Boiler temperature advice please

[Stotty1]

Hi
I am after a bit of advice on boiler temperature settings please.

We had our boiler serviced yesterday and the first thing the guy said when looking at the boiler was the boiler temp was on max and shouldn't be.
We have never touched the boiler itself only the thermostat. So he thinks it was left like this after the last service, as they test it on max setting.

So he has put it to where he says it should be, the only problem is, it came on this morning at a starting temp of 12 deg. and 2 hours later it had only got to 14.5 deg. the boiler ran continuously for the 2 hours and all the rads still get hot enough that you can't leave your hand on them (they feel no cold than they used to), but the house is not warming.
It used to warm to about 17 deg. In this time period (which to be honest we thought was a bit slow).
The thermostat is based in the hallway so the rooms generally get warmer.

The house is a detached house with loft insulation, new double glazing fitted 3 years ago, new heating system fitted 2 years ago (Worcester Bosch 32cdi boiler running 10 new rads and new copper pipework throughout)

My gut is saying it should not have been left on max as he said, but the house only heating 2.5 deg. in 2 hrs seems a bit slow.
He did say the lower settings would save on energy costs as well, which is great as we are spending far to much currently but at the same time we don't want issues of damp/mould due to the house not being heated well enough.

Has anyone got any advice?
How does this compare to other people's heating system?

Thanks

 

[oldbutnotdead]

The boiler will run more efficiently if the return is cool enough to allow condensing. But, if your radiators were sized assuming a 70 degree flow and you've set the boiler at 60 then they are not going to emit their rated heat output.
If your house is well insulated there's an argument for starting the heating earlier (to achieve setpoint when you want it) but if the house is dropping to 12° overnight I'd say you have some significant heat loss going on, may be better for your comfort to experiment with the boiler temperature - object is keep boiler temp as low as possible while still achieving your comfortable heating level.

 

[oilhead]

I listen to all the light hearted TV pundits who tell you about turning down the flow temperature to run more economically, but at the end of the day, if you want the house at a certain temperature, then you need to input a certain amount of heat. If you lower the flow temperature, then you need to lengthen the time that it runs.
The old saying about quarts and pint pots comes to mind.

 

[Harry Bloomfield]

I listen to all the light hearted TV pundits who tell you about turning down the flow temperature to run more economically, but at the end of the day, if you want the house at a certain temperature, then you need to input a certain amount of heat. If you lower the flow temperature, then you need to lengthen the time that it runs.
The old saying about quarts and pint pots comes to mind.

The boiler temperature setting should track the needs of the house for heat input, which is determined by the outside temperatures, and the heat loss /level of insulation.

If the boiler also serves hot water, then that can also determine how low the boiler stat can be set. The boiler flow temperature has to be set to higher value than the cylinder stat, otherwise a demand to heat a cylinder of water will never be satisfied. A cylinder needs to be heated to 60C, at least once per week, to kill off the Legionella. To get a cylinder to 60C, the boiler flow needs to be around 60 + 10 = 70C.

 

[Stotty1]

Thank you both for replying.
Sounds like he was right in lowering the temp but it may just need tweaking to get the best efficiency.
I will read the manual and find out how to adjust it.

but if the house is dropping to 12° overnight I'd say you have some significant heat loss going on

Kind of glad you mentioned that as we did think the same about there being to much heat loss. You do notice the temp difference within an hour of the heating going off.
We just can't work out where we are loosing it, we have changed the windows, got insulation throughout the loft.
We have noticed pretty bad Condensation in the loft so re-siliconed around the loft hatch and any holes we could find in ceilings (going to arrange for some tile vents to be fitted in the spring but that doesn't help with the heat loss).

The only other thing I can think of is we fitted a PIV unit a few years back as we were getting major condensation issues on the walls and windows, ideally don't want to switch this off though as don't want to get mould back.
But not sure if this is the culprit.

Thanks

 

[oldbutnotdead]

Have you got the loft up to 300mm thickness and uncrushed (if the loft is boarded may be time to think about lifting boards and getting more insulation in). And make sure you haven't blocked the eaves.
Annoyingly, even levels of insulation that comply with building regs still permit significant heat loss. Shoddy building techniques don't help (like not sealing dot and dab plasterboard, window reveals causing thermal bridges, lots of details that really matter).
Until recently, cost/benefit calcs reckoned more than 300mm in the loft wasn't worth the investment. That number will have changed, and it'll change again next year when energy prices may double from the current capped costs.
Before you go mad, it'll be worth monitoring your (presumed gas) consumption on a day to day basis- heat the house so you're comfortable, use the hot water when you want it, see what your energy consumption is.
That'll give you some numbers to aid your decision making.
Other easy fixes- heavy curtains on doors and windows, carpets/rugs on bare wood or tiled floors, wear more clothes

 

[Stotty1]

Thanks @oldbutnotdead

Not sure on the loft insulation thickness the stilts I used when boarding it were only 175mm so it has to be under 300mm, I did make sure none of it was compressed though.
Will have to think about how to increase the loft floor height to get more insulation in.

I actually pulled all the insulation out of the eaves in the summer due to condensation last year and I fitted vents in the felt but neither has worked, it has actually been worse condensation wise this year.
So come spring was actually thinking about pushing the insulation back into the eaves to hopefully reduce heat loss around the edge of ceilings and then get some proper tile vents fitted in the roof.

wear more clothes

Already on this one, I'm starting to sound like a stuck record the amount of times I've told my kids to just put a jumper on, although the mother in law seems to be the worse at moaning

Regarding the boiler, it was on 61 deg. I have turned it up to 65 so will see how that works.
It's max seems to be 74 deg.

 

[JohnD]

You said that all the radiators were too hot to hold your hand on

But the heat they emitted was not enough to make the house warm.

So, the radiators are too small to heat the house in such a cold spell.

Either you reduce the heat loss (insulation, draughtproofing, curtains, closing internal doors)

Or you increase the heat output (bigger radiators)

Or both.

 

[Stotty1]

You said that all the radiators were too hot to hold your hand on

But the heat they emitted was not enough to make the house warm.

So, the radiators are too small to heat the house in such a cold spell.

Either you reduce the heat loss (insulation, draughtproofing, curtains, closing internal doors)

Or you increase the heat output (bigger radiators)

Or both.

Thanks for replying.
Yes they are, although a little cooler at the bottoms of rads but still too hot to leave your hand on for any length of time, which is why I was unsure on the boiler temp making a difference, but it sounds like it does due to flow and it definitely got hotter when the boiler was on max.

I have questioned the rad sizes a few times, although before we got the new heating system we got 3 quotes and most the rad sizes were similar on each quote.
The company we went for actually measured the rooms and supposedly worked out the rad size.

We didn't seem to have any problems last year but I suppose it has been particularly cold this year.

Reducing the amount of heat loss seems to be the way to go, especially as we are going through £8 a day in gas currently

 

[Harry Bloomfield]

Reducing the amount of heat loss seems to be the way to go, especially as we are going through £8 a day in gas currently

Not that unusual, for these outdoor temperatures.

 

[oldbutnotdead]

Not that unusual, for these outdoor temperatures.

And the long duration of the cold spell means the building fabric is colder than normal.
£8 a day isn't an outrageous amount of energy to heat a standard UK home in this weather. Last year it would have cost about £3
EDIT With the loft insulation it's worth fixing some thin sheet material to the rafters at the eaves, you can then pack insulation at the wall edges without risking blocking airflow
Re the loft legs/boarding- do you really need all the stuff that's up there?

 

[Stotty1]

£8 a day isn't an outrageous amount of energy to heat a standard UK home in this weather

Thank both,
That's good to know, it just sounded a lot after talking with a work colleagues whos in a new build, they are using only half what we currently are.

Good shout on the material in the waves to stop the insulation filling it, I have spare silver backed bubble wrap which could do the trick.