HVACopediaGlow Brand · Boiler
Loc 33 Low water cut-off circuit open
What the control is telling you
The LWCO input (terminals 1 and 2) is open. Either the factory jumper or an LWCO switch must be across these terminals.
Applies to: B85, B120, B160 (NG and LP)
Likely causes
- Factory jumper removed and no LWCO installed
- LWCO tripped on low water
- Loose terminal strip connection
Test and repair steps
- Check terminals 1 and 2 on the field terminal strip: the jumper or the LWCO leads must be connected (Fig. 9.1).
- If an LWCO is fitted, check the water level and the LWCO itself.
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
- Loc 21 Flame detected before ignition
- Loc 22 Three flame failures in one demand
- Loc 23 Error code memory corrupted
- Loc 3 Safety relay fault
- Loc 38 Blocked flue switch tripped more than 3 times in 24 h
- Loc 4 Blocking error lasted over 20 hours
- Loc 5 Fan not running for more than 60 seconds
- Loc 6 Fan running too slow for more than 60 seconds
Save it for the next call
Star this code in the HVACopedia app and keep the whole library on your phone for jobs with no signal.
Source: Glow Brand B85/B120/B160 Installation & Operation Manual V20231025, Table 12.1 p.63. 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.