Danfoss TP9 replacement

[diy_dude]

I have a Danfoss TP9 programmable thermostat with remote probe and DHW control. It is starting to fail and I want a replacement.

I have looked at the new TP9000 and unfortunately this does not support the gravity option which I will need until I can afford to have my fully motorised zone valve replaced by either a 3-way or 2 2 port valves.

Are there any other option for replacing the unit?

Thanks

 

[mogget]

How about another TP9 from a well known auction website?

 

[diy_dude]

I had thought about that, but the feature we really wished the controller to have was to extent the current temperature for an hour or two. Eg. In the evening after the heating temp had been turned down, we sometimes turned the temp back up again. The heating then stayed on until the next timer event (next morning) which meant the heating was on until we actively switched it or, sometimes it was on all night.

 

[JohnD]

does not support the gravity option

Are you sure? I got an ACL Drayton programmer with no mention of Gravity, but the makers supplied me with a diagram on request (it is not normally published as it does not meet modern standards)

 

[mogget]

OP, you mention that you have a gravity hot water system, but you say you have one motorised valve already? How is this set up?

 

[diy_dude]

not sure of the correct terminology, so please forgive me if I get it wrong.

The pump is connected directly to the pump - the pump runs whenever the boiler is on and for a short whole afterwards. Whenever the boiler switches on is starts to heat the water in the tank in the airing cupboard. There is a thermostat on the hot water tank which turns off the boiler when it reaches the correct temperature. When the programmer requests heating the motorised zone valve opens allowing the radiators to heat up. In practice the DHW output switches the boilder on/off while the CH output opens/closes the valve.

With this setup I cannot have heating without hot water - hence the need for a controller with gravity support.

I have contacted Danfoss and they confirm there is no support for gravity mode on the TP9000 controller. Have checked the manual too.

I have found the Heatmiser PRT/HWTS which includes DHW control. The wiring diagram shows a 240V relay used to provide the boiler control when the CH is required without DHW. I'm guessing I could use the same setup with the Danfoss TP9000.

 

[diy_dude]

The heatmiser prt/hwts does not support a remote sensor. As the controller is located in the kitchen this makes it a no go.

 

[mogget]

What wires do you have on this motorised valve?

Usually there are Blue, Brown, Grey, Orange and earth.

 

[diy_dude]

Can not remember the colours, but it is a 2 port fully motorised zone value.

 

[mogget]

Just thinking that if the end switch on the zone valve is spare, you could use it to switch in the boiler when heating is required. This would do away with the need for a gravity-compatible programer. The hot water would still come on with the heating but you could use any programmer you choose.

 

[mogget]

Untitled

• mogget
• 7 Jun 2009
• 1

 

[diy_dude]

mogget, This is the diagram I drew when I last looked at my central heating wiring:

 

[mogget]

I'm assuming that this is a motor-on-motor-off valve, and that the orange wire is a switched live.

If this is so, you can use any dual channel programmer, such as the TP9000, without changing the wiring.

The only side effect would be that the hot water would heat up when the heating is on, regardless of whether it switched on at the programmer.

To confirm, you can switch the TP9 to fully pumped and check that the heating operates with the HW channel turned off.

 

[JohnD]

would you be able to post some pics showing the pipework, pump, valve etc around the boiler and at the cylinder?

//www.diynot.com/forums/viewtopic.php?t=129539

Is there a cylinder stat and a room stat?

Although I am a householder not a pro, I recently did some work on my old mum's gravity HW and am interested to see how others approach the problem. I got a lot of help on here, and ACL Drayton also provided diagrams

 

[diy_dude]

Mogget, you are correct. I switched to pumped mode and everything works as normal. Will try to find am affordable TP9000 now. Thanks for your help.

I'll try to port some photos tomorrow.