HVAC and Radiant heat

I'll probably get into a pissing contest over this but it's my opinion that most of the current high efficiency radiant systems today do a very good job on their own with their own hardware/firmware in place. They have their own outdoor re-set's that regulate floor supply temperature based on outside temp and all there's really needed is a thermostat to regulate the room temp. You can obviously use a Crestron thermostat for that along with a slab sensor so you can monitor it but I think it's overkill as (in my opinion) radiant is something that should be set_and_forget.

1. You don't want two high tech systems fighting over control.
2. The guy that comes out at 2:00 AM for a no heat call is not going to be a programmer.

Agreed, just use a communicating thermostat (Crestron preferred.)

From our experiences with radiant heat inside the home, once you set a comfortable temperature, you almost never shut it off, unless you are away for a few weeks or a month. Once the preferred temperature is reached it uses little energy to keep up that temperature.
Most of the time we suggest that the radiant is left off of the control system, just use the stats provided with same.

Would be nice to control the radiant floor heat t-stat's vacation mode, from a central controller.

I know the NuHeat t-stats (rebranded Aube, I think) aren't very intuitive, for the homeowner. Making even a slight change requires a review of the instructions.

Just a thought - leave the radiant floor heat thermostat instructions in a nearby closet, in an envelope thumbtacked to the wall.

I keep a copy in a MBa vanity drawer.

Crestron thermostats have an option for slab sensor that can control radiant. This would be the way to go in my book

What type of radiant heat do you plan on installing? Hydronic or electric? Is it just for the comfort of not having a cold tile floor, or is it the primary source of heat for those rooms?

If it's for actually heating the rooms, and not just to keep the tile floors from feeling cold, then I'd have to disagree with most of what I've seen with regards to replies. I think you should do a little more research on radiant heat, and thermostats for such, before worrying how to integrate the controls with your home automation.

A hydronic radiant heat system either in the slab or a mud job, deals with a very large thermal mass, which initially requires a good amount of heat to reach temperature, but once there ideally it should remain fairly stable. A key element in efficient and comfortable operation is a slab sensor. I saw reference to slab sensors in some other replies, but I think those mentions refer to something that only reports back what its reading as opposed to using it as a controlling factor. A good radiant heat thermostat has both a room temperature sensor and a floor slab sensor. Similar to a typical thermostat, it allows you to set the desired room temperature, but additionally you set slab max and min temps, and these basically act as overrides. If the room temperature is satisfied, but the slab temp is not, it will continue to cycle (important word here, more later) until the slab is at it's min, alternatively, if the room temp is not satisfied, but the slab is at it's max, it will shut off.

Now more on cycling, a good radiant thermostat 'learns' it's environment, and will determine the optimal cycle times (on vs. Off) to maintain the desired temp. Without this, and a slab minimum set, the temperature could vary more than desired. The slab would heat up too much before the room reached the desired temperature and by the time it shut off it would be too late and because of the large thermal mass the temperature would 'creep' higher, on the other end of the spectrum, when the slab, and room start to cool down, by the time the thermostat calls for heat, it's again too late, as the slab ( because of it's large thermal mass) will take more time to warm up before it can actually heat the room, and then the temp drops below that desired.

I have three different manufacturers thermostats, operating various radiant setups (1. heated conc. slab on grade with a laminate flooring, 2. tile on a mud job, 3. tile over a traditional subfloor with aluminum heat track below, 4. carpet over subfloor with aluminum heat track and 5. carpet over subfloor with suspended tubing) and have to give Kudos to TEKMAR, the mfg. of what I consider a superior radiant heat thermostat.

I had been searching for a radiant heat thermostat to integrate with my home automation for quite some time, there's a handful of thermostats out there that can be integrated, but none that I considered suitable for radiant heat due to the lack of a 'functioning' slab sensor. About two weeks ago I discovered that TEKMAR now makes a gateway that links a line of their thermostats with a number of home automation systems via RS232, it looks just like what I've been waiting for, it supports a ridiculous number of thermostats, way more than I need it to, BUT its retail price is in the $1,400 range! Hopefully the price drops significantly over time, and maybe one day I can afford the upgrade.

http://www.tekmarcontrols.com/access...l?view=product

Thanks for the info, Zellarman. I looked at Tekmar briefly, a couple years ago, when we remodelled our MBa. Their website has changed considerably, iirc.

Maybe that driver list will get longer soon.

I am curious to know what are the costs of installing HVAC for a four-zone setup ?

A couple of things here. I don't like to give the end user the ability to control to many things especially those that I've spent hours calibrating.

I don't have a problem using automated t-stats and monitoring floor temps but as stated earlier, most new high end boilers and HVAC controls do a great job of making sure you get the most out of your energy dollar.

My system uses three sensors (not even counting the t-stat).
It uses a supply sensor, a return sensor and a outdoor temp sensor.

As the outside temp goes up, the system knows that less energy will be required to keep the floor warm. The boiler will run at a lower firing rate.
It will ramp down while it's monitoring the return sensor. If the return starts to come back cooler than the floor design temp, the return sensor will see this and tell the boiler to ramp up.

If you get a radiant heat system with bacnet/ip creston can pull in the setpoints and you can have setpoint control through the creston touchpad. My company does this stuff all the time as we are one of the BIG Hvac controls companies. The perferred way to go. Is find a vendor who is Bacnet/ip or MSTP or Modbus use a babblebuster to translate to a language creston can understand and pull that system into the creston display for setpoint control.

Chipkin Automation Systems can translate the protocol between Modbus/BACnet and Crestron so the devices can communicate with each other.

We recently implemented a driver for the Tekmar gateway. It's something that I would not need to use myself, so I can't speak for the Tekmar system as a user, but from a control standpoint it seems solid. It asyncrhonously reports almost all changes, which is important when the gateway can have almost a hundred thermos connected to it. Each thermo can support heat, cool, fan, and/or slab. The gateway can be set to either expose a single set back mode to the controller or expose the separate setpoints for the various set back modes.