What are the specs for this Transformer?

The correct replacement for Tempstar model T8MPL125J20B2 — 115V to 24V Class II | Ships Today 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 Tempstar equipment which lists the model number T8MPL125J20B2 — 115V to 24V Class II | Ships Today.

Is this transformer compatible with Bryant or Payne systems too?

Many Tempstar 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.

Tempstar

Tempstar 40VA Transformer for T8MPL125J20B2 — 115V to 24V Class II | Ships Today

Name: Tempstar 40VA Transformer for T8MPL125J20B2 — 115V to 24V Class II | Ships Today
Brand: Tempstar
SKU: 1172810-GEN
Price: 28.95 USD
Availability: InStock

SKU: 1172810-GEN Brand: Tempstar

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Overview

This OEM control transformer (part #1172810) steps 115-volt line power down to the 24-volt control voltage that your Tempstar T8MPL125J20B2 furnace uses to operate its thermostat, gas valve, igniter, and control board. Rated at 40VA, it supplies enough capacity to drive the full low-voltage control circuit. When a transformer fails, the entire 24V control system goes dead: the thermostat screen may go blank, the furnace won't respond to a heat call, and you may smell a faint burnt-electrical odor or find a blown low-voltage fuse on the control board. A buzzing or overheating transformer is also a sign the windings are breaking down.

Specifications

Spec	Value
Part Number	1172810
Type	Step-Down Control Transformer (Class II)
Brand	Tempstar (ICP / Heil / Comfortmaker)
Primary Voltage	115 VAC
Secondary Voltage	24 VAC
Rating	40 VA

Compatibility

Direct OEM fit for the Tempstar T8MPL125J20B2 gas furnace and other ICP-family models (Heil, Comfortmaker, Arcoaire, Keeprite) that specify part 1172810. Always confirm your existing transformer's VA rating and voltage match before ordering.

Installation Guide

Safety First — Disconnect power at the furnace switch and breaker, then verify zero voltage at the transformer leads with a multimeter.
Access — Remove the furnace control/blower access panel.
Document — Photograph all primary (line) and secondary (24V) wire connections before disconnecting anything.
Remove — Disconnect the primary and secondary leads, then unbolt the transformer from its mounting bracket.
Install — Mount the new transformer, reconnect the line and 24V leads exactly per your photo, and confirm the ground.
Test — Restore power and verify 24 VAC across the secondary terminals and normal furnace start-up.

Signs You Need a Replacement

Blank thermostat or no response to a heat call
Repeatedly blown 3A or 5A low-voltage control-board fuse
Audible buzzing or hot/burnt smell from the transformer
No measurable 24 VAC on the secondary side

Shipping & Returns

Ships same day on orders placed before 3 PM CST. 30-day returns. Backed by the National HVAC Parts fitment guarantee.

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

Tempstar 40VA Transformer for T8...

$28.95

Frequently Asked Questions

Does this Transformer fit my Tempstar T8MPL125J20B2 — 115V to 24V Class II | Ships Today?

Yes. This is the factory-specified OEM transformer for the Tempstar T8MPL125J20B2 — 115V to 24V Class II | Ships Today. 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 Tempstar T8MPL125J20B2 — 115V to 24V Class II | Ships Today?

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 Tempstar 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 Tempstar 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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