Sterling ProSwitch32 Auto Change over (Fridge Question)?

[EuroTrotters]

Hi

I am considering installing a Sterling Auto Change over.

3 inputs
1 output

In Inverter mode, the battery charger is not powered from 240v

So, the question is?./.....................

How do I wire the AES Fridge?
Is it possible to tag to the Battery Charger output?

Any ideas welcome please?

 

[EuroTrotters]

Still no reply from sterling products

 

[eddie]

Still no reply from sterling products

They may sleep?

 

[autorouter]

As I understand it, the battery charger output connection on the Sterling Auto Changeover Unit is a very low power signal, that is intended to be used only to switch a relay. (A relay is an electrically operated switch, typically used to switch a heavy current using a very low power control signal). This relay has its heavy current contacts wired into the battery charger mains input wire, and disconnects it when Input 3 (Inverter) is selected.

In the instructions it shows other loads, like a water heater, connected to the relay as well. It's intended for any load that you would otherwise have to switch off manually when using the inverter. The mains power to the AES fridge sounds to me like another candidate for connecting to this relay.

Sterling say that a suitable high power relay can be obtained from your electrical supplier. However they also sell a suitable relay, complete with a box to protect it.

 

[BDM]

Can you advise what you are trying to achieve by using this unit please?

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[EuroTrotters]

Can you advise what you are trying to achieve by using this unit please?

okay,

so, existing setup was as follows.

EHU
Inverter

Wired up using Clive Mott 's Contacter method.

Worked Great with our 1200w Inverter. But the conactor was noisy.

This was replaced with Techno 's Relay version when we added a Generator input and upgraded to a more powerful Victron Inverter via a manual switch over. However, the delay on the relay is not slow enough. This is wired so that when the inverter input is selected, the fridge 240v and battery charger are not powered.

Auto changeover relay for inverter

First picture is a selection of relays from RS components. The one on the right is my choice as it is 10 amp rated through the normally closed contact set which will be used for the inverter when off hook up. The normally open contact set is 30 amp rated and will be used to power a skt/skts as...

www.motorhomefun.co.uk

I contacted Sterling who suggested the relay is too slow and requires their 32amp auto switch over unit.
https://sterling-power.com/products/automatic-manual-ac-power-selector-switch .

So, the setup I am looking for is.

Input 1 Shore/EHU = Powers All 240v circuits
Input 2 Generator = Powers All 240v Circuits
Input 3 Inverter = Powers all 240v withe the exception of Battery and Fridge

So, I suppose I will have to investigate wiring the Battery Charger to output to a relay for the Fridge and Charger.

Just trying to work that one out.

(We only use the Generator on the move).

 

[autorouter]

So, I suppose I will have to investigate wiring the Battery Charger to output to a relay for the Fridge and Charger.

When I said

the battery charger output connection on the Sterling Auto Changeover Unit is a very low power signal, that is intended to be used only to switch a relay.

I was referring to what Sterling call the 'Battery Charger Disengage Signal', labelled F in the installation instructions. This is a 2-way screw terminal connector. If you connect this to the coil of one of their relays, it will switch the relay ON when the Hookup or Generator are selected, but will switch it OFF when the Inverter is selected. This is exactly what you want for the battery charger.

The relay to cut off the battery charger is an extra that is available separately. This relay should have a pair of input terminals (Live and Neutral), and a pair of output terminals (Live and Neutral). It will also have a pair of coil terminals, and the signal to the coil will turn the relay on and off.

Run a wire from where the other loads are connected to the input of the relay. Connect the battery charger mains supply to the output of the relay. The relay will switch the battery charger off when the Inverter is selected.

If you also connect the AES Fridge mains supply to the output of the relay, it will switch that too, which I think is what you want.

 

[EuroTrotters]

They may sleep?

Ive sent another email. I work during their office hours but will try to phone them.

 

[eddie]

Ive sent another email. I work during their office hours but will try to phone them.

Do you know if the are open? We are in a National lockdown till next week, and the are hardly ‘Essential’

 

[EuroTrotters]

if anyone could help me out with a diagram and or link to RS components part number for relay. That would be appreciated

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[autorouter]

Looking at the Sterling manual again, it says that the battery charger (and the AES fridge) can be disconnected when the inverter is running by an external relay.

A relay is an electrically operated switch. A tiny current through a coil causes a magnetic field that moves an electrical contact. The Auto Changeover unit has an internal switch (labelled F in the diagram) that closes when the inverter is running, and opens when it is not. If that switch is connected to the 240V power, it could switch on a relay coil, which would control a large current.

Simple relays just have on/off contacts. When the coil is powered, the contacts are connected; when the coil is not powered, the contacts are disconnected. These contacts are called Normally Open (NO), because when the coil is not powered the contacts are Open.

Unfortunately that's the opposite of what you want. You want a relay that has Normally Closed (NC) contacts, so that when the coil is not powered the contacts are Closed. Such relays are difficult to find. However you can use a Changeover relay.

A changeover relay has a Common (COM) contact, that flips from the NC to the NO contact when the coil is powered. You can just ignore the NO contact. You want to switch both live and neutral wires, so a relay with two sets of changeover contacts is what you want.

In the technical jargon, such a relay is called a Double Pole Double Throw (DPDT) relay. In some places they call such contacts 'Two Pole Form C'. It is important to get one with a 230V coil. Relays with 12V and 24V coils are very common, so it's easy to get the wrong one.

For your application, you wire the coil so that the mains is applied to the switch F all the time. When the Auto Changeover unit selects Inverter, it turns on the switch F, and power goes to the coil. This opens the NC contacts and disconnects the battery charger.

When the Auto Changeover unit selects Generator or Shore Power, it turns off the switch F, and no power goes to the coil. The NC contacts close, which reconnects the battery charger.

 

[autorouter]

There are many relays that will do the job, and the ones suggested in Techno's thread, like the Finder one, will be fine for this.

Depending on your location on the geekiness spectrum, you may prefer a transparent version like this, so you can see how it works:

56.32.8.230.0040 | Finder Plug In Power Relay, 230V ac Coil, 12A Switching Current, DPDT | RS

uk.rs-online.com

 

[eddie]

Why not simply put the relay on the ring main (I know it’s not)

I assume when the generator is used is plugged into the normal blue 16 amp inlet? So it would mean everything normal on either hook up or generator and your 13 amp sockets only are available when the inverter is being used

 

[EuroTrotters]

There are many relays that will do the job, and the ones suggested in Techno's thread, like the Finder one, will be fine for this.

Depending on your location on the geekiness spectrum, you may prefer a transparent version like this, so you can see how it works:

56.32.8.230.0040 | Finder Plug In Power Relay, 230V ac Coil, 12A Switching Current, DPDT | RS

uk.rs-online.com

Thank you so much for you help on this.

I have the relay from techno’s post, currently in use (pardon the pun).

just need to rework the wiring. Did you mean a/c in to the left of drawing ?

if I can get my head around it.

 

[EuroTrotters]

Why not simply put the relay on the ring main (I know it’s not)

I assume when the generator is used is plugged into the normal blue 16 amp inlet? So it would mean everything normal on either hook up or generator and your 13 amp sockets only are available when the inverter is being used

I have a separate 16amp connector at the rear for generator. Though in practice, it doesn’t matter which one you use for ehu or gennie.

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[eddie]

I have a separate 16amp connector at the rear for generator. Though in practice, it doesn’t matter which one you use for ehu or gennie.

Well in which case you could use a second relay on the generator "input" and make it even more automatic

On my camper I have a 5kva Onan generator, shore power and Victron inverter charger all on demand all automatic

 

[EuroTrotters]

Well in which case you could use a second relay on the generator "input" and make it even more automatic

On my camper I have a 5kva Onan generator, shore power and Victron inverter charger all on demand all automatic

Wish I had gone with the victory 3k instead of 2. It has auto change over

 

[autorouter]

Did you mean a/c in to the left of drawing ?

Yes, the AC Out from the mains Consumer Unit is the AC In to the Relay

 

[autorouter]

Well in which case you could use a second relay on the generator "input" and make it even more automatic

That's the reason for the Auto Changeover unit. It contains all the relays, wired up to give the right priority, all in one box. It's unfortunate it doesn't include a proper battery charger output instead of a pair of dry contacts to use as a switch.

 

[eddie]

That's the reason for the Auto Changeover unit. It contains all the relays, wired up to give the right priority, all in one box. It's unfortunate it doesn't include a proper battery charger output instead of a pair of dry contacts to use as a switch.

It’s really designed for a boat

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[eddie]

Wish I had gone with the victory 3k instead of 2. It has auto change over

Not an issue though as you have already added a parallel 16 amp input, use a changer relay on that, safer really as you could forget and leave it plugged in and plug shore power in afterwards!

The Dometic transfer switch when we dissectEd one is 3 change over relays in a £140 case lol

 

[EuroTrotters]

As I understand it, the battery charger output connection on the Sterling Auto Changeover Unit is a very low power signal, that is intended to be used only to switch a relay. (A relay is an electrically operated switch, typically used to switch a heavy current using a very low power control signal). This relay has its heavy current contacts wired into the battery charger mains input wire, and disconnects it when Input 3 (Inverter) is selected.

In the instructions it shows other loads, like a water heater, connected to the relay as well. It's intended for any load that you would otherwise have to switch off manually when using the inverter. The mains power to the AES fridge sounds to me like another candidate for connecting to this relay.

Sterling say that a suitable high power relay can be obtained from your electrical supplier. However they also sell a suitable relay, complete with a box to protect it.

Hi is this the item ?

Sterling Power Contact Relay for AC Automatic Crossover Switch 32A ? CON1

Sterling Power Contact Relay for AC Automatic Crossover Switch 32A ? CON1 product brought to you by BMS Technologies LTD Offering free next working day delivery.

www.batterymegastore.co.uk