(Conrad) FHT / FS20 system - 8-10 zones?

[TimJWatts]

** I have seen odd posts in other places that say having lots of FHT senders (room programmers) causes problems due to radio packet collisions.
This I understand - the protocol is simplex, retried 3 times per message IIRC, so has no way to know if collisions drowned out some messages.

So - in practise - has anyone used an FHT system with upto 10 zones in a single 2 storey house?

Cheers!

Tim


More details;

I like the simplicity of the FHT system.
I also like the fact that the room programmer/stat is separate to the radiator motor unit - one big failing of TRVs is that they have a big hot lump of metal right next to them!
I also like the fact the the FHT has a boiler control relay that works out of the box (OK, pairing, but not much effort).
I like the fact that I can fall back to a simple boiler timer and adding TRV heads if it all goes horribly wrong (though this is true of several systems)

I did also like the look of the HomeMatic with the CCU2 programmer, but it's not as simple and the room programmer is in the rad motor unit which is a PITA to get at in some cases, plus the point above regarding sensing temperatures.

Mine would be set up:

7-8 FHT80b room controllers
paired with:
10 FHT 8V rad motors
1 FHT 8W (boiler call-for-heat)

PLUS

2 FHT80b room controllers
paired with:
2 FHT 8V rad motors
1 FHT 8W

The latter is for 2 rooms with underfloor heating - needs a separate pump and mixer valve - will use a relay to cause this to also call-for-heat from the boiler.

[TimJWatts]

Just before I get accused of wasting folks' time, I *just* came across this post:

http://www.automatedhome.co.uk/vbull...ll=1#post17850

which the poster says he has 22 FHT 8 thermostats etc and it works.

To which someone replied "My system struggles with more than 8 FHT 8"

Seems a bit random? Perhaps sensitive to other EM noise? I'm in a bungalow so apart from a load of 2.4GHz WIFI/DECT we should be fairly quiet.

[Fon]

They key is possitioning.

If you can get your central PC interface in the middle, and move all the room stats, you can get good coverage.

I personally have 6 room stats, and 7 rads.

Sometimes a command will not be followed for 30 mins, but I finally have locations where im certain it will eventually be followed.

PS, im led to believe if you use different house codes for your floor heating, and rads, they will actually be on different frequency's. Im not certain of this as haven't done it, just read it.

Check out fhem.de for the pc side of things, and more comments on people using the system. Also http://forum.fhem.de/index.php/board,52.0.html

Fon

[TimJWatts]

Hi Fon,

In my case, the boiler relay is the critical element - FHT8W - that *must* operate.

There is no reason that has to be near the boiler - I am replacing all my wiring so I have enough access under the floors to install that where I want - probably the hall which is central in my house.

Thanks for pointing out fhem - I will be happier if I can do some tests with one of the USB radio modules and a laptop, then I can be fairly certain how the system is behaving

Thanks!

Tim

[Fon]

The easiest way to install the fht8w is just to put it where your house thermostat is. It will just need the same wiring (in my case)

Iv never had problems with the fht8w hearing that it needs to turn the boiler on. The main problems have been sending commands to the room stats to change temperature etc.

Fon

[TimJWatts]

Hi Fon,

No house stat - this is a new heating system (as in not yet installed) so I have the freedom to site equipment where I like

OK - so the biggest problem is remote control of the room stats? That is encouraging - I will not be doing this on a regular basis. What I care most about is that the room stats a) control the radiator valve and b) control the boiler relay reliably.

Many thanks for that!

Tim

[TimJWatts]

I'm wondering if ZWave might be worth a closer look - just come across it. Danfoss have the valves. There seem to be various room stats that may or may not work with the valves plus boiler interlocks.