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Wiring Drayton MiTime T721R Dual Programmer

Postby Nottmtrucker » Sun Mar 06, 2016 12:05 am

Hi everyone,
Can anyone help me? I purchased a dual channel programmer for central heating and hot water off eBay. I am a little confused to the supplied wiring diagram. It shows where the feed L and N go but then shows the following:
1. Hot Water Off
2. Central Heating Off
3. Hot Water On
4. Central Heating On
What l need to know is which wire ( live or neutral) from boiler and cylinder goes to where? Is it as simple as neutrals to Off and Lives to On?
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Postby ericmark » Mon Mar 07, 2016 1:21 am

Neutral is not switched all neutral wires go together.
1. Hot Water Off
2. Central Heating Off
Are not used with some systems, however the grey wire from the mid position valve and the off or N/O on the cylinder thermostat some times go to the domestic hot water off with some of the plans.
In the main the older central heating follows one of the Honeywell plans, This ... -Diagrams/ should take you to main Honeywell page which has all the different plans.
[img][/img] I hope it shows the image as an example this is the Y plan there is also S, W, and C. Some use two motorized valves some use a mid position valve as shown and some have the domestic hot water using thermal syphon.

Not checked your programmer but often there is a electric and mechanical switch which changes the programmer from 10 to 16 programs. With thermal syphon you can't turn hot water off and leave the central heating running so just 10 options with pumped domestic hot water you can.

The basic idea is if you use a motorised valve then the thermostat controls the valve and the valve then controls the central heating boiler, some boilers just switch off when not required and some have to be left running for a time with no flame to cool down. So with some the pump is direct and others the boiler controls the pump.

Today the programmer is hardly used. You can now get thermostats which include a program function and instead of turning the whole heating system on and off it swaps between different programmed temperatures. So in my house at night set to 16 degrees which means it rarely switches on at night and 20 degrees during the day. Should we get a really cold night the central heating will come on. This also means no need for a frost stat which over rides all controls at around 6 degrees.

So first job is work out what you have. Second job is decide if the programmer is really the way forward. With my mothers house I replaced programmer and wireless thermostat which at today's price will cost around £200 for a Horstmann HRFS1 Programmable Room Thermostat at £60 OK there are some issues but it still works better than the old Honeywell Y6630D Wireless Room Thermostat and separate programmer.

In your case you may need a method to heat the hot water at set times, but often it is simpler to just leave hot water on 24/7 unless thermal syphon. With thermal syphon the only limit to water temperature is the temperature of the boilers circulating water. As a result in the summer a timer is required or the boiler would be cycling all the time.

Until I know what you have can't really help further.
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