Combi boiler/thermostat settings

FreeBear

Yorkshire_Pud said: Also the hot water temp if set (too) high may be wasting gas energy as we usually blend it with cold so why heat it to scalding then add cold?! Mine set at around 55deg especially if running a bath where I don’t  need to add too much cold and cools naturally. Otherwise I set at 52deg. HSE have their rules about water temp though to avoid legionaries disease risk from stagnant water and state 55deg minimum. Read up yourself to see if you think the ‘risk’ is worth it.

Legionella is only of a (very small) risk if you have a hot water tank and an open header tank. With a combi or a pressurised HW tank, the risk is next to zero as the incoming water will have been treated to kill off any pathogens.

Even if you do have a HW tank with an open header tank, maintaining a water temperature of 50-55°C will be enough to kill the bacteria (it takes hours rather than minutes if the water is heated to 60°C).

User_Name_1

We only have the hot water on for two one hour periods a day, that's enough for us.

For them two one hour periods the flow temperature goes up to 65 and the water is boiling hot. outside this two hour period I set the flow temperature too what ever keeps the house comfortable.

Surely the advice of not lowering your flow temperature to below say 65 to heat the water in the cylinder to 60 should only count when you are heating hot water and not the central heating. For me for 22 hours a day I can lower the flow temp to whatever I want without the threat of legionaries disease.

Maybe I'm wrong, if so can someone with better knowledge explain why.

Yorkshire_Pud

User_Name_1 said:

We only have the hot water on for two one hour periods a day, that's enough for us.

For them two one hour periods the flow temperature goes up to 65 and the water is boiling hot. outside this two hour period I set the flow temperature too what ever keeps the house comfortable.

Surely the advice of not lowering your flow temperature to below say 65 to heat the water in the cylinder to 60 should only count when you are heating hot water and not the central heating. For me for 22 hours a day I can lower the flow temp to whatever I want without the threat of legionaries disease.

Maybe I'm wrong, if so can someone with better knowledge explain why.

The heating flow temperature and hot water temperature settings are separate settings on a combi boiler.

70sbudgie

Woodsy said:

70sbudgie said:

A few points:

I also have a WB Greenstar and haf a quick look through the manual last night. It suggested that when setting the flow temp, it has a function that lets you know when it is more efficient (ECO pops up on the screen). I am just working myself up to going out in -4° to go and check. I'm guessing it must be to do with how the system was set up when the boiler was installed.

Also, I understand that it is possible to get double glazed sash windows. But they're not cheap. (I'm guessing that you may be in a conservation area and that you have to retain the sash windows for that reason). Would thick / thermal curtains be an option, as they would help? I notice the difference even with our modern double glazing.

I also have a Greenstar boiler 24i but the "ECO" only refers to the fact it is NOT on pre-heating as far as I can see, nothing to do with the flow temp so I would double check that if I were you.  Either way "ECO" is good!

I thought there were two uses of Eco on the WB Greenstar. The Eco button, which as you said is about the preheat function. And a digital ECO text which appears when adjusting the flow temperature. 

I would quite happily be shown to be wrong as it will mean that someone understands the manual better than me. I didn't feel like it explained how to set the boiler for optimum efficiency very well. There were no temperature values included and I was left with the impression that the boiler can tell me. My guess, based on this conversation, is that as every set up is different, (number of radiators, TRV settings), the boiler has some way of identifying the optimum efficiency. Does it measure the return temp as well, and therefore knows the temp drop as the water circulates?

And I have still to go out in the cold to check on my boiler. 

skycatcher

I was wondering the exact same thing. Last time i checked the eco setting was 67°c on my ch flow.

bullinn1

Good morning, in case anyone is following my ‘experiments’ the figures are from Monday and those in brackets Tuesday:

11 hours (11) flow temp 60 (65) thermostat target 18c (17) … meter read £9.64 (£7.00).

… so really not a scientific approach but increasing FT and lowering comfort temp. saved a couple of quid. It was bearable but not warm, we can survive and my wife doesn’t seem to feel the cold as much as I do.

I’m basically trying to keep warm for as little money as possible especially as my son, his wife and two young kids are here for 5 days at Christmas and I will not be allowed to be ‘mean’.

BUFF

rogertb said:

Good morning, in case anyone is following my ‘experiments’ the figures are from Monday and those in brackets Tuesday:

11 hours (11) flow temp 60 (65) thermostat target 18c (17) … meter read £9.64 (£7.00).

… so really not a scientific approach but increasing FT and lowering comfort temp. saved a couple of quid.

I would hazard a guess at the drop in required temp. being responsible for all of the saving especially as the house started out already with some pre-heat.
Now try dropping the flow temp back & see if you save any more ... 

bullinn1

Worth a try buff though when the ft was 60 it seemed to be struggling to reach 18, maybe it won’t have to try so hard to reach 17 … what fun.

BUFF

Tbh, I was being slightly facetious. I imagine that any saving over a day (if even measurable) will be minimal & probably more affected by any changes in the local weather rather than the 5C drop in flow temp (as it should still be within the condensing zone at 65C flow).

BiliousGreen

My combi boiler has marking for ECO on flow rate as being 69. Should that be ignored or is that where I would be best setting it rather than dropping it to 60 in line with general advice? Like someone said, not sure if raising from 60 -69 it will reduce the time the boiler is on and make it more efficient