When ordering an MT3021 replacement for a Daikin-McQuay chiller, start with the complete installed part number and the equipment serial number. A similar Siemens module name is a starting point for an enquiry; it does not establish an approved replacement.
This guide reviews manufacturer catalogue information and gives a procurement checklist. No hands-on interchangeability test, firmware comparison or power-failure trial is documented here. Sources were checked on 14 October 2026.
What the Model Numbers Establish
Daikin’s parts portal lists MT3021, POL94U.00/MCQ under reference SPM04089360017E. Siemens identifies POL94U.00/STD as a Climatix extension module for electronic-valve stepper motors, with UPS. Siemens’ ECV family documentation distinguishes POL94U from POL94E on that UPS feature.
Those descriptions establish product identities and the stated UPS capability. They do not prove that an STD module can run the installed Daikin application, or that an MCQ module is an approved substitute in a different Climatix system. Do not infer software, parameter or service compatibility from the presence of energy storage alone.
POL94U.00/MCQ and POL94U.00/STD: A Procurement Comparison
| Check | POL94U.00/MCQ / MT3021 | POL94U.00/STD |
|---|---|---|
| Manufacturer identification | Daikin’s portal lists MT3021 with this complete Siemens marking. | Siemens lists the standard Climatix ECV extension module. |
| UPS claim | POL94U family documentation describes the UPS option. Verify the exact OEM supplied unit and required safe-position sequence. | Siemens explicitly describes this model as having UPS. STD does not mean “without UPS”. |
| Replacement approval | Match the current Daikin service part or documented supersession to the equipment serial number. | Obtain written OEM confirmation before proposing it for an MT3021 installation. |
| Price and availability | Request a dated quotation for the exact service part, condition, accessories and warranty. | Request a quotation for the complete Siemens part number. A lower asking price does not establish compatibility. |
Can STD Replace MCQ?
Not established by the sources reviewed here. The earlier advice that the swap is acceptable whenever UPS is unnecessary was too broad. Both controller compatibility and the power-loss sequence need review. An OEM service instruction or an approved substitution record must establish what can be installed in the particular machine.
Send the OEM or qualified service provider the equipment model and serial number, photographs of the original labels and connections, controller identification, application or firmware information available from the service records, and the proposed replacement’s full marking. Ask whether configuration, programming, addressing, connector changes or additional commissioning steps are required. Do not assume any of those differences exist; ask for evidence.
Checklist Before Ordering
- Record the installed identity. Transcribe every suffix and revision shown on the module and compare it with the parts list for the exact machine. Record any superseded service part separately.
- Confirm the controller and valve combination. Ask the service provider to verify the driver, valve motor, supply and connection requirements against the selected replacement. Do not treat a matching enclosure as an electrical check.
- Preserve the intended power-loss response. Obtain the machine’s required safe-position sequence and the approved method of verifying it. UPS presence alone does not demonstrate that a particular valve will reach the required position.
- Get written substitution approval. The response should identify the original part, proposed part, machine applicability and any setup instructions. A seller’s general “compatible” description is insufficient.
- Check what the quote includes. State whether the module is new, used or refurbished, whether connectors or software preparation are included, and the applicable warranty, return terms and delivery date.
- Plan commissioning. Use the OEM service procedure to verify communication, valve operation, alarms and the required power-loss behavior. Retain the results with the equipment records.
Where to Source the Module
Use the Daikin MT3021 / POL94U.00/MCQ parts listing to identify the OEM reference, and the Siemens POL94U.00/STD catalogue entry to identify the standard module. Siemens also labels the exact STD model as having built-in UPS in its official product record.
Published prices, stock and delivery vary by region and account. The previous 2025 dollar ranges were not supported by dated quotations and have been removed. Confirm the current part and commercial terms directly with the manufacturer channel or an identified distributor before purchase.
Frequently Asked Questions
Does POL94U.00/STD have UPS?
Yes, Siemens explicitly describes this exact model as having UPS for moving the electronic valve to a safe position on power loss. Do not confuse POL94U with the POL94E family.
Does having UPS make STD interchangeable with MCQ?
No. It establishes a hardware feature, not approval for the installed OEM application. Obtain machine-specific replacement confirmation and setup instructions.
Which number should I put on an RFQ?
Include the complete installed module marking, equipment model and serial number, and the OEM service reference from the applicable parts record. Attach clear label photographs and request confirmation of any supersession.
Are used modules a safe purchase?
A warranty or return policy alone cannot establish suitability. Confirm identification, condition, configuration and an approved commissioning procedure before accepting a used or refurbished module.
Keep the approved part mapping, quotation and commissioning record together. This makes the next replacement enquiry reviewable and helps prevent a similar-looking module from being accepted on its name alone.
