Q: Multiple zones one thermostat

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Old 03-03-14, 10:12 AM
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Q: Multiple zones one thermostat

I have a weekend cottage in the country with a simple hydronic heating system comprising five zones. While I am away, I set the thermostat in each of these zones to 55F. Since installing a high-efficiency gas boiler, the house takes longer than previously to come up to temperature when I visit at the weekends. I could solve this problem by turning on the heating in advance remotely by using WiFi thermostats such as NEST, but at $250- each installing 5 of them is an expensive conversion.

As an alternative I was considering purchasing a single NEST unit, installing it somewhere fairly central and putting it in parallel with the five existing thermostats. If my existing thermostats are simple switches I would imagine that I would then be able to switch on all zones using the single NEST unit. I would use this arrangement to bring all five zones up to some pleasant ambient temperature in advance of my arrival, and achieve a useful level of remote control for only $250.

Has anyone done something like this? Am I right in thinking that if thermostats are simple switches (they each have two wires, red and white) and my heating system is pretty uncomplicated (I only have heat, no a/c), wiring in parallel should cause a call for heat when either of two thermostats closes (ie up to the higher of the two temperatures). Is there any issue in joining all 5 circuits via a "master" thermostat like this?
 
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Old 03-03-14, 10:47 AM
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Welcome to the forums.

Definitely a do-able project. You would need a thermostat and five basic normally open relays to isolate that thermostat from the other five.

You can't put all the thermostats in parallel or use a parallel connection as one of those thermostats would affect all the other zones.

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Last edited by PJmax; 03-03-14 at 11:10 AM. Reason: added diagram
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Old 03-03-14, 02:56 PM
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PJmax,

Thank you for you welcome and thank you also for your remarkably rapid response to my question - complete with a diagram to boot!

Of course, it makes complete sense that I would need relays to keep the 5 circuits separate.

Do you (does anyone) have any tips on sourcing relays like this? I am guessing I will need something just robust enough to carry whatever the thermostat would (I think it is a 24 volt system, but cannot remember why i have that impression).

thanks again,
leo
 
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Old 03-03-14, 06:55 PM
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If all 5 stats are fed by a single transformer a single relay could be used to break R at the transformer.

Heavy Duty Fan Relay, 24V: Amazon.com: Industrial & Scientific

Nest stats work Much better when they are supplied a common wire from the transformer. Do you have an available common terminal at your boiler?
 
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Old 03-03-14, 10:08 PM
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I was thinking about that but with five zone valves there must be at least two transformers
 
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Old 03-03-14, 10:17 PM
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Two transformer R's can be interrupted with a double pole double throw relay.

White Rodgers 90-340 Switching Relay - Amazon.com

It is tough to guess what is there without a better description or some pictures.
Many posters don't even have a C terminal on the boiler.
If this is the case a fan center might be an option.
Honeywell model R8285B1038 Fan Control Center - Amazon.com


https://customer.honeywell.com/resou...0s/69-0482.pdf
 
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Old 03-05-14, 03:30 AM
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Thank you both - and thanks for the product suggestions. I will do some research on what i have. It is a pretty modern installation, since it came with the high efficiency boiler.

I have a question about breaking the supply from the transformer. It strikes me that this would ensure effectively that all thermostat switches are open when the master (eg the nest stat) is open. What I think I need is to ensure that all 5 are closed when the master is closed. I think this is not the same thing. Can you clarify?
 
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Old 03-05-14, 08:38 AM
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We would have you set up the relay, whether one pole or two poles, to open the connection to the regular thermostats and close the circuit to the nest.

You don't need the five thermostats connected. You just want to temporarily take control of what they control.

It would not be the type of relay in my drawing or the one in Houston's link.
 
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Old 03-09-14, 09:45 PM
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ok, i have looked at the installation - the switching box is an Argo ARM-6P, which (on researching the literature) claims to include a "Powerful 30 VA transformer" that will "operate up to 15 zones". I wonder if this means i could operate 5 relays per PJmax's original schematic...
 
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Old 03-10-14, 07:20 PM
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Looks like 1 relay would work if you were using the ARGO IR822 isolation relays at this time. Those things are pricey.



Probably not that lucky.
You will need common. A transformer may also be required.
 
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Old 03-10-14, 08:32 PM
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A Nest can be connected to this setup with 3 relays If you do not already have those isolation relays...
 
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Old 03-10-14, 08:38 PM
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You can take some of the load from your thermostat by adding another relay to isolate the thermostat from the other 3 relays...





3 (or 5) relays wouldn't stress the thermostat isolated in this manner.
 
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