Temperature Sensing Woes with Wiser.

I have been forced to use the 5104DTSI due to the demise of the C-Bus wall mounted temperature sensors.
I am using two in conjunction with a Wiser. I have run into multiple levels of ?Oh crap?.
I am controlling multi-zoned underfloor ?in slab? water heating.
There is a header tank that sits at 40 degrees.
When a zone requires heat, I turn on the appropriate pump and manifold to ensure the water is sent to the correct zone.
The floors are laminated wood covering and the floor temperature must not reach or exceed 28 degrees or it will warp the laminated wooden floor.
I have that basics working without issue.

The problems arise when I start to consider the exceptions to the rules.

1/ What happens if one of the sensors fails or becomes disconnected.
The DTSI appears to read ?0 degrees?. This in turn indicates to the Wiser that the room is freezing and will heat the floor up to 40 degrees and keep it there. (I have coded to disregard any 0-degree readings)
There is error reporting available on the DTSI but I can find no references anywhere that tells me what the DTSI actually reports and under what conditions.
Can this be used to test if the sensor/s are present?

2/ The next issue is what happens if I were to lose the DTSI from the network.
If the heating is active when the unit is lost then I have a temperature runaway situation again.
I will need to test if the DTSI is available for me to read to ensure the readings are valid.
I have been unable to find any reference code that would enable me to perform this test.

3/ What happens should I lose the Wiser.
This could occur if the circuit breaker trips the circuit that feeds the Wiser or the wiser becomes unplugged.
If the heating is active then I am left in the situation once again.

Does anyone have solutions to the above noting that the house is now complete and no further costs can be incurred.

Product suggestion for Clipsal:
What would be nice would be to have a relay that has its own timer (Say 5 minutes in my case).
The LOGIC would need to address the relay regularly to restart the timer to maintain the ON state.
This way if the LOGIC disappears then the system would ?FAIL SAFE?.
Yes this can be done in logic but any logic unit on the network is susceptible to the physical/ power loss scenario, so it needs to be part of the relay.

• This would address the issue if the relay unit itself becomes disconnected from the network. (Fails Safely)
• If power to the relay is removed the relay again fails safely.

At the end of the day ? Who is ultimately responsible for the floor replacement costs when this occurs?

 

The reality of life is that things fail. If this is a problem you have two choices: provide redundancy if you want continuous operation, or add a safety cutout if you don't. If the Wiser is running, checking the temperature is easy. If the heating is on, the temperature should go up. If it doesn't, turn it off and holler for help. If the heating is off the the temperature still goes up, holler for help just in case the relay is stuck on.

For the Wiser, you can buy a second one and run them in Master/Slave mode. Otherwise, put a re-triggerable timer/contactor in the supply line and trigger it from the Wiser periodically (via a Cbus relay probably).

You don't say who installed this in the first place, but it wasn't done adequately so you can't expect it to be fixed for nothing.

This is the easy one. You are of course.

 

Sounds like you would be better off with a little smart relay ( Something like the Siemens LOGO8! ) have it look after the heating and then just have it talk back into the Wiser using a TCP socket or 2 way analogue.

 

If you can't spend any money, a suggestion may be to lower the header tank temp to 28deg so you won't ever have a problem. Obviously the floor will heat up more slowly, but it will be safe.

If you can spend money you could install a separate temperature sensor (standalone/non-cbus) to cut the heater power if the floor exceeds 28deg. If you can't fit a new sensor to the floor, you could consider monitoring the return pipe water temperature instead.