Greetings,

I'm new to the forum and radiant heat, but have been searching quite a bit, and starting to see the picture.
Just looking for a little help to get over the hump.

We have a 45 year old 50-foot ranch with original copper-in-slab hydronic radiant heat.  The slab is about eight
inches thick and all above grade.  The furnace is a typical Burnham boiler which services three radiant zones,
one forced-hot-water baseboard heating zone, plus hot water, and a Modine for the garage.  Last year,
I added an Intellicon low-limit controller.  I have the low-limit set for 135, as the hot water tank is set for 125.

The bathroom radiant zone is just that one room, and run on a classic round Honeywell, and that's just fine.
The bedrooms' radiant zone works OK with a standard programmable thermostat, as I'm not that aggressive
with the setback temp.

The "problem" I'm having is with the kitchen/livingroom radiant zone.  This is a fairly large open space, about
650 square feet, with some large windows and a sliding-glass door, and this room just doesn't hold the heat,
so I've been setting the heat down to 54 at night (though it seldom actually gets that cold, even in the dead
of winter).  As you can probably guess, I used to get a huge overshoot in the morning.  Using a 4-program
thermostat, I've gotten the overshoot down to maybe 3 or 4 degrees by staging the morning warmup in
3 steps, but it's still got a 5-6 degree swing through most of the day during the winter, and takes a couple
of hours to come up to temp.  Reading on the forum, I now understand why.

So now I see the Tekmar 5xx family of thermostats recommended here, and I'm getting excited to see that
this might be the solution.  Given the mass of the slab, I like the idea of a floor sensor, but I have no idea
where the pipes are, and would be very concerned about drilling into the slab.  There are a couple of places
where I could probably lay the sensor on top of the slab, and then cover it with insulation or some such,
if that has any hope of working.

Given this data, are there specific recommendations on how to use a Tekmar to do what I would like to do?

Many thanks for your input!