More radiators = new boiler?

[A_Novice]

Hi,

Having an extension in the spring that will increase the number of rads from 8 + towel rail to 9 + 2 towel rails.

We have 1 existing bathroom and are going to be adding a downstairs loo and ensuite.

Currently the house is a 3 bed semi.

The boiler is a Potterton 24 ECO HE which is 25.2KW.

Am I likely to need a new boiler for the extra load?

Thanks

 

[Mottie]

I’m no expert but I’d say....nah!

 

[ianmcd]

very unlikely but you will need to calculate what heat load you need not how many radiators,

 

[snb]

a 3 bed semi, 24kw boiler is unlikely to be too small unless you have at least a 5 bed detached

 

[ant2]

Towel rails are between 200-500 watts, unless it's massive.
How is your boiler coping at the moment? Is your boiler running at full burn for long periods of time to heat up the house and set at 24KW? I would have thought very unlikely
Your only adding one extra radiator, boiler wise I would doubt it, 25KW is quite big for a 3 bed semi.

 

[fezster]

You need to do a whole house heat loss calc with your extension added. The boiler output is determined by the heat required to heat your house in the depths of winter. As said already, 25KW will probably be more than adequate for a 3 bed semi, even with an extension.

The extra radiators you are adding may necessitate a larger pump or increasing the pump speed. This will depend on where they are located and how they are connected to the existing system, including existing pipe sizing.

Do you have a HW cylinder? If so, this should be included in any heat loss calculation. Although, it is usually advised to have it heated outside of the central heating coming on, otherwise it may take longer for both radiators and the cylinder to heat up.

 

[A_Novice]

Thanks guys

The towel rads are small. The house currently heats up very well and the boiler doesn't burn for that long.

There isn't a HW cylinder.

To complicate the matter when the boiler goes cold for say 6 hours the primary heat exchanger leaks slightly. (As per another post I made a few months ago)

I have read the cost for the exchanger and labour for this model aren't expensive so was thinking of getting it repaired but if it needs scrapping because of the extension I don't want to waste money.

The extension starts in March.

It's a Potterton 24 ECO he .

Thanks

 

[fezster]

If it's a combination boiler, keep in mind that the HW flow rate is going to be compromised when more than one hot outlet is in use. I see you are adding an ensuite, so this may be a factor to consider.

 

[A_Novice]

True. Currently we can only run 1 hot tap at a time. Can some combi boilers allow for more?

 

[fezster]

Combi boilers are usually chosen based on HW requirement, rather than heating requirement. This means that combi boilers are usually oversized for the heating side, in order to give required HW flow rates.

You can get very large combis which can allow 2 hot outlets (depending on flow rate), and some combis even have a built in storage vessel to give an initial boost. Remember, though, that your water main needs to be able to deliver the required flow rate also.

 

[muggles]

My 4-bed late 60's semi does quite nicely with 14kW so 24kW should be loads for yours.

A Vaillant Green iQ 843 would probably be ok with two outlets at a time, but it's a £1700 boiler. You pays your money...

 

[A_Novice]

My 4-bed late 60's semi does quite nicely with 14kW so 24kW should be loads for yours.

A Vaillant Green iQ 843 would probably be ok with two outlets at a time, but it's a £1700 boiler. You pays your money...

Thanks.

I am thinking if I can replace the heat exchanger (obviously not me doing it) then it might be good for a few more years with the extension.

For it to be economical I'll need to get a refurbished one and find someone to fit it and doesn't charge a ridiculous amount. Mpn is 5112431.

 

[muggles]

What do you hope to achieve by replacing the heat exchanger? If it's more boiler power, you're going to be very disappointed (unless your current one is blocked)

 

[A_Novice]

What do you hope to achieve by replacing the heat exchanger? If it's more boiler power, you're going to be very disappointed (unless your current one is blocked)

There is a small leak in my current one as per posts above.