BUYER'S SHORT ANSWER
An E-House interface register should identify every physical, electrical, control, civil, environmental and documentation boundary, with one responsible party, required input, due date, drawing reference and acceptance status. It should be approved alongside the general arrangement and single-line diagram.
Use this note alongside the governing standards, applicable certificates and the responsible engineer's approval.
Why interfaces cause more trouble than equipment ratings
A switchboard can meet its ratings while the project still fails at the boundary around it. Cable bend radius may conflict with the floor opening, a protection trip may have no agreed owner, or the HVAC supply may disappear when the auxiliary transformer is isolated.
The buyer benefits from reviewing these conditions as a register rather than scattering them across meeting minutes. Each row becomes a decision that can be closed, revised and traced.
Capture the physical and civil boundaries
List foundation reactions, anchor locations, module dimensions and weights, transport splits, lifting points, wall and floor openings, drainage, external stairs and platforms, fire-zone interfaces and site access constraints. State who provides each item and which drawing controls it.
Cable entry needs its own detail: source and destination, quantity, size, minimum bend radius, gland or sealing responsibility, segregation and fire-stopping. A rectangle marked “cable trench by others” is rarely enough.
Define electrical and control ownership signal by signal
Record system voltage and frequency, fault level, earthing arrangement, auxiliary supplies, neutral treatment, metering boundaries, protection zones, CT and VT data, time synchronisation, communication protocol and hardwired trips.
For SCADA and plant control, issue an I/O list with signal source, destination, normal state, fail-safe state and test method. Generic phrases such as “Modbus available” do not settle addressing, gateways, cybersecurity ownership or data responsibility.
Include operation and maintenance interfaces
Define access control, emergency escape, lighting, sockets, fire alarms, gas detection where applicable, HVAC modes, filter access, spare-part storage and the isolation needed for maintenance. Confirm which alarms appear locally and which are exported.
If a subsystem must remain available while the main bus is de-energised, show its source and autonomy. The operating philosophy should be visible on drawings and testable at FAT.
Turn the register into an approval gate
Do not approve “for manufacture” while critical interfaces remain labelled TBC without an owner and due date. The register should show open, agreed and superseded status, with links to the drawing revisions that implement each decision.
A disciplined register protects both sides: the buyer can see unresolved project risk, and the supplier can distinguish a changed requirement from the original contractual scope.
QUESTIONS BUYERS ASK
Frequently asked questions
When should the E-House interface register be issued?
Start it during tender clarification, then freeze critical rows before general arrangement and detailed drawing approval. Update the register through FAT and site handover.
Is an interface register the same as a responsibility matrix?
It includes responsibility, but should go further by naming the technical input, document reference, due date, acceptance status and verification method for each boundary.
Reference publications
Always confirm the edition named in the contract and obtain authorised copies of the applicable standards.
IEC Webstore — IEC 62271-202:2022 ↗IEC Webstore — IEC 61936-1:2021 ↗