Reusing Siemens Enclosures for Honeywell Systems

This guide covers best practices for reusing existing Siemens control panel enclosures when migrating to Honeywell building automation systems.

Benefits of Enclosure Reuse

Benefit	Details
Cost savings	Avoid new enclosure purchase ($200-800+)
Time savings	No new tub installation required
Built-in features	Existing receptacle, power supply, terminal blocks
Reduced disruption	Less demolition work
Established location	Conduit routes already in place

Compatibility Assessment

Physical Dimensions

Before committing to reuse, verify:

Siemens Component	Check Against Honeywell
Backpan depth	Controller mounting depth
Width/height	Component spacing requirements
DIN rail positions	Honeywell DIN rail components
Knockout locations	New conduit entries if needed

Common Siemens Enclosure Sizes

Model Series	Typical Dimensions	Suitable For
Talon	20" x 16" x 6"	Small Spyder systems
APOGEE MEC	24" x 24" x 8"	Medium systems
APOGEE MBC	30" x 24" x 8"	Larger systems

Honeywell Component Dimensions

Controller	Dimensions	Notes
Spyder	~6" x 4" x 2"	Multiple per enclosure
Excel Web	~12" x 8" x 3"	Controller + expansion
WEBs-N4	Variable	Depends on JACE model

Step-by-Step Reuse Process

Phase 1: Assessment

1. Photograph existing panel (before disconnecting anything)
2. Document wire labels and terminal assignments
3. Measure available space after removing Siemens components
4. Identify reusable components:
   • Power supply (if 24VAC output matches)
   • Terminal blocks
   • Receptacle
   • Fuses/breakers
   • DIN rails

Phase 2: Removal

1. De-energize panel and verify lockout/tagout
2. Label all field wiring before disconnecting
3. Remove Siemens controllers carefully
4. Keep mounting hardware (may be reusable)
5. Clean enclosure of debris and old labels

Phase 3: Preparation

1. Evaluate power supply:

   • Siemens typically uses 24VAC
   • Verify VA rating sufficient for Honeywell load
   • Replace if undersized or not 24VAC

2. Plan component layout:

   • Controllers at eye level
   • Power supply at bottom (heat rises)
   • Leave space for wiring
   • Consider future expansion

3. Install new DIN rails if positions don't match

Phase 4: Installation

1. Mount Honeywell controllers
2. Install any new terminal blocks
3. Route wiring to new terminals
4. Verify power supply connections
5. Apply new labels

Wiring Considerations

Terminal Block Reuse

Siemens terminal blocks can often be reused if:

• Rated for appropriate voltage/current
• Proper wire gauge range
• Not damaged or corroded

Wire Landing Changes

Siemens Typical	Honeywell Equivalent
AI terminals	AI inputs on Spyder
AO terminals	AO outputs on Spyder
DI terminals	DI inputs on Spyder
DO terminals	DO outputs on Spyder
Comm (Lon/P1)	BACnet MS/TP or IP

Note: Maintain clear separation between low-voltage signal wiring and line voltage.

Power Supply Compatibility

Siemens Power Supplies

Model	Output	Compatible with Honeywell?
24VAC 40VA	24VAC	Yes, for small loads
24VAC 75VA	24VAC	Yes, typical Spyder system
24VAC 100VA+	24VAC	Yes, larger systems
24VDC	24VDC	Only for DC-powered devices

Load Calculation

Calculate total Honeywell system load:

• Controller power consumption
• Sensor power (loop-powered devices)
• Actuator holding power
• Add 20% safety margin

If existing supply < calculated load, replace.

Common Issues

Insufficient Space

Solution: Use smaller form factor controllers or add adjacent enclosure

Different Mounting Patterns

Solution: Install adapter brackets or new backpan

Incompatible Power Supply

Solution: Replace with appropriately sized 24VAC transformer

Outdated Receptacle

Solution: Replace with new GFCI receptacle if required by code

Documentation Updates

After migration, update:

• As-built drawings
• Panel schedules
• Wire labeling
• Controller addressing
• Point lists

Code Compliance

Verify installation meets:

• NEC requirements for low-voltage wiring
• Local building codes
• Fire marshal requirements (if in rated space)
• Owner electrical standards