.

Radiators were original 1970s single pane radiators which struggled to heat rooms
New radiators similar size but alot are P+ radiators 

matelodave

TBH I think there is a lot of paranoia about legionella, especially in a domestic environment and even more so when you've got a non-vented or combi boiler.

Water from the mains has a fair amount of chlorine in it  which kiills legionella before it even get into your hosue and I guess in most houses there's a reasonable throughput of clean fresh water.

Perhaps not so much if you've got an open vented system with a tank in the loft where the water can sit for a few days festering gently, when a weekly or fortnightly temp boost to 60 will do the trick.

Its different in multi occupancy building like hospitals, care home s and even factories where there are long pipe runs and shared washing facilities.

I just think that people need to get a sense of perspective about it when trying to compare H&S advice to a factory, hospital or care home and then try to translate it to a domestic environment.

We heat our tank to 45 degrees which is more than hot enough for us and have a good throughput from the mains via our non-vented tank. The system does a sterilisation boost once a week. There is no need to keep the tank red hot 24 hours a day, nor in my opinion do you need to run a combi at 60+

We can also run our central heating at around 30-35 degrees, but that's because we are at home all day, have underfloor heating and dont need it to reheat the place quickly.

Going back to the OP's original query, the only way to get a handle on what is going on, is to monitor your system, take daily readings of your gas meter for at least a week to get some idea of your consumption and  then tweak the temps down a bit and do it again. Rinse and repeat weekly until you've optimised your heating and reheat recovery times at the lowest temperature that you can get away with.

You do need to take into account the weather as well - we've had outside temperature differences this week between 2 degrees and 17-18 degrees in the course of 24 hours.

FreeBear

matelodave said: TBH I think there is a lot of paranoia about legionella, especially in a domestic environment and even more so when you've got a non-vented or combi boiler.

With some 400-500 cases reported each year in the UK (about half contracted overseas), the risk is extremely low. If the same degree of paranoia had been show towards Covid when it first kicked off, we could have probably avoided many of the lockdowns & restrictions that were imposed.