One pipe system conversion

[franktank]

Hello again everyone,

As mentioned previously I'm in the middle of a house renovation and I'm trying to sort the previous CH installation out.

Basically, the system used to have a back boiler downstairs, which was replaced as part of the Warmfront?!? scheme with a Worcester Bosch 24Ri in the kitchen.

The system to me seems pretty poor, the rads downstairs output half the heat of those upstairs so I've been doing some investigation. It appears the system is a one pipe type system, which may go some way to explaining why some radiators are cold in comparison to others.

Anyway, whilst a lot of the floorboards are up (next door neighbours leak flooding our foundations) I may as well try and address the CH system. I have no problem with coverting to a 2 pipe system, however I just need a little guidance. As far as I can tell the system looks like:

Apologies for the poor diagram. My questions are, does anyone know why the valve between the flow and return is there? Is it required? There can never be a total block to the flow as far as I'm aware (Single pipe system so even if all rads are off water will always flow)? Would it still be required with a two pipe system, assuming I make the radiator in the bathroom permenantly on?

Secondly, the pipes from the boiler are 22mm, about 1m after the pump all the pipes become 15mm in the CH system. Is it OK to keep all the radiators feeds and returns at 15mm? I should point out, the pump and diverter valve are all in the airing cupboard if this makes any difference? Should I consider running 22mm downstairs then branching off 15mm to each rad?

Thanks all

Ben

 

[Fluffster]

Hi Ben
Your diagram is very helpful. The bypass is there to ensure you always have a decent flow through the boiler, most boiler manufacturers demand it no matter what your system layout is. For example you could have your valve set to hot water and have a blockage or restriction in the coil which would reduce the flow to the boiler.
Ideally you need 22mm primary flow and return with 15mm feeds to the rads to ensure efficient flow and return.
Pete

 

[franktank]

Thanks Fluffster.

I've done some more investigation tonight and it appears its a somewhat interesting installation!

Upstairs appears to be a dual pipe system. The pump etc are in the airing cupboard, whilst the boiler is in the kitchen. Pretty much straight after the diverter valve the 22mm is reduced to 15mm to feed every radiator in the house (7 in total)

Anyway, upstairs works fine, which I would expect, however downstairs works poorly, if at all and I think this is due to it being a single pipe system down there.

My Proposal...

I plan to take 22mm pipe from the mid port, and T off to 15mm to feed the front bedroom and bathroom radiator. I will remove the bypass in the bathroom and fit a towel rail with lockshields both sides. I will then continue with the 22mm pipe downstairs, using individual T pieces for the two back room radiators.

Downstairs I will carry the 22mm on into the kitchen, branching off for the hall radiator, then a T piece off into the lounge rad, and terminating the 22mm into 15mm to feed the kitchen rad, and then repeat the whole lot for the return.

So gents, is this a good idea? is running 22mm downstairs overkill? I was thinking of potential further expansion if needed. Please let me know if I'm barking up the wrong tree....

Cheers

Ben

 

[Fluffster]

Ben

Your plans are all good to use 22mm primary flow and returns. Make sure you put in a few drain cocks too.
I take it your system is sealed and you have an automatic air vent on the highest points?

It would be a good time to flush the entire system too.

Pete

 

[franktank]

It a vented system with head in the loft if that makes any difference?

cheers

Ben

 

[Fluffster]

Hi Ben

My mistake I missed the header tank in your first drawing. In that case make sure you have the vent, feed and pump arranged correctly.
Pete