Strange Thermostat/Zone Valve behavior recently..

eblend

Hi All

I have a Rinnai i120cn Combi boiler, which is hooked up to a Taco ZVC404-4 Zone Valve controller. I have 4 Zones and each zone has a Honeywell T6 Pro Hydronic thermostat (TH6100AF200). When I originally got this all commissioned, it worked exactly as expected. I could increase the heat at each thermostat, and it would turn on every zone all at once, and the system would run nicely heating the floor. I have since moved into this place full time, and noticing some strange behavior. All of my thermostats are set to 23c, but the temperature drops below 23c, and then Heat On will flash on the Thermostats, without anything happening. Eventually it does start to heat that Zone, but it's just not performing the same way as it originally did. Reading online people say that flashing Heat On means it's in a delay (people say usually 5 min), but sometimes I see it flash for hours without anything happening. When Heat On is flashing, there is nothing on the Zone controller, no call for heat. It almost looks like the relay isn't kicking off on the thermostats to actually call for heat.

On the thermostat I have it set with the following advance options:

120 - Scheduling Options = 0 (Non-programable)

129 - Wired Floor Temperature Sensor = 1 (Wired)

205 - Heating Equipment Type = 10 (Hot Water Radiant Floor Heat)

299 - Temperature Control Mode = 1 (AF Mode)

370 - Heating Cycles Rate (Cycles per Hour) = 1 (Recommended settings for floor heat)

388 - Minimum On Time = 0 (Off)

425 - Adaptive Intelligent Recovery = 0 (No)

Anyone have any clue? It's still fairly warm outside, but winter is coming, and I'm a bit worried that something is a bit off. This morning for example one of the thermostats was at 21.5 with Heat On flashing, but did turn on later and heated the zone. If this Heat On is a delay, what is it delaying for. I touch the distribution side of the heat pipes, and they are all cold, so the system hasn't run any zone for a while, so it's not like it's somehow doing some short cycle protection or anything, so I'm a bit lost. Will the Zone controller somehow restrict the thermostat from turning the system on when it's calling for heat, or cause the Thermostat to back off and delay. My understanding of these things is that it's simple on/off process, no signaling of any kind.

Jamie Hall

You have wired in-floor thermostats I think you said? Are you measuring the temperature for on or off at the floor, or preferably in it? Remember that radiant floors can take a long time to change temperature.

eblend

https://forum.heatinghelp.com/discussion/comment/1811214#Comment_1811214

Hey, thanks for the reply. So the thermostat has 3 temperature modes, as described here:

A mode (Air temperature only): Controls and displays the ambient air temperature only.

F mode (Floor temperature only): Controls and displays the floor temperature only using an external floor temperature sensor. This control mode is typically used in areas such as bathrooms where floor temperature could be scheduled to be warm only during occupied, morning and evening periods. • Actual floor temperature is indicated by “FLR” text above the actual floor temperature value. • Floor temperature setpoint is not displayed until you press or setting it. for • Actual ambient air temperature could also be displayed in the thermostat MENU/ TEMP.

AF mode (both Air and Floor temperatures): Controls and displays the ambient air temperature as well as maintains the floor temperature within desired floor temperature limits using an external floor temperature sensor. Setting the minimum and maximum floor temperature limits is done by your local heating professional and is a way for you to enhance the comfort and to protect your floor covering at the same time. • Minimum floor temperature limit will override the air temperature in this mode, and if set too high, may overheat the room. Please contact your installer if this occurs. • Actual floor temperature could also be displayed in the thermostat MENU/ TEMP.

Initially for a few days I had it set to F mode, but noticed that it was overheating the room. The room would be like 22 but the floors were only 17 for example, so it would keep going and heating the floors despite the room already being warm. Honeywell seems to state that the F mode is only for bathroom floors and something that's for temporary heat. After this I switched to AF mode, and found it works better. The thermostat stops heating when the ambient temp matches the setting, and I set the min and max floor heat to something much lower. For example, my floors min is set to 15c, and max set to 23c.

Now that I think about it….I wonder if my floors are already at 23c…but room Ambient is lower…and because of that it's not firing off! Could be on to something here, thanks Jamie, while not directly answering the question, you may have pointed me in the right direction. I will check tomorrow morning what the floor temp is when it's flashing Heat On…and see if it's actually already proper at the floor, but lower ambiently. I have a big open space now, no furniture or anything, so radiant might the struggling to heat the ambient air, while the floor is already at max temp that I set. I really hope this is it! Will report back!

hot_rod

is it a PWM type thermostat? Those can cycle on and off a bit

The manual should explain control logic of the thermostat