15 radiatrors which size of pipe

[pantsmachine]

Thanks for the replies. I used Kevs radiator calculator and came up with a figure of 49,000 btu's(new wet system) to keep all my rooms including the loft conversion at 15 degrees with a 1 degree drop per hour. Checked my existing boiler and warm air side is 31,000 btu and hotwater side is 11,500 btu's. That would put me around 85,000 btu's for the new boiler as i have roughly doubled up my requirements.(Is this an alright way to do it or am i missing something)?

I was planning on running in the pipes myself as i can't do anything else with my loft conversion until they are in. The boiler itself i wouldn't touch as i know my limits. So 15 radiators, 85,000 btu boiler, 2 zone valve to seperate upstairs/downstairs and a unvented hotwater cylinder(150 to 200 ltrs), radiator ring main in 22mm and dropping down to 15mm off the T's to the radiators themselves? Is that OK? On the mains water pressure side there is plenty. For example in the bathroom i've got one of those telephone handset bodywashers T'd off the bath taps and it's hooked to mains and will practically jump out its cradle when turned on quickly.

 

[doitall]

Don't like it too hot then 15°C, try again at 23°C

 

[pantsmachine]

Wow, ran it at 20 degrees and got 65,000 btu's, quite a step from 49,000 btu's at 15 deg. I think a 85,000 btu boiler will still cover it? Thanks for that its an eye opener. I'm going to have a good look at the Potterton HE boiler recommended by Fitz1, large water storage capacity.

 

[doitall]

Wow, ran it at 20 degrees and got 65,000 btu's, quite a step from 49,000 btu's at 15 deg. I think a 85,000 btu boiler will still cover it? Thanks for that its an eye opener. I'm going to have a good look at the Potterton HE boiler recommended by Fitz1, large water storage capacity.

No harm in looking.

How many bathrooms did you say you will have

 

[Agile]

Another example of a DIYer trying to specify his system without any knowledge or understanding.

If he had been on the energy efficiency course, he would have remembered that over sizing a condensing boiler quickly reduces the efficiency.

If the whole house calculations say 65,000 BTU then thats what the boiler should be rated ( or set ) at.

Consult a properly qualified engineer at the outset to prevent costly mistakes!

Tony Glazier

 

[kevplumb]

the name of this forum is ?
the idea is to point people in the right direction
not get on the soapbox with the holier than thou attitude mister

fwiw
yes i can
want my number

 

[pantsmachine]

I'll have two bathrooms. The one downstairs has a bath HP shower and a sink. Upstairs will have a HP shower and two sinks. In time there will be a cloakroom downstairs which will have a single sink. Since its obvious that i'm a noob at this can someone tell me if i have to set the boiler spec to radiator requirements alone and not account in any way for hot water requirements for all listed above. Kev cheers for sticking up for new guys. Agile consider your soapbox kicked but thanks for the heating engineer advice.

 

[kevplumb]

calc your rads, add the hot water demand . add 10% ball park

 

[Agile]

Yes kevin, DIY!

DIY is fine and gives a feeling of achievement, reduced costs and the opportunity to learn new skills. To avoid costly mistakes though it is essential that the project is properly designed and researched. This will often involve using a professional to assist at the design stage.

In this particular case a CORGI engineer is to be used to fit the boiler and it would be useful to call him at an early stage to assist in selecting the best boiler for the job.

My last posting gave pointers on correctly sizing the boiler, although that is based on a heat calculation which I am not party to.

There is now a suggestion of using a storage combi. The manufacturers dont highlight the problem and many installers dont seem to understand that once the storage has been used up in a few minutes the HW flow reduces to the same or less than any other combi.

Tony Glazier

 

[doitall]

Exactly Tony it's my opinion that a combi would be unsuitable in a big way.

An 200litre unvented cylinder would suit your needs provided the pressure and volume is exceptable, but that would also be the case with a combi.

Calculate the heating at 23-25 C and an outside temperature of -5 add 10-15% for hot water.

15 rads at a good guess would require 30-35 KW with hot water, obviously that would depend on insulation, glass area, walls, materials and size of rooms, etc etc.

And yes you would need 28mm from the boiler MINIMUM.