Frying Transformers...

I recently replaced some old metal pipe that ran from the water supply to two sprinkler valves for my lawn with PVC. I also replaced the valves with two new ones and wired them to the existing automatic timer/controller. Everything worked fine for a couple of days, then one of the valves stopped turning on. I was in the middle of a project and didn't have time to investigate, so I just ran that one manually for a few days. Then they all (6) stopped working.

I measured the voltage coming from the transformer that powers the system and found that there was none, where there should have been 24 V. I replaced the transformer with a new one. Again everything worked fine for a couple of days and then the new transformer went dead.

Can anyone tell me what they believe is causing these transformers to fry?

Are all of the heads on at the same time? COuld the new ones take more current than the old ones, and are overloading the transformer? Do you need a larger transformer? I've never worked with sprinklers, so keep that in mind!

transformer

If there is a short circuit and the controller does not have an overload button it it, that will destroy a transformer.

At the risk of stepping over the line as far as brands/manufacturers, and potential advertisers to this website, for which we could get in trouble discussing, could you tell me what brand of sprinkler/irrigation timer you are using? That could tell a lot....

timer

Not usually a factor since all of them have transformers that will operate the panel and at least two valves simultaneously, even though good practice puts only one valve on a circuit.

Most timers have the capability to operate a pump start relay or a main valve in addition to one zone valve. But there are some wimpy transformers on the market, so it is important to check the milliamp rating.