Combi boiler/thermostat settings

lohr500

Dolor said:

It's good to see that graph matches the figures on the spec sheet for my boiler.

The graph applies to all condensing boilers: it is based on basic physics.

If I were you, I would invest in a couple of the thermometers in the above link and try to get a 60c flow/40c return.

That requires the owner to balance the heating system. Playing around with the boiler set temperature will not achieve a 20C differential.

https://www.bestheating.com/info/a-best-heating-guide-how-to-balance-radiators/?gclsrc=aw.ds&gclid=EAIaIQobChMI_IC_nN7z-wIVDuR3Ch2RmQjgEAAYASAAEgJ2gPD_BwE

I believe I pointed out the need for balancing in my post.

If I were you, I would invest in a couple of the thermometers in the above link and try to get a 60c flow/40c return. To achieve this does need some experimentation. In my case, I had to play around with the boiler thermostat setting, the circulation pump speed and balance the flow through some of the radiators. 

diystarter7

matelodave said:

The optimum setting is the lowest that you can get it commensurate with keeping you warm enough and having reasonable reheat times.

Generally running it a bit longer at a lower temperature is more efficient and cheaper than having it blasting out heat at full bore. Don't get hung up on precise temperatures, just use then as a guide.

One of these will indicate your return temperature - https://www.amazon.co.uk/Clip-pipe-thermometer-hot-water/dp/B00GYV0L5I but one of these would be better as you can measure both the flow and return temps at the same time https://www.amazon.co.uk/Thermometer-Thermocouples-Temperature-Thermocouple-Agriculture/dp/B07923Z2VK/ref=sr_1_13?keywords=differential+thermometer&qid=1670834996&sr=8-13

If you are looking at the smart meter IHD then that isn't everso good at giving you precise info, especially for gas. 

It only updates once every 30 minutes, it may not have the correct tariff set and bear in mind that the boiler will be working at full bore for the first hour or two to get the house up to temperature when the thermostats will then control it. 

For more precise monitoring you need to read the actual meter (the one that's fixed to the incoming gas mains) 

Hi

The highlighted bit makes sense but is there a link etc that answers that in simple terms, please?

We have ours on at high settings and the condensation on colder days like last few days, it smokes like a chimney - could it be because it is on too high? It is set within the figures at the high end by the boiler fitter. 

What you said does make a lot of sense, eG heats slower/longer but then not blasting out masses of heat and losing it quickly is what I think you are saying.
Thanks

BUFF

diystarter7 said:

matelodave said:

The optimum setting is the lowest that you can get it commensurate with keeping you warm enough and having reasonable reheat times.

Generally running it a bit longer at a lower temperature is more efficient and cheaper than having it blasting out heat at full bore. Don't get hung up on precise temperatures, just use then as a guide.

One of these will indicate your return temperature - https://www.amazon.co.uk/Clip-pipe-thermometer-hot-water/dp/B00GYV0L5I but one of these would be better as you can measure both the flow and return temps at the same time https://www.amazon.co.uk/Thermometer-Thermocouples-Temperature-Thermocouple-Agriculture/dp/B07923Z2VK/ref=sr_1_13?keywords=differential+thermometer&qid=1670834996&sr=8-13

If you are looking at the smart meter IHD then that isn't everso good at giving you precise info, especially for gas. 

It only updates once every 30 minutes, it may not have the correct tariff set and bear in mind that the boiler will be working at full bore for the first hour or two to get the house up to temperature when the thermostats will then control it. 

For more precise monitoring you need to read the actual meter (the one that's fixed to the incoming gas mains) 

Hi

The highlighted bit makes sense but is there a link etc that answers that in simple terms, please?

We have ours on at high settings and the condensation on colder days like last few days, it smokes like a chimney - could it be because it is on too high? It is set within the figures at the high end by the boiler fitter. 

What you said does make a lot of sense, eG heats slower/longer but then not blasting out masses of heat and losing it quickly is what I think you are saying.
Thanks

Possibly. You certainly expect the plume to become more visible at lower outside temp.

 There is another variable that I don't think has been mentioned in this thread & can be germane especially in a cold snap such as at present - the radiator outputs especially in older systems that simply had a boiler replacement.
Older systems probably had their radiator outputs sized based on  a higher flow temp (tyoically 80C flow, 60C return). With lower flow temps they will not output as much heat, will take longer to bring a room up to target temp. & in extreme cases may not output enough heat to heat the room to target temp. especially in cold snaps such as at present. 

So it is a balancing act between efficiency, comfort & convenience & every user/system will be different.

Woodsy

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!

Nebulous2

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.

My eco setting turns off the preheating for the hot water, but doesn't do anything else. 

My house is grade B listed, and I understand they wont let me have double-glazed windows.   The stuff I got is something like this Secondary Double glazing | Magnetic Secondary glazing systems (ecoease.co.uk) I can't remember if it was that company or not, but it has made a significant difference, and is not visible from the outside. 

bullinn1

Hi again … so I kept the boiler on for 11 hours yesterday, flow temp 60 ‘stat target 18c … 5 radiators on with 3 (in 3 rooms not being used and their doors closed) It took most of the day to reach 18c on the thermostat. It’s -3 outside but got up to +1 yesterday, very little hot water use and the smart meter read £9.64. That will make this cold spell expensive as I cannot think of a way of getting it lower, could turn it off and go down the pub but that will be £8 for two pints and I’ll still need to turn the boiler on when I get back !

lohr500

Did the rooms where you have the radiators turned on feel warm and are those radiators fitted with thermostatic valves?

Is the room thermostat in a room where you have switched off the radiator? If so, that room will only reach 18c from heat "leaking" from other rooms and with no radiator it is likely that it will take a long time for the thermostat to reach 18c. So the boiler will keep cycling in and out based on the 60c boiler setting, because the room thermostat is not reaching temperature.

If this is the case, try setting a lower room thermostat setting and see if the rooms in use still feel warm, or open the radiator valve in the room with the thermostat. Alternatively, if the room thermostat is wireless, relocate it into the room you use most.

bullinn1

Thanks lohr, the rooms with rads on do get warm after 4 or 5 hours, we can live with that, the ‘stat is in the hall, it might be an idea to move it to where we’re sitting.

Yorkshire_Pud

rogertb said:

Hi again … so I kept the boiler on for 11 hours yesterday, flow temp 60 ‘stat target 18c … 5 radiators on with 3 (in 3 rooms not being used and their doors closed) It took most of the day to reach 18c on the thermostat. It’s -3 outside but got up to +1 yesterday, very little hot water use and the smart meter read £9.64. That will make this cold spell expensive as I cannot think of a way of getting it lower, could turn it off and go down the pub but that will be £8 for two pints and I’ll still need to turn the boiler on when I get back !

I’ve read up a bit on the flow temp. Have a WB Greenstar. Rule of thumb the combi theory is it works most efficiently at FT of 45c but that doesn’t tend to give enough heat so needs raising until the house heats up efficiently, so in say October try 50c FT in November set FT at 55c and in December, and/or when it’s coldest months set at 60deg. Too low FT and there’s just no oomph to the system and won’t heat the house up unless boiler  left on all the time, which I don’t do, but always aiming to go towards the 50deg FT when the weather warms up, i.e. it’s less cold.

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.

My long term plan for my single glazed sliding sash windows is good old fashioned solid pine window shutters. Thermal insulated solid wood air column between shutter and window. Funny how the old ways are often the best solution for old buildings.

lohr500

rogertb said:

Thanks lohr, the rooms with rads on do get warm after 4 or 5 hours, we can live with that, the ‘stat is in the hall, it might be an idea to move it to where we’re sitting.

If you can move it easily then I would try that 1st and set it so you end up with a comfortable temperature in the main room you sit in. But make sure that you fully open any radiator thermostatic valve/s in that room otherwise they could close before the room stat reaches temperature which will cause the boiler to cycle. Is it a wireless room thermostat that you have?