What are the specs for this Transformer?

The correct replacement for National HVAC Parts model 40VA 120/208/240V to 24V Transformer — Universal HVAC Replacement is this exact part. It is the factory-specified replacement with exact OEM specifications. Using a part with different specifications can cause equipment damage or void your warranty. You can verify this by checking the data plate on your National HVAC Parts equipment which lists the model number 40VA 120/208/240V to 24V Transformer — Universal HVAC Replacement.

Is this transformer compatible with Bryant or Payne systems too?

Many National HVAC Parts parts are cross-compatible with Bryant and Payne systems since all three brands are manufactured by Carrier Global Corporation. The same physical part is often used across multiple brand labels with different model numbers. To verify cross-compatibility, check your Bryant or Payne equipment service manual for cross-compatible part numbers, or contact info@nationalhvacparts.com with your model number for confirmation.

National HVAC Parts

40VA 120/208/240V to 24V Transformer — Universal HVAC Replacement

Name: 40VA 120/208/240V to 24V Transformer — Universal HVAC Replacement
Brand: National HVAC Parts
SKU: NHVAC-XFMR-40VA-MT
Price: 19.99 USD
Availability: InStock

SKU: NHVAC-XFMR-40VA-MT Brand: National HVAC Parts

$19.99 $29.99

Order before 3PM CST — ships same day.
Standard delivery 2-5 business days. Express options at checkout.

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40VA control transformer stepping down from 120/208/240V to 24V AC. Universal replacement for most residential furnaces and AC systems. The transformer provides the low-voltage 24V power that runs your thermostat, control board, gas valve, and contactor coil — without it, your entire HVAC control circuit is dead.

When to replace: No power to thermostat (blank screen), system completely unresponsive, burning smell from furnace, tripped breaker when system runs, buzzing from transformer with no 24V output, or measured secondary voltage below 22V.

VA Rating: 40VA
Primary (Input): 120/208/240V
Secondary (Output): 24V AC
Type: Class 2 Control Transformer
Application: most residential furnaces and AC systems
Mounting: Foot mount with screw terminals
Warranty: 1-year replacement warranty

Install difficulty: 2/5 — Turn off all power at breaker. Disconnect wires from old transformer (photograph first). Remove mounting screws. Mount new transformer, reconnect wires to matching terminals (primary to line voltage, secondary to 24V circuit). 15-25 minutes.

Sizing guide: A 40VA transformer handles most single-zone residential systems. If your system has multiple thermostats, zone dampers, or a communicating system, consider upgrading to 50VA or 75VA.

Shipping Information

Orders placed before 3PM CST ship same business day
Standard delivery: 2-5 business days
Express shipping available at checkout
Free shipping on orders over $75
Tracking number emailed upon shipment

Return Policy

30-day returns on unused parts in original packaging
Electrical parts (capacitors, contactors, control boards) are final sale once installed
Email info@nationalhvacparts.com to initiate a return
Refunds processed within 5-7 business days

Frequently Asked Questions

Does this Transformer fit my National HVAC Parts 40VA 120/208/240V to 24V Transformer — Universal HVAC Replacement?

Yes. This is the factory-specified OEM transformer for the National HVAC Parts 40VA 120/208/240V to 24V Transformer — Universal HVAC Replacement. It is a direct drop-in replacement that fits without modification. Always verify the model number on your equipment nameplate before ordering.

How do I replace the transformer on my National HVAC Parts 40VA 120/208/240V to 24V Transformer — Universal HVAC Replacement?

Difficulty: Medium (30–45 min)
Step 1: Turn off breaker. Step 2: Photo wiring connections. Step 3: Disconnect wires from old transformer. Step 4: Remove mounting hardware. Step 5: Install new transformer, reconnect wires matching voltage ratings. Step 6: Verify 24V output with multimeter.

My thermostat has no power. What failed?

Thermostat with no display = failed 24V transformer (or blown control board fuse). Check the 3A/5A fuse on the control board first ($1–$5 fix). If fuse is good but no 24V output from transformer, replace transformer.

Is this transformer compatible with Bryant or Payne too?

Many National HVAC Parts parts are cross-compatible with Bryant and Payne since all three brands are manufactured by Carrier Global Corporation. The same physical part is often used across brand labels with different model numbers. To verify: check your Bryant or Payne equipment service manual for cross-compatible part numbers, or email info@nationalhvacparts.com with your model number.

Should I use OEM or aftermarket for my National HVAC Parts transformer?

OEM recommended for reliability and warranty compatibility. OEM parts match exact factory specifications for proper fit, performance, and safety. While aftermarket alternatives cost less upfront, the risk of improper fit and reduced lifespan usually makes OEM the better value long-term.

How fast does National HVAC Parts ship?

Orders placed before 3:00 PM CST ship the same business day. Standard delivery is 2–5 business days anywhere in the continental United States. Express shipping available at checkout. We ship from Houston, TX to all 50 states. 30-day return policy on all parts.

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40VA 120/208/240V to 24V Transformer — Universal HVAC Replacement

Shipping Information

Return Policy

Frequently Asked Questions