Electricians at St James's Hospital in Dublin were staging a one-day strike.
The dispute is over outsourcing of responsibility for fire alarms.
Electricians are currently paid a minimum four hours' pay for resetting fire alarms out of normal working hours.
On Sundays, a call-out would trigger a minimum of eight hours' pay.
In addition, they are entitled to a minimum of four hours of compensatory rest in accordance with the European Working Time Directive.
The Technical Engineering and Electrical Union said management at the hospital has handed fire alarm services to an outside contractor and maintains that electricians are the appropriately qualified people to carry out activities involving fire alarms.
In a statement, hospital management said: 'security personnel have traditionally been part of the hospital fire response team and are now engaged in the resetting of fire alarms for which they have been appropriately trained to the satisfaction of experts on fire services management.'
Talks between the trade union and hospital management have taken place at the Labour Relations Commission, but those talks adjourned last week without any significant progress.
There have already been two half-day stoppages as part of this dispute.