radiant t stats

mike terry_4

would anyone know if there is a better suited thermostat than the honeywell t8400c for radiant slab heat.
thanks Mike Terry.

Jay_12

tekmar thermostats

Hello Mike,

Consider using tekmar 500 series thermostats for your radiant floor application. The 508, 510, and 512 have the ability to have slab sensors installed that measure the floor temperature in addition to the air temperature. This allows for minimum temperatures to be so that the floor always feels warm. It also is able to provide a slab maximum temperature to limit floor temperature. This is important when installing hardwood floors.

The thermostats have been specificly designed for radiant applications and use Pulse Width Modulation operation to reduce /eliminate temperature swing.

The 508 is non programmable while the 510 is programmable and the 512 is programmable with 2 stage heating or heat /cool.

Check them out at the tekmar website: www.tekmarcontrols.com and go to products.

Jay www.tekmarcontrols.com 250-545-7749

m dewolfe

tekmar

I love my tekmar 511! Throw out everthing else.

Unknown

Tekmar 500 series tstats are great. At least, as great as you can get without Tekmar RTUs

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hydronicsmike

Rob, You Rock!!

Unknown

you know, I keep telling people that, and they don't believe me!!!

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Tom_35

Question for Jay

We have a job going that will have 2 367's, 2 268's, and 9 150's. The 150's will be mounted in the 2 separate mechanical rooms using slab sensors. We will have tile floor, wood floor, marble floor, and carpet.

Is the 500 series a better stat for the purpose we are looking at? This is a really large home and night setback is not going to be used.

Tom

Unknown

I can't imagine using all those controllers without at least adding a mixing control and using RTUs! If you did that you wouldn't even need the slab sensors, just set the max water temp on the controller low enough to protect the concrete, and let the indoor feedback/outdoor reset keep it all comfortable all the time. 370 or 371.

I'm guessing you just wanted staging and slab temperature monitoring? Then yeah, I'd go for the Tekmar T-stats if I didn't do full indoor feedback. I think it's the 511 that is two stage (512 Heat/cool, right jay?) and both have slab sensors if I'm not mistaken.

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hydronicsmike

Tom...

...you may wanto to talk to someone about the Controls selection again, as Rob mentioned. (By the way Rob, don't listen to the rest. You Rock!:) )

The 509 T-Stat is a Stat that is non-programmable and comes packaged with a Slab Sensor.

The 511 T-Stat is a Stat that is programmable for Night Setback that also comes packaged with a Slab Sensor.

Either of the two Stats will do at least as good of a job as the 150's can, but are first of all more cost effective (cheaper) and personally I find they are also physically more attractive than the 150s. So Yes, for Slab Warming or Slab Protection, I would always recommend a 500 Series Stat before a 150. The Stats can also Control Air Temperature while operating between preset Slab Min (optional) and Slab Max limits, where the 150s will only maintain the slab at a fixed setpoint.

The rest of the Controls I would like to talk about when you get a chance. You may want to call the office on Monday or send me an email over the weekend if it can't wait until then. Office number is 250-545-7749, Ext 214 for Mike, or Ext 234 for Jay.

You have a lot of options and I would like to list those to you. The 367s use non digital RTUs and if you like RTUs, you may want to look into the digital ones. Then you would use a 369 instead of the 367 and 062/063RTUs instead of 054RTUs. The 063 are digital RTUs that can have Slab Sensors wired to them for Slab Protection and could be used in place of the 150s as well. Regardless whether or not you will end up using the 367s or 369 in the end, you need to use a Control that those can actually talk to. None of the Controls mentioned in your post are able to communicate with one of those Zone Controls. Then you mentioned that you are using two 268s. The 268 operates up to 9 Boiler Stages and usually there is only one per job, at least the jobs I come across daily.

Anyways Tom, hope to hear from you.

Regards,

Mike

Jay_14

controls

Hello Tom,

The 508,510,512 thermostats allow for auxiliary slab sensors to be mounted in the floor. Both the 500 series and the 150 setpoint control use the same PWM algorithm which reduces or even eliminates temperature swing in the room, making the room feel comfortable. I would recommend the 508 since it is non-programmable and has the least cost even when compared to the 150.

I'm not sure of your intention regarding the 367's and 268's and the use of 150's/500 series thermostats. Usually if you are using indoor feedback and would like to maintain a slab temperature, the 369 with 063 RTUs is the recommended method. Also, there is no communication between the 367's and the 268's.

Give me a call on Monday and we can discuss the application in more detail.

Jay www.tekmarcontrols.com 250-545-7749

Ron Schroeder_3

Tom,

If you have both floor heat AND some other form of heat in the same room, the 512 is the way to go. It can be either heat/cool or in this case 2 stage heat.

With 2 stage heat, it will run the floor up to keep the room at the setpoint until the floor reaches the max floor temp that you have set and then it will add in the other source of heat to keep the room at the setpoint. What I really like about the 512 is you don't have to wait for the room to drop several degrees before the second stage comes on.

Ron

Tom_35

Tekmar on job I mentioned

Let me claiify a few things about the job I mentioned earlier. It is a large home that has a total of 10 systems on it. 6 of them are ECR direct exchange heat pump systems, and 4 of those will be providing the radiant floor heating. The north end will have 2 and the south end will have 2. Each of these zones is staged and has a buffer tank. Our plans are to use the 268 for controlling the heat pumps for 1st and 2nd stage radiant heating.

The 6 hp's will be the main source of heating and cooling for the home. During the fall when the Arkansas weather is really unpredictable, the units will operate through the normal heat pump mode and heat the home via the ductwork. When the weather finally gets cold (it still hasn't got below 45 yet), the 4 heat pumps will switch to heating the concrete slab, and the heat will be through the radiant. If we have a cold snap and the radiant can't keep up, the systems will switch back over to heat via the ductwork, satisfy the heating call, and then go back to heating the slab.

This comes down to 2 completely separate systems under 1 roof---thus the reason for 2--268 controls. Each system will be controlling hydronic modules from the heat pumps that will feed heat exchangers for the buffer tanks.
De-superheaters are also going to be used on the same 4 heat pumps for domestic hot water heating during the summer. There will be 1 hydronic unit heater for a garage.

We roughed in sensor sleeves in the slab when the he-pex was installed, and our plans have been to let 150's control each of the 9 radiant floor zones. We were plannng on mounting the controls in the mechanical rooms. All the fan-coils have variable speed fan motors and we were wanting to take advantage of a cooling control that would recognize humidity levels and have a small override(like the Carrier Thermidistat or Infinity).

But, we are completely open at this point. We are planning to start fabbing the hydronic panels after Thanksgiving.

Thanks so much for your input.

I have e-mailed Jay and will discuss this on Monday.

Tom