D_Hailsham - Many thanks for the wiring instructions to replace three wire dial thermostat with digital two wire, red=A; yellow=B; blue=isolate in connector , boiler now fires up without long delay and house stays warm. Excellent advice!
Hi guys, I'm looking to do the same thing as the op, is it still the case of using the Honeywell? I'm looking to set a maximum on the upper temperature as my kids like to roast at 25degrees lol, I had the old RTS1 set to around 21degrees, this worked well until the clip broke so I thought instead of changing the stat to the same, I found this site and thought hey why not go digital.
Thanks
Mark
You can replace a RTS1 with a DT90, whether it is preferred or not is entirely up to you. You may wish to replace a Ford with a VW, others would prefer to replace their Ford with a Vauxhall. All thermostats have the same function they are simply switches they turn the central heating 'on' or 'off' and that's it. [Nothing to do with the Megaflo that's for the hot water]
The difference with the DT90 to the RTS1 is that the DT90 has a display and so is battery operated to maintain the display when the programmer switches off the power to the thermostat.
The RTS1 connections are:
As the DT90 is battery operated, it doesn't need a neutral, so the wire in the N terminal shown above should be isolated / insulated and tucked safely out of the way. The remaining two wires in 'L' and 'Call for Heat' would be connected to the DT90E as follows:
Digital thermostats are more accurate than the old mechanical devices, and so maintain a more stable temperature. They also display the actual and set temperatures digitally, which may or not be an advantage to you personally.
A programmer is a different device and serves a different purpose. It is just a time switch that turns the heating on and off, as well as the hot water, if you happen to have a system with a hot water cylinder. It has no control of the room temperature.
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