How to Replace a Potterton Promax 28 Diverter (UK)
Fit a new diverter on the Potterton Promax 28. UK part number, isolation and torque steps.
Potterton
Part number
The Potterton Promax 28 uses the diverter motor. Check the GC serial number sticker inside the case — Potterton revised the diverter at least once during production.
Isolate
Turn off the gas at the isolation cock. Switch off 230 V at the fused spur. Drain to just below the diverter: on the Potterton Promax 28, the drain-off is on the return pipe.
Fit
Unclip the diverter. Transfer the O-rings if OEM includes new ones — always fit the new seals supplied. Torque any brass unions to 25 Nm. Refill to 1.2 bar, bleed and fire for a wet check.
Frequently asked questions
- OEM or compatible?
- For gas-carrying components on the Potterton Promax 28 always fit OEM. Non-gas parts (fans, PCBs, pumps) — OEM keeps the warranty valid.
- Do I need to re-commission?
- Yes — record combustion CO/CO₂ ratio after any gas-side work per BS 6798.
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