Baxi combi 105e instant - Drain Primary circuit

[newrick1962]

I have a leak coming from the back of the pump. I'm guessing the O rings need to be replaced.
The installation guide says I should drain the primary circuit but gives no instructions on how to do it.

So, I'd appreciate some help on how to drain and then re-fill this boiler.

Thanks

 

[Baxmax]

To be fair the instant is a bit of a pig to drain all the water completely if you have never done this before you will wet the P.C.B and clock.But if you need to know.Isolate flow and return valves under boiler extreme right and left put a bucket under the drain point small white knob to right of pump and undo This will let some of the water go but you must get the stored water out of the expansion vessel,to release this remove the diverter valve motor and with a short screw driver or simalar push the divertor pin down it will gurgle and start to release more water.
This is of coarse after you have done all your eletrical safety checks to ensure the boiler is safe to work on.When you have completed all of above you re-fit pump and shut of drain point sopen flow and return valves and represurise the boiler to 1.5 bar.Then do all your Gas Safety Checks to ensure the boiler is safe to use.

 

[Boilerman2]

Turn off Electrical supply to boiler, turn off the heating flow & Return valves (under the boiler) to the right hand side below and behind the pump you should see a drain valve (with a thumbwheel,) open tis and let the water drain into a bucket or similar

It is unlikely that ALL of the water will drain, as the heat exchanger is the highest part and it has no vent. so expect some water to come out when you start to dismantle.
BAXI/POTTERTON boilers of this type have a badly designed subframe, that allows spilt water to find it's way effortlessly directly to the PCB where it works it's magic!! so caution required!

other than that, good luck.

 

[newrick1962]

Thanks to you both for this.
Good advice re the PCB, I'll take care of it.