Advice About Boiler Flow Temperature For Gas Savings Please

AfxTwn

Hi, I live in a small, rented, mid-terraced, 2 bedroom house on my own and would like some advice about saving money/gas usage on my bills. My house only has single-panel/convector radiators in each room but all except the largest radiator in the living room have TRV valves on.

I have a Glow Worm Compact 24c boiler and a ESI ESRTP4RF+ walkaround thermostat.

Anyway, I have been watching a lot of YouTube videos about boilers and efficiency etc and it seems the current trend is to reduce your boiler flow temperature to save money and make use of things like OpenTherm or similar thermostat controls.

My boiler's current flow temperature is set to 65 degrees Celcius so would lowering it to 50-55 degrees be better? I normally set my thermostat temperature to 18 degrees as this is quite comfortable for me and all my radiators TRV valves are set to number 3 out of a maxium of 5.

I think my ESI thermostat is capable of something similar to OpenTherm as the controls say it has Chronoproportional control (TPI) and you can choose a set back temperature as well as delayed/optimum start and stop times.

Normally I don't use the timer/program function on the thermostat and just turn the heating on manually when I want it on. So for example, I might put it on at say 8 in the morning and then switch it off at 9-10am. And then put it on again later at say 4pm and maybe switch it off at 8:30pm, depending on how cold it is in the house. Usually the temperature drops down to between 14 and 15 degrees on cold days before I turn the heating on.

I am just wondering whether it would be beneficial to reduce my boiler's flow temperature to say 50 degrees and make use of set back temperatures of say 15 degrees on the thermostat and use the optimum start/stop settings also so the thermostat will automatically start and stop the heating when it's best?

Sorry for the long post but I am new to this and a little unsure if any of it would be beneficial to me.

Thanks for any advice.

FreeBear

AfxTwn said:

Hi, I live in a small, rented, mid-terraced, 2 bedroom house on my own and would like some advice about saving money/gas usage on my bills. My house only has single-panel/convector radiators in each room but all except the largest radiator in the living room have TRV valves on.

I have a Glow Worm Compact 24c boiler and a ESI ESRTP4RF+ walkaround thermostat.


My boiler's current flow temperature is set to 65 degrees Celcius so would lowering it to 50-55 degrees be better? I normally set my thermostat temperature to 18 degrees as this is quite comfortable for me and all my radiators TRV valves are set to number 3 out of a maxium of 5.

I think my ESI thermostat is capable of something similar to OpenTherm as the controls say it has Chronoproportional control (TPI) and you can choose a set back temperature as well as delayed/optimum start and stop times.


I am just wondering whether it would be beneficial to reduce my boiler's flow temperature to say 50 degrees and make use of set back temperatures of say 15 degrees on the thermostat and use the optimum start/stop settings also so the thermostat will automatically start and stop the heating when it's best?

Yes, running a condensing boiler at a lower flow temperature will improve efficiency up to a point. I run mine at anywhere between 40°C and 60°C and can get 96% - I have a device that monitors how much heat is being used by the radiators, but have to rely on the gas meter for energy input readings. One thing that I have noticed is if the boiler starts to short cycle, it knocks efficiency right down..

With just a 2 bed terrace, I'm guessing you only have 5 or 6 radiators, and being single panel (is that with fins on the back ?), not a huge heat load. Running the Glow Worm at 50°C flow, 30°C return, the manufacturers specs say that the boiler will deliver 5.3kW to 21.2kW of heat - I'm afraid you will be short cycling quite a bit, although there are ways to reduce that a little. Open up all the TRVs to max - This will increase the heat load on the boiler. Glow Worm boilers also have a setting in the service menu called "Burner anti-cycling time". Increase this, and you'll reduce the number of burner starts per hour (this is when the boiler efficiency is at its worst).

Opening up all the TRVs sounds counterintuitive, but when TRVs cut in on my heating system, the heat demand drops below the minimum that my boiler can run at. Consequently, it starts to short cycle.

Your Glow Worm boiler (if modern enough) will have eBUS (same as OpenTherm, but not not compatible), so with the right thermostat, it can do modulating control - In a nutshell, adjust the flow temperature "on the fly" with the goal of maintaining a constant room temperature. Unfortunately, the ESI Chronoproportional control is a very poor way of regulating a condensing boiler output - It basically switches the boiler on & off multiple times an hour and will kill any hope of efficiency. Imagine trying to drive a car with an on/off throttle

Balancing your radiators (aiming for a flow temperature * 0.3 drop) and adjusting the pump speed for minimum flow would be the first step in maximising efficiency. Increasing anti-burn time will reduce short cycling. Increase pump over-run time will extract a little bit more heat from the boiler once the flame has gone out. Turn down the flow temperature in say 5°C increments until you reach a point where the boiler runs for a reasonable time yet still heats the property up at an acceptable rate.

The above suggestions won't cost anything to make. Improving insulation levels (particularly in the loft) and plugging cold draughts will reduce the amount of energy needed to heat the place up. Replacing some/all of your radiators is another option, all be it, at some expense - This would allow you to make better use of the energy the boiler produces and see the property heat up faster, so less gas consumed over all. Having larger radiators will put you in a better position when the day comes to install a heat pump

TroubledTarts

One observation if you turn your heating on manually and are getting good results in one hour. I think you said you turn it on at 8am and turn it off at 9-10am. The reason you can do this and feel hot enough is because your flor temp is set high.

If you turn down your flow temp the consequence will be a slower time until you manually turn it off and maybe some savings but perhaps not massive savings as you are using your heating frugally as it is it seems.

Worth some experimentation though even if it's 5oC at a time and tracking your usage and how you feel for warmth.

kassy64

Good advice above, and agree don't really see point of reducing TRV's down below max, unless in rooms that aren't used much. Otherwise your boiler will have to keep running longer to get the required stat temperature. Personally I keep them on max in rooms that are used and turn down to 2 or 3 in rooms that aren't used and maybe bedrooms. Does your thermostat have 'tolerance where it kicks in and off. For example mine comes on when 0.4c below required temp and goes off at 0.4c above required temp, so keeps temp around 18.6c to 19.4c. having this tolerance where boiler comes on and off means it has a good down time especially if your house is well insulated, even in cold weather when we reach 19.4c it can be 2 hours before the boiler kicks in again. Hope this makes sense.

AfxTwn

Thanks very much for all the advice. It sounds like the thermostat I have isn't really compatible with my particular boiler in terms of OpenTherm or equivalent technology. As FreeBear mentioned, my boiler uses it's own version called eBus so I would need a compatible thermostat. However, given the size of my property and my current usage, I am not sure I am going to see any huge gains in making use of eBus or indeed in dropping the flow temperature. I may try turning all the radiators up to full except maybe the bathroom (which is is a small room with a tiny radiator in it) and the bedroom where I sleep (the other bedroom I use for going on my computer).

I can't really do much about the radiators as I can't afford to change them (I have looked into this already and was quoted nearly £2,500 pounds) and I know my landlord won't be paying for it. Same goes for loft insulation etc, from what I can tell the insulation in the loft is just your bog-standard yellow stuff that makes you itch and cough. I think the house was built in the early to mid 90's and hasn't been changed much since. My living room also has an open-plan set of stairs in it so a lot of the heat will escape upstairs (having said that, upstairs does feel colder than downstairs). The radiators are the type with fins behind them but just one set of fins and a single panel. I have put some foil behind the radiators on the outside walls (both bedrooms as they are at the front and back of the house and the living room) but I am not sure how much of an effect that's having but it was cheap and can't do any harm.

Getting back to the boiler, Glow Worm suggest a flow rate of between 60 and 70 degrees for best efficiency, so mine being set at 65 suggests it is set right. I am not sure about cycling rates or burner stats etc and wouldn't feel confident in messing with that. The ESI thermostat I have will have just been the cheapest one the installer could find that provided programming functionality etc and my landlord wouldn't have been bothered about any OpenTherm controls or efficiency etc. I think the cost of replacing it with an eBus one and an installer fitting it would probably not be worth the amount of savings it may deliver.

My thermostat's manual says it has a temperature sensor type of +/- 0.5 degrees Celcius at 20 degrees so presuably this tolerance applies at all temperatures, I am not sure, it does allow you to set the temperature in increments of 0.5 degrees.

When I turn the heating off manually, it isn't always at 18 degrees, sometimes it can be less say 16-18 but I either turn it off because I am warm enough or because I don't want it on too long to save money. Although when it is especially cold, I do often leave it on all day set to 18 but the boiler isn't constantly on, I think it kicks in when the temperature drops 1 degree.

I don't think I use a huge amount of gas and the system seems relatively efficient but given the constant price rises for energy, I was getting a little worried about the future and next winter. I am with Octopus on their flexible tariff and last month used 854 kWh of gas and 638 in December (we had quite a bit of snow and cold days recently) so that works out around £50-60 a month for gas but obviously we have more price rises in April and later in the year so it's a worry.

FreeBear

OK. Being a rental property, there is very little that you can do in the way of improvements. Draught proofing where you can and hanging thermal curtains is about the limit (possibly stick-on secondary glazing). Worth bugging the landlord and talk him in to increasing loft insulation to 300mm (you probably have 100mm at present). Depending on the size of the loft, probably £200 for 200mm thick rolls - It would improve the EPC rating and make it more attractive to a new tenant after you move on.

The existing heating system was probably designed around a 70°C flow temperature, perhaps even 80°C - A good chance that the radiators were oversized a little, so 60°C may well keep you warm. The only way to find out is to try it.

kassy64

AfxTwn said:

Thanks very much for all the advice. It sounds like the thermostat I have isn't really compatible with my particular boiler in terms of OpenTherm or equivalent technology. As FreeBear mentioned, my boiler uses it's own version called eBus so I would need a compatible thermostat. However, given the size of my property and my current usage, I am not sure I am going to see any huge gains in making use of eBus or indeed in dropping the flow temperature. I may try turning all the radiators up to full except maybe the bathroom (which is is a small room with a tiny radiator in it) and the bedroom where I sleep (the other bedroom I use for going on my computer).

I can't really do much about the radiators as I can't afford to change them (I have looked into this already and was quoted nearly £2,500 pounds) and I know my landlord won't be paying for it. Same goes for loft insulation etc, from what I can tell the insulation in the loft is just your bog-standard yellow stuff that makes you itch and cough. I think the house was built in the early to mid 90's and hasn't been changed much since. My living room also has an open-plan set of stairs in it so a lot of the heat will escape upstairs (having said that, upstairs does feel colder than downstairs). The radiators are the type with fins behind them but just one set of fins and a single panel. I have put some foil behind the radiators on the outside walls (both bedrooms as they are at the front and back of the house and the living room) but I am not sure how much of an effect that's having but it was cheap and can't do any harm.

Getting back to the boiler, Glow Worm suggest a flow rate of between 60 and 70 degrees for best efficiency, so mine being set at 65 suggests it is set right. I am not sure about cycling rates or burner stats etc and wouldn't feel confident in messing with that. The ESI thermostat I have will have just been the cheapest one the installer could find that provided programming functionality etc and my landlord wouldn't have been bothered about any OpenTherm controls or efficiency etc. I think the cost of replacing it with an eBus one and an installer fitting it would probably not be worth the amount of savings it may deliver.

My thermostat's manual says it has a temperature sensor type of +/- 0.5 degrees Celcius at 20 degrees so presuably this tolerance applies at all temperatures, I am not sure, it does allow you to set the temperature in increments of 0.5 degrees.

When I turn the heating off manually, it isn't always at 18 degrees, sometimes it can be less say 16-18 but I either turn it off because I am warm enough or because I don't want it on too long to save money. Although when it is especially cold, I do often leave it on all day set to 18 but the boiler isn't constantly on, I think it kicks in when the temperature drops 1 degree.

I don't think I use a huge amount of gas and the system seems relatively efficient but given the constant price rises for energy, I was getting a little worried about the future and next winter. I am with Octopus on their flexible tariff and last month used 854 kWh of gas and 638 in December (we had quite a bit of snow and cold days recently) so that works out around £50-60 a month for gas but obviously we have more price rises in April and later in the year so it's a worry.

I think your doing pretty well if only paying £50-£60 per month for gas (and not getting cold obviously).