Vaillant EcotecPlus 831 - Very High Gas Usage

[razorhazor]

Hi,

I live in a rented house and we have a Vaillant EcoTec Plus 831 installed. I've noticed that Gas bills are coming in very high since we've had the heating on, the house is a 3 bed semi 5 large rads, 2 small rads and 2 towel rail heaters. With the heating on for an hour with Rad temperature set at 60, I can use 25p worth of gas. This morning I managed to burn that in 19 minutes, with the same setup!

I've not changed any settings other than reducing the temperature of the central heating dial on the boiler to 60.

I've read some posts about looking at the return temperature but not too sure where to start, are there any obvious checks I can do before getting the boiler serviced?

I'm looking at more than £70 a month on gas at the moment based on very frivolous use of the heating, which doesn't feel right.

Thanks
Matt

 

[dcawkwell]

You would need to perform the same test from cold.
The boiler will work much harder heating the radiators up to temperature
than when it is just ticking over keeping them at temperature.
You can work out if the boiler is burning correctly.

Start the boiler from cold.
Go to the gas meter and measure gas usage over 2 minutes.
Look at the last 3 digits on the meter if your meter is metric.

So say it said .120 and after 2 minutes is said .200
You then do the calculation (0.200-0.120)*322=25kw

 

[razorhazor]

thanks for the quick response.

So this morning I started the boiler from cold, unfortunately I took the two readings over 19 minutes, but that equated to:

(9516.5-9516.4)*322 = 32.2Kw

Does that help, or is the 19 minute gap too large?

 

[gazdaz36]

How long does it take for the boiler to reach temperature on the central heating?

If it is quick your boiler will cycle and cause more gas usage. I'm betting the heating hasn't been range rated and is still set on the 24kw ( I think) factory setting which by the sounds of it is a little too much for your house.

 

[razorhazor]

How long does it take for the boiler to reach temperature on the central heating?

If it is quick your boiler will cycle and cause more gas usage. I'm betting the heating hasn't been range rated and is still set on the 24kw ( I think) factory setting which by the sounds of it is a little too much for your house.

Thanks for the quick response again.

It doesn't take long at all, literally a couple of minutes.

I've checked the D.0 setting and its 24Kw which I think is the default setting, I've seen a few posts mention dropping that value, any suggestions what to?

 

[gazdaz36]

First I would definitely drop the value on d.0 to about 16 which should help.

Also if the boiler is reaching temperature so quick there might also be a circulation problem in your heating system. Do you have trv's fitted and turned down restricting flow?

Is the hot water ok?

 

[picasso]

How many people live in your house ? your hot water usage could go a long way to explain your high gas bills although £70 a month aint that high, how did you work out you used 25p worth of gas ?

 

[razorhazor]

If it helps, I've ran through a BTU calculator I found online: http://www.radcalcs.com/ and total BTU's for the house is 48379 which apparently works out at 14.17Kw.

 

[razorhazor]

First I would definitely drop the value on d.0 to about 16 which should help.

Also if the boiler is reaching temperature so quick there might also be a circulation problem in your heating system. Do you have trv's fitted and turned down restricting flow?

Is the hot water ok?

ok, I'll give that a go thanks.

We have TRV's on the rads upstairs and most of them are turned off as the heat tends to contain upstairs in the evenings.

Hot water is absolutely fine.

 

[razorhazor]

How many people live in your house ? your hot water usage could go a long way to explain your high gas bills although £70 a month aint that high, how did you work out you used 25p worth of gas ?

Two adults and one child, I worked out the 25p by entering the meter readings into an app I have for my iPhone, it uses my Kw/h cost and a conversion ratio of 31.5 from the meter reading to Kw/h.

 

[D_Hailsham]

I took the two readings over 19 minutes, but that equated to: (9516.5-9516.4)*322 = 32.2Kw

Does that help, or is the 19 minute gap too large?

1. Is your meter metric (cubic metres) or imperial (hundreds of cubic feet). It will say on the meter. The calculation assumes metric.

2. 19 minutes is too long. The constant of 322 assumes two minutes.

3. Is there only one red number to the right of the black numbers?

 

[linkyplumb]

Unless you have your heating on 24/7 with all the windows open, then on a combi, the highest gas use is going to be for hot water.
As you quote figures of 25p etc, are you on a prepay meter, as quite often these are higher prices than credit meters.

 

[razorhazor]

Unless you have your heating on 24/7 with all the windows open, then on a combi, the highest gas use is going to be for hot water.
As you quote figures of 25p etc, are you on a prepay meter, as quite often these are higher prices than credit meters.

Hi, I agree with you, the hot water is certainly using the gas more than the CH but I guess the point is that the time to take 2 showers and run a small bath is alot less than having the heating on, so we are noticing that the CH is sapping more gas than the water.

I've made a couple of adjustments since posting this morning which I think may have helped, although I wont know until tomorrow mornings cold start; I've raised the radiator temp to 60 degrees and reduced the D.0 setting from the standard 24 Kw to 14Kw based on the calculations I made in a previous post. That seemed to heat the room quicker, although time will tell if reducing the D.0 setting has made a difference!

 

[ALEC1]

Where I have replaced on off controls with modulating controls savings have been reported as high as 15%...


Whether you would want to pay for the up grade is debatable though...

 

[Agile]

I am surprised your consumption is so low!

Most three beds have an annual gas bill over £1000 with most used over the winter!

To reduce consumption you need to insulate the loft and draught proof everwhere.

£800 pa is about the lowest for comfortable living.

Tony