B
breezer
wont work, what if both pullcords were pulled?
2 X 10.5kW showers
- Thread starter stead
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, I'm thinking a diagram might be easier to understand, I might prepare one in a few minutes
B
breezer
what if the pull cords were "non latching"
so to have shower you pull the cord then this operates contactor, if no mains contactors wont work, which ever person pulls their pull cord first stops the other one from working (as it did before)
so to have shower you pull the cord then this operates contactor, if no mains contactors wont work, which ever person pulls their pull cord first stops the other one from working (as it did before)
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Use standard, latching pull switches. This gives you the isolation you need, just as though these were independent showers. I've often been tempted to design some fancy relay logic into house wiring but I've always ended up asking the same question. If I sell the house, will the new owner ever be able to figure it out?
In this case consider what will happen if a relay fails and a shower won't stay on. It's a pretty good bet that they'll think the non-latching switch is faulty and replace it with a new, latching one.
The relay logic is simple enough. You have a beefy contactor at each end. After the pull switch the circuit splits. In one branch is an NC auxiliary contact from the remote contactor feeding the coil of the local contactor. In the other branch is a local NO power contact feeding the shower itself. When you pull a switch, the local contactor closes, turning the shower on but cutting power to the remote contactor's coil. You can do what you like with the remote switch after that. The remote coil has no supply so the shower can't come on and the remote NC auxiliary can't upset the local shower.
I have one gripe about this setup. If the remote shower is left on, it will come on as soon as the local one is switched off. It's not a serious problem - people leave showers switched on all the time - but it's a nuisance. This will become clear if you inadvertently switch your shower off and can't get it back on again because the other one has grabbed control.
The solution requires an extra, low power relay at each end - a lockout relay. You take a third branch from the switch. This goes through an NO contact on the new relay to its coil. An NC contact on this same relay goes in series with the feed to the local contactor coil. Once this thing is energized it will stay on until you switch off and the shower can't work. How do we get it energized? Answer, with an NO auxiliary from the remote contactor wired in parallel with the new relay's NO contact.
What does all this amount to? You switch on the local shower. It works. You try to switch on the remote one. It doesn't work but its lockout relay does. You switch off the local shower but the remote one stays off. You can switch the local one back on again. The remote lockout relay can only be released by turning off the switch. Once the local shower is off you can use the remote one but you must switch it off and on again.
I would put all this on a diagram but I don't seem to be able to post attachments from here. I'm still working on that one.
PS: In the event of a momentary power loss with both switches on there WILL be a logic race. I'm still working on that one too. I think the ideal outcome is for both lockout relays to energize.
In this case consider what will happen if a relay fails and a shower won't stay on. It's a pretty good bet that they'll think the non-latching switch is faulty and replace it with a new, latching one.
The relay logic is simple enough. You have a beefy contactor at each end. After the pull switch the circuit splits. In one branch is an NC auxiliary contact from the remote contactor feeding the coil of the local contactor. In the other branch is a local NO power contact feeding the shower itself. When you pull a switch, the local contactor closes, turning the shower on but cutting power to the remote contactor's coil. You can do what you like with the remote switch after that. The remote coil has no supply so the shower can't come on and the remote NC auxiliary can't upset the local shower.
I have one gripe about this setup. If the remote shower is left on, it will come on as soon as the local one is switched off. It's not a serious problem - people leave showers switched on all the time - but it's a nuisance. This will become clear if you inadvertently switch your shower off and can't get it back on again because the other one has grabbed control.
The solution requires an extra, low power relay at each end - a lockout relay. You take a third branch from the switch. This goes through an NO contact on the new relay to its coil. An NC contact on this same relay goes in series with the feed to the local contactor coil. Once this thing is energized it will stay on until you switch off and the shower can't work. How do we get it energized? Answer, with an NO auxiliary from the remote contactor wired in parallel with the new relay's NO contact.
What does all this amount to? You switch on the local shower. It works. You try to switch on the remote one. It doesn't work but its lockout relay does. You switch off the local shower but the remote one stays off. You can switch the local one back on again. The remote lockout relay can only be released by turning off the switch. Once the local shower is off you can use the remote one but you must switch it off and on again.
I would put all this on a diagram but I don't seem to be able to post attachments from here. I'm still working on that one.
PS: In the event of a momentary power loss with both switches on there WILL be a logic race. I'm still working on that one too. I think the ideal outcome is for both lockout relays to energize.
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