Wiring it altogether

[phantom]

HI All,

I've been putting together my new Tarm Excel system for a couple months and now I'm finally near the finish. I still have some leaks to fix in the black pipe that makes up the plumbing to and from the boiler and then I have to wire it altogether and that's where my questions come in.

The system is plumbed according to the diagram below:

Could someone please explain to me how to close the storage tank zone valve in these scenarios:
-tank circulator is running
-tank has reached temperature
-Oil burner on Excel is running

The aquastat for the storage tank is a Johnson Controls unit (I don't know the model # off the top of my head) which can be configured for a heating or cooling scenario. I'm thinking I may need an additional aquastat for the storage tank to function in a heating source capacity.

thanks in advance for any help,
Aaron

 

[free75degrees]

You could do it with a few relays and an aquastat. It sounds like you want it closed based on an OR'ing of 3 conditions:
-tank circulator is running
-tank has reached temperature
-Oil burner on Excel is running

To "OR" the 3 conditions, you need a signal for each one and you need to set them up in parallel. What signals do you have for each? For example, do you have a end switch for your circ? An aquastat for the tank (open on rise or open on fall?)?

Once you get a signal for each on, you can feed the signals into 3 separate relays which would be wired in parallel. Then you would put 24V AC going through the 3 relays into the zone valve. Then if any of the relays close, the zone valve goes on. Does this make sense?

 

[phantom]

Thanks free75 degrees

It sounds like you want it closed based on an OR'ing of 3 conditions

- yes thats absolutely right

What signals do you have for each? For example, do you have a end switch for your circ? An aquastat for the tank (open on rise or open on fall?)?

- if you mean a thermostat for an end switch yes. The heating zones will have a thermostat or an aquastat, the only one I'm not sure about would be the oil burner but I think I can probably tap into the signal the Excel sends the burner for this one. The aquastat is configurable for either open on rise or open on fall.

Once you get a signal for each on, you can feed the signals into 3 separate relays which would be wired in parallel. Then you would put 24V AC going through the 3 relays into the zone valve. Then if any of the relays close, the zone valve goes on. Does this make sense?

- yes I think I understand the general idea but wouldn't wiring them in this fashion cause the zone valve to open upon power to one of the three relays? I guess this is where I get confused since the zone valve is normally closed.

thanks, Aaron

 

[WoodNotOil]

Thanks free75 degrees

It sounds like you want it closed based on an OR'ing of 3 conditions

- yes thats absolutely right

What signals do you have for each? For example, do you have a end switch for your circ? An aquastat for the tank (open on rise or open on fall?)?

- if you mean a thermostat for an end switch yes. The heating zones will have a thermostat or an aquastat, the only one I'm not sure about would be the oil burner but I think I can probably tap into the signal the Excel sends the burner for this one. The aquastat is configurable for either open on rise or open on fall.

Once you get a signal for each on, you can feed the signals into 3 separate relays which would be wired in parallel. Then you would put 24V AC going through the 3 relays into the zone valve. Then if any of the relays close, the zone valve goes on. Does this make sense?

- yes I think I understand the general idea but wouldn't wiring them in this fashion cause the zone valve to open upon power to one of the three relays? I guess this is where I get confused since the zone valve is normally closed.

thanks, Aaron

You would want relays that have a NO and a NC contact points (most do). If your zone valve is NC, then you want the electricity to go through the relay to the NO contact so that when the relay is not charged the electricity gets through and keeps the valve open. When it closes the electricity is cut off closing the zone valve.

Note: Zone valves can come NO or NC, so check which you have. Either way there is a way to do it with relays.

 

[free75degrees]

If you use the same type of relays that come with the taco relay boxes, they are dual pole, which means you can use one pole in the normal operation mode where an "on" signal to the relay cause the relay to close, and the other pole does the exact opposite. So if one of the 3 signals is reversed from what you want, you can just connect to the other pole on the relay.

You can get the right relays at You Do It Electronics in Needham for about $5 each and a nice socket for each one for a few more bucks each.

 

[Nofossil]

There may be an additional requirement: I assume that you want to prevent the oil from coming on if there's usable heat in the storage tank. I have a little writeup on that in the 'simplest pressurized storage' sticky. Basically, you'll want to interrupt the demand signal from the thermostat(s) before it gets to the oil burner.

 

[phantom]

thanks for the info guys. I think I understand a bit better with your additional explanations of the relays. You Do It Electronics is great, I've been there many times before for unrelated projects (usually video related).

I'll check out that write up Nofossil thanks.

The storage tank is one of the STSS ones and has it's own controller. I believe that I can wire all the demand signals (other than the tank demand) into it's box and as long as it has enough heat it supplies it otherwise it calls the boiler for heat.

thanks, Aaron