Voltage Killing Zone Valve Power Heads?
The power heads on my Taco zone valves seem to burn out every 2-3 years. The oil burner service guy was here today and I had him check the voltages. The primary line was reading 123V. The two transformers feeding the power heads were reading ~27V and ~29V. The service guy did not know what to make of that. (FWIW, the transformer producing 27V is newer (2 yrs), and the one power head attached to it has never failed. The 29V transformer feeds 3 power heads, which have each failed more than once.)
My electrical knowledge is slightly above zero, so any help you could provide is appreciated:
> Is it normal for a 24V rated transformer to be outputting 29V or 27V?
> Could 29V be the reason the 24V rated power heads are frying/dying prematurely?
> Could the fact that the primary line voltage is a bit high contribute to the transformer producing a higher output voltage?
> Should I replace one or both transformers?
Thanks for any advice.
-RG
Replies
It is normal to see the voltages you are seeing because the transformer voltage spec will be at the rated power output of the transformer. So if you have a transformer rated at 50va (thats approximately 2 amps) you will see 24 volts if you are drawing 2 amps. If you only draw 1 amp the voltage will be higher and 29 volts is not unreasonable in that situation. The 29 volts will of course put more current thru your solenoid or motor and could very well be the reason for early burn out of your valve. Using a transformer of a higher power rating than the load draws will result in higher voltage output.
If you are running 3 valves off of one transformer, the voltage seen will depend on the number of valves in operation at the same time.
It could well be the excess voltage causing this. I suggest a regulated power supply. Like the ones used in a PC but set for 24 volt. http://www.surplussales.com/PowerSupplies/PowerS-4.html might have what you need scroll down a little for a unit at $50.