Splitting radiators into 2 zones

[Gaz the Sparky]

What you want to do is fine. My point only applies if you were to change the returns so that the hot water return joins the other returns other than as the last junction before the boiler.

That’s great I just wasn’t sure if the returns to the radiator had to be the same or similar length/root to the flows to get even flow/heat.

In that case I will leave the returns as they are and will just lift the flows off and put in a new manifold back to a new zone valve off the main flow

Also doing this won’t mess up the last flow from the hot water cylinder

I have also contacted Ariston the makers of my boiler and they have said my boiler has an internal bypass valve fitted so I don’t need to worry about fitting an external one

Cheers

 

[oldbuffer]

Not sure I'd trust just an internal bypass. Given that the point of the bypass is to provide a route for hot water to flow and cool if there is otherwise no flow, then I'm not convinced there is sufficient length of pipe work in the boiler to accommodate the cooling. If you can find the space on the pipe work just before the zone valves I'd be tempted to fit a Honeywell DU144 or DU145.

 

[Gaz the Sparky]

Not sure I'd trust just an internal bypass. Given that the point of the bypass is to provide a route for hot water to flow and cool if there is otherwise no flow, then I'm not convinced there is sufficient length of pipe work in the boiler to accommodate the cooling. If you can find the space on the pipe work just before the zone valves I'd be tempted to fit a Honeywell DU144 or DU145.

Ok cool I have lots of room so I will install an external bypass valve before the valves

 

[Gaz the Sparky]

Im in the middle of re-piping the flows of the upstairs radiators onto a new zone valve pipe to make a separate zone upstairs. But I now have a question regarding fitting towel rails in the ensuite and bathroom. I am currently refitting the 2 rooms and buying new towel rails. The 2 towel rails come with 15mm valves and are chrome so I am looking to fit 15mm chrome pipe to under the floor.

The current radiators are plumbed in in 10mm plastic pipe so my question is as I'm re-piping the upstairs radiators to a new zone manifold on the landing should I replace the 2 bathroom radiator runs for 15mm right back to the new 22mm run ?

If I do this will it unbalance the system ?

or would I be best to leave the 10mm plastic pipes to the bathrooms and just use 10mm to 15mm adapters to adapt the 10mm plastic pipe to 15mm size of the radiator

Cheers

 

[endecotp]

You'll be fine keeping the 10mm, if that's easiest.

 

[John D v2.0]

Not sure I'd trust just an internal bypass. Given that the point of the bypass is to provide a route for hot water to flow and cool if there is otherwise no flow,

Nowadays It's not a heat dump to cool it as that would be wasteful, it's just too provide minimum flow through the hex to protect from localised boiling where the parts of the boiler are still above water temp. The boiler would shut down the burner before damage occurred due to high return temperatures.
If the burner was even on minimum, you'd need an extremely long externalexterna to dissipate 4+kw without boiling the water