New boiler has resulted in increased Gas usage

[bmxboy]

Two weeks ago i had my old boiler (old gravity fed system) replaced with a worcester bosch 37 cdi and have noticed that my gas usage has increased from approx 2 units to 5 units per day.

The settings on the thermostat are still the same, 21 degrees from 8.00am to 10.00pm and the 16 during the night. The shower is electric and there has not been an increase in hot water usage.

The house is a standard 3 bed semi.

I thought that a new condesnsing boiler would reduce the amount of gas used.

Any help or advice will be much appreciated.

 

[jackthom]

A 30kw boiler sounds like a lot of output for a standard 3 bed semi. Maybe it's just heating up the house quicker than the old boiler and you're actually acheiving the target temp of 21C more of the time.

I'd consider 21 degrees a pretty high setting personally, but everyone to their own preferred climate.

 

[bmxboy]

It is heating the house and reaching 21 much quicker which should mean less gas consumption as the boiler would switch off quiker ........ or am I missing something ?

 

[JohnD]

it has also been quite cold the last couple of weeks. I see you are heating your house night and day, so it will use a lot on a frosty night.

Tell us about your TRVs and your insulation.

Does the boiler fire up for brief periods?

 

[rssteve]

It is heating the house and reaching 21 much quicker which should mean less gas consumption as the boiler would switch off quiker ........ or am I missing something ?

yes you are missing the obvious, what KW was your old boiler?

 

[bmxboy]

The TRV's are set to max and the insulation is average for a semi, loft insulation but no cavity wall insulation.

I have checked the boiler and it only switches on when the desired temperature falls.

Maybe it is the colder weather but if it continues that'll mean a quarterly gas bill of £600.

 

[bmxboy]

Unsure what KWH the old boiler was, it was an apollo fanfare s.

 

[JohnD]

chances are that your old boiler was less powerful, and with gravity flow your rads will not have been so hot, and the house would have been generally colder, and taken longer to get warm.

you are now shovelling more heat into your house, so you are using more energy. If you have left your TRVs on max you are doubtless heating some rooms excessively.

The hotter it is, and the longer it is hot, the more you will lose (mostly through your walls and roof) So what thickness insulation do you have in the loft? ten inches? six? four? are there gaps?

you can get subsidies and grants on insulation, check out the web sites of your gas and electricity suppliers to see what offers they have. They are generally reliable and do a good job.

If you put some thermometers in your rooms and adjust the TRVs down, the house will get cooler and you will use less gas.

 

[bmxboy]

The thickness of the loft insulation is approx 10 inches and the windows are double glazed, I will not get cavity wall insulation as it causes dampness.

The only part i can't understand is that the new boiler heats the house faster and reaches the desired temperature quicker resulting in the hall thermostat switching the boiler off.
The old boiler took a very long time for the rads to heat up and reach the desired temperature so the boiler was on for much longer which means that it should have used more gas than the new boiler ?

 

[bengasman]

the idea of adjustable valves (trv) is to regulate the temperature, not to leave them on max.
The most economical way is to set them all to 1, and only up those that are in a room that is consistently too cold.
Do not adjust more then once a day; you need to get used to the temperature.
If this is a heat only boiler, and not the combi, it is waaaay too big.

 

[JohnD]

The old boiler took a very long time for the rads to heat up and reach the desired temperature so the boiler was on for much longer which means that it should have used more gas than the new boiler ?

No, if the boiler was lower power, it would have been unsuccessfully trying to warm the house for a long time, using a trickle of gas. A bit like a mouse trying to push your car along, it would not be very good at it, but it would not need much food

The new boiler is likely to be far more powerful, and if you have turned all the TRVs up to max, it will be pumping out lots of heat (and using lots of gas) as it runs.

likely the new boiler, if you turned everything down, could deliver the same amount of heat as the old one, and leave you with a cold house, but you now have a warmer house, and are using more gas to get it warm.

 

[htgeng]

I will not get cavity wall insulation as it causes dampness.

hmmm, could you explain more on why you belive it cauases dampness?

 

[bengasman]

I will not get cavity wall insulation as it causes dampness.

hmmm, could you explain more on why you belive it cauases dampness?

insulation installers, or whatever they are called, do the same to the insulation as we do in the tank when the customer does not see it.

 

[gavinda]

speak for yourself

 

[simond]

Re: dampness

It is known that latent defects in the cavity can be exposed in certain circumstances by the application of blown fibre insulation. Older cavity walled houses can be plagued by damp even with an unfilled wall. Have it done at your risk, because the cavity wall company will deny responsibility citing constructional defects.

Re: The boiler

The amount of energy you need to heat a space is proportional to heat loss. And the heat loss is dependent on the internal vs external temperatures. If your insulation was perfect you wouldn't need a boiler.

Your internal temperature requirement is unchanged, but it has been many degrees colder outside.

Since these have been exceptionally cold over the last two weeks, that is where your excess energy is going. it is not the boiler being less efficient.