New Boiler Using More Gas

[goodgoalie]

I had an 'A' rated Worcester Greenstar condensing boiler fitted two weeks ago, which works well and I'm very happy with it; also had an extra radiator fitted in the main downstairs room.

I'd taken a reading before the fitting and took one today and was alarmed to see that I've used nearly double what I was using in the previous few weeks. I have not increased how often I have the heating/hot water on, so can the increase be due to the extra radiator? I only took a reading today to cheer myself up by seeing how little gas the new super-efficient boiler was using. Really hacked off.

[davebro]

//It's a 24Kw boiler, and a 2 bedroom, 1 bathroom property//

Same as me but with an older (non-condensing) Worcester boiler.

[Atheist]

Teapots; I don't think it matters that the stat will call for heat without being satisfied. If the stat's not satisfiedm then the room temperature would not be achieved. If the boiler was bigger, then it would produce heat in abundance but would provide more heat than the smaller boiler, and therefore use more gas while it was burning. The overall energy needed to produce the required room temperatures would be the same with either boiler. In any case the OP suggests that the heat provided is sufficent for his needs.

[youngmafbog]

A greenstar should run much more efficiently, although you dont say what sort of boiler you had before e.g. combi or whatever.

Also you dont say what the rads are and do they have TRV's? Old rads can be sludged up wont perform on a new 'smart' boiler, are they reasonably new? TRV's can be used to balance the system but the problem that can arise when moving to a combi is that if you set a load of them low then the flow through the system will be fast and so the return temp is too high. This will cause inefficiency in most boilers but even more so incondenser. I have two temp dials (attached to in/out pipe) so I can see the temp.

As a last thing did they do a full flush of the system? Hope they did as that is really important for these new boilers.

Personally I have stuck with my big old boiler, one thing that has put me off moving is the relatively low life expectancy of the new ones and the continual repairs. A gas boiler is a hostile environment to electronics and I know of many people who have had problems. Plus the cost to replace mine (for a large Edwardian 6 bed house) just isnt viable.

[youngmafbog]

//I'm not using the thermostat//

OK, so nothing to do with your comparison but that may not be the best method. Get a multi time/temp thermostat and set it up so the property never goes too low. Otherwise the boiler sits on for longer whilst you are cold so knackering your savings. I have done this method for around 20 years and the difference was minimal (And you never forget to turn it off!)

A24KW for that size property sounds a little large especially if well insulated.

[Atheist]

goodgoalie; Do you have a room thermostat? If so, why not use it?

[Teapots1]

Its all very iffy the link dave provided proves that and I'm no expert at all. But I act on common sense. I have a 3 bed 1 bath. I had a combi put in a few years back, I ignored advice i was given regarding size of boiler, i had a 37 kw put in and saw my gas bill drop, WB 37cdi. If you do 70 mph in a small car you will use more fuel than doing 70mph in a larger car. Well that used to be the case?

[bhg481]

ymb - //one thing that has put me off moving is the relatively low life expectancy of the new ones//

We lived next door to a plumber several years ago and he advised us to hang on to our old boiler as long as possible as the new ones are prone to problems and are designed to have a short life. The fuel savings nowhere near match the cost of replacement.

[youngmafbog]

I know BHG.

If I had replaced I would have been on my third by now. And for the size of boiler I need that would be ridiculous.

[goodgoalie]

ymb - there are now 6 radiators and only one - the new one - has a TRV. It's an old stone barn conversion.

[Teapots1]

Did they flush the system out?

[Teapots1]

13.06 24kw I believe is the smallest one you can get in a combi.

[Teapots1]

Another thing to consider, then I'm off out, is that the old radiators you have ( don't know how old they are) will be made of a lot thicker steel and will take longer to get hot. The newer radiator you will find is made of much much thinner steel, therefore the new radiator will get hot a lot quicker that the old ones.

[The Builder]

Goalie... modern super-efficient boilers are completely different from ones from even just 19 years ago.
One day swaps are commonplace. It (apparently) keeps the price down so the installer remains competitive. I much prefer allowing 2 days.
The swap is easy. It's the setting up and final "tuning" that matter most.
Radiator layout/TRVs etc are critical.
The traditional systems (usually airing cupboard and hot water cylinder) often don't properly match the characteristics of modern Combis. No problem. Attention to flow rates/water return temperatures/even pump speeds can be adjusted.

I think you have 2 main problems.
A stone barn conversions, of which I've done quite a few, are notoriously difficult to heat efficiently without internal wall insulation.
This is linked to the second issue.
NOT leaving the boiler on, so not allowing it to settle into an efficient run-mode.
Every time it fires up, it has to heat up a stone cold boiler. Plus all the water in the (stonecold) system.
Stone barn walls act as a giant storage heater. With each firing, it takes a massive amount of heat to warm up all that stone.

I would let the system warm up to running temperature, then have the installers adjust as necessary (flow rates etc).
Modern combis work more efficiently with TRVs on ALL the rads. (Except maybe a "heat-leak" rad. But that's just a technicality.)
This time of year, let the system keep the heating temperature up. Thus avoiding all the "stop-start" running.

I know this would cost. But it would be so much more efficient.

[Canary42]

Surely your "comparison" method is flawed. Let me try an analogy.

You had a car which would only do 20mph, you drove for an hour, covering 20 miles.

You then replaced it with a car which would do 40mph and drove it for an hour, covering 40 miles.

Which won would use most fuel ?

[goodgoalie]

Many thanks for all the replies, esp The Builder.

What I was trying to get across is that I've been using the boiler in exactly the same way as I did the previous (Worcester) one, which I think was a 28 kw, as I simply cannot afford to have the boiler running for long periods of time.

As an experiment, yesterday I ran the boiler for just over an hour, used no hot water. Today I looked at the meter and saw I'd used 1 unit, which is just over 11Kwh, which with my tarriff of 3.18p is around 35p - to run the boiler for just one hour. That is what has been upsetting me, particularly as the boiler, radiators and hot water are all working really well. The old boiler would never have used that much, and I used to put it on for relatively short periods of time.that's what's getting me down.

With their permission, I'm going to take readings of the meters of two neighbours I'm friendly with and see how many units they use on average over several days. They're both in their eighties and at home all day - one is housebound - so it will be interesting (to say the least) to see what they clock up. Do any ABers know roughly how many units they use per day?

[davebro]

Dec & Jan I will use 1000kwh of gas pm - about 33 kwh per day.
I have the thermostat set at 22C 7am-7pm. Off at night.

[davebro]

//I'd used 1 unit, which is just over 11Kwh//

I'm not sure what the "unit" is that you refer to.

[davebro]

ah - just checked. It's Cubic Metres.

[barry1010]

I can understand how you feel, gg. I'd be very disappointed - may I ask how much you paid for the boiler?

[bhg481]

We live in a well-insulated 3-bedroom detached house and use gas for heating, hot water and cooking (hob only); our boiler is 40 years old. We have the heating on for a couple of hours in a morning and from 3:30 until 10:30 pm, thermostat set at 22 deg. If it's particularly cold we put the heating on in the middle of the day. Looking at our bills (we read our meter every month) we have used about 2 cubic metres a day for the last two months.