Here is the scenario. I have 7 zone valves operated on 110V for my hydronic heating system. They are all powered individually and controlled by thermostats. What I want to do is to be able to turn on a pump when one or more of the thermostats is calling for heat. My problem(?) is that if I wire all of the zone valves through to the pump, all of the valves will open when one is energized. What I was thinking (and I could be way off here) is to put a diode in each line between the zone valve and the pump. It is my understanding that the diode will only allow current to pass one way, thereby preventing the other valves to be energized. The total load of the pump is 25W - 70W.

Am I on the right track?
Is there a specific type of diode I should be using?
Is there a size of diode I need?
Where to find such a beast?

Any help and or suggestions would be greatly appreciated!

Thanks
Lano in Canada

 

Is the thermostat/signaling done at the standard 24V, or is it all 110V?

If it is all 110V, I'd strongly suggest having an electrician work on it, as a diode won't help. Even the 24V control is an AC control, so a diode would still pass half of the waveform.

 

It is all 110V.
Thanks

 

A simple but somewhat kludgy way would be to have seven 110VAC relays with each relay coil controlled by one of the thermostats. Wire the contacts of each relay in parallel to control the 110V to the motor (which makes a sort of AC "OR" gate). That way the motor will be powered only if one or more of the thermostats is closed.

 

Not as simple but maybe more elegant would be to detect an AC signal (ie. current) on the power line going to all the valves. I assume current is zero when they're all off. If any of them turn on, a current could be detected and a DC circuit could throw a relay to turn on the pump.

 

A simple but somewhat kludgy way would be to have seven 110VAC relays with each relay coil controlled by one of the thermostats. Wire the contacts of each relay in parallel to control the 110V to the motor (which makes a sort of AC "OR" gate). That way the motor will be powered only if one or more of the thermostats is closed.

I don't see that as being kludgy. I see it as being the simplest, most reliable way to do it. What's kludgy about it?

 

Not as simple but maybe more elegant would be to detect an AC signal (ie. current) on the power line going to all the valves. I assume current is zero when they're all off. If any of them turn on, a current could be detected and a DC circuit could throw a relay to turn on the pump.

Sounds interesting, that being said, with what do I detect a current?? I'm in construction by trade but raised on the farm... that's where my DIY spirit comes from!
Thanks

 

A simple but somewhat kludgy way would be to have seven 110VAC relays with each relay coil controlled by one of the thermostats. Wire the contacts of each relay in parallel to control the 110V to the motor (which makes a sort of AC "OR" gate). That way the motor will be powered only if one or more of the thermostats is closed.

Thanks Carl, this indeed might be the ticket, thanks!

 

An accumulator tank, check valve and pressure switch, similar to a deep well water system? In those, the pump only runs when water flows.

 

Sounds interesting, that being said, with what do I detect a current?? I'm in construction by trade but raised on the farm... that's where my DIY spirit comes from!
Thanks

Something like this, there are many "Snap On one wire" current sensors Some will light an LED, some will output a voltage relative to the current, some will operate a relay.

Different type, Installed, with description

 

lmtxprss,

crutschow,s suggestion would be the way I'd go. I did a simple diagram showing how it might look (see attached). I only showed three zones but you get the idea.

good luck and be careful,
williamj

 

lmtxprss,

crutschow,s suggestion would be the way I'd go. I did a simple diagram showing how it might look (see attached). I only showed three zones but you get the idea.

good luck and be careful,
williamj

So i'm looking for a (7) 110VAC SPST relay?

 

 

I don't see that as being kludgy. I see it as being the simplest, most reliable way to do it. What's kludgy about it?

Only that it's perhaps not as elegant as converting the signals to DC and using digital logic which would require just one relay. But kludgy is in the eye of the beholder.

 

Seven of those should work.

Edit: Question -- Are the valves driven directly from the thermostat?

 

Seven of those should work.

Edit: Question -- Are the valves driven directly from the thermostat?

Yes, voltage is sent to the thermostat and then back to the valve when condition met. I have a junction box in the utility room where all the pumps are located that I can easily access the circuits. Thanks for all your help!!

 

Yes, voltage is sent to the thermostat and then back to the valve when condition met. I have a junction box in the utility room where all the pumps are located that I can easily access the circuits. Thanks for all your help!!

The reason I ask is to determine if the thermostat is capable of providing the current to the relay. If it drives the valves directly, then there should be no problem. If it goes through some circuitry before driving the valve, then you may need to determine how much current the thermostat can deliver.

 

lmtxprss,

crutschow is again on point. Seven of those relays should work. If the zones can handle the solenoid current draw you should be able to parrallel the relays with the solenoids. And if there is physically enough room, you might consider mounting the relays along side of your solenoids. I've modified the first diagram to illustrate.

again, good luck and be careful,
williamj