New combi boiler = double the gas usage

FreeworldImpossible

Hi, in September I finally bit the bullet and got rid of our old back boiler and had a Worcester Bosch 30CDI installed via a Worcester approved installer.

We kept the existing pipework and rads, had it powerflushed, and one extra rad installed in the bedroom.

Just received our quarterly gas statement from September 25-December 25 and I'm stunned! We used 8400kwhor so, costing £278. Last years bill from 31 August-1 December used 4100kwh. :eek:

We only use gas for the boiler, cook with electric, the boiler stat is set at five for heating and the room stat is set at 20degrees for two hours in the morning then 19.5 degrees from half five till midnight. We run two baths per day (no shower fitted yet). The house is a 1960's end link with double glazing and cavity and loft insulation done recently.

Does this sound reasonable? I expected a much lower gas bill than before, not double!:mad:

evoke

I had exactly the same shock with exactly the same boiler! It does use a lot of gas. My house is as insulated as I can make it. Not sure what the solution is.

FreeworldImpossible

My brother has a WB 30Si fitted in a brand new 3 bedroomed house. I know it's brand new but with heating and cooking done with gas he used £37 worth of gas in December :eek:

Both he and my dad have the 30Si, and they both claim the stat on the boiler for heating on mine is too high. They have there's at 4 mine is at five, but if I turn mine down anymore the furthest rad away from boiler doesn't heat up properly. Maybe it's not properly balanced, I dunno!! I thought the idea was to have the boiler up to the maximum for the heating system, so it gets hot as fast as it can, the the room stat will turn it off at say 19.5'C and the TRV's will control the temp in all the other rooms. Is this so?

HappyMJ

FreeworldImpossible wrote: »

My brother has a WB 30Si fitted in a brand new 3 bedroomed house. I know it's brand new but with heating and cooking done with gas he used £37 worth of gas in December :eek:

Both he and my dad have the 30Si, and they both claim the stat on the boiler for heating on mine is too high. They have there's at 4 mine is at five, but if I turn mine down anymore the furthest rad away from boiler doesn't heat up properly. Maybe it's not properly balanced, I dunno!! I thought the idea was to have the boiler up to the maximum for the heating system, so it gets hot as fast as it can, the the room stat will turn it off at say 19.5'C and the TRV's will control the temp in all the other rooms. Is this so?

That is so...The boiler should also modulate the heating output so if the return temperature of the water is high it will reduce the amount of gas burnt.

Is your house warmer than when you had the back boiler? You will use more gas.

southcoastrgi

your back boiler was heating a cylinder full of stored hotwater which doesn't req a great deal of heat input, so i'm guessing your old boiler was around 60,000 btu's which is 17.5kw, you now have a 30kw boiler which is nearly double the heat input, you need this amount (or more) to be able to heat the hot water however you don't need anywhere near this amount for the heating side, modern boilers will modulate down with regard to the heating side but some are better than others at doing this, my advise would be to get your installer back to range rate the heating side, unless you have alot of rads the heating side will prob only need to be around 12kw, it won't effect your hot water but will save you gas when the heating is on.

FreeworldImpossible

We have

HappyMJ wrote: »

That is so...The boiler should also modulate the heating output so if the return temperature of the water is high it will reduce the amount of gas burnt.

Is your house warmer than when you had the back boiler? You will use more gas.

No, it's actually colder. I think this because we used to have the hot water on a few times a day with the old boiler, and some of the radiators used to heatup upstairs. Thus warming the house without actually having the heating on.

southcoastrgi wrote: »

your back boiler was heating a cylinder full of stored hotwater which doesn't req a great deal of heat input, so i'm guessing your old boiler was around 60,000 btu's which is 17.5kw, you now have a 30kw boiler which is nearly double the heat input, you need this amount (or more) to be able to heat the hot water however you don't need anywhere near this amount for the heating side, modern boilers will modulate down with regard to the heating side but some are better than others at doing this, my advise would be to get your installer back to range rate the heating side, unless you have alot of rads the heating side will prob only need to be around 12kw, it won't effect your hot water but will save you gas when the heating is on.

We have nine radiators on the system.

If the pressure drops does this indicate a leak? I looked at it today and it was down to half a bar. Its the first time its dropped like that though since it was installed! I topped it up and bled the radiators, should I be calling the installer over this?

zoominatorone

FreeworldImpossible wrote: »

We have

No, it's actually colder. I think this because we used to have the hot water on a few times a day with the old boiler, and some of the radiators used to heatup upstairs. Thus warming the house without actually having the heating on.



We have nine radiators on the system.

If the pressure drops does this indicate a leak? I looked at it today and it was down to half a bar. Its the first time its dropped like that though since it was installed! I topped it up and bled the radiators, should I be calling the installer over this?

If it's not on the "safe zone" and you've only had it since September, then yes you should.

southcoastrgi

zoominatorone wrote: »

If it's not on the "safe zone" and you've only had it since September, then yes you should.

safe zone ???????????????

OP i'd see how the pressure goes for a couple of days & if it's still dropping then get them back as you will be losing inhibitor & re-filling with fresh water neither will be good for your boiler

zoominatorone

southcoastrgi wrote: »

safe zone ???????????????

OP i'd see how the pressure goes for a couple of days & if it's still dropping then get them back as you will be losing inhibitor & re-filling with fresh water neither will be good for your boiler

My boiler has a green bit marked out on the dial where the pressure needle is. I call it the safe zone, forgive me if it isn#t correct parlance

southcoastrgi

zoominatorone wrote: »

My boiler has a green bit marked out on the dial where the pressure needle is. I call it the safe zone, forgive me if it isn#t correct parlance

aha now i know what you mean, i thought you were going all star trek on us for a min

diywhynot

OP: did you always use the old boiler to heat your water i.e. year-round not via an immersion heater in the cylinder during non-heating season?