Boiler CH temp?

Novice_investor101

I have an Ideal Logic 30 combi boiler, which was new about 4 years ago. I've never had a problem with it and it's been great. I'm just wondering what temp I should set the CH temp on it?


I live in a 2up/2down style Victorian mid terrace. It's a small house, with high ceilings and a cellar under the lounge. The back of the house (kitchen, bathroom and small spare bedroom) get the sun all day and the front (big bedroom and lounge) not so much. The lounge tends to be about 0.5c cooler than the kitchen downstairs possibly due to the cellar beneath and the main bedroom about 1c cooler than downstairs. The attic is well insulated and it is solid brick walls. This possibly also contributes to the lower temp as there is more external wall area in these rooms. Heating is on an hour in the early morning each day.


This winter I have been using the heating a bit more and the gas bill is higher, obviously. I had been running the boiler CH temp at about 83c, which had the house toasty warm in no time. The timer is set to come on at 17.00 on weekdays, 16.00 on weekends, and off again at 20.00. The thermostat is set at 18c (its on a cold wall) which gets the rooms downstairs to about 20c in about 1.5 hours and then switches off. Upstairs main bedroom tends to be 18c, which is fine.


I have realised that the boiler never goes into condensing mode at 83c, so I read the manual and dropped it to 73c, which it says is optimum for high efficiency. However, the house heats up much slower and the thermostat never now clicks off. It is a particularly cold week, tho.


I read the meter every month, so I will give it a month to see if the usage reduces. But is it likely I'm using more gas as the boiler is running for the whole 3/4 hours or should I whack it up again and let the thermostat do it's thing? I have TRV's on all rads which I keep on full and the lounge has a full room length rad.


I am on a Scottish Power tariff that has low standing charges as I am a low energy user and the standing charge in the summer months is usually higher than the usage. I have an electric shower and DHW is 60c, but not an issue.


Any thoughts on the CH temp? Does condensing mode really lower gas usage, or should I just put it back to 83c?

CashStrapped

Having the heating on for lower for longer will be more efficient than short burts of very hot radiators.

However, being able to do that depends on your set-up. If your radiators are not appropriately sized to give off enough heat at a lower temperature then they will struggle to compensate for the background heatloss of the house.

In addition, the TRVs should not be set to full. That just defeats the point of having a TRV. A TRV does not control the temperature (how hot) a radiator gets).

A TRV is like a mini thermostat for the room. All it does is turn off that individual radiator when the room is up to temperature. 18 degrees is normally around the middle or number 3 ish. That assumes they still work. The idea is when a single room is up to temp, it turns the radiator off for a bit, which in turn means the boiler has less work to do.

If you have them on maximum, that temperature will never be reached and the radiators will never turn off when the room is warm.

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A central (whole house) thermostat is trying to give you an rough average temperature for the whole. Again, this just turns the central heating pump on/off and calls for heat.

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You will probably find it is actually more efficient to run the boiler at a lower temperature for longer (especially if you are in). Trying to maintain an average temperature of 18 rather than it going up and down, up and down all day.

Is the thermostat digital or analogue? An analogue thermostat has a much bigger margin of error. That margin of error grows with age on analogue ones.

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Novice_investor101

The thermostat is at the bottom of the stairs between the lounge and kitchen. It is analogue. It is on the party wall, which is solid brick and thus quite cool. I tend to find that 18c on that has the downstairs rooms at 20c before it switches the boiler off.


I will definitely lower the TRV in the spare room to 3 as that is unused ( I dry laundry in it, twice a week) and the upstairs landing does seem warm, I never thought about it the way you put it with the boiler doing less work.


The guy who fitted the boiler did a calc at the time and said the rad sizes were fine. I also keep the main bedroom and bathroom windows 'on the latch' slightly open for ventilation and have no condensation issues at all.


I am usually at work all day weekdays so don't have the heating on, and the lowest temp is usually about 14-15c before 5pm when the heating comes on. The house is about as well insulated as it can be without adding internal insulation to the external wall surfaces. I also have door curtains for the front and back door.


I will give it a month on it's current setting and see if that lowers the monthly gas usage a bit.

CashStrapped

It is a bit of trial and error, which is also difficult to test due to ever changing outside temperatures.

I understand that the rads maybe the correct size for the property. However, if you want to run the boiler in condensing mode it is often recommended to oversize the radiators. This means that the boiler can run at a lower temperature as the radiator has a much larger surface area from which to give off heat.

A smaller radiator, while correctly sized, may not be able to do this as well at a lower temperature.

But there is no point in considering radiator replacement or anything drastic.

There are lots of variables to consider.

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One option I would consider is getting a wireless digital thermostat. It does not have to be an expensive one.

https://www.plumbcenter.co.uk/product/center-radio-frequency-programmable-room-thermostat/

That is a good value option. It is actually a re-branded honeywell with a few features disabled. Much cheaper than most other brands, but still well made.


This will be more accurate and you can also place it in an area of the house that you think gives a better average temperature reading. Rather than it being on a cold wall near an outside door.

I doubt it will result in any perceptible saving if you are already monitoring the controls closely, but it may help run the system more efficiently with less input from you.

matelodave

I'm a great believer in programmable thermostats - these are pretty good as well https://www.amazon.co.uk/s/?ie=UTF8&keywords=salus+rt310rf&!!!!!googhydr-21&index=aps&hvadid=226498732707&hvpos=1t1&hvnetw=g&hvrand=1961799053913862070&hvpone=&hvptwo=&hvqmt=e&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9050369&hvtargid=kwd-412189769004&ref=pd_sl_9k3g4h9i64_e

You have the option of setting up to six differnt temperatures on each day of the week and because they are wireless, they allow you to locate the thermostat in the best place in the house to control the temperature.

Instead of having the boiler roar away at full blast to get a quick heat-up when you get home, you can set it for an intermediate temperature a hour or so before thus allowing the boiler to run at a lower temperature as you don't need to heat the place as fast.

Ideally the cooler you can run the boiler, comensurate with it actually heating the house satisfactorily, the better. The boiler is least efficient when it starts up and more efficient when it's allowed to modulate and go into condensing mode.

As Cash says it's all a bit of trial and error but it helps when you've got more control over the temperature at different times and on different days.

Even at weekends there's an advantage having the thermostat set to a lower temperature during the day when you are more active and increasing in the evenings when you are sitting watching the telly.

It's better to have luke warm rads most of the time, rather than them alternately being red hot or stone cold

Novice_investor101

I think as the house is only small and the only rad that could do with being bigger is in the main bedroom, changing rads won't have much value. I use a 3kw fan heater in that bedroom in the morning and evening for about 30 mins to get that room warm for when I want it (immediately after getting up and going to bed).
The lounge one is about 8-9 feet long and can't get much bigger, either they are all flat-ish panel rads, so swapping them for double panel ones may be an idea?


For now, I'll stick with setting the TRV's appropriately and leaving the boiler at 73c for the month til I do the monthly meter read and see what difference it has made, if any. My annual usage for the last 12 months is Gas 7904 kWh, Elec 1506 kWh, which is pretty low anyway.


I do wonder if I've just got used to the house being hot, rather than warm and just need to put a jumper on and adjust...


I have a thermometer and Hygrometer on order from Amazon to check the humidity in the main bedroom. I know I have no condensation issues at all but wonder if the atmosphere is too dry....
The house tends to stay warm in winter and cool in summer, which is perfect.


I'll have a look into getting a better thermostat and timer. The current one is the immovable analogue thermostat on the wall and a timer that lets me set the on/off times for 3 periods each day - but not at varying temps.

CashStrapped

Haha - I would take the 7904kwh and be happy, that is well below national average. Lower than the average for "low users" even.

Fancy swapping with my 29,000kwh?

Smodlet

CashStrapped wrote: »

Haha - I would take the 7904kwh and be happy, that is well below national average. Lower than the average for "low users" even.

Fancy swapping with my 29,000kwh?

If I could afford to live in Highclere...

Novice_investor101

CashStrapped wrote: »

Haha - I would take the 7904kwh and be happy, that is well below national average. Lower than the average for "low users" even.

Fancy swapping with my 29,000kwh?

Lol, yes it is very low! In true money saving style, I wondered if I could get it lower!
My monthly DD is currently £55 a month for gas and electric, in the summer SP wanted to set it at £36, which I upped to £45 and now £55. The only tariffs I look at when switching are the ones with low standing charges - I use practically no gas in the summer and until I switched to my current tariff I was being billed about £8 standing charge and £2 gas use a month..... Electric was equal S/C to usage.
I'm thinking of leaving it at £55 all year so i'll be less bothered come next winter about bills!
My water is on a meter and is £14 a month. The single life is cheap!

CashStrapped

Novice_investor101 wrote: »

The only tariffs I look at when switching are the ones with low standing charges

If you are a super low user, then no S/C tariffs may make sense and normally come up cheapest....

but!

Regardless of a standing charge or not, as long as your annual figures are accurate, whatever the comparison site spites out as being cheapest, including those with standing charges, will be cheapest.

The comparison site works it out for you....so do not be afraid of choosing one.

It is a bit of a red herring to get too caught up on the standing charge.

Novice_investor101

I was pretty annoyed when the Gov practically abolished no standing charge tariffs. Ultra low users like me suffered.
I get my annual usage in kWh's from my latest bills (which I get monthly with actual readings).

Current fixed deal is up in June. I'll be doing another comparison, but I remember being thoroughly annoyed with EDF when pretty much the whole of my gas bill from May to October was standing charge & no actual gas usage!

My current tariff was £150 a year cheaper (supposedly, according to USwitch) due mainly to the standing charges.

365 days X 25p a day X2 (gas & elec) is £185.50 a year in charges alone on the old tariff.
365 days X 8p a day X2 is £58.40 in annual charges on this tariff.
Not sure the slightly higher unit prices cost more than the difference, but I definitely notice the reduced cost in the summer.