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Navien Expansion Vessel 30013993A

Navien

Navien Expansion Vessel 30013993A

6 litre expansion vessel for Navien NCB-CE ERP system and combination boilers.

Manufacturer part no.
30013993A
Showing prices

£98.81

£82.34 ex. VAT · VAT at 20%

Available to order · 3 working days
Available to order · 3 working days
Not certain it's the right part? The technical team verifies fitment before dispatch — no charge, and it stops a second trip.Call the technical teamSend a technical question

Same-day dispatch

Ordered by 4pm Mon–Fri, 10:30am Sat.

30-day returns

Unused, in original packaging.

What it is

The Navien 30013993A is a 6 litre expansion vessel used in Navien NCB-CE ERP system and combination boilers. It absorbs the volume increase of water as the heating circuit heats up, limiting pressure rise within the sealed system. The vessel is a serviceable component and is replaced when the internal diaphragm or charge is lost.

Signs this part needs replacing

  • System pressure rises sharply when the boiler heats up and falls again as it cools.
  • The boiler loses pressure repeatedly and needs frequent topping up.
  • Water discharges from the pressure relief valve during normal heating cycles.
  • Water is present at the vessel's air charge valve when the Schrader valve is depressed.
  • The vessel feels heavy or full of water when tapped, indicating a failed diaphragm.

Before you order

  • Confirm your appliance model against the fit list above before ordering.
  • Check the existing vessel's capacity and connection arrangement match the 6 litre unit.
  • Isolate the appliance, drain the heating circuit and depressurise before removal.
  • Check the system charge pressure and relief valve operation once the new vessel is fitted.

Not sure which part?

Search by part number, product name or brand — our technical team confirms fitment before anything is dispatched.