Read the 11th character of the York YMC2 model number on the nameplate: it is the Mod level, A or B. York renewal parts form 160.84-RP1 lays the string out as YMC2 (positions 1–4), stage (5), capacity in kW (6–9), refrigerant (10) and Mod level (11), so YMC2-S0050AB is a Mod B and the Mod A example in form 160.78-RP1, YMC2-S0756AA, is a Mod A. The compressor model confirms it: Mod A manuals name M1-family compressors (for example M1B-197FAA), while Mod B manuals list M2C and M6C compressors.
How do you read a YMC2 model number?
This is the system nomenclature table from York form 160.84-RP1 (page 5).
| Position | Example (YMC2-S0050AB) | Meaning |
|---|---|---|
| 1–4 | YMC2 | YMC2 chiller model |
| 5 | S | S = single stage compressor |
| 6–9 | 0050 | Rated capacity in kW |
| 10 | A | Refrigerant: A = R-134a, B = R-513a |
| 11 | B | Mod level: A or B |
Don't mix up characters 10 and 11. Both can be A or B. In YMC2-S0756AA (the example in 160.78-RP1) the 10th character is the refrigerant and the 11th is the Mod level. The Mod A renewal parts manual lists R-134a for that edition.
York form 160.78-RP1 says the unit nameplate is on the side of the control panel, and asks for a clear photo of it for parts identification.
What else is different between YMC2 Mod A and Mod B?
| Item | YMC2 Mod A | YMC2 Mod B |
|---|---|---|
| Capacity range | 215 ton to 380 ton (755 kW to 1340 kW), 160.78-EG1 | 165 ton to 1,000 ton (580 kW to 3,520 kW), 160.84-EG1 |
| Refrigerants in the engineering guide | R-134a or R-513A | R-134a, R-513A or R-1234ze |
| Compressors named in York manuals | M1B-197FAA and M1B-205FAA (160.78-O1); 160.78-RP1 has separate parts tables for M1B-197FAA/-205FAA and M1B-197FAB/-205FAB | M2C-197FAC, -205FAC, -218FAC, -233FAC, -246FAC and M6C-295FAC to M6C-331FAC (160.84-RP1) |
| Operation manual | 160.78-O1 | 160.84-OM1 |
| Renewal parts manual | 160.78-RP1 | 160.84-RP1 |
| Engineering guide | 160.78-EG1 | 160.84-EG1 |
Both are oil free. Both engineering guides say the chiller is "completely oil free, with no oil management system required."
How do you read the compressor model on a Mod A?
Form 160.78-O1 says the compressor model number ends with its gas path revision level:
- Gas path revision A includes pre-rotation vanes (PRV). The form names M1B-197FAA and M1B-205FAA as the models that use PRV to reduce capacity.
- Gas path revision B has fixed inlet vanes. These compressors use the variable geometry diffuser (VGD) for capacity control instead.
Every YMC2 has a VGD at the impeller exit to mitigate stall, regardless of compressor model (160.78-O1). So a Mod A can have PRV parts or not, depending on its gas path. Check the compressor model before ordering vane parts.
Form 160.78-RP1 also flags early and later Mod A parts. It lists a rigid motor adapter for early units and an accordion style for later units, and says to use the later style if the part needs replacement. It also lists early and new balance piston diameters for the 197F-A and 205F-A impellers and seals, and says replacing one early part means replacing both.
Which parts are shared, and which are Mod-specific?
| Part | 160.78-RP1 (Mod A) | 160.84-RP1 (Mod B) |
|---|---|---|
| 331-01771-000 display panel kit | Table 25, item 28 | Table 21, item 28 |
| 031-01743-002 I/O board | Table 25, item 106 | Table 21, item 3 |
| 025-43553-000 flow sensor, 1/4 in. NPT (qty 2) | Table 21, item 52 | Table 22, item 52 |
| 03630 microboard replacement kit | 331-03630-610, Table 25 (item 10F) | 331-03630-614, Table 21, item 10 |
| 022-10078-000 relief valve, 1-5/16 in.-12 UN-2A | Table 19 | Tables 19 and 20 |
| 022-10079-000 relief valve, 1-5/8 in.-12 UN-2A | Not listed | Tables 19 and 20 |
The microboard kit is the one to watch. The Mod A manual lists kit 331-03630-610, and the Mod B manual lists 331-03630-614, which the store titles as the YMC2-B kit. For a blank or frozen panel, see York OptiView panel blank: microboard, display or I/O board.
Parts involved
| Component | Role | Where to find it |
|---|---|---|
| OptiView microboard kit (Mod B) | Listed in 160.84-RP1 (Mod B); Mod A uses 331-03630-610 per 160.78-RP1. | York 331-03630-614 Microboard (YMC2-B) Kit | OEM Chiller Part |
| Display panel kit | Listed in both YMC2 RP manuals. | York 331-01771-000 Display YM Panel Kit | OEM Chiller Part |
| I/O board | Listed in both YMC2 RP manuals. | York 031-01743-002 Control, Board (I/O), YM | OEM Chiller Part |
| Flow sensor | Listed in both YMC2 RP manuals, qty 2. | York 025-43553-000 Sensor, Flow 1/4" NPT 20 CM/S | OEM Chiller Part |
| Relief valve, 1-5/16 in. | Listed in both YMC2 RP manuals. | York 022-10078-000 Valve, Relief (235.0 PSI), 1-5/16-12 UN-2A | OEM Chiller Part |
| Relief valve, 1-5/8 in. | Listed in 160.84-RP1 (Mod B). | York 022-10079-000 Valve, Relief (235.0 PSI), 1-5/8-12 UN-2A | OEM Chiller Part |
| All YMC2 parts | Browse by product line. | York YMC2 Magnetic-Bearing Chiller Parts |
Which York units this applies to
- YMC2 Mod A: 11th character A; M1-family compressors; forms 160.78-O1, -RP1, -EG1.
- YMC2 Mod B: 11th character B; M2C and M6C compressors; forms 160.84-OM1, -RP1, -EG1.
- YZ Mod A: York's other magnetic-bearing centrifugal, a separate model family with its own manuals.
If the 11th character is any letter other than A or B, your chiller is outside the forms covered here. Send us the nameplate photo before ordering.
Scope: York forms 160.84-RP1 (YMC2 Mod B renewal parts, 825), 160.78-RP1 (YMC2 Model A renewal parts, 825), 160.78-O1 (YMC2 Mod A operation, 425), 160.78-EG1 (YMC2 Style A, 625) and 160.84-EG1 (YMC2 Mod B, 625). York notes that units built with special options, modifications or conversions are not covered by the RP manuals. Products are listed by live title, not as a fit confirmation for your chiller.
Before you order
Take a clear photo of the nameplate on the side of the control panel. Note the full model number, serial number and the compressor model. Read the part number off the old part if you can. Then contact us at help@totalhvacparts.com or 610-487-7999 to confirm fit.
Frequently Asked Questions
Which character in a York YMC2 model number is the Mod level?
The 11th, the last character. York form 160.84-RP1 lists positions 1–4 as YMC2, 5 as stage, 6–9 as capacity in kW, 10 as refrigerant and 11 as Mod level A or B.
What does the 10th character mean on a York YMC2?
It is the refrigerant code. York form 160.84-RP1 lists A = R-134a and B = R-513a.
Does a YMC2 Mod A have pre-rotation vanes?
It depends on the compressor's gas path revision. York form 160.78-O1 says gas path revision A (M1B-197FAA, M1B-205FAA) has pre-rotation vanes, and revision B has fixed inlet vanes and uses the VGD for capacity control.
What size range is each YMC2 Mod?
York engineering guide 160.78-EG1 gives 215 to 380 tons for the Style A (Mod A) unit, and 160.84-EG1 gives 165 to 1,000 tons for the Mod B.
Is the OptiView microboard the same on YMC2 Mod A and Mod B?
No. The Mod A renewal parts manual (160.78-RP1) lists microboard kit 331-03630-610, and the Mod B manual (160.84-RP1) lists 331-03630-614. The display kit and I/O board appear in both.
Sources
- York form 160.84-RP1, YMC2 Mod B Magnetic Bearing Centrifugal Liquid Chillers, Renewal Parts (system nomenclature p. 5; Table 4 compressors; Tables 19–22 parts; Table 23 power panel)
- York form 160.78-RP1, YMC2 Model A Centrifugal Liquid Chillers, Renewal Parts (nomenclature example; Tables 2–3, 10, 19, 21, 25; nameplate note)
- York form 160.78-O1, YMC2 Mod A Operation Guide (gas path revision p. 10; capacity control pp. 13–14)
- York form 160.78-EG1, YMC2 Style A Engineering Guide (cover capacity and refrigerants, p. 8)
- York form 160.84-EG1, YMC2 Mod B Engineering Guide (cover capacity, refrigerants pp. 7–8)
- Live product titles for the parts listed above, as shown on each product page
YMC2 chillers carry high-voltage drive circuits and refrigerant under pressure. Service should be performed only by qualified personnel, following York's manuals for your unit and your facility's lockout/tagout procedures.