Changing the pump bypass setting on a Vaillant Boiler

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We put a new radiator in by t'ing off an existing radiator pipe buried in the wall.

The radiator is [2kW] the existing one is about 2kw.
That is where the problem begins. The common pipe serving both rads is now carrying 4kW, so it may not be large enough.

You say that you have balanced the system. How far open are the lockshield valves?
 
The OP should check his installation instructions for the rad.

It was only about three months ago when I diagnosed a lack of much heat in a rad like that was because it was connected backwards.

But I really cannot remember just why it was so important to be connected correctly when at first sight it was symetrical. The builder was surprised too.

Tony
 
Tony, I have a similar one in my bathroom except mine has eight 1/2" connections (4 horizontal and 4 vertical if you can imagine, 2 at each corner). It came with a screw-in "bolt" with an allen key head which fit through any of these 8 connections and screws internally to the radiator into a (I guess) 3/8" hole to block it. Instructions say this must go in the same hole as the entry of the flow pipe/rad valve to force the water round the radiator. I imagine this cheaper eBay version simply has this blocked orifice built into the radiator with no option to change it.

Edit: found an image

diverter-system-circolo-grigio.jpg
 
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The one that I encountered actually had virtually no flow through it. It was not just a circulation issue.

But I just cannot remember why.

Tony
 
So if anyone cares.. it's fixed now

The key to resolving this problem was that the flow and return got hot within a few minutes of each other. This was despite all the radiators in the house having a cold return pipe.

So despite being an amateur plumber, I started taking up the chipboard floor and as I suspected the plumber who put in the system has not put a break in between the flow and return pipes so the water was not flowing to the new radiator as it had an easier route back to the boiler.

A bit of rerouting the pipework to create a break and now we have a warm entire house for the first time in 5 years.

I'm just waiting for the gas bill to go through the roof now!
 
Looking back over previous posts I see that 66 has mentioned a vertical rad and the "bolt" that has to be fitted.

Since he posted that, I have fitted three of that make.

They require the bolt, or stopper as I prefer to call it, to be fitted to ensure the flow goes up the first tube and come down the others.

Makes me wonder how a professional plumber could make such a basic mistake!

Tony
 

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