New boiler installation, pipe size question and controls please

[larneylee]

Hi,

About to complete on a 3 bedroom semi detached house, upstairs downstairs. Current combi is upstairs in the bathroom and the intention is to buy a new Baxi HE33 and put it downstairs just off the kitchen so nearly directly below the old current boiler.

Total number of radiators for the house will be 10, 4 upstairs, 6 downstairs. Can I run the whole flow and return pipe work in 15mm? I know 1m leading off the boiler must be in 22mm copper. Flow and return pipe work to upstairs radiators, should these also be in 15mm or 22mm?

I know there is a science and a practical approach to understanding whether the boiler will cope flow wise etc. I can't be bothered with the science I just want to know whether for the downstairs rads I would need to run 22mm pipe directly to the rad, with a short 15mm reducer to the rad valve? or can the run be 15mm direct from the 22mm pipe work off the boiler. Would this apply to the upstairs rads too?

Can I have 2 wire temperature controllers in the house, say one in lounge entrance and one on the upstairs landing? What is the best means of controlling the boiler? I dont want anything wireless please.

Any further help and advice would be greatly appreciated.

Thank you.

 

[Rob Foster]

I would but there are probably others that will give you chapter and verse why you should not. If the rads are big enough then they will get rid of the heat finestyle and the worst that could happen is the boiler might modulate too often. But I don’t understand why you want to do this unless that’s what’s there already

 

[Harvest Fields]

The main flow and return should be in 22mm. Reducing down to 15mm when branching in for the flow and returns to each radiator.

You can have a stat upstairs and down (this is called zoning) but the upstairs and downstairs rads need to be on a separate circuit and each circuit needs to be operated by a zone valve and room stat/programmer.

 

[ShaunCorbs]

I would but there are probably others that will give you chapter and verse why you should not. If the rads are big enough then they will get rid of the heat finestyle and the worst that could happen is the boiler might modulate too often. But I don’t understand why you want to do this unless that’s what’s there already

best to get the gas safe engy whose doing the boiler to plumb it

 

[Riley]

Definitely get the gse to advise as it’s very dependant on house heat loss etc

 

[Bibbs118]

The manufacturers instructions will also certainly state 22mm flow and return. Read them for yiurself to find out.