Faulty programmer?

[GeoffTitch]

I have an old Siemens RWB2 which acts as a timer controller for the filter pump (connected to boiler) and heating (hot water - activates a pump on the central heating circuit to pump the hot pipes out through a heat exchanger) for a swimming pool.

The central heating/hot water has it's own separate controller.

The RWB2 lights up on the timed sequences, but fails to operate the filter pump. If I connect the filter live directly to the incoming live then it works normally (but I have to turn it on and off manually).

I did a test across all the live feeds and everything seems to be ok, except I am getting no live current from the incoming feed to the RWB2 and the output to the pump, even when the controller light is on showing it is working.

Is it likely to just be faulty programmer? Is it possible for the light to be on but the thing to not actually be working? Or is it likely to be something else?

I've followed the wires through, and it all appears to be connected correctly in accordance with the instructions (Live to L (through fuse), Neutral to N, nothing on 1 or 2, 3 feeds to filter/boiler, 4 feeds to heating pump/hot water). Only thing I don't have is a thermostat in the loop (as the filter in particular is either on, running on the timer, or off - temperature is not relevant).

 

[ALCPlumbing]

If the light is on on the timer indicating it should be live but there is no live being output from timer to pump then the relay within the timer isn't working and the timer will need to be replaced.

 

[ALCPlumbing]

Isn't that a two channel programmer? If so have you tried switching the other channel?

 

[GeoffTitch]

2 channel... presumably that refers to the ability to control the boiler (filter pump) and pump (heating pump).

When the heating pump comes on (on the timer) I can feel it running.

I did try connecting them the other way (i.e 3 to the pump and 4 to the filter) but the filter still didn't work (yet I know the filter works if I bypass just the controller). Must admit, I didn't check if the heating pump was working

 

[ALCPlumbing]

It's two channel as it has two outputs. Usually one is for hot water and the other is heating. Terminals 3 and 4 on the timer are the outputs for the separate channels. Presumably if this timer only controls the heating of the swimming pool can you not run it all off one channel, the channel that is working. Just run a live from the pump to the filter. This way they will both be live at the same time. However you said that when you switched 3 and 4 you had the same problem? In that case I would be checking the neutral is connected and not clamped on the rubber of the cable as opposed to the copper core.

 

[GeoffTitch]

Sorry, yes, 2 channels.

Channel 1 (the boiler channel) I'd used to run the filter pump twice a day. If I bypass the programmer and connect the incoming live directly to the live feed to the filter pump on the output side of the programmer it works fine (which indicates to me that the rest of the circuit, including the neutral, is correct).

Channel 2 (the hot water channel) is used to operated a pump that diverts the central heating pipes out to a heat exchanger then back to the house. That only runs when we decide we want to warm the pool a little.

A heating plumber looked at it a while ago and said the actual system was not very efficient, as the only way of getting hot water to the pool heat exchanger was to run the central heating in the house - the pump is not an either way valve.

My confusion was that the timer appeared to come on and off, but there was no live throughput. However I didn't want to go to expense of buying a new programmer if it turned out to be a case of something simple.

That said, this programmer is several years old and the reviews on it seem to indicate that it is prone to failure of the control buttons (?)

 

[MeldrewsMate]

I suspect that the current drawn by a swimming pool filter pump is in excess of the capacity of the programmer relay, and may have fried the circuit track inside the RWB2, or the relay itself.

Strange that the other output also did not work the filter pump though, yet it still works the boiler?....could that have been a wiring error during your diagnostics?

The programmer should be fused no higher than 3A using a BS1362 fuse.
Is it fused at 5 or even 13A ?

In short you may have to change the programmer, and also install a slave relay to control the higher current load of the filter pump.

 

[GeoffTitch]

The house boiler and hot water are on a separate programmer. This one only controls the filter pump on the boiler channel (0.75hp - it's been controlling it fine for the last 20 years or so, so can't see that it had overloaded the circuit) and a pump to drive the hot water to the heat exchanger on the hot water channel. Yes, it goes through a 3A fuse whenever it is routing through the programmer