Fitting a new radiator, and connected flow & return?

Xeorix

So it's a 2 part question.

We had a new boiler fitted in a new location. The plumbers left the old flow and return, however they connected them together with a valve.

The new boiler connects to the same flow and return but at a different location on the pipes. Is this right, it seems a bit backwards to me, so should we close the value or simply cut and blank the pipes off?


The next part is were fitting a new radiator. We've got a 22mm pipe we can connect to and taper down to 15mm, but can the return from this radiator go straight into the return for the boiler?

Crinkmeister

The valve has probably been set up as a bypass. Leave it alone.

Your new rad can go into the return as long as it is not the last tee off, otherwise you may get reverse circulation through heating circuit when heating hot water.. I'm assuming it's not a combi?

Xeorix

The heating is a pressurised system, but the hot water is open vented.

Looking at the old setup, there is a radiator in the return which is the last tee off. This one will tee off which will be the last one on the return to the boiler also. There is always going to be a final tee before the boiler return though isn't there? I don't get this part

As for the bypass, what is the benefit of it, it doesn't make sense for cooler return water to flow back into the main flow does it?

I'd have thought the return should have been connected to a tee in the new return should it not?

Crinkmeister

The return from the hot water heating coil should be the last tee, ie closest to boiler otherwise you may get warm radiators when they should be cold and the water tank is being heated as the return from the heating coil reverse circulates round the radiators. The bypass is required for some boilers.

Xeorix

Crinkmeister wrote: »

The return from the hot water heating coil should be the last tee, ie closest to boiler otherwise you may get warm radiators when they should be cold and the water tank is being heated as the return from the heating coil reverse circulates round the radiators. The bypass is required for some boilers.

Ok, interesting as it seems that wasn't even the case in the old system. I've drawn a crude diagram of what the original system looked like at the top, and what the new system looks like at the bottom.

The pink pipe is what I don't know what's going on, and the green is where we wanted to fit the new radiator



Any suggestions?
The new radiator will be running 15mm pipe, the flow and return are 22mm

Crinkmeister

The best way I can describe it, looking at your diagram, is if your tank return were to go where your new rad return goes, then that would be better. So the tank return is closest to the boiler. However, it's not always the easy/practical option. Look up 3 tee rule or ask any decent plumber.