Navien
Navien O-Ring EPDM 18.8 x 2.4 70 BK 20027347A
EPDM O-ring, 18.8 x 2.4 mm, 70 Shore A, black, for Navien NCB300 and NCB500 combi boilers.
£3.91
£3.26 ex. VAT · VAT at 20%
Same-day dispatch
Ordered by 4pm Mon–Fri, 10:30am Sat.
30-day returns
Unused, in original packaging.
What it is
The Navien 20027347A is an EPDM O-ring measuring 18.8 x 2.4 mm with a 70 Shore A hardness, supplied in black. It is a sealing component used within Navien NCB300 and NCB500 combi boiler assemblies, where it compresses between mating faces to prevent water or condensate escaping from the joint.
Signs this part needs replacing
- Water or condensate weeping from the joint the O-ring seals
- The ring has hardened, flattened or lost its round cross-section
- Cracks, splits or surface perishing visible on the rubber
- Scale or corrosion deposits built up around the sealing face
- A recurring drip trace or pressure loss traced back to the joint
Before you order
- Confirm your boiler model and serial number against the fit list above
- Measure the old O-ring to confirm an 18.8 mm bore and 2.4 mm cross-section
- Inspect the sealing face for scoring or corrosion that could damage a new ring
- Check how many O-rings the joint requires before ordering
No specification data held for this part.
| Make | Model / assembly | Reference | Years | Fitment |
|---|---|---|---|---|
| NAVIEN NCB300-28K COMBI - (Serial Number 3710) | — | — | — | |
| NAVIEN NCB300-28K COMBI - (Serial Number 3710) | — | — | — | |
| NAVIEN NCB300-37K COMBI - (Serial Number 3734) | — | — | — | |
| NAVIEN NCB300-37K COMBI - (Serial Number 3734) | — | — | — | |
| NAVIEN NCB300-41K COMBI - (Serial Number 3711) | — | — | — | |
| NAVIEN NCB300-41K COMBI - (Serial Number 3711) | — | — | — | |
| NAVIEN NCB500-1S+/32K COMBI - (Serial Number 3924) | — | — | — | |
| NAVIEN NCB500-1S+/32K COMBI - (Serial Number 3924) | — | — | — | |
| NAVIEN NCB500-2S+/41K COMBI - (Serial Number 3712) | — | — | — | |
| NAVIEN NCB500-2S+/41K COMBI - (Serial Number 3712) | — | — | — |
Showing 10 of 12 compatible appliances.
Documents & drawings
Everything we hold for this part. Where a document exists but we don't hold it, the technical team will source it from the manufacturer — usually the same working day.
NAVIEN appliance manual — NCB300-28K COMBI - (Serial Number 3710), NCB300-37K COMBI - (Serial Number 3734), NCB300-41K COMBI - (Serial Number 3711)
manualmanualNAVIEN appliance manual — NCB500-1S+/32K COMBI - (Serial Number 3924), NCB500-2S+/41K COMBI - (Serial Number 3712), NCB500-2S/37K COMBI - (Serial Number 3735)
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