Quick answer: A pool heater transformer converts the incoming 120V/240V line voltage down to the 24VAC that powers the control board, igniter circuit, thermostat, and display. For Raypak Digital heaters (R185A, R265A, R335A, R405A) the OEM part is 006736F-A (120/240V to 24V, roughly $103-$113); Pentair MasterTemp and Max-E-Therm use the 42001-0107 (50VA, 120/240V, roughly $90, with an older 42001-0057S number still showing up at some retailers); Hayward’s current Universal H-Series Low NOx line (H150FD-H400FD) uses the IDXL2TRF1930 (roughly $138-$176), while older H-Series Millivolt/ED2 models take the different CHXTRF1930 (roughly $99); and Zodiac/Jandy LXi/JXi Low NOx 250/300/400 heaters use the R0456300 (roughly $120-$133). Per TroubleFreePool’s own troubleshooting threads, the standard diagnostic is checking for 24VAC on the transformer’s secondary side — no voltage there, after confirming full line voltage reaches the heater, points to the transformer rather than the control board.
A dead transformer is one of the few pool-heater parts that can look exactly like a dead control board from the outside — both show up as a heater that simply won’t power on. Getting the diagnosis right before you order a part saves buying the wrong $100-$175 component.
Pool heater transformers at a glance
| Transformer | Fits | Voltage | Price |
|---|---|---|---|
| Raypak 006736F-A | Digital R185A, R265A, R335A, R405A | 120/240V → 24V | $103-$113 |
| Pentair 42001-0107 | MasterTemp, Max-E-Therm | 120/240V → 24V, 50VA | ~$90 |
| Hayward IDXL2TRF1930 | Universal H-Series Low NOx H150FD-H400FD | 120/240V → 24VAC | $138-$176 |
| Hayward CHXTRF1930 | Older H-Series Millivolt/ED2, H100-H250 | Dual voltage → 24V | ~$99 |
| Zodiac/Jandy R0456300 | LXi/JXi Low NOx 250, 300, 400 | Not published → 24V | $120-$133 |
1. Raypak 006736F-A — For Digital R185A, R265A, R335A & R405A
Raypak 006736F-A Transformer Kit
- The OEM transformer for Raypak's Digital line — the same heaters covered in our best Raypak pool heater roundup and our manifold guide, which uses the same R185A-R405A model range.
- Converts either 120V or 240V incoming line power down to the 24V the ignition control and thermostat circuit run on.
- Retailer pricing runs $103-$113 depending on source — narrower than most parts on this site, since only a handful of retailers stock this specific kit.
- Works alongside the control board — if the board shows no signs of life at all, test the transformer's output before assuming the board itself has failed.
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2. Pentair 42001-0107 — For MasterTemp & Max-E-Therm
Pentair 42001-0107 Transformer
- Pentair's current OEM transformer for the MasterTemp and Sta-Rite-badged Max-E-Therm line — the same shared platform documented on our control board guide.
- An older part number, 42001-0057S, still shows up at some retailers around $76-$80 when in stock — both appear to be the same 50VA transformer under different catalog numbers, but confirm against your heater's own parts diagram if a listing seems unusually cheap.
- Rated 50VA, enough headroom to run the board, igniter circuit, and any add-on accessories wired into the same low-voltage circuit.
3. Hayward IDXL2TRF1930 — For Universal H-Series Low NOx
Hayward IDXL2TRF1930 Transformer
- The correct transformer for the current Universal H-Series Low NOx line — the same "FD" platform used by the igniter, pressure switch, and manifold guides on this site.
- Don't confuse this with the CHXTRF1930 — that's a different transformer for Hayward's older Millivolt/ED2-style H-Series heaters (H100-H250 range), a distinct generation from the FD-series this part fits.
- Priced higher than the other three brands' transformers, $138-$176 across current retailer listings — worth comparing a couple of sources before buying.
4. Zodiac/Jandy R0456300 — For LXi/JXi Low NOx 250, 300 & 400
Zodiac/Jandy R0456300 Transformer
- Retailer listings for this part reference both the LXi and JXi model names for the same 250/300/400 Low NOx size range — Jandy's naming overlaps here more than it does on some of our other Jandy OEM parts pages, so match the exact part number rather than the model name alone.
- No retailer or manufacturer source we checked publishes an input-voltage spec as clearly as the other three brands — confirm your heater's own rating plate before assuming a specific configuration.
- Sale pricing runs around $120, full retail closer to $133.
Transformer or control board? Test before you buy
A dead transformer and a dead control board can look identical from outside the cabinet — both leave the heater with no display and no response to any input. Per TroubleFreePool’s own troubleshooting threads, the standard test sequence starts upstream: first confirm full line voltage (120V or 240V) is actually reaching the heater’s power center, since neither the transformer nor the board can be blamed for a problem in the incoming supply. From there, check for 24VAC on the transformer’s secondary side — the low-voltage output wires feeding the board. No voltage there points to the transformer. Voltage present but the board still won’t power up points to the board itself, or in some cases a blown low-voltage fuse (often a 3-amp fuse) mounted directly on the board rather than the transformer at all. Skipping this test and guessing which part failed is the fastest way to buy a $90-$175 part you didn’t need.
Power surges and lightning strikes are cited consistently across pool-repair troubleshooting sources as a leading cause of both transformer and control-board failures together — which is also why the two parts sometimes fail in the same event, and why testing both rather than assuming just one is worth the extra five minutes with a multimeter.
The bottom line
A pool heater transformer is a cheap part with an outsized job — every electronic component in the cabinet depends on the 24V it supplies, so a blank display doesn’t automatically mean a failed control board. Test for 24VAC on the secondary side before ordering anything. Match the exact OEM part to your brand and model generation: Raypak 006736F-A, Pentair 42001-0107, Hayward IDXL2TRF1930 (current Universal H-Series) or CHXTRF1930 (older Millivolt/ED2 models), or Zodiac/Jandy R0456300. If the transformer tests fine and the board still won’t respond, our control board guide and not-heating troubleshooting guide cover what to check next.
Sources: TroubleFreePool — Troubleshooting pool heater low voltage issue, InTheSwim — Spark Ignition Pool Heater Troubleshooting Guide, PoolWeb — Pentair 42001-0107 Transformer, PST Pool Supplies — Pentair Transformer, ePoolSupply — Jandy R0456300 Transformer, E-Z Test Pool Supplies — Hayward H-Series Transformers