Thermostat with tekmar control

Ross_4

Hi there
Can I use a generic programmable thermostat in place of the tekmar Indoor Sensor #076 that I am currently using? My radiant system is controlled by a tekmar 361 Mixing Control. I already have a timer beside the 361 which is just used for switching it to 'Occupied' or 'Unoccupied'. But I would like to be able to program the heating so that I'm not wasting fuel during working hours also.
I know tekmar now makes programmable thermostats, but they are a LOT more expensive than the ones I can get at the hardware store. I figure I could just anticipate the lag time for heating the 1 1/2" slab when I programmed the thermostat.
Thanks

Ken Wickre_2

Yes, but...

Yes, thermostats can be connected to terminals 1 & 2 (mix demand) to bring the system on. You will have to isolate power robbing thermostats with a relay or the control can continously sense a call for heat. If you have a single, high mass radiant zone with the 076, check to see if you have muliple setbacks available on your present timer. A tekmar 031, for example, has up to two occupied and two un-occupied events per day.

Remember, the 076 is an indoor sensor, providing feedback to the 361 in order for it to more precisely manage the water temperature based on what is happening in the space. In my estimation, this would be a better way to more efficiently operate your system, maximizing the capability of the control - rather than "step-on-the-gas/slam-on-the-brakes" control method of on/off thermostats (yes, the close differential offered in most electronic thermostats does help to minimize this in high mass slabs).

Pick-up and lag times are important to consider in maintaining comfort levels of high mass slabs. I don't like daily residential setback for this reason. Lengthy un-occupied periods, as encountered in a weekend closure of a business or residential vacation - yes.

Ross_4

Thanks Ken. The timer I already have connected to the 361 will accept enough events to put the system in and out of Warm Weather Shut Down when we are at work or away for some other reason. I'm trying it with a couple of hours lead time; I guess this will change as winter sets in (I'm in Whitehorse,Yukon).
Unfortunately, my wife's working a nine-day cycle so I'll have to make some changes to the programming each week. But I would have had to do that anyway.
I really appreciate your advice. I'd like to post again sometime soon with some pics and more info about my whole system. Even with an R-2000 house and radiant heat, my energy bills are not as low as I had anticipated. It'd be great if I could get some specific suggestions from you and/or some of the other pros here to tweak my system to perform as it should.
Thanks again.
Ross