Danfoss TP9 problem

[Manek]

My system, installed by the previous owner aout 8 years go, uses two TP9s, one downstairs, one upstairs. The lower one failed about six months ago and it looks like the upper one is about to fail: bizarrely, it has started refusing to switch the system on in the morning -- later on in the day it works fine.

I attribute the problem to the controller because a) if one has failed, it must be close to the time when the second one will fail and b) there's no relay click when I attempt to make it work manually (in the morning). The valve seems to operate fine and we get heat elsewhere in the house.

This seems to me to be very odd behaviour. Has anyone experienced this

- -a known bug or problem?

And if I do replace it, are there any better controllers worth looking at?

[Michael Chare]

I have just bought a TP9. The first one I had died on me after 1 week when I did a lot of button pushing to change the program prior to going on holiday.

The problem that I had was that the battery warning indicator came on and the unit would not switch on the boiler or the pump. Fortunately as a last resort I gave the unit a good smack and it obliged by working. I did not touch it again until I got back from holiday. I assume some sort of fault on the circuit board so I got the unit changed. Plumbworld were very good about changing the unit without any fuss. Even sent out a replacement unit before I had to return the old one.

The TP9 provides both timed hot water and a six change per day programmable thermostat. I have not managed to find any direct competitors. An alternative approach would be to use something like the Honeywell CM67 to control the central heating and a separate timer to control the hot water. The ease of installing this really depends on what you have now.

There are various versions of the CM67. You can use a remote sensor like the TP9 or you can site the CM67 where your TP9 sensor is now. There is also a version that links to a base station by radio waves.

Given that you had two TP9s, my guess is that at the most only one of them can be controlling your hot water.

The Drayton Intelligent programmable Thermostats and the Sunvic TLX 6501 are competitors to the CM67

Michael Chare

[IMM]

Have you checked the battery? Charge it and then check the programme. Two failing within a short period is odd.

programmable

The cm67 has optimisation start, which the TP9 does not. The TP9 is neat though.

[IMM]

[Michael Chare]

The Tempus is an electronic programmer. It has no ability to monitor and control temperature. See

!

Michael Chare

[IMM]

though it was one of the many stat/programmers around.

[Manek]

Think I'm going to try a reset and see what happens. Either that, or try some percussive maintenance...

[Manek]

Managed to shed a bit more light on this issue by pin-pointing the conditions under which this problem occurs. When the HW is on, there doesn't appear to be enough power within the device to throw the relay that switches on the CH, and vice versa. The evidence is that the HW LED dims a bit when the heating is switched on (although nothing else happens) and vice versa. This also explains why there was no HW the other night whe we'd had the CH on all day.

Is it worth my while taking it to bits to see if there's any evidence of a problem or chance of a fix, or shall I just bite the bullet and buy a new one?