The ESB is facing the threat of industrial action from Monday from over 500 network technicians represented by a union which the company does not recognise.
The Independent Workers Union has confirmed that a work-to-rule will commence on Monday, with a full 24-hour stoppage on Thursday 22nd April, and a further two day strike on Thursday 29th and Friday 30th April.
The ESB confirmed that it had received a comunication from the Independent Workers Union in relation to a trade dispute.
It said that at this stage, the company is "seeking to understand the nature of this correspondence" and will not be making any further comment at this time.
IWU Regional Secretary Gerry Corbett said the initial work-to-rule would include an overtime ban, and no covering of on-call or standby functions, which are essential for breakdowns, accidents and emergencies.
There would also be no "structural support" for electrical contractors, which can only be done by staff with certain qualifications.
IWU members would also refuse to cooperate with new technology including systems for recording working time, and other training functions.
Mr. Corbett said the union had been unable to discuss emergency cover as the company was not talking to them.
The IWU claims to represent over 550 of the 1200 network technicians, who perform essential functions such as repairs, and vital safety services to assist external electrical contractors on outsourced projects.
The ESB engages with a group of union comprising Connect, SIPTU, Unite and the Energy Services Union.
However, around 550 network technicians have now defected to the IWU, which is not recognised by the ESB.
The IWU now claims to represent the majority of the 1250 strong grade - compared to Connect with 370, Unite with 220, and SIPTU with 120.
IWU Regional Secretary Gerry Corbett said the row centres on the failure of the company to consult adequately with them and other unions through Local Implementation Groups (LIGs) over the outsourcing of work to external contractors.
He said that where previously the management had engaged in genuine consultation through LIGs, they were now presenting "briefings" as a fait accompli.
He said the IWU had sought to invoke its rights under consultation legislation, but that the ESB had failed to comply, and had also refused to attend the WRC or the Labour Court to resolve the issues.
Mr. Corbett said members had voted almost unanimously in favour of strike action.
He said the company had accused the IWU of engaging in an unlawful action, and threatened to take legal action, but he insisted the IWU was acting within the law.
Other recognised ESB unions are being contacted for comment.