Replacing a Diesel Generator: What to Check Before Reusing an Existing ATS

You may be able to keep an existing automatic transfer switch when replacing a diesel generator. Matching the old generator's kVA rating is not enough to confirm that. Before ordering, identify the installed ATS and controller, check the replacement's electrical and control requirements, and agree who will verify the complete system at the site.

This guide is for a buyer with an actual replacement requirement and either China purchasing experience or a China forwarder. It helps you prepare the information a supplier and your site technician need. For an introduction to transfer equipment, start with the ATS selection guide.

Begin with the ATS manufacturer's name, exact model, rating plate and the manual and drawings for that version. Add the existing generator's model, electrical output and controller model. A photograph of a similar cabinet is not a substitute for the installed equipment's details.

Ask your site technician to record any changes made since installation and any known faults. Explain why the generator is being replaced: an engine problem, unavailable parts, a changed load or another reason. That helps the supplier understand whether the request is for the same duty or a different application.

Keep the equipment references together in one enquiry file. If a plate is unreadable or a drawing is missing, mark the item as unconfirmed. Have a qualified technician collect information from inside electrical equipment under the appropriate isolation procedure; the purchasing enquiry does not require you to open a live cabinet.

There are two questions to resolve: is the transfer equipment suitable for the electrical supply and loads, and will its controls work with the proposed generator controller? “Automatic start included” does not answer both.

For the electrical review, provide voltage, frequency, phases, the load information and the ATS ratings. Have the technician check the applicable current and fault ratings, protection and neutral/earthing arrangement. The Cummins transfer-switch application manual treats equipment ratings, controls and neutral switching separately; they should not be reduced to one ampere figure.

For the control review, ask the supplier to identify the proposed generator controller and the documents defining its start/stop and monitoring interfaces. Compare those requirements with the actual ATS documentation. If additional interface equipment is needed, request its description and inclusion in the quotation. Do not approve compatibility from an engine brand, a cabinet photograph or the phrase “ATS ready”.

Give the technician and supplier the current load list and any planned additions. Mark the equipment that must operate together and anything whose starting requirements need assessment. Replacing a generator does not establish that the old selection still suits today's use.

State whether the set provides backup power or runs regularly, along with expected operating hours and site conditions. Compare the proposed power on the required rating basis. If the load requirement remains uncertain, complete the generator selection checks before treating a replacement model as agreed.

Also explain which loads can tolerate an interruption and which cannot. Ask the site technician to confirm the required transfer arrangement and any separate continuity provision. An ATS is not a UPS. Avoid promising uninterrupted power simply because a new generator or switch is described as automatic.

Ask for a written equipment and work list. It should distinguish the retained ATS, the new generator and controller, any interface equipment, and the cables, protection, drawings and site work that are included or excluded. Where information is still missing, ask the supplier to name the condition on which the offer depends.

If the proposed generator includes an integrated ATS, have the supplier and site technician explain how it fits the existing arrangement. Do not approve an extra switch just because it is offered with the machine. First agree which equipment will perform each function and what is to remain at the site.

ZHONGCHAI supplies generators on EXW terms. Site design, modification, installation and commissioning are separate scope questions; they are not automatically included in an equipment quotation. Confirm responsibilities in the order documents and read the purchasing terms. Keep this technical discussion linked to the exact quotation revision you intend to accept.

Ask the supplier and site technician to agree what can be checked before dispatch and what requires the installed system. Record the equipment models, the drawings used, the planned checks and the person responsible for each stage.

A factory video can document the equipment and arrangement shown in that test. It cannot establish the condition of your existing ATS or demonstrate that a different site installation works. For supplied equipment, request records tied to the identified unit; the pre-shipment evidence guide explains that distinction.

Have qualified personnel define and carry out the site commissioning procedure using the applicable equipment instructions. Ask for a record of the agreed operating sequence, transfer and return functions, relevant settings and unresolved items. The supplier and technician should explain what evidence is still needed before the system can be accepted. This article is a purchasing checklist, not a wiring or live-testing procedure.

Use one line for each requirement and leave unknown entries marked “to confirm”. Send this file during the technical discussion after your initial enquiry.

• Existing ATS: manufacturer, model, rating plate, manual, drawings and known service issues.
• Existing generator: model, electrical output, controller model and reason for replacement.
• Site and loads: supply details, equipment to power, operating pattern and planned changes.
• Continuity requirement: backed-up circuits and the interruption each load can accept.
• Proposed set: exact configuration, rating basis, controller and interface documents.
• Retained and new items: equipment to keep, items to change, exclusions and responsible parties.
• Review outcome: confirmed points, required modifications and unresolved questions, with the supporting documents.
• Acceptance plan: checks before dispatch, checks at the site, responsible people and records to be provided.

Ask the supplier to respond to the same list. If a controller or other relevant component changes after review, reopen the affected checks before accepting the substitution. Keep the final configuration and supporting confirmation together so the installer receives the version that was actually agreed.

ZHONGCHAI's 37.5 kVA Cummins order for Kenya records a customer's requirement for a built-in ATS, pre-dispatch test material and handover to the nominated Guangzhou forwarder warehouse on 8 December 2025. The case illustrates why the requested transfer equipment belongs in the order discussion.

It does not describe reusing a customer's existing ATS, and it does not document installation or operation in Kenya. Treat it as a reference for that supplied configuration, not proof that the same arrangement will fit your site.

Possibly, but the power and control reviews still need to be completed. The rating alone does not confirm the installed equipment's condition or its suitability for the proposed system.

Clear photographs help identify equipment. Ask what remains to be checked against the manuals, drawings and site information before accepting a compatibility statement.

Ask a qualified technician to investigate and record the missing information. Keep reuse unconfirmed until the equipment can be assessed. Request any alternative proposal as a separate configuration with its own scope and cost.

Open the enquiry form from the contact page with the basic power requirement, intended use and China purchasing experience requested by the initial form. After saving those answers, continue on WhatsApp with the existing ATS details, proposed replacement requirement and enquiry file. Include your destination, purchasing schedule and China forwarder details if available. Mark anything still unconfirmed so it is addressed before the order is placed.

Prepared by ZHONGCHAI. Check current model documentation and the actual site assessment before approving an equipment combination.