Tekmar 356 question

ajping3830

I had initially installed the Tekmar 356 controller for my radiant heat system near the boiler since there was a significant amount of wiring, with a Tekmar 561 thermostat away from the boiler more in the center of the shop. When setting up the program on the 356 for outdoor reset, it asks for desired room temperature and indoor design temperature. Is it just asking for these values to calculate the mix temp target or does the controller have a thermister that is actually measuring the room air temperature meaning I should not have the controller near the boiler? The manual doesn't specify an install location that I can see.

hot_rod

It can be located anywhere in the building. The data brochure details how it operates and the settings available.

The settings available depend on what sensors you connect and their placement. You need at least the outdoor and supply sensor. You could add a sensor to the room if you don't have tekmar thermostats connected to it.

The main missed point is you need to send a powered signal to the control to get it to turn on. This could come through the zone valve end switch, or from a relay box.

https://www.watts.com/dfsmedia/0533dbba17714b1ab581ab07a4cbb521/42849-source/638820695660000000/356-d-06.pdf

ajping3830

Ok another question but this one's about the Tekmar 561 thermostat.

My system has been running well for the last couple months since the install with the 561 on radiant floor heat mode. The manual states that it will run 100% when 1.5 deg below the heat to setting, 50% when at the heat to setting, and 0% when +1.5.

My concern is that when it runs while at the heat to temp, it usually only calls for heat for a few minutes which doesn't allow the boiler to come up to temp, which means the 356 controller isn't mixing much or any hot water into the loop. So it seems like a waste of fuel? However the system has been extremely consistent and holding room temperature dead on with almost zero variance, usually only +1 degree at most.

I have been monitoring the usage through the app and figured I would try the regular heat mode just to compare. The usage seems to have dropped significantly, but it's definitely not holding room temp as consistent, and will have swings from -2 to +2 from target temp.

So in the radiant mode, where is it getting that 50% run time from? 50% of what? Is there a way to get it to run longer to let the boiler come up to temperature?

hot_rod

It is the load the system presents that control the boiler operating condition.

So what is the load that the thermostat is in control of, and what is the boiler output as compared? Is it just that 4 port manifold?

This gets a little tricky when you have a fixed output boiler and a small load, the boiler is covering the load before it hits control temperature.

As long as the boiler operates at a safe operating temperature, you may need to accept the short cycles.