Convert Open vented for Combi

[teddysmith]

Hello all!

Heres a quick sketch of my current set up and I want to swap it for a combi.

The hot water side I'm fine, the central heating is what is confusing me.

What would be the best way to convert this ready for a combi?

Many Thanks

 

[omegaman]

Something like that. Most boilers have the feeds coming out from the bottom. From there you can branch off to feed the other radiators. Will you be replacing any pipework?

Who is doing the boiler?

 

[teddysmith]

Thanks for that.

The boiler is going to be fitted by an RGI, I'm just getting the pipework up to the jig in place. He will size up the gas line and commission the rest.

So the indirect flow and return from the cylinder can be removed completely from the old boiler as its not needed any more?

There is a 22mm flow and return for downstairs I have traced but there is a 15mm Tee off from this flow and return which from initial looks serves all of upstairs 4 rads.

I'll pipe the two flow and return into the boiler and complete the loop for upstairs as I'm hoping that is the full central heating circuit.

I'll have to run some new 15mm for hot to upstairs bathroom and then drop down to the kitchen. It looks like the bathroom is running from the cold main rather than fed from the tank which is good.

 

[omegaman]

So the indirect flow and return from the cylinder can be removed completely from the old boiler as its not needed any more?

Yes

There is a 22mm flow and return for downstairs I have traced but there is a 15mm Tee off from this flow and return which from initial looks serves all of upstairs 4 rads.

What size are these rads? If they're small then you might be ok but ideally you would want 15mm pipe to supply around 2 maybe 3 medium sized rads.

Will you be powerflushing the pipework?

 

[teddysmith]

Thanks, yeah I know I thought 4 rads was a bit much for the 15mm. I might replace this with 22mm and feed one of the big rads to this?

Once the pipework is in place will definitely be powerflushing, don't want it to kill my new boiler!

 

[omegaman]

I might replace this with 22mm and feed one of the big rads to this?

Didn't understand what you meant here. If you replace the main flow and return pipes with 22mm and tee off in 15mm you'll be fine.

 

[teddysmith]

Yeah that what I meant, I'll run the main flow and return up further down and Tee straight into that.

For the Hot to supply the bathroom is it worth piping in 22mm since the bath will need this or will I be OK piping it all in 15mm?

 

[omegaman]

It would be worth doing and you will notice the difference.