Furnas 42BF35AF Retrofit-Ready DP Contactor for DP Series

Furnas 42BF35AF Retrofit-Ready Definite Purpose Contactor for DP Series Control Systems

The Furnas 42BF35AF is a 2-Pole, 30A, 24VAC coil Definite Purpose (DP) contactor engineered for seamless retrofit integration into legacy DP series control panels, HVAC control cabinets, refrigeration systems, and light industrial automation enclosures. As OEM production of many legacy Furnas DP contactors has been discontinued or consolidated, the 42BF35AF remains a critical drop-in replacement for aging control infrastructure where panel redesign is not feasible. SMARTNEXMSK maintains verified stock of the 42BF35AF with full functional testing, dimensional inspection, and a 12-month warranty on every unit shipped.

Whether you are managing a planned upgrade cycle, responding to an unplanned field failure, or executing a phased modernization of a multi-panel facility, the 42BF35AF delivers the electrical and mechanical compatibility required to restore control continuity without rewiring or reprogramming the host system.

Upgrade Compatibility Table

Retrofit Planning for Existing Automation Systems

Retrofitting a Furnas 42BF35AF into an existing control panel requires a structured pre-installation review to avoid commissioning delays. Begin by auditing the control cabinet’s power distribution: confirm that the 24VAC control transformer — often a Acme Electric or Square D Class 9070 transformer — is sized to handle the inrush current of the replacement contactor coil without causing voltage sag that could affect adjacent relays or PLCs sharing the same secondary winding.

Next, inspect the terminal block layout. Many legacy DP series panels use Weidmüller or Phoenix Contact terminal strips routed directly to the contactor’s load and coil terminals. Verify that existing wire ferrules and ring terminals are compatible with the 42BF35AF’s screw-clamp terminal pitch. If the panel uses a Furnas 42CF or 42BF series contactor with a different footprint, a DIN rail adapter bracket may be required to maintain the original wiring harness geometry.

For panels that include auxiliary contact blocks — such as the Furnas 42-A-A1 or 42-A-A2 add-on auxiliary contact kits — confirm that the auxiliary contact mounting interface on the 42BF35AF accepts the same snap-on or screw-mount accessories. This is particularly important in control systems where the auxiliary contact feeds a status signal back to a PLC digital input module or a SCADA system’s discrete input card.

In HVAC and refrigeration applications, the 42BF35AF is frequently installed alongside a Furnas 48BSC3M20 or equivalent overload relay. Verify that the overload relay’s current range matches the motor FLA (Full Load Amps) of the connected compressor or fan motor, and that the overload’s trip class is appropriate for the application. If the existing overload relay is also end-of-life, plan to replace it concurrently to avoid a second service call.

Control panels that integrate a Siemens LOGO! or Allen-Bradley Micro820 programmable relay for sequencing logic should have their output wiring to the contactor coil verified for current sink/source compatibility. The 42BF35AF’s 24VAC coil draws approximately 7–10VA at seal-in; confirm the PLC or relay output module is rated for this inductive load. If the output module uses a transistor (DC) output, a control relay interposing stage — such as an Omron MY2N or Phoenix Contact PLC-RSC series relay — will be required to drive the AC coil.

For panels with a Furnas 42CE or 42CF series contactor that includes a built-in mechanical interlock for reversing duty, note that the 42BF35AF is a standard (non-reversing) contactor. If the application requires reversing duty, a separate mechanical interlock kit or a dedicated reversing contactor assembly must be specified. Document this requirement in the retrofit bill of materials before ordering.

Downtime Control During System Migration

Minimizing production downtime during a contactor replacement is achievable with disciplined pre-staging and a clear isolation procedure. Before the maintenance window opens, pre-wire the replacement 42BF35AF on a temporary DIN rail segment or a spare panel section, replicating the load and coil terminal connections from the as-built wiring diagram. This allows the swap to proceed as a plug-and-play exchange rather than a live wiring exercise.

During the isolation phase, de-energize the panel at the upstream disconnect or circuit breaker and apply LOTO (Lockout/Tagout) per site safety procedures. Photograph the existing contactor’s terminal connections before removing any wires — this provides a reference if the as-built drawing is outdated or missing. Remove the failed or end-of-life contactor, install the 42BF35AF, and reconnect terminals in the documented sequence.

Before restoring power, perform a continuity check across the load contacts (open-circuit with coil de-energized) and a coil resistance check to confirm the unit is undamaged. Energize the coil at 24VAC and verify audible contact closure and correct load-side voltage. If the panel feeds a motor, perform a no-load test run before reconnecting the mechanical load. Log the commissioning results — including coil voltage measured at the terminal, contact closure time, and load current at full load — in the panel’s maintenance record.

For multi-panel facilities executing a phased replacement program, SMARTNEXMSK can supply the 42BF35AF in batch quantities with pre-shipment functional testing documentation, reducing the per-unit commissioning burden and supporting a predictive maintenance schedule that avoids unplanned outages.

Retrofit Support FAQ

Q1: Is the Furnas 42BF35AF a direct drop-in replacement for the 42BF35A?
The 42BF35AF and 42BF35A share the same 2-pole, 30A load rating and 24VAC coil voltage. The “F” suffix typically denotes a factory-installed coil or terminal variation; verify the coil voltage and terminal configuration against your panel’s wiring diagram before installation. In most DP series panel applications, the 42BF35AF is a functionally equivalent replacement for the 42BF35A.

Q2: What wiring changes are required when replacing a failed DP series contactor with the 42BF35AF?
In most cases, no wiring changes are required if the replacement contactor shares the same terminal layout and coil voltage. Confirm load terminal positions (L1/L2 and T1/T2) and coil terminal polarity (A1/A2) match the existing wiring. If the panel uses a different terminal pitch or wire entry angle, a short jumper or terminal adapter may be needed. Always verify with the panel’s as-built drawing.

Q3: How is the 42BF35AF tested before shipment?
Every 42BF35AF unit shipped by SMARTNEXMSK undergoes pre-shipment functional testing: coil energization at rated voltage, contact closure verification, and insulation resistance check between load poles. Units that fail any test parameter are quarantined and not shipped. A 12-month warranty covers manufacturing defects and functional failure under rated operating conditions from the date of shipment.

Q4: Can the 42BF35AF be used in a reversing contactor application?
No. The 42BF35AF is a standard (non-reversing) definite purpose contactor. For reversing duty applications — such as motor forward/reverse control — a mechanically interlocked reversing contactor pair or a dedicated reversing contactor assembly must be used. Contact SMARTNEXMSK to identify the correct reversing contactor for your application.

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