TStat Question

[Time2Jet]

Have a client with a boiler system with baseboard units in each room with a 2 wire tstat opening and closing the valves back at the head end.  I'm sort of at a loss for the best solution to integrate the heat in this home.  I know the previous gen C4-TStats could run on battery power and would work with two wires (like a basic relay).  But I am not sure how the latest gen would work here.  In this scenario we'd need several relays, so I don't think a Control4 tstat solution would work.  Any help would be appreciated.  This is not crazy uncommon in the NE US homes.

[BDavisNJ]

@Time2Jet I also live in the Northeast USA and have encountered this issue.  Here is my suggestion based, of course, on the assumption that you / end user do not want to open walls and want to minimize revisions to the wallboard.

1. In the boiler room, identify the hydronic zone controllers (1 for each zone of heating).  These are very likely Honeywell branded.  These devices will have 4 wires (2 black, 2 red).  One set goes to the boiler, the other set (most likely red) will be connected to a wire going to the 2 wire thermostat.  Leave the set of wires going into the boiler alone.

2. Disconnect the wires going to the thermostat.  Connect these to a relay (see Note A, below).  I used Functional devices model RIBRL1S because these are DIN rail mounted, have a manual override, and an indicator light so you can visually determine when the relay is on (helps with troubleshooting).  Wire each relay to either a C4-IOX (Control4 IO Extender) or a Shelly device (I prefer hardwired).  Note that RIBRL1S requires 12vdc.  You can get a DIN rail mounted step down transformer (120vac to 12vdc).  I also place a LED panel light on the transformer so I can easily confirm that the 12vdc power is indeed on (helps with any troubleshooting). 

3. You will now be able to control each zone on the heating system using the relays and therefore via Control4.  I created a separate "room" called HVAC and used a custom icon for each zone of heat (one icon for ON and one icon for OFF).  Pressing the custom icon turns the heat zone on (closes the relay) and displays the ON icon.  Pressing again toggles the sequence.

4. Now, we connect the thermostats because we have no intention of manually controlling the heat.  Remove all of the as-built thermostats and expose the as-built 2 wires which run from each thermostat location to the boiler room.  Use a meter and ensure that a) no power is running through the wires (remember you disconnected these in step 2) and b) you have affirmatively determined that each of the wires is correctly identified as the wire running from the thermostat location to the boiler room.

5) Install one unit of C4-THERM to replace each as-built thermostat.  Set the C4-THERM to "powered" and not "power stealing" (there is a physical switch that needs to be set).  Connect one of the wires to common (usually white) and the other wire (usually red) to 24vac on the back of the C4-THERM.  Also put 4 "AA" batteries in each C4-THERM.

6) Supply the as-built 2-wire cable starting from each of the thermostat locations and terminating in the boiler room with 24vac.  You can get a DIN rail mounted transformer (step down 120vac to 24vac) and position on the same DIN rail as the relays in step 2 (looks nice).  I also place a LED panel light on the transformer so I can easily confirm that the 24vac power is indeed on (helps with any troubleshooting).  Make certain to get sufficient amps to power all of the C4-THERM units.

7) At this point, all of your C4-THERM should be powered and functioning.  Follow the instructions in Composer Pro to register each on the Zigbee wireless network.

8.) Using programming in Composer Pro / HE, you are going to create an action for each of the C-THERM devices (WHEN any HEAT CALL --> turn on (close) ZONE RELAY).  And, of course: WHEN heat call OFF --> turn off (open) ZONE RELAY.  The thermostat driver will provide the Navigator GUI with scheduling and other virtual thermostat features for each zone.

9) here is the best part.  Many older houses in NE have central air that used a separate thermostat.  You can now use programming to provide the homeowner with one single thermostat for both heating and cooling using the same logic as above.

I hope the above provides a good starting point.  The usual caveats and disclaimers apply: licensed electricians for line voltage, HVAC specialists if needed.  I also would make certain that the gauge of the as-built wire is rated to carry 24vac.  Given that thermostat systems use 24vac as a standard, I strongly suspect that the as-built wire will be sufficient.  That said, better to check and verify than to assume.

Reach out with any questions of follow-ups.

 

Note A: Honeywell seems to have a dominant market share for the hydronic zone controllers.  Most of these devices call for heat from the boiler when 24VAC is supplied to the 2 red wires.  Thermostats simply act as switchs.  Our goal here is to substitute the relay for the thermostat.  Therefore, direct 24VAC to the common on the relay and then normally open (NO) to one leg of the hydronic zone controller.  Wire the other leg of the hydronic zone controller back to the 24VAC supply.  Make certain that your version of the hydronic zone controllers requires external power before wiring.  Some versions (older) were self-powered.

[lippavisual]

Based in NE as well here.  I wouldn’t do any of that above.

install temp sensors at each thermostat location and move all thermostats down to the boiler.  Install a separate 24VAC power supply and wire each thermostat to it for constant power.

This is what I’ve done in my own house and many others that have the same systems.

[Time2Jet]

Based in NE as well here.  I wouldn’t do any of that above.
install temp sensors at each thermostat location and move all thermostats down to the boiler.  Install a separate 24VAC power supply and wire each thermostat to it for constant power.
This is what I’ve done in my own house and many others that have the same systems.

I hope this isn’t more confusing.

I was more inclined this direction, but I’m confused. Are you then running several separate smart C4-TStats in the boiler room? I was considering having 1 for the sensor connections and a main zone and then an IOX or 2 to open and close the individual room contacts per the individual C4-sensor readings. I assume there are variable exposed on the tstat driver for each sensor?


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[Cyknight]

12 hours ago, Time2Jet said:

I know the previous gen C4-TStats could run on battery power and would work with two wires (like a basic relay).

NOOOOOOO they sure didn't! They could work on powerstealing using battery to bridge voltage drops. Powerstealing support however was VERY dependant on the heating unit and it was dropped as a truly 'advertised' method early on.

 

In fact the NEW thermostats ARE fully capable of running on battery only. That said, I don't recommend it. I don't like to rely on batteries to ensure a house doesn't freeze. Silly maybe but there it is.

@lippavisual has the right method.

 

[Cyknight]

1 minute ago, Time2Jet said:

I was considering having 1 for the sensor connections and a main zone

You can only have one sensor per t-stat.

You COULD use other sensor options and use relays, but it's going to feel clunked together (because it is)

[Time2Jet]

You can only have one sensor per t-stat.
You COULD use other sensor options and use relays, but it's going to feel clunked together (because it is)

So a current Control4 TStat can run solely on a battery and basically act as a wet contact to open and close the 2-wire circuit per temp measurements?

If so, I’d likely power them from a 24v supply in the boiler room with battery as backup.

My issue was that I didn’t realize the current C4-TStat would work with two wires (relay/wet contact). That’s where I got stuck.


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[RAV]

Fast-STAT Common Maker  $62            (Fast stat has many models to create "fake" extra thermostat wires)
https://www.amazon.com/Fast-STAT-Common-Maker-Popular-Thermostats/dp/B07G2NGFKH

[Cyknight]

2 hours ago, Time2Jet said:

So a current Control4 TStat can run solely on a battery and basically act as a wet contact to open and close the 2-wire circuit per temp measurements?

If so, I’d likely power them from a 24v supply in the boiler room with battery as backup.

My issue was that I didn’t realize the current C4-TStat would work with two wires (relay/wet contact). That’s where I got stuck.


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It can yes, but as @RAV more or less indicated, how to wire it can be more complex than a normal relay as a T-Stat is assumed to be powered from the same furnace providing the power to go across the relay of R - W (or R - Y for cool).

So either an isolation unit is needed if that relay isn't the same 24vAC (rare enough) - OR only power the T-Stat and use a controlled relay for control plus programming.

I strongly suggest using an isolation unit as it maintaince the T-Stat's ability to fully function as a stand alone device. I've only in rare occasions done it via a controlled relay and then only for secondary heating control, not a house/building's main heat.

 

Basic way of isolation using standard relays (this would still fully leave the t-stat working as a stand-alone item is system were down) as was detailed with the original t-stat (and still works though the C/TS is now just a C connection):

 

[Cyknight]

Note that the relays above are standard 24VAC coil relays - should be able to source them for $5 or less a piece...

[Shoe]

Fast-stat common maker for the win.

[BDavisNJ]

@lippavisual if you install temp sensors and remove the thermostats, how do you offer local control (absent a T4)?

[Shoe]

Phone, watch, voice...

If you use a fast-stat common maker you can use almost any thermostat like an Ecobee etc.

[Cyknight]

6 minutes ago, BDavisNJ said:

@lippavisual if you install temp sensors and remove the thermostats, how do you offer local control (absent a T4)?

Everyone's phone, any remote control, SR series or other.

[BDavisNJ]

@lippavisual and @Cyknight One of the many positives of C4 is that there are multiple ways to get to a solution.  As long as the end user / homeowner is happy.  The Navigator GUI from the thermostat driver is excellent and T4s will also permit HVAC adjustments.

I, for one, strongly prefer the physical thermostat.  Staff know immediately how to use the device, I am not glued to a cell, and remotes get moved about -- plus the screen is a bit small.

Sometimes technology is best experienced in the background -- there is something rewarding about tactile interaction associated with traditional devices.  But to each his / her own.

 

[Shoe]

A retired professor might have a tendency to over engineer.

10 minutes ago, BDavisNJ said:

there is something rewarding about tactile interaction associated with traditional devices.

[Cyknight]

29 minutes ago, BDavisNJ said:

I, for one, strongly prefer the physical thermostat

Then I would assume you also prefer the walk to the thermostat: it's just a bit of a longer walk to the mechanical room now.

[lippavisual]

I for one don’t play around with my stats.  I set a schedule and that’s the way it stays.  But yes, using any other interface with the stat works perfectly fine.

I also have mini splits at home for AC in the summer, so when I shut down my boiler for the season, the stats can be used for temp in the rooms, even though they are set to off.

And because there isn’t an official Mr. Cool driver, I use an http driver to send commands to the mini splits, if needed.

[BDavisNJ]

This board is a terrific resource.  Hearing different perspectives and approaches is of tremendous value.  In just under 17 hours @Time2Jet has three different approaches to consider with the pros and cons of each outlined.

Thank you all for a robust discussion and have a great weekend.

[eggzlot]

1 hour ago, BDavisNJ said:

@lippavisual if you install temp sensors and remove the thermostats, how do you offer local control (absent a T4)?

I am not lipp but I have the set up he mentioned with remote TStats

The walls look nicer (remote t stats are painted over) and for the most part with schedules there is not much of a need to interact with the tstats.  once in a blue moon if we have to, we can pull up a phone or a touchscreen.