46-TLT75 – STEP-DOWN TRANSFORMER (120V, 208, 230V, 480V to 24V, 75VA)

Trueline 75 VA control transformer with a multi-tap primary of 120, 208, 240 and 480 VAC and a 24 VAC secondary, supplied pre-wired with a built-in fuse and a foot mounting bracket. It supplies 24 V control power for thermostats, contactors, gas valves and control boards in commercial and residential HVAC equipment.

Specifications published by the manufacturer. Source: manufacturer documentation.

Specs

• BrandTrueline
• TypeControl transformer, foot mount
• Primary voltage120 / 208 / 240 / 480 VAC
• Secondary voltage24 VAC
• Capacity75 VA
• Frequency50/60 Hz
• FeaturesPre-wired leads, built-in fuse

Cross-reference numbers

This part replaces the following OEM and aftermarket numbers:

• X13550266010
• TRR00825
• TRR0825
• TRR825
• 101192-01
• 46W11
• CBX32M-060-230-6-06

Not sure if your number matches? Call (214) 340-9421 or bring the old part in — bench-testing is free.

How do I pick the right VA rating?

Add up what the 24 volt side has to carry. A 40VA transformer gives you about 1.7 amps at 24 volts and a 75VA gives you about 3.1. A plain furnace with a single-stage stat is fine on 40VA. Once you add a zone panel, powered dampers, a humidifier, a communicating stat, a condensate safety, or a two-stage outdoor unit, move up to 75VA. Going bigger does not hurt anything, since the load only draws what it needs. Undersizing shows up as chattering contactors and dropped calls on a 105 degree afternoon when everything pulls at once.

What are the primary taps for?

Multi-tap transformers have separate primary leads for 120, 208, 240 and sometimes 480 volts. Use the lead that matches your actual measured supply and cap off the ones you do not use. Feed 240 volts into the 208 tap and your secondary climbs to roughly 28 volts, which cooks boards and thermostats over time. Do it the other way and you get a weak 21 volts and relays that will not pull in.

My transformer is dead. Why did it fail?

Usually because something else shorted. Transformers rarely just quit. They get killed by a short on the 24 volt side, a pinched thermostat wire, or a seized damper motor. Find and fix the short before you energize the new one or you will buy two. And check the secondary with the load disconnected. If you read 24 to 28 volts open, the transformer is good and your problem is downstream.