National Standard for CH Boilers in respect of req'd output.

[nec]

Hi All

Have searched through looking to see if there is a standard set down in respect of Boiler size to adequately run CH system in houses i.e. x btu's req'd in a modern 4 bed house - similar to scale of calculating room sizes v radiators.

Our daughters brand new house is comfortable but at a cost far higher than our older larger property. I am suspecting the builder has installed a boiler that is struggling to cope with demand making it uneconomical to operate.

Any thoughts would be appreciated.

 

[pannierstan]

Dear me NEC to many variables!!

Do you both have it set at the same temperature and run it at the same times every day and have the same number of baths and showers as each other
And have the same number of people living in the house as each other, and have the same boiler as each other and have the roomstat set at the same temperature and have the same size rads.

You get the drift. There is little you can do to compare 2 completely different houses with different systems in them regardless of the boiler.
If the house is getting to the right temperature it is very unlikely to be the boiler and even undersized boilers usually cope to a greater or lesser extent without costing more to run

Stan

 

[bster]

There are specific guidelines detailed in on the 'energy saving trust' website regarding boiler and radiator sizing. It can get complicated!

Though there is a more basic 'whole house' calculation that will give you a good idea of the required output.

 

[chrishutt]

I am suspecting the builder has installed a boiler that is struggling to cope with demand making it uneconomical to operate.

An undersized boiler would be more economical to operate than a correctly sized one. The only problem would be that it wouldn't heat the house adequately in very cold weather.

If, on the other hand, the boiler was seriously oversized, then it would be relatively inefficient to run. However there are many other factors that might contribute to inefficiency in operation. You need a competent heating engineer to assess the installation.

 

[timbalcombe]

60kw/hr max

 

[chrishutt]

60kw/hr max

What's that supposed to mean?

 

[nec]

Dear me NEC to many variables!!

Stan

Stan thanks and yes I know where you are coming from.

If it helps the house has 50% less people, 50 % less occupation (worker v retired) probably 50% better insulated (new house), settings at comfortable level in both houses yet daughters house is using 30 - 40% more gas to achieve the same.

Having been trained by me the level of useage will be similar i.e. rads right down in rooms with no-one using, showers at the gym, use CH rather than the gas fire, dinner out or at ours etc etc .

I can understand that a smaller boiler will be working harder and so achieving optimum efficiency but wonder what else might be causing the difference - and it is quite a difference.

 

[JohnD]

Perhaps she leaves the doors open, and turns up the stat when you aren't looking.

 

[nec]

Perhaps she leaves the doors open, and turns up the stat when you aren't looking.

John

Don't think so as she has to pay the bill!!!

 

[pannierstan]

Hmmm it is a baffler

Window size can make a big difference or wall construction.

Maybe it is the rads are smaller or larger.
Are they detached/semi/Terrace. Again big differences

Are you sure they have the timer set as you. Water on 24hrs or such and vice versa for heating??

 

[cross thread]

what size gas bill?,may be the meter at the old house was "running slow".
most people i know pay on average around 40 quid a month

 

[Agile]

On a modern 4-bed detached house where the occupants are reasonably careful about economy the gas should be about £800-£900 per annum.

Many people have forgotten the gas price has doubled over the last two years. You cannot compare the cost on the bills its the gas consumption which matters.

A small terraced house might still be £500 if they wear pullovers but not a 4 bed!

Tony

 

[nec]

Thanks everybody for their thoughts / advice.

I am starting at the beginning and will work through from there and hopefully come up with an answer.

The beginning is

http://www.est.org.uk/housingbuildings/calculators/boilersizing/

 

[ChrisR]

What are the two boilers?

 

[nec]

What are the two boilers?

The suspect Boiler is a Potterton Pro Max 15 HE (12 months old) and the comparison is a Vaillant ECO max 224 E (10 years old).

According to the 'guide' figures from the Energy Saving Trust they indicate that the boiler for the size of property should be 16kw. The Potterton falls below this figure 15.24 in the Non Condensing mode - but above it 16.49 in the Condensing mode.

I am now getting well out of my depth.

Any help would be appreciated.