How to Connect a 24VAC thermostat to a 220V FCU?

I have an FCU that gives out 220VAC line voltage which should be relayed at 220V as well for fan control and the compressor.

I purchased a 24VAC wall thermostat which i wish to use with the FCU. How can this be done? or is it an absolute must to replace the FCU? What products should i be looking at and where can i buy them online?How to Connect a 24VAC thermostat to a 220V FCU?I am assuming that you wish to control a 220 Volt AC powered fan coil unit (FCU) with a 24 Volt AC thermostat. There is nothing odd about this but it would have been easier to use a 220 Volt AC thermostat.



You will need a 220 Volt to 24 Volt transformer to power the thermostat and you will need an OCTAL relay and base to link the thermostat and the FCU. The relay will have to have 24 Volt AC operating coil and its contacts will have to be rated at 220 Volts AC and have a current rating to match the current drawn by the starting circuit of the FCU.



To find a shop that sells OCTAL relays and bases, do a Google search for OCTAL relays. Other brands of relay will also be suitable so long as they have the appropriate ratings.



The transformer will supply 24 Volts AC to the contacts of the thermostat and these contacts will be in series with the 24 Volt AC operating coil of the relay. The contacts of the relay will be in series with the starting circuit of the FCU, If the FCU has a low power rating, the contacts of the relay can be in series with the FCU's motor. When the room temperature drops, the contacts of the thermostat will close and supply 24 Volts AC to the operating coil of the relay. The contacts of the relay, will close and supply 220 Volts AC to the FCU.



If you are not sufficiently qualified and experienced to do this work, you should call someone who is.How to Connect a 24VAC thermostat to a 220V FCU?Are you sure that the FCU control input is 220 V? most things in heating and air conditioning systems use 24 vac controls.