Danfoss Tp9 controller fault

[Andrew]

My system, installed by the previous owner aout 8 years go, uses two TP9s, one downstairs, one upstairs. It has started refusing to switch the system on in the Night - earlier in the day it works fine.

I attribute the problem to the controller because a) it has failed before so 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]

My TP9 is connected to separate relays which switch on the boiler, so the load on the TP9 contacts is not to high. My original TP9 was replaced under warranty.

For a separate application I have just bought a Heatmiser Smartstat. Unlike the TP9, this is a single channel controller and only has 4 switching times per day rather than 6 that the TP9 has. However it can either use its own internal temperature sensor or a remote one; and if you have a broadband router connected to the Internet, and with WiFi you can control the Smartstat using a smart phone. The phone will show both actual current temperature and the temperature the thermostat is set to reach.

[pamela]

I have the mpresion there's some plug-compatibility between central heating controller although I don't know about your Danfoss TP9.

I was looking for a replacement for my ACL Lifestyle programmer and I seem to recall Drayton make some programmers which are plug compatible with mine. Your post has reminded me I still need to get a replacement for my programmer.

[Michael Chare]

What do you mean by plug-compatibility?

[pamela]

By plug compatible I meant you could keep the wall mounting plate (with electrical contact) and attach a new programmer to it. I hope that description makes sense.

[Michael Chare]

Thanks. The TP9 sits on its own mounting plate. I doubt it is compatible with anything other than other Danfoss products as it has the connectors for two channels, CH and HW

The TP9 uses some sort of proportional control and so switches the boiler off and on every ten minutes or so giving a very accurate temperature control. The Heatmiser SmartStat appears to wait for the temp to drop by 0.5C and then turns the boiler on until the target is reached. The 0.5C can also be 1C, 2C, or 3C.