hot water cylinder thermostat

Postby cylinder » Tue Mar 11, 2008 12:40 pm

Need to replace my hot water cylinder as immersion heater broken and it refuses to be removed. The hot water temperature is controlled by a Danfoss Ravi 3 port valve. The thermostat is stuck onto the tank by a label and connected to the valve by a wire. It is mechanical no electric wires. This valve has not worked for a while and as I am putting in a new tank then I need a new valve at £105. 00. The system is controlled by a Drayton Tempus Seven microprocessor programmer about 12 years old. Can I connect the inflow/outflow to the tank without diverting it through a new ravi valve and use one of the more modern electronic thermostats (around £15-£20) linked into my programmer. Would it be easy to wire up. What about the wireless thermostats I have read about as a simple option?
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Simply Build It

Postby ericmark » Thu Mar 20, 2008 2:05 am

I have a wireless cylinder thermostat ready to fit. At £100 I hope it works OK but it seems there are variations of the basic system. Basic consists of three items. Tank sensor this straps to tank and is wired to a control box/transmitter and this both tells you temperature of tank and sends the on/off signal to the other unit. Another version of this is also available which includes an electronic timer. In both cases they are powered by two AA batteries. They both have a base with same hole spacing as a single socket or light switch but the timer version is same size and shape as a programmer and unless the box was sunken would not fit nice on the wall. The units at the boiler also have two versions available one simply receives the signal from the sender and works a set of contacts. The other is a programmer as well. Both are the size of a programmer and again designed to fit on a single socket base. This is why it is not fitted yet I need to sink the box in the wall and I was trying to persuade my son to use his special tool to do this job. Fits on SDS drill. But it is looking like a cold chisel job. I did copy instruction book and have it in PDF format my email I expect I will fit it over Easter as to if temp or done correct depends on help I get. Due to mauled hand I can't use any hammer drills or cold chisel so not straight forward for me. I hope that helps a little all best Eric

Postby ericmark » Fri Mar 21, 2008 11:00 pm

Sorry to say we had problems although not with the wireless cylinder thermostat. A disturbed wire behind the programmer short circuited and because the fuse was wrong size (13 instead of 3 amp) this burnt out micro switch in motorised valve. Now must wait until after Easter before either repairing or replacing electric head on valve. But the radio link does work even with a long route and sender wrong side of the tank. The LCD window on sender shows temperature set and if the tank is at the correct heat or not. The unit at the boiler shows when heat is called for with red light and quick flash of green as information is updated. Found sender too small for surface box and I need to add a blank plate.

Postby ericmark » Mon Mar 24, 2008 5:28 pm

Oh I am sorry jumped in both feet without reading question fully. If you have a motorised valve it would normally be connected to your boiler so the boiler will not run until the valve is in the correct place. But this does not have to be the case. There are two types of three port valves one has a centre position. This must connect to the other controls but with the either or then it would be possible to control the valve remote from the boiler. If when tank is cool it diverts water to cylinder and when warn to central heating all you need is power. The boiler will run and if no flow switch off again. It seems waste full and today would not be used but that’s just how my dads boiler was designed to work. I did get wireless thermostat working but this was with two port valve not three and I don’t think it would work with what you have?

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