1 circulator & 1 switching relay for 6 zone valves?

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  #1  
Old 12-07-16, 03:33 PM
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1 circulator & 1 switching relay for 6 zone valves?

In my new boiler installation there are 6 zone valves, 6 thermostats and 1 circulator.

Can 1 switching relay be used instead of 6 switching relays? That is- connect the thermostats to the one switching relay?

Thanks,

Craig
 
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  #2  
Old 12-07-16, 03:56 PM
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No, you can't connect all the thermostats to one relay as they have to be kept separate to control the zone valves.

What you could do is connect each thermostat to its zone valve (you will need an external 24 volt transformer) and then connect the end switches on the zone valves to a relay to control the circulator and boiler. That way each thermostat opens the correct zone valve. When at least one zone valve opens the circulator runs and the boiler fires.
 
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Old 12-07-16, 04:49 PM
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How are they presently wired and what brand of zone valves do you have. If you have Taco you can put 3 on a 24V transformer.

Do you have gas or oil, how do you get your hot water and what do you have for an aquastat.

Hope this helps a little.
 
  #4  
Old 12-07-16, 05:40 PM
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Carbide,

Well, what I assumed is that I would only be connecting 3 zone valves using only 1- 24v transformer.

There's a schematic on the Taco 570-2 (3-wire) zone valve box that shows 6 zone valves and 2- 24v transformers. But, I gather from what I see on the schematic that they're using only 1 switching relay.

I think you're describing what I want to do.

What are your thoughts on this?
 
  #5  
Old 12-07-16, 05:46 PM
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Ok, let's step back like spott suggested... give us the big picture..what do you have and what are you trying to do?
 
  #6  
Old 12-07-16, 05:47 PM
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Spott,

They aren't wired. The old system was ripped out a few years ago. My father didn't use zone valves but used B&G circulators to provide 3 zones. Each circulator had a Honeywell RA89A switching relay, so there were 3 switching relay boxes mounted on the wall. In the house there were 3 thermostats.

I'm still in the installation phase of the project.

The new boiler system is natural gas fired and the DHW is natural gas fired by a separate hot water heater. The aquastat is built in to the CGA-A Weil-Mclain boiler and is adjustable on the boiler's controls providing a nice digital display of the boiler temperature.
 
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Old 12-07-16, 06:03 PM
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So you have a cold start boiler meaning it operates on demand for heat and does not maintain temp.

What you can do is get two 24V transformers. One for every 3 zone valves and wire them to your TT terminals on your boiler. You do not need a relay with ZV's in your case.

From the transformer to 1 term on stat, term#2 on stat to #1 on ZV, #2 on ZV to transformer. That completes the stat circuit and on a call for heat the ZV will open making the end switch.

Then terminals #2 & #3 from ZV go to TT on boiler to start boiler and pump to complete the entire circuit.

That's the inexpensive way or you can get a Taco 6 zone relay control panel for zone valves. Makes a neater job at an expensive cost.

Hope this helps.
 
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Old 12-07-16, 06:46 PM
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Spott,

Very helpful. Here's an update- Just to experiment with the Honeywell RA89A switching relay I connected power 120 VAC to the proper terminals of the unit- 1 & 2 (pretty sure they are the ones- no matter- I wired them correctly per the diagram on the cover). Next the "T T" terminals (thermostat) terminals on the unit were connected together. The relay clicked. I put a volt meter on the "Load" terminals, I think they're 2 & 4 (they were wired correctly per the diagram on the cover). Guess what? The voltage between the Load terminals 2 & 4 was 120VAC!

Translated- if I had connected the boiler's "T T" wires (as they're marked) to the "Load" terminals I would've destroyed whatever is connected on the boiler's very expensive looking control box.

Glad I experimented first!

I had a assumed, incorrectly, that an "isolation relay" is a switching relay. The boiler's instructions make it clear not to connect 3-wire zone valves to the boiler's "T-T" terminals. But, the zone valve "end switch wires" to the isolation relay coil and the isolation relay contact across the T-T terminals of the boiler.

Phew. Live and learn

Craig
 
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Old 12-07-16, 07:31 PM
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Craig,

As you pointed out 2 & 4 on that relay are load terminals for 120V, basically for a circulator. They make a relay R832A where the terminals can be used for line or low voltage if wired by the schematic. The 89A is very basic. The others have more options.

What they don't want you doing with the TT on the boiler is using it as the transformer to power up the ZV's. It's not made for that. You must use a separate one and use that just to activate the boiler and pump.

The reason you need only need the transformers and not the relays is because the ZV's are 24V. You only need a relay for circulators because they are 120V and the voltage must be reduced to 24V which is the voltage of the TT terminals on the aquastat to operate the boiler and pump.
 

Last edited by spott; 12-07-16 at 07:53 PM.
  #10  
Old 12-08-16, 05:51 AM
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Spott,

There's a copper jumper between terminals 1 & 3. Once I removed that jumper, terminals 3 & 4 become "dry"- no voltage between them.

Is the following correct?

- The RA89A can be connected to the boiler's T-T connection as follows;

1- With the jumper between terminals 1 & 3 removed, terminals 3 & 4 become "dry" with no voltage present so the T-T wires from the boiler can be connected directly to terminals 3 & 4.

2- The ZV's terminals 2 & 3 are connected to the T-T terminals on the RA89A.

Does that make sense?

I'm going to experiment with this idea today and see how it works. The objective for the moment, and in part, is to keep any voltage being applied to the boiler's T-T connection.

I'll let you know how it goes.

Thanks,

Craig
 
  #11  
Old 12-08-16, 07:19 AM
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The method I described above works. It's pretty simple.
 
  #12  
Old 12-08-16, 09:09 AM
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Craig,

You seem to want to use that relay for some reason and that is your prerogative but this is just out of curiosity. What do you see as the advantage of putting a 24V control to a 120V switching relay to break back down to 24V to go to the TT terminals on the boiler. If you went straight to the boiler with your 24V control isn't that like eliminating the middle man and getting the same result with 1 less control that may fail.

Not criticizing just curious. I understand you don't want to fry the aquastat but I don't think you will accomplish your mission with the 89A. It's a line voltage relay made to accomadate a line voltage load.

To put your mind at ease a little I will tell as an experiment when I put my own system in I have 8 zones, all with Taco zone valves and no relay and I haven't had a problem in 32 years.
 
  #13  
Old 12-08-16, 03:57 PM
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Spott,

The RA89A works perfectly with my zone valves (only 3 have been connected so far). But it only works because I removed the RA89A jumper between terminals 1 & 3 rendering the relay, that would normally go to a circulator directly, as a "dry relay" using terminals 3 & 4.

Weil-Mclain, makes it clear DO NOT attach zone valve switch wires to the T-T terminals on the boiler.
The problem being is that one of the wires from the zone valves is a neutral. I'm just the user and installer and don't want to any warranty matters.

8 zones? That's great!

Craig
 
  #14  
Old 12-08-16, 04:21 PM
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Glad to hear it's working. I did check a new WM and found what you're talking about. That is what they want but I don't know why because technically there is no neutral on a 24V circuit. Will investigate though.

SKIP
 

Last edited by spott; 12-08-16 at 04:59 PM.
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