Hi Mark
If you do go down that route it is worth embedding a 15mm copper tube in the screed for the temp sensor. If the sensor ever fails you can just pull it out of the tube and slot in a new one. I actually used a piece of HEP but had a piece of copper on the end for the sensor to be inside.
Iain
Yes, I was thinking that the sensor needs to be replaceable. I thought there were corrosion issues with copper pipes embedded in screed and that plastic would be more long-lasting. I guess we don't care about leaks so it's not such an issue as long as it doesn't weaken the screed too much or block the removal/replacement of the sensor if the pipe corrodes.
A plastic pipe would add a small amount of insulation and slow down the response of the sensor, but probably not significantly.
