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Help with identifying what this hot press knob

ongarite · 2022-02-25 17:27:30

Someone had an adventure in my hot press & playing with this knob. I don't recognise the symbol on it & what is does? The red section below the white knob has numbered graduated lines. Anyone know what it's for & what normal position should be?

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25-02-2022 6:27pm

#1

ongarite

Registered Users Posts: 8,201 ✭✭✭

Join Date: August 2006

Posts: 8046

Someone had an adventure in my hot press & playing with this knob.
I don't recognise the symbol on it & what is does? The red section below the white knob has numbered graduated lines.
Anyone know what it's for & what normal position should be?

0

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#2 25-02-2022 11:08pm
John.G

Registered Users Posts: 3,466 ✭✭✭

Join Date: April 2018

Posts: 3373

It looks like a ABV (automatic bypass valve) which opens on boiler pump overrun when the zone valves close, It might be numbered 0, 0.1, 0.2 etc up to 0.6, try setting it at say 0.35 which means it will open when the pump pressure reaches 3.5M, or else close it fully (0.6), wait for pipework on either side to cooldown then slowly open it very slowly (with all zone valves open) until the pipes start to get hot and close it back down say a 1/8th or 1/4 turn. (make a note of the setting).

2