HVACopediaGlow Brand · Boiler
Loc 38 Blocked flue switch tripped more than 3 times in 24 h
What the control is telling you
The blocked flue pressure switch opened more than three times in a day.
Applies to: B85, B120, B160 (NG and LP)
Likely causes
- Vent blockage
- Moisture or condensate in the silicone tubing to the flue switch
- Failed blocked flue switch
- Open wiring harness
Test and repair steps
- Check venting for blockages.
- Check the silicone tubing to the flue switch for moisture or condensate (Fig. 15.5).
- Check continuity across the blocked flue switch terminals. No continuity: replace the switch and press RESET.
- If the switch is good, check the harness for continuity; replace the harness if open and press RESET.
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 22 Three flame failures in one demand
- Loc 23 Error code memory corrupted
- Loc 3 Safety relay fault
- Loc 33 Low water cut-off circuit open
- 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
- Loc 7 Fan running too fast for more than 60 seconds
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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.