HVACopediaGlow Brand · Boiler
Err 116 Low water pressure (FILL)
What the control is telling you
Water pressure fell below the minimum (4 psi / 0.3 bar). The display also shows FILL and the burner is blocked.
Applies to: B85, B120, B160 (NG and LP)
Likely causes
- System not filled or leaking
- Expansion tank precharge wrong
- Dirty or failed pressure sensor
- Pressure sensor wiring
Test and repair steps
- Raise system pressure to at least 16 psi (1.1 bar), then cycle power.
- If the external gauge reads over 20 psi while the error is still on, inspect the pressure sensor and its harness; clean a dirty sensor gently with a calcium/rust remover.
- Replace the pressure sensor if it still misreads.
Settings for these units
Maintenance intervals · Glow B85/B120/B160
| Item | When |
|---|---|
| Annual inspection by a technician | Every year (warranty) |
| Relief valve try-lever test | Annually |
| LWCO test | Annually |
| Condensate trap clean | Annually (14.3) |
| Heat exchanger combustion-side wash | Annually or when combustion drifts (14.4) |
| Burner door silicone gasket | Replace if damaged or after 2 years |
| Service reminder | 2.203 on, interval 2.204 (default 1000 days) |
Operating pressure should sit 5 psi under the relief valve rating (max 25 psig on a 30 psi valve); water never above 180 F.
Models that show this code
3 models in Glow B85/B120/B160
Other codes on the same units
- Err 111 Internal software error (blocking)
- Err 112 Internal software error (blocking)
- Err 113 Internal software error (blocking)
- Err 114 False flame detected
- Err 119 CH return temperature sensor open
- Err 120 CH supply temperature sensor open
- Err 122 DHW tank temperature sensor open
- Err 123 Flue temperature sensor open
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Source: Glow Brand B85/B120/B160 Installation & Operation Manual V20231025, Table 12.2 p.64. 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.
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