Taco needs to create an animation of how the 570 series zone valve works.

Jamie Hall

@Steamhead 's comment just above is why if I'm going to play with electrics I ALWAS use both a non-contact and a contact type tester to verify that the circuit really is dead. I don't like shocks…

Alan (California Radiant) Forbes

@Steamhead "There was no polarity in the early days…."

Even back then, there was always a "hot" and always a "neutral", no?

And they usually fused the hot side.

109A_5

The thing is with @Steamhead's comment above and if you understand the 3 wire actuator circuit situation and you understand the 24 VAC in the heating equipment (the power for the T-T) may be bonded to ground in the heating equipment or Aquastat, etc., then the other 24 VAC power source for the thermostat and wax motor can NOT be bonded to ground, it needs to be 'Floating'. Or if it is bonded to ground it needs to be phased correctly and someone else can unknowingly easily screw that up.

An isolation relay or Multi Zone control boxes (Isolated X-X) does make whole ground bonding, either by mistake or intent irrelevant. Since it adds another layer of isolation to the overall circuit situation.

4 wire actuators by design provide the isolation.

109A_5

Can't 100% tell, but the white neutral in the picture looks cut, maybe the receptacle to the right does not work. Maybe the wire loops under the box, it looks cut to me.

Steamhead

https://forum.heatinghelp.com/discussion/comment/1898075#Comment_1898075

That thing looks scary.

I once knew an old-timer electrician (this was back in the 1970s and he was an old-timer then) who told me that. I had run into an old fuse panel where the neutrals were fused as well as the hots. Back when electric wiring was first being installed, in order to get 120v you might have 60v on either side, just like today's 120/240v service where 120v on opposite sides makes 240v. It all depended on how the local grid was set up. In those days, you only had to break one side of a circuit like that to control a light or other load. Obviously Codes have come a long way since then.

109A_5

You know what is amusingly funny. The 3 wire actuator and two transformer secondaries is the same basic 120/240 circuit that powers most homes in the U.S. and Canada. It's just with the utility transformer the two secondaries contained and wired in a sealed can it is hard for others to mess it up. Each secondary has its own load and each secondary only 'Touches' the other at one point.