What is this relay for - Burford?

Hi,

The attached photo shows a black relay, near the floor, in a cupboard under the sink counter and next to the cooker.

What is it for?

Could it be for the fresh water tank heater?

It is mildly warm to touch - not hot.  If it is the tank heaters they are off as is everything else except the battery charger (on EHU).

At the moment at a loss to understand why it would be warm?  On the underside of the relay I can just make out a resistor.

Any advice welcome.

Thanks

If it's warm, the coil is energised.  It's either a 'normally open' switch which is held closed or a 'normally closed' switch which is being held open. The choice of operation is governed by which contacts are being used.
So an answer to part of your question is...it's energised.    Why, from where I sit, is a mystery.
Sorry.  Someone who knows the Burford wiring may be along to help. Keith

Peter,

Sorry the photo is just rotated 90 for some reason, the black frame in the photo is actually the vertical edge of the cooker to the right side.

The relay is identical to your picture with the same purple wires.

Will check as you suggest tomorrow.

Thanks

Sargent seem to use purple wires for the water pump circuit. Is the water pump working correctely?

Took the relay out last night and it is a standard 4 pin 30A NO relay. Have checked this morning and the water pump and sensors are all working fine.  So this is for something else - have read handbook cover to cover and can't find mention of it.

The photo is of the underside of the connector block and you can just see the black diode Peter mentions but I can't make out the numbers on it though.

Hi Peter, yes the step works (with and without relay), have checked fuses and nothing has blown.  

Followed your suggestion to see if I could feel the relay closing when the Tank heater button was switched on and off at the control panel and could feel nothing. Maybe I will run through it again switching the waste water tank heater switch on and off as well.

Am starting to think that it must be a faulty relay.

Just had a very quick response from Mark at AutoSleepers:

".....the relay is for the water tank overfill cut off float. If the water tank is completely full and you walk down the vehicle or rock it side to side you will hear the relay clicking from the float switch in the tank switching on and off....."

I will leave alone until the m/h goes in to the Service Centre in a few weeks time.

MikeJJ wrote:Just had a very quick response from Mark at AutoSleepers:

".....the relay is for the water tank overfill cut off float. If the water tank is completely full and you walk down the vehicle or rock it side to side you will hear the relay clicking from the float switch in the tank switching on and off....."

I will leave alone until the m/h goes in to the Service Centre in a few weeks time.

And its a very annoying click! I have found that when the fresh water tank is full to the brim the float switch continues to operate with the slightest movement of the vehicle - particularly annoying at night. Consequently, I always run a few kettle fulls of water off a full tank to stop the clicking.
Liam

So does it stop the whale pump when the tank is full?

palette wrote:So does it stop the whale pump when the tank is full?

Yes it does! 
Liam

Peter Brown wrote:

Liam wrote:

palette wrote:So does it stop the whale pump when the tank is full?

Yes it does! 
Liam

I presume you mean the external tank fill pump, not the internal pressure to taps pump?

Sorry Peter, yes I meant the external pump. It's never occured to me that the external whale pump would be switched in this way. I'm tempted to loose my relay, can't really see the point, you know when the tanks full when water starts pouring out of the overflow!

Peter Brown wrote:

Liam wrote:

palette wrote:So does it stop the whale pump when the tank is full?

Yes it does! 
Liam

I presume you mean the external tank fill pump, not the internal pressure to taps pump?

Yes, Peter, it stops the external Whale fill pump. 
But of course when the tank is full or slightly less - the float rises and falls as the surface water moves within the tank which in turn causes the relay itself to click between open and close. 
Once the water level drops sufficiently so that the float is not moving (i.e. not resting or affected by the water surface) then I assume that it leaves the relay in the open position. 
Perhaps that is why the OP found his relay to be slightly warm to touch? I have never tried mine but will check it next time we are out!
Liam

Hi All
You have just answered a question I have been seeking an answer to ever since we took delivery of our Beckford.
Even the agent here in New Zealand could not give me the answer to what the clicking was but I always noticed that as soon as the water level in the tank dropped it stopped.
Also stops if you turn the pump off on the control panel.
Regards Geoff

Just for completeness, the diode will very likely be a 1N4000 series diode. It's function is to prevent arcing caused by the load it is controlling (Pump), when it is switched OFF by the relay. The coils of the motor generate a magnetic field when energised, which is what makes the pump motor turn against permanent magnets in the motor body (there are variants). when the power to these coils is turned off, the magnetic field rapidly collapses and without the diode would generate a very high voltage which has a reverse polarity to that which created the field in the first place. The diode "Clamps this high voltage so it cannot rise to more than approx 0.6V. Without the diode, there is enough energy generated by the motor turning off to create an arc across the relay contacts which would burn the relay contacts in a short space of time. This only applies to control of DC (Direct Current) circuits.

It is often called a "Flywheel Diode" in this application.

Now that I know what it's use is; I have started wondering why they have designed the relay to be energised (and getting warm) when the tank is less than full (ie most of the time), for example when empty and everything switched off for the winter.

I have read that the consumption when energised is about 30mA, that's nearly 0.7AH per day which might flatten a battery in a 2-3 months or so.

So may be adding a simple on/off switch would be useful to turn it all off when not required?

But if the control panel is turned off the relay is not energised.