Navien
Navien Main Heat Exchanger 30023251A
Main heat exchanger for Navien LCB 700 21KW combi, regular and system boilers in internal and external variants.
£589.27
£491.06 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 main heat exchanger is a Navien component designed for the LCB 700 range of 21KW boilers. It transfers heat from combustion into the appliance water circuit, serving the heating system and, on combi models, the domestic hot water supply. It is supplied under part number 30023251A.
Signs this part needs replacing
- Reduced heating output or hot water performance that does not recover
- Kettling, banging or gurgling noises from the boiler during operation
- Water leaking from the heat exchanger body or nearby connections
- Discoloured system water or persistent sludge build-up in the heat exchanger
- Repeated boiler lockouts or fault codes linked to heat transfer or flow
Before you order
- Check the boiler data plate to confirm the model is a Navien LCB 700 21KW variant
- Confirm whether the appliance is the internal or external version
- Verify the existing part number is 30023251A before ordering
- Confirm the fault lies with the heat exchanger rather than a pump, sensor or diverter valve
No specification data held for this part.
| Make | Model / assembly | Reference | Years | Fitment |
|---|---|---|---|---|
| NAVIEN LCB 700 COMBI EXTERNAL 21KW (Serial Number 1705) | — | — | — | |
| NAVIEN LCB 700 COMBI EXTERNAL 21KW (Serial Number 1705) | — | — | — | |
| NAVIEN LCB 700 COMBI INTERNAL 21KW (Serial Number 1704) | — | — | — | |
| NAVIEN LCB 700 COMBI INTERNAL 21KW (Serial Number 1704) | — | — | — | |
| NAVIEN LCB 700 REGULAR EXTERNAL 21KW (Serial Number 1474) | — | — | — | |
| NAVIEN LCB 700 REGULAR EXTERNAL 21KW (Serial Number 1474) | — | — | — | |
| NAVIEN LCB 700 REGULAR INTERNAL 21KW (Serial Number 1472) | — | — | — | |
| NAVIEN LCB 700 REGULAR INTERNAL 21KW (Serial Number 1472) | — | — | — | |
| NAVIEN LCB 700 SYSTEM EXTERNAL 21KW (Serial Number 1471) | — | — | — | |
| NAVIEN LCB 700 SYSTEM EXTERNAL 21KW (Serial Number 1471) | — | — | — |
Showing 10 of 12 compatible appliances.
Documents & drawings
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