castle-docs/content/equipment/heating/wood-fire-heater.md

title	description	tags	aliases
Wood Fire Heater (GBT Boiler)	Complete operating guide for the GBT wood-fired boiler	equipment heating wood-fire priority	GBT Boiler Wood Boiler

Wood Fire Heater (GBT Boiler)

[!info] This is the primary heat source for the property

Quick Reference

Item	Details
Location	TBD
Make/Model	GBT Wood Boiler (Geminox)
Firewood Location	TBD
Min Water Temp	70°C (to prevent tar/condensation)

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How to Start the Boiler

[!warning] Before You Begin

1. Check water pressure gauge reads above 1 bar (when cold)
2. Confirm boiler has electrical power

Step-by-Step Startup

1. PUSH the bypass lever (#3) (opens flue gas bypass)

!flue-open.jpg

2. OPEN loading door (#4) → add paper, kindling, then logs

3. LIGHT the paper

4. OPEN ash door (#7) slightly (improves draft)

5. WAIT a few minutes until fire catches

6. CLOSE ash door (#7)

7. PULL bypass lever (#3) toward you (closes bypass)

!flue-closed.jpg

8. TURN ON main switch (#8) (orange light illuminates)

9. ADJUST temperature knob (#5) (keep above 70°C)

[!danger] Never use liquid fuel (gasoline, lighter fluid) to light the boiler

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Boiler Components

!

#	Component	Purpose
1	Loading door handle	Opens door to add wood
2	Thermometer	Shows boiler water temperature
3	Bypass lever	Push to open, pull to close (see below)
4	Loading door	Add wood here (top front)
5	Temperature knob	Left = cooler, Right = hotter
6	Secondary air adjustment	Fine-tune combustion (2 screws)
7	Ash door handle	Opens door to access ash pan
8	Main switch	On/Off - orange light when on
9	Primary air adjustment	Controls main air flow
10	Flame sight glass	View fire through ash door

Bypass Lever Positions

OPEN (for lighting/reloading)	CLOSED (normal operation)
!flue-open.png	!flue-closed.png
Push lever away from you	Pull lever toward you

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Reloading Wood (Fire Already Burning)

1. PUSH the bypass lever (opens bypass)
2. Open loading door
3. Add wood moderately - prefer 3-4 small loads over 2 large ones
4. Close loading door
5. PULL bypass lever toward you (closes bypass)

[!tip] Mid-season advice Don't overload the boiler, especially in mild weather. Smaller, more frequent loads are better.

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Temperature Adjustment

Boiler Water Temperature

• Turn the temperature adjustment knob:
  • Left = decrease (-)
  • Right = increase (+)
• Keep temperature at or above 70°C to prevent tar buildup and condensation

Room/Radiator Temperature

• Adjust the mixing valve on your heating circuit (not on the boiler itself)
• Turn gradually from minimum toward maximum until comfortable

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Air Controls (Fine-Tuning)

Primary Air (Main Adjustment)

• Air control adjustment knob on front
• Left = less air (slower burn)
• Right = more air (faster burn)
• Goal: maintain glowing ember bed

Secondary Air (Combustion Quality)

• Two adjustment screws near ash door
• Right = decrease air
• Left = increase air
• Adjust with ash door closed
• Check flame through sight glass - should be neither too weak nor too harsh

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Shutting Down the Boiler

1. Press main switch to STOP position (orange light goes out)
2. Keep doors open to ventilate the interior
3. Allow to cool completely

[!warning] Frost Protection If the building may be exposed to freezing temperatures, contact a qualified professional to add antifreeze or drain the heating circuit.

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Summer Operation

If Connected to Hot Water Tank

• Set mixing valve to minimum position
• Keep boiler temp at/above 70°C
• Make 1-2 good batches of dry wood per day rather than continuous low operation
• Adjust hot water temp via thermostat on the tank

If NOT Connected to Hot Water Tank

• Stop the boiler (see shutdown procedure above)
• Leave doors open for ventilation

Prevent Mixing Valve Jamming

[!warning] Important During summer, manually operate the mixing valve 3 times to prevent jamming.

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Firewood Requirements

[!tip] Wood Quality is Critical Use the driest wood possible: 2 years seasoning, including 1 year under shelter

Recommended Wood Types

Type	Quality
Oak	Excellent
Hornbeam (Charm)	Excellent
Beech	Excellent
Maple	Excellent
Fruit trees	Good (except cherry & plum)

Log Sizes

Model	Max Log Length
GBT 20	50 cm
GBT 30/50	70 cm

Storage Location

TBD - Add firewood storage location

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Maintenance Schedule

Daily

• Remove ashes from ash pan

Weekly

• Check central orifice between combustion chamber and loading area is clear
• Remove ash pan and clean exchanger fins with metal brush
• Clean flame sight glass if needed

Quarterly

• Disassemble and clean smoke box (4 screws attach it to boiler body)

Twice Yearly (Mid-season & End of Season)

• Have installer/service check and clean:
  • Fan cleanliness
  • Air passage openings
  • Joint/seal condition
• End of season: complete cleaning, leave doors open for ventilation

Annually

• Professional inspection of all adjustment and safety components
• Chimney flue cleaning and verification

[!warning] Adding Water Frequently? If you need to regularly add water to your heating circuit, call a qualified professional immediately.

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Troubleshooting

Problem	What to Check	Solution
No heating	Wood supply	Ensure boiler has wood
No heating	Mixing valve position	Move from minimum toward maximum
Heating but no hot water	Hot water system	Call qualified professional
Hot water but no heating	Mixing valve	Check it's not on minimum
Smoke in room	Bypass lever	Push open before lighting/loading
Poor combustion	Wood moisture	Use drier, well-seasoned wood
Tar buildup	Temperature too low	Keep boiler water above 70°C
Tar buildup	Wet wood	Use properly seasoned wood

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Emergency Procedures

Chimney Fire

[!danger] Signs of chimney fire

• Loud roaring sound
• Excessive smoke
• Very hot chimney/stovepipe
• Flames visible from chimney top

If chimney fire occurs:

1. Call 112 (fire department)
2. Close all air controls
3. Get everyone out of building
4. Do not use water on the boiler

Carbon Monoxide

• Install CO detector near boiler
• Symptoms: headache, dizziness, nausea
• If alarm sounds or symptoms occur: evacuate and call 112

Water Leak

• Stop the boiler immediately
• Call qualified installer or after-sales service

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Service Contacts

Service	Contact
After-Sales Service	TBD - Add local contact
Geminox Consumer Service	08 20 00 60 00 (France)
Chimney Sweep	TBD
Installer	TBD

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Safety Reminders

[!danger] Critical Safety Rules

• Never use liquid fuel to light the boiler
• Never overload the boiler, especially mid-season
• Always open bypass lever before lighting or reloading
• Always keep water temperature at/above 70°C
• Never store combustible or corrosive products near boiler
• Never block ventilation openings in the boiler room
• Only qualified professionals may work inside the boiler

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Documentation

• Geminox GBT Manual (PDF, French) - Original manufacturer manual

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Related Pages

• heating-system
• fire
• power-outage - Heat during outages