Replace transformer

[Ed from chicago]

Hi Everyone!

I'm back with another question. I just noticed that the transformer on my boiler is cracked, so I'd like to replace it. However I'm not sure what I should replace it with. It says 120V 60cy sec25v 20va. Can I use a transformer rated: Input voltage 120VAC, Secondary Output voltage 24vac, power rating 40 Volt Amps. Can someone interpet this for me?

Thanks very much...you guys are great!

 

[Bob NH]

Yes, you can replace it with the 120 V / 24 Volt 40 VA transformer.

120V 60cy sec25v 20va Mean that that the input is 120 Volts, output 25 volts, and it will deliver 20 volt-amperes (meaning roughly, Watts).

The 24 Volt output will probably actually put out 25 to 27 volts and systems are designed to accept that.

 

[Sponsor]

 

[Ed from chicago]

So, if I understand this correctly...output voltage is 24, and 40 is the maxium VA or watts that should be connected to the new 120V / 24 V 40VA transformer, anything under 40VA is ok...right?

 

[Bob NH]

"anything under 40VA is ok...right?"

Yes. Any load not exceeding 40 VA is OK.

In some cases they put multiple zone valves on a transformer for which the total VA of the individual valves exceeds the VA rating of the transformer but it works because of the way the zone valve loads are operated. It just causes a delay in opening the valves. Most of the 40 VA transformers are self-protected against overload, but they won't deliver much more than 40 VA.