I recently bought a Danfoss RT52 hard wired room thermostat. It has a night function which we do not actually use since our CH is usually off between 2130 and 0600. Despite this, I did set the internal clock to the correct time and entered a “set-back” time of 0550 in case we do decide to have it on H24 and use the night mode. (I also set the “Chrono Proportional” jumper to ON.)
However a problem which has emerged is that if during the evening we turn the desired temp down from say 23 to 20°C but then select 23 again before turning in, the next morning at 0550 it changes to a different temp to that which was set, eg., 20°C. ( Often it is the second-to-last temp we selected, but not always.) So it seems to ignore the last commanded temp set late in the evening and either gives a previous one or a random one the next morning. This of course means that if this uncommanded temperature is lower than the ambient, then the heating fails to come on. Alternatively, we have awakened sweltered because it’s gone to a random 25°C.
We sent the unit back to Honeywell who replaced it, but the new one’s doing the same.
I don’t believe the way we've had the stat wired up has any relevance, but just in case, here’s how it was done. ( Incidentally the Danfoss instructions regarding this are not very good.) Our CH system is a sealed, “S”-plan system with one 2port valve near the boiler in our garage and another attached to our immersion tank pipework. The previous stat was fed by flat 3&E, with the blue conductor connected to the CH mains neutral, the red to the time programmer and the yellow to the 2port valve’s motor in the garage.
Inside the RT52, the earth conductor and the neutral (blue) were isolated as per the instruction booklet. Then the red conductor was connected to terminal B(COM) and the yellow to C(N/O).
I’d be grateful if anyone could say firstly whether the connections sound correct. Secondly, have any other people had this weird, random behaviour with a Danfoss RT52. And if so, have you sussed a remedy for it, or am I doing something wrong?
However a problem which has emerged is that if during the evening we turn the desired temp down from say 23 to 20°C but then select 23 again before turning in, the next morning at 0550 it changes to a different temp to that which was set, eg., 20°C. ( Often it is the second-to-last temp we selected, but not always.) So it seems to ignore the last commanded temp set late in the evening and either gives a previous one or a random one the next morning. This of course means that if this uncommanded temperature is lower than the ambient, then the heating fails to come on. Alternatively, we have awakened sweltered because it’s gone to a random 25°C.
We sent the unit back to Honeywell who replaced it, but the new one’s doing the same.
I don’t believe the way we've had the stat wired up has any relevance, but just in case, here’s how it was done. ( Incidentally the Danfoss instructions regarding this are not very good.) Our CH system is a sealed, “S”-plan system with one 2port valve near the boiler in our garage and another attached to our immersion tank pipework. The previous stat was fed by flat 3&E, with the blue conductor connected to the CH mains neutral, the red to the time programmer and the yellow to the 2port valve’s motor in the garage.
Inside the RT52, the earth conductor and the neutral (blue) were isolated as per the instruction booklet. Then the red conductor was connected to terminal B(COM) and the yellow to C(N/O).
I’d be grateful if anyone could say firstly whether the connections sound correct. Secondly, have any other people had this weird, random behaviour with a Danfoss RT52. And if so, have you sussed a remedy for it, or am I doing something wrong?
