Electrofusion welding equipment: control units, documentation and generators

Three things the control unit must be able to do

An electrofusion control unit must be able to do three things: deliver the power required by the fitting, follow the fitting's specific welding program, and document the process. It sounds simple, but these three points determine whether the control unit can be used in practice on a project with documentation requirements.

The fitting's barcode contains welding time and voltage, and the unit must be able to read it using a scanner or allow manual data entry. Some control units have a simplified function where the fitting code is read and welding is started with a single press – fast, but requires that voltage and time are still verified against the fitting.

Documentation: memory is the hidden limitation

The capacity of the fusion record memory varies more than you might think: from a few hundred records in the smallest and oldest units to 20,000 in the largest. It is not a question of how many joints you make in a day, but how often you clear the memory.

The records must contain the project number, welder ID code, fitting data, and actual values. Offload them regularly to USB or documentation software, and do so before service or repair – many control units cannot restore deleted data, and full memory stops the welding process.

If the records are needed on site, units with built-in printers are available so the joint can be documented immediately instead of waiting for a printout from the office.

Site power: the generator must be large enough

An electrofusion socket draws a lot of power over a short period. For fittings from approx. d20 to d160, count on at least approx. 3.2 kW, and for larger fittings up to around d450, 4-5 kW, with the largest requiring an electronically regulated generator. An undersized generator leads to voltage drops, causing the unit to abort or weld incorrectly.

Output decreases when the generator is loaded by other equipment at the same time, and long extension cables cause voltage drops. Therefore, do not start heavy consumers such as hot air tools or compressors while a socket is being welded.

If power is unavailable on site, a mobile power bank is an alternative to a generator: it is noiseless, produces no emissions, and can deliver a stable sine wave voltage to the control unit. See advantages and caveats in power supply on site.

When working on fixed installations: check that the mains socket is fused as specified in the manual, and that the cable is uncoiled from the reel to prevent overheating.

Generator requirements: d160, d315 and d450+

The size of the fitting determines how much power the generator must deliver. A small fitting up to d160 can manage with a generator of approx. 3.2 kW, while fittings in the range d160-d450 require approx. 4-5 kW. Size d315 lies in the upper end of that interval, and for d450 and above, there is no single universal figure: you must consult the control unit's data sheet, as welding time and current surges grow with the surface area of the fitting and thus with the dimension.

The kW figure on the generator represents active power, but generators are often specified in kVA. At a power factor of approx. 0.8, 3.2 kW corresponds to approx. 4 kVA and 5 kW to approx. 6 kVA. Always allow a margin, as the generator's active power output drops when it heats up, and because more than one machine is rarely running on site.

Regulation is at least as important as output power. An electrofusion control unit monitors voltage and current throughout the welding process and aborts if values fall outside tolerance limits. Therefore, the generator must feature AVR regulation (automatic voltage regulation) or be an inverter generator producing a pure sine wave. A cheap, unregulated generator may deliver sufficient power yet still cause the unit to stop mid-fusion due to voltage fluctuations.

Requirements become stricter as dimensions increase: for d160, an AVR-regulated generator of approx. 4 kVA is often sufficient; for d315, it should be approx. 6 kVA with stable regulation; and for d450+, you must follow the control unit data sheet – often requiring a 400 V three-phase supply or a significantly larger generator. A rule of thumb is to dimension for twice the measured power output required by the largest fitting to be welded, allowing for startup surge current and cable voltage drop.

If no motors need to run on site, a mobile power bank with a 230 V outlet and stable sine wave voltage can be used instead – advantages and caveats are detailed in power supply on site. Always check the voltage under load before welding the first fitting, and keep the cable as short as possible. Power ratings, fuse requirements, and cable lengths are described in power supply on site, and control unit requirements in electrofusion welding equipment.

Drainage and pressure pipes are not the same

Electrofusion welding is used for both pressure pipes and drainage pipes, but the equipment is not necessarily identical. Some control units are approved only for building installations and drainage pipes, and must not be used on buried pressure pipelines. This is specified in the manual's application section, and is one of the points most commonly overlooked when borrowing equipment between jobs.

Therefore, check both the fitting approval and the control unit's scope of application before starting work – and record it for the job documentation.

Before taking the control unit on site

Check that the scanner reads, that the memory is cleared and has available space, that the cable to the welding terminals is intact, and that contacts are clean. Poor contact leads to a faulty weld, which will only show up in the record.

Always bring clamps or other fitting alignment devices so the fitting cannot move during welding, and ensure you can wipe down the fitting and pipe if the weather is wet. Moisture in the joint is the most common cause of failed electrofusion socket welds.