Megaflo and Central Heating

[skylined_gtr]

Hello all,

It's coming to the time of year again when the mrs is going to want the heating going 24/7 and at 30 degrees (joking!). I've got to drain down the system to fit a new PRV on the boiler and top up with some rust inhibitor.

I've always had problems with air locks in this system when I've done a drain and fill, I've tried all sorts of tips that I have read on the forum but they don't seem to work for me. I wonder if it's because of the megaflo - Is there a recommended method for refilling the system when you have a megaflo in the circuit?

I have tried refilling with all ground floor radiator TRV tops removed and bleed valves open, I have tried it with the diverter in the hot water position then switching to central heating, tried bleeding from the pump.... in the end the only thing that seems to work is to fill the system, then keep flicking the PRV on the boiler so it 'shocks' the system. I then hear a lot of air moving around in the system.

I've drawn a crude diagram of my system layout but the important thing to note is that the boiler is on the ground floor and the megaflo is on the upper floor. It's a sealed system with an expansion tank in the boiler, the filling loop is upstairs next to the megaflo. Althought the boiler is on the ground floor, I believe the upper floor rads fill first.

Any help with techniques would be really appreciated

 

[Agile]

One of the best ways to minimise air in a system when adding chemicals is to add them in a towel rad or ordinary rad via the drilling for the air vent which is usually on a 1/2" tapping.

 

[oilboffin]

Yup true

 

[skylined_gtr]

Thanks for the tip. I'll try that. When I do a full drain down and refill, is there a method to do it with the megaflo?

 

[Rob]

megalfos not really any different to a normal cylinder when it comes to filling.

Just add manual vents at all the hight points on a system.

 

[skylined_gtr]

I've got an auto-bleeder in the airing cupboard, it's just off the Diverter valve and sits near the megaflo. I have noticed that it sits lower than the height of the megaflo, could that be the issue?

 

[ianmcd]

why would you drain the system to change a PRV ??? just manually open the PRV till it stops running then swap it and top up the pressure , the only reason that you dont use a PRV to drain is because it might stick but for some reason you are swapping it anyway