Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Tekmar 363 Mixing problem...I think?

I have a Tekmar 363 controller with a 369 zone controller. Six radiant floor zones and DHW. One zone is a slab.

Two winters ago, the controller was replaced. I'm guessing the settings the contractor put on the replacement aren't correct. I haven't been able to get adequate heat since then. (Boiler JUST cleaned this week. Still no luck.)

Four zones are operating fine. DHW fine. Two zones I cannot get close to enough heat. Cannot get ambient temps above 64. (Yes, very cold where I am in Northwest Montana, but this wasn't an issue two years ago.) RTU signals are correct in that 369 showing accurate temps from the zones.

I'm not an expert by any means, but it seems like the mixing value is cutting out too soon. Well before mixing target is reached.

A few questions and/or notes:

1. Manual section "B2 Alternate Boiler Demands" indicates 10K 1 should be set to Boil with 369 attached. This doesn't seem to address the problem. (When I started looking at system it was set to Mix.) With this setting, the mix temp heading out to the system just never getting anywhere. Suggestions on what might be wrong here?
2. I've tried adjusting the room settings up 2 degrees (from 70 to 72) per the FAQ on Tekmar website. Doesn't seem to matter.
3. I have the "Boiler Minimum" on boiler stage set to 150 with "Boiler Minimum on mixing stage at 130, per the FAQ.
4. Could there be a sensor problem somewhere that is causing the mixing to cut out too soon?

Any suggestions/pointers helpful!