replacing programmer & room stat

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I was hoping someone would be willing to sanity check my plan to replace a separate CH/HW programmer and room stat. The programmer is next to the boiler and the stat is in the hallway. It is a gravity fed system with a stat on the tank, built 1999.

The programmer is inflexible and I am a bit of a gadget fiend so I have been looking at the Heatmiser wifi solutions. Since I want the wifi unit to be able to control both the CH and hot water but do not want to site the unit (which includes the stat) next to the boiler, my initial plan was to use a RF model:
http://www.heatmisershop.co.uk/ther...i-rf-kit-wifi-programmable-with-hw-output-p94
This basically is a mains powered programmable room stat, but uses RF to wirelessly command a receiver. The receiver then controls the boiler etc.

The existing Horstmann C21 programmer is wired to L (red), N (blue), HW-on (yellow), CH-on (blue), and I assume I can swap it out and wire the RF receiver like for like.

The existing stat is a Honeywell T6360B 3 wire (plus earth). The new stat however does switching via RF, so only has permanent L and N. I plan to site the new stat in the same place as the old, but I am unsure if this is possible after having done some testing with a multimeter. When the stat calls for heat the contact is closed hence there is 230V across pole 3 (yellow) and 2 (blue neutral). But pole 1 (red) is not a permanent live, it is only live when the programmer also calls for heat.

So far, my plan is scuppered because I have no permanent live feed. The easy option is to keep the crappy programmer for water control, leave it set to "24 hours" for CH and replace the stat with a 3 wire wifi stat/programmer (non RF). But I was wondering if perhaps I can either:
A) bridge the switched output from the old stat (yellow) to live, then take permanent live for the new stat from the lighting circuit (there is a light switch immediately below).
B) try to figure out where the old stat wiring terminates, and swap connections over so the switched live from the timer goes off to the boiler instead of the hallway, and permanent live goes to the hallway instead.

Does this sound typical? Am I forgetting something? Where should I look for wiring termination?
 
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Blimey... I think you should stop before you start.

Leave extraneous circuits out of this.

Why do you want Wi-Fi control of hot water?

Why even Wi-Fi control of heating?

Wireless programmable room thermostats are to get over expensive decoration costs not to give you the ability to walk around with it. How often to do need to play with your heating controls....really....stop for a moment and really think how often.

Think you'll be surprised ;).


Anyway. If you must play. Leave you existing timer for hot water. Now. Go go the wiring centre. Make a note of where the room staff's red and yellow wires join. Remove them, along with the neutral and earth wires.

Get your new receiver and wire the L terminal to where the red one was. Add a neutral, and the the s/l return wire to where the old yellow was.

Now, leave your heating on constant, or jump the wire in the clock back plate to the L terminal.


Find the datum point in the house for the new room stat and leave it there.
 
Thanks for replying. To clarify, the point of the RF wireless is not to walk around with the stat (you can't, it's permanently wired into the mains) but because running another wire is not an option. The wifi part is for remote access - I want to be able to turn the heating to frost mode when I am away at short notice. I hate coming home to a cold house, so being able to turn it back on again when I land would be good too.

In fact what has prompted me to replace the system is precisely because I -do- often have to fiddle with the heating controls, made especially worse because the timer is so crap (i.e. no away mode, can't do independent days etc). So this would actually be very useful for me. In fact fitting any sort of modern programmable stat with a vacation mode (set stat to frost, turn off hot water) would require the same considerations, so the wifi thing is perhaps something of a red herring.

The hot water is not the be all and end all however. If it stays on for an hour every day when I'm away, it is not the end of the world (hence why I included this option). I just wanted to confirm the options. I was thinking along the lines of what you suggest, but I am confused as to why you suggest keeping the old timer AND fitting a new receiver/changing wiring. If I am to keep the old timer for hot water and leave it set to constant heating, surely I don't need the RF wireless model at all and can just wire the new stat in as is? And if I am going to change over the wiring, would it not be just as well to replace the old timer with the receiver at the same time?
 
The reason for my suggestion is that you are confusing so many terminologies I am not really sure what you are after.

RF is just a means to an end... Receiver box uses a proprietary protocol to communicate to a dedicated unit that may or may not have timer functions as well as thermostat functions.

Wi-Fi (in the context of a heating system) is a means to control the system remotely, or VERY remotely. Either way, it will need hard wiring to a home computer network or the GSM network.

Look at the Honeywell CM927. It as all the options you have listed... except turning stuff on and off when away. But as long as you no to within a day or few, then the holiday function should be plenty.


I had a client recently who insisted that she wanted more control over the heating and hot water. Listed a whole load of requirements that when repeated back to her logically made little sense. You could see her brain starting to overload. She was so sure of what she wanted, but didn't know why.

It was all based on what she THOUGHT she had before. Which it turned out, she had no idea what her original controls could do.

Thank god the builder was paying my bill :LOL:



the point of the RF wireless is not to walk around with the stat (you can't, it's permanently wired into the mains)

A case in point ;).
 
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Perhaps I need to start again and explain better. The RF is irrelevant in terms of any functional benefit, I mention it only because it affects how the system is wired. I chose the particular model I linked to because:
1. The "wifi" allows me to remotely set a vacation mode on and off, which I want because I am often called away without notice and some distance away from the house. This is provided by all of the wifi models to some degree or another.
2. It has a second switched output for the hot water, which means I will be able to set it differently for certain days and as a bonus do so remotely and without having to explain two different systems to family etc.
3. The thermostat can be located across the house from the boiler.
4. I do not need to run a fourth wire for the hot water to accomplish point 3

The choice is quite logical, it is nothing to do with an attachment to any specific method of wiring it in or misunderstanding of the features. So I apologise if I have not explained things well enough. I'd rather not have RF involved at all in fact. For example, my ideal product would have all the timing logic, switching, wifi, boiler control wiring etc in a main unit sited next to the boiler, and a room stat that simply reports the temperature to the main unit (via 3 wires, wifi, RF, carrier pigeon etc). But no such product appears to exist.

So all of this is just to explain what it is that I want. Functionally, the product I linked to provides everything, but will need wiring differently. This is option one. Option two is to select a different model which will be very easy to install, require no wiring changes, but will not control hot water:
http://www.heatmisershop.co.uk/ther...wifi-wifi-enabled-programmable-thermostat-p96
This one has no RF - it doesn't need it because it only has 1 switched output and I already have that with my existing stat. I leave the timer where it is, set it to 24 hour CH, and let the stat control heating.

So my questions are:
1. Are the the wiring changes in option one difficult or uncertain, and what is the "best" way of making them.
2. Is my understanding of option two correct?

Answers to these will help me decide whether my desire for more control over hot water is enough to do some rewiring and have RF radiation buzzing around the house.

What you suggested so far seems to be a hybrid of both options (rewire OR keep timer), where you suggest to have both a RF receiver AND the old timer, needing wiring modifications whilst also giving up better control of hot water. That leads me to believe that my option two is not possible, and since this solution appears to me to be the worst of both worlds I would like to understand why.

Cheers
 

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