Navien · Combi boiler

E517 DIP switch setting fault

Medium severity Navien NCB-HNavien NFC-H

What the control is telling you

The DIP switch settings are invalid or inconsistent. NFC-H manual lists the reset type as: Manual reset.

Applies to: Navien fire-tube combi boilers, NFC-H series (NFC-250/200H, NFC-250/175H) and NCB-H combi boilers (NCB-250/150H, NCB-240/130H, NCB-240/110H, NCB-190/080H, NCB-190/060H)

Likely causes

DIP switch set to an unused combination
NFC-H: model DIP switches SW1 5&6 not matching the model

Test and repair steps

Warning: turn power off before touching the DIP switches.
Check DIP SW1 and SW2 against the DIP switch tables (SW1 1&2 OFF/OFF for normal operation; SW2 5&6 OFF/OFF for US/Canada).
NFC-H SW1 5&6 = OFF/OFF for NFC-250/200H, ON/OFF for NFC-250/175H.
Code keeps returning? Phone Navien Technical Support, 1-800-519-8794.

Settings for these units

Minimum installation clearances (indoor) · Navien NCB-H

Side	Minimum
Top	9 in (229 mm)
Back	0.5 in (13 mm)
Front	4 in (100 mm)
Sides	3 in (76 mm)
Bottom	12 in (300 mm)

Indoor wall-hung only; ambient must stay above 32°F (0°C).

Do not install on carpet; leave room for service.

Water quality limits (DHW and system fill) · Navien NCB-H

Contaminant	Max allowed
Total hardness	200 mg/l (12 grains/gallon)
Aluminum	0.05 to 0.2 mg/l
Chloride	250 mg/l
Copper	1.0 mg/l
Iron	0.3 mg/l
Manganese	0.05 mg/l
pH	6.5 to 8.5
Sulfate	250 mg/l (DHW table); 205 mg/l (fill table)
Total dissolved solids	500 mg/l
Zinc	5 mg/l
Chlorine (fill water)	4 mg/l

Scale damage from poor water is not covered by warranty.

Manual shows sulfate 250 mg/l on p.23 and 205 mg/l on p.29 - check local guidance.

Minimum installation clearances (indoor) · Navien NFC-H
Water quality limits (DHW and system fill) · Navien NFC-H

Models that show this code

7 models in Navien NCB-H, Navien NFC-H

NCB-190/060HNCB-190/080HNCB-240/110HNCB-240/130HNCB-250/150HNFC-250/175HNFC-250/200H

Other codes on the same units

E439 No DHW flow detected / flow sensor fault
E441 DHW outlet 2 sensor fault
E445 Mixing (bypass) valve fault
E515 PCB fault
E594 EEPROM fault
E615 Memory fault (input and memory)
E736 Cascade communication fault
E740 Outdoor sensor not detected

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Source: Navien NCB-H Installation & Operation Manual, 11.7 Understanding Error Codes, p.129-130; Navien NFC-H Installation Manual, 11.7 Understanding Error Codes, p.127-128. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.