What is a Uni-Control or Unitrol?
This is a Robertshaw uni-control valve, this is a temperature sensor that controls the temperature and thermostat, connected to a thermocouple that holds down the pilot. This system is also equipped with a sacrificial anode to protect from rusting and calcium build up – these should be checked every 3-4 years.
The photo shown is a gas storage 135 litre hot water system. Gas storage 135 litre external hot water unit has two components including the uni control which controls the temperature within the unit. Including being equipped with 2 magnetic strips that hold the pilot in place once the temperature is achieved the bi-metal strip inside the control valve opens up allows the flow of gas through the pilot tube and within in seconds ignites burner this will continue to run until temperature is reached at what the valve is set at.
For instance, as soon as a tap is turned on and water flows through an outlet in the house, cold water begins to enter at bottom inlet point and drops temperature which in turn causes the uni-control to start heating unit till the temperature is reached again. The tank also has a sacrificial anode which covers the entire centre of the tank this should be changed at intervals of 3-4 to save the life of the tank.
Problems that can arise with these units are as follows:
- Faulty thermostats that continually heat can cause extreme temperatures plus also the hot and cold valves can actually continue to run.
- If temperature relief valves fail they can cause pressurising in the tank which can cause the tank to rupture and explosions to occur.
- The uni control valve has an eco which is an energy cut switch which is for safety reasons.
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