UK trade guideBoiler Spares 7 min readUpdated 9 July 2026

How to Replace an Ideal Logic Heat Exchanger (UK)

Fit Ideal Logic primary heat exchanger 174485 and plate HEX 173418. Full flush required.

Ideal

Symptoms

Whistling under demand — primary scaled. Weak hot water only — plate HEX blocked.

OEM part numbers

  • Primary HEX — 174485.
  • Plate HEX — 173418.
  • Gasket kit — 173417.

Flush and fit

Powerflush the system first. Fit both HEXs with new gaskets. Refill with fresh Fernox F1 inhibitor (500 mL for a 10-rad system).

Frequently asked questions

Is the plate HEX cleanable?
Yes with citric acid at 40 °C for 4 h — but if scale has caused ignition faults, replace.
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