I choose to DIY remove my older in-wall radiators and install a suspended pipe radiant heat system a few months ago. The tubes are 1" from the subfloor and 2 per joist bay, 2" air gap, staple in reflective radiant barrier and R13 insulation in the joist cavity. I have 3/4" T&G subfloor with 3/4" hardwood on top of it.
I currently have an old Burnham boiler running off of an on-board aquastat (Low fire on 140, cut off 165, climbs to 175). Primary circulator (Taco 007) runs full time. Radiant zone is piped as a secondary circuit connected with 4 way mixing valve and a Tekmar 360. The secondary circulator runs full time and is an Grundfos Alpha 15-55F. The Tekmar outdoor reset (for the mixing valve) is configured with values from LoopCAD where I did as close to a heat loss analysis as possible.
Indoor temp desired: 70
Outdoor temp: 10
Water temp required: 160
T-T jumped and secondary circulator runs constantly
I have the indoor feedback sensor for the Tekmar installed in my largest room with the most heat loss (most windows, 12' ceilings) which is located at the top of the below drawing.
My issue is I'm having a lot of trouble achieving an even 68-70 throughout the house utilizing just the flow control valves (Uponor EP manifold). Some days it seems I have it then instantly days later it changes drastically. What commonly happens is the bedrooms (three rooms at bottom of the drawing) overheat to 72-76 and the large great room (top of drawing) sits at 64-66.
I think this has to do with outdoor temperature change- the heat loss of that large room is ~3-4 BTU/HR more than the bedroom with the most heat loss. One thing to consider is the lower level of this home has no insulation at all. Additionally when I use the flow control / balancing valves on the Uponor EP manifold I can dial in the flow LoopCAD tells me to, but 45 minutes later I will find the loop's flow meter level at nearly 0 GPM. I have found more success last night opening the balancing valves all the way then using the caps on the isolation valves to control the flow. Not sure if this is a good method or not.
1. The construction in the basement (70% above grade), lack of insulation and temperature swings are causing a slow responding system (suspended tube) to work even worse / harder to retain setpoint.
2. The inside temperature sensor being in the room with the most heat loss, but also the most sun exposure is providing incorrect feedback to my controls. I had the sensor in the middle of the house (hallway), but experienced the great room to get very cold at night.
3. I should have bought thick heat emitting "joist trak" plates so I don't have to run 120-130' water just to keep the house at temperature.
3. I'm considering buying parts to go with zone control instead of constat circulation. (Tekmar thermostats with floor sensors, Uponor actuators and a Tekmar zone controller). Is this a band aid or the correct solution?
Any advice is appreciated!