Some Sort of Pressure Problem

[smudgersmiffy]

A friend of mine has a conventional gravity fed central heating system.

Potterton Kingfisher floor standing boiler, hot water cylinder, expansion tank in loft etc.

There's a problem at the moment whereby when the domestic hot water is on by itself, everything is fine.

However, when he switches on the heating, a load of water shoots up the vent and into the expansion tank, then starts over flowing continually.

Anyone got any ideas?

Any help would be much appreciated.

 

[twgas]

Probably due to a blockage somewhere, need more info on the system - motor valves etc.

 

[DP]

HW is possibly gravity looped and CH pumped leading to pump over due to incorrect plumbing.

Could be blockage as well as mentioned already.

 

[smudgersmiffy]

I doubt it's been incorrectly plumbed, as it's been an installation that's been there for years, and this problem has only just started happening.

My initial thought was a blockage somewhere as well. Mainly as I don't think he's ever had any inhibitor in the system ever.

Do you think if we drain some water out of the rads, then put in a couple of tubs of Fernox, it will dissolve any blockage?

As always, any help would be gratefully received.

Graham

 

[Steve69the69Gas]

Stroke a magnet around the pipes in the airing cupboard and note any attraction- that'll be the blockage

 

[smudgersmiffy]

Does that hard black stuff turn magnetic then?

 

[Steve69the69Gas]

Yep it's called magnetite.

 

[smudgersmiffy]

Will Fernox dissolve it, or is the only way of getting rid of it is to cut out and replace the blocked part of the pipe?

 

[Steve69the69Gas]

2nd option is the only way to be sure imo