oh no, were these thermostats a mistake?

[BigAl]

Hi, I am brand new here and very glad to have found this website. My husband and I are committed to getting our new Control4 system to work right, it will be really neat when/if it does.

Issue at hand: the CCZ-T1 thermostats. Dealer provided them but did not install them, advised we get HVAC or electrician to do so. HVAC didn't want to, said "it's easy, just wire them exactly the same as original Honeywell thermostats". My husband is an electrical engineer and handy with DIY stuff, so he installed them. They seemed to be working fine, but recently we had serious misbehavior from one. Dealer essentially doesn't know what to make of it and says we need to get the electrician or HVAC in to be sure they are wired right. Once HVAC heard "power stealing", "bypass resistor", "home automation system", he said it's out of his league, we need an electrician. Electrician says "I don't do thermostats". Apparently, homeowners can not contact Control4 tech support, only Control4 dealers/installers.

Wow. We are on our own.

At this point, we've simply pulled the thermostats off the wall, and they are serving as very expensive room thermometers.

First, will the CCZ-T1s actually work with a radiant floor heating system? I am reading here that they don't work with some HVAC equipment. We have 4 wires available but only 2 were wired in the original thermostat. The installation sheet mentions using the bypass resistor if you're using power stealing, but nothing about where that bypass resistor is supposed to go. We have no AC and no fan. We don't have a heat pump or a furnace, just a boiler and a mechanical room that looks like a submarine - many recirculating pumps, etc.

Any advice on which of these wiring diagrams applies to us, and where that bypass resistor should go?

[Chas]

C4 Stats will work with Radiant, but not with just 2 wires. Power stealing will not work that way. What needs to be done is a 3rd conductor to access the common of the HVAC transformer. That assumes there there is a single transformer in your system. You need to find a different C4 Dealer than the one you have if they cannot do this for you. I am a dealer, and we do it all the time. The other option is to get 1 or mor 3vdc regulated power supplies and run that power ove the 2 conductors you are not using.. They would need to be hardwired onto he terminals where the battery is now and the battery would be removed. A good dealer shoul be able to do this.

[R_Willis]

Make sure to review this:

http://www.c4diy.com/wiki/images/6/6c/Reducing_Power_Stealing_Side_Effects.pdf

[henniae]

Since you have 4 conductors it might be possible to hook up the t-stat without power stealing. It would be useful to have a diagram of the heating controller and some pictures. We need to find the common terminal for the power transformer and hook that up to the t-stat. Some switches will also need to be changed on the t-stat.

I would not recommend replacing the battery with a 3volt transformer. The purpose of the battery is to keep power to the t-sat when there is no mains power.

[ELECTRICDON]

Your Boiler is a two wire system. The above remarks are correct, you need a common wire. If you husband is an EE he should be able to read the diagram and figure it out. Also, sounds like your C4 dealer, HVAC tech, and Electrician all do not want the resposibility of hooking it up...Your C4 dealer should train him/herself a little better if he/she is selling products that he/she can't install.

[BigAl]

This feedback is helpful. Clearly we need to figure out ... and possibly get diagrams/pictures of ... our HVAC system wiring. We are new to radiant floor heating, it's really different from forced air we've had before. We'll be back when we have a round of more specific questions to ask. Thanks so much!

[CFUG]

I have no doubt a C4 stat can switch on and off but I have a mental block when it comes to how this device possesses the smarts to anticipate setpoint approaching and start modulating power to the floor grid much like a common PID loop strategy. Isn't the shear heat-mass of a slab floor going to continue to transfer heat long after the stat reaches setpoint?

[ILoveC4]

^That was my thinking exactly. I don't see this working well...it isn't like when you it off the floor stops radiating heat immediately. I think you'll have a roller coaster of temperature swings based on how long the radiant system takes to react.

[BigAl]

We sure have had the "rollercoaster", which I think is a common complaint about radiant floor heat regardless of the thermostats involved, no? The HVAC guy said that this system supposedly "learns" over time to smooth out the rollercoaster. We'll see. We have not been into the heating season very long and so are discovering the pleasures and pains of radiant floor heating as we speak. Still, assuming we DO get the C4 t-stats wired correctly, isn't it possible that these C4 t-stats could work even better than the original Honeywells, since the C4s have all those settings you can dink with? In Composer HE, when I open a t-stat, there are 70 different adjustments that can be tweaked. OK, maybe not 70, but a lot.

[BigAl]

... and by the way, I am happy to see the username "ILoveC4", that is encouraging. At the moment, I do not love C4, but I want to. At the moment, we are calling our C4 system "our HAL 9000" system. But, hope springs eternal ...

[wingzz]

Ha too funny, my wife calls the system Hal, she tells her friends that Hal did this or that

[CFUG]

or ROC (as in the movie Airplane).

[EagleMoon]

I have several C4 Thermostats in my house with only radiant floor, no cooling. I was only here a little over 2 months last year with the C4 system and heat on but as far as I could tell they worked just fine. We have a Munchkin boiler with its own high-tech controller. Last year I left the thermostat at the default settings. I've since added two more and may try tweaking the undershoot/overshoot and other settings this winter and I'm hoping to spend more time here this year.

I did have a lot of variation in the upstairs main zone but I think that was solar gain from lots of south-facing glass. And the temperature seemed to drop a couple degrees overnight, but that is probably due more to the design of the house than with the thermostats. In hindsight, we have way too much glass for the Colorado mountains. But it makes for nice views.

You DO need to use a dedicated wire for power, not "power-stealing". You just need a spare conductor. And if you can use dedicated power then you don't have to mess with a bypass resistor. BE SURE TO DISABLE POWER STEALING with the slide switch in the thermostat if you use the common wire for power. It'll be a costly mistake if you don't. I'll let you guess how I know that.

My system only needs two wires since I don't have AC. Unfortunately, the HVAC installers ran only two-conductor wire to some of my thermostat locations. That's a pain. I replaced one yesterday -- it was fairly easy because I access from conditioned crawlspace. But another is a downstairs interior wall. If they stapled that wire or wrapped it around a nail, it will be a challenge. I hope yours has a free conductor available.

[EagleMoon]

We sure have had the "rollercoaster", which I think is a common complaint about radiant floor heat regardless of the thermostats involved, no?

Actually, that's the opposite of how I understand it. Also it's opposite of my experience both in my own house and others I've visited.

A big advantage of radiant floor heat is the constant, even temperature. Forced air heat is the one with the roller-coaster of temperatures and wide variations around the rooms in my experience. Seriously, I've never experienced a house as comfortably heated as ours in Colorado was last Christmas though February, even with the variation due to the excessive glass.

A downside of radiant floor where the tubes are in any kind of concrete material is that it can't react quickly due to the thermal mass of the concrete. So if you have doors opening frequently you might have trouble. That also means you can't effectively do a nighttime setback. Edit: And you can't be changing the temperature throughout the day. Trying to do it would likely be a frustrating, losing proposition.

Assuming your house is well insulated, any wide variation in temperature is either the fault of the controller on the heating system (and how it was programmed if it's a programmable controller like my Munchkin has) or it's too much over/under-shoot in your thermostats.

There is some information that the C4 thermostats measure to the tenth of a degree and their over/under shoot settings are actually a "greater than" number using only the integer portion of the temperature measurement. That means if you set it for +/- 1 degree, the state doesn't change until the temperature is more than +/- 1.9 degrees, effectively 2 degrees each way. I haven't tried to verify that but if it's true, that means to actually have close to +/- 1 degree you have to set both to zero. It didn't feel that way to me, but that might explain my overnight drop that I mentioned above. I'm going to do some experimentation over Christmas this year to try to verify it.

Even if they don't measure to the tenth of a degree I would expect they basically round off, so it doesn't change from +1 to +2 until the actual temperature changes about 1.5 degrees, so you'd still have have 3 degree swing. The real question is whether the state changes based on "greater than" or "equal to" the measured temperature plus the offset.

Seems like Control4 could give a definitive answer to that.

My apology to all for running on there.

[BigAl]

Eaglemoon - Nope, that's not "running on", it's all interesting because we are new to both radiant floor heating and to the C4 t-stats.

[EagleMoon]

The real question is whether the state changes based on "greater than" or "equal to" the measured temperature plus the offset.

There was some imprecise/incorrect wording my post. That statement above, in particular, should say:

The real question is: does the state change based on whether the measured temperature is "greater/less than" or is "equal to" the setpoint plus/minus the offset.

So with a setpoint of 70 degrees and 1 degree Cutoff offset, does it turn off when the room temperature is 71 or when it's 71.9 (or even 72) degrees. That's pretty important distinction and one that should not be a kept a mystery for owners who might like to adjust the thermostat in their house from time to time.

The definitive answer can only come from the developers who designed the hardware (and thus know its precision) and those who implemented the algorithm (and thus know what logic was applied to the settings). Everyone else is just assuming.

[Letran]

Since you have 4 conductors it might be possible to hook up the t-stat without power stealing.

I looked at my current non-c4 tstat to be replaced it has 4 wires. Green black whte & red. Does that mean I just copy how it is currently connected and voila. The c4 tstat is this simple most of time right?

Just checkng before I actually replace it.

[henniae]

Since you have 4 conductors it might be possible to hook up the t-stat without power stealing.

I looked at my current non-c4 tstat to be replaced it has 4 wires. Green black whte & red. Does that mean I just copy how it is currently connected and voila. The c4 tstat is this simple most of time right?

Just checkng before I actually replace it.

The quote you referenced above was about a specific install of the t-stat in a heat only situation for radiant floor heat and does not apply to a heat and AC systems.

If you have 4 conductors and have heat and AC your only option is to use power stealing.

I would not trust the colors of the wire as guide. I would look at which terminals the wires are connected to on the existing t-stat and use that as a guide. You probably have R/RH, W, G and Y. If you hook the wires on those terminals of the existing t-stat to the corresponding terminals on the C4 t-stat it *should* be that easy. You will also need to set all the switches on the C4 t-stat correctly for your type of system.

If you can run new wire from the t-stat to the HVAC unit I suggest you do and use a common wire so you don't have to do power stealing.

[BigAl]

Update: We're making progress. We've had a consultation with our HVAC guy. Even though he's not familiar with the C4 t-stats or with using more than 2 wires in a radiant floor heating system (no AC) like ours, wiring into the common made sense to him. He showed us where that was on the Uponor control modules for the zones we want on C4 t-stats. Rereading comments here, I wonder what to make of us having at least three (3) transformers, not a single one as "Chas" mentioned.

By the way, our radiant floor heating under the control of the original Honeywell t-stats is fabulous. We are having virtually NO "rollercoaster" now. No overshooting by 7 degrees, no waiting until 3 or 4 degrees under the temp setting before kicking in. I'm crossing fingers the C4 stats will work this nicely.

[EagleMoon]

Update: We're making progress. We've had a consultation with our HVAC guy. Even though he's not familiar with the C4 t-stats or with using more than 2 wires in a radiant floor heating system (no AC) like ours, wiring into the common made sense to him. He showed us where that was on the Uponor control modules for the zones we want on C4 t-stats. Rereading comments here, I wonder what to make of us having at least three (3) transformers, not a single one as "Chas" mentioned.

By the way, our radiant floor heating under the control of the original Honeywell t-stats is fabulous. We are having virtually NO "rollercoaster" now. No overshooting by 7 degrees, no waiting until 3 or 4 degrees under the temp setting before kicking in. I'm crossing fingers the C4 stats will work this nicely.

Sounds like you have a separate transformer for each zone? Unless they are tied together on one side, you'll have to get your common wire for each thermostat from that zone's corresponding transformer. (You probably knew that.) Who knows why they used separate transformers.

I have three C4 thermostats. One downstairs area and our master bath do not vary more than a degree throughout the day. Downstairs is built into a the hillside on three sides, so that may not count. The upstairs main area does vary a lot (upward from 68 to low/mid 70s) throughout most days, but we have practically the entire SW side in glass and the Colorado sun is blistering at 8300 ft, even in winter. The Hunter Douglas shades help a lot, but still... On the other hand, it doesn't cool off much below the setpoint at night. Of course, this zone is not heating during the day on any of the 330 sunny days each year.

[BigAl]

UPDATE: ok, we've reinstalled the t-stats with power stealing disabled and using the common for power. We're trying to get the "Advanced Device Configuration" settings right for our system, in particular, "Heating Cutoff Point" and the "Delta" ones. Remember, we have a heat-only system with radiant floor heating. We have been unable to find documentation that describes exactly what these different settings do. Anyone know where we can find this documentation, if it exists? We don't want to make assumptions about which settings do/don't apply to us or about what these things mean. Any input from you knowledgeable folks is appreciated. thanks!

[EagleMoon]

UPDATE: ok, we've reinstalled the t-stats with power stealing disabled and using the common for power. We're trying to get the "Advanced Device Configuration" settings right for our system, in particular, "Heating Cutoff Point" and the "Delta" ones. Remember, we have a heat-only system with radiant floor heating. We have been unable to find documentation that describes exactly what these different settings do. Anyone know where we can find this documentation, if it exists? We don't want to make assumptions about which settings do/don't apply to us or about what these things mean. Any input from you knowledgeable folks is appreciated. thanks!

The details of how the cutoff and engage points actually work is a mystery I'd like to solve. I may have to take some time in February after I've left the "workaday" world and just measure it. I'd think that would be documented but it's apparently not.

I have noticed that my upstairs cooled down to 64 on more than one morning last week when the outside was near or below zero, even though it was set for 70 with 1 degree offset. But that's not the thermostat's fault, it's either a poor radiant design or an ineffective configuration on the Munchkin boiler. The Munchkin varies its flame and thus the outlet water temp in accordance with the outdoor temperature and several settings, one of which is the maximum outlet water temp. I think that must be set too low at 120 degrees. That temp was to protect the wood flooring but I think it doesn't deliver enough heat to the floor to make up for the heat loss when it's single digits outside. I'm going to bump it up to 125 or 130 to see if that fixes the problem.

Are you running into something similar?