How to wire solar divert alongside ASHP immersion controller

[rangorgubbins]

hi,
Can anyone offer advice or point me in the right direction on how to wire in a solar divert feed into our existing wiring?
The existing wiring looks like this (see photos below). There's an input feed coming from a secondary consumer unit in the utility room, into an isolator switch, then to a control switch box with a contactor switch in it with 'on', 'off', 'auto' settings. 'Auto' mode allows the Nibe ASHP to control the immersion heater (for legionella and boosting the water temps). I want to wire in a second input feed, which is coming from a solar diverter on the main consumer unit (not the same as in the utility room). The solar diverter is an 'mk2router' as designed by Robin Emery and popular on the OpenEnergyMonitoring site.
I'm not quite sure how i should wire this second feed in so that it doesn't cause problems with the ASHP control of the immersion. I don't really need to run both the ASHP control circuit and the solar diverter circuit at the same time.
The house is single-phase, and the secondary consumer unit is connected to the main consumer unit.

 

[flameport]

You will need a changeover relay or contactor, so that the solar diverter is connected most of the time, and when the ASHP switches it to anti-legionella mode, the solar diverter is bypassed and the heater is connected direct to the supply.

The Eaton device in the box may already be suitable, can you get a much closer photo of it, particularly the model number and the wiring diagram at the top right side.

 

[rangorgubbins]

That would be handy if the contactor in there can already do it!
Its an Eaton DIL EM-10-C XTMCC9A10. See photo.

 

[flameport]

Unfortunately that has 4 NO contacts so not suitable.

Wiring as below - changeover relay or contactor is required, or one with two sets of NO and NC contacts.
When not energised, heater is connected to the output of the solar diverter.
When contactor is energised by the ASHP controls, heater is connected directly to the supply.

Contactor needs to have a 230V AC coil. Other wiring is the same as it is now - the wires to A1 and A2 on the existing contactor go to A1 and A2 on the new one. The thin blue / brown wires connected to the input side of the existing contactor connect to the L&N terminals connected to the supply.

 

[SUNRAY]

Unfortunately that has 4 NO contacts so not suitable.

Wiring as below - changeover relay or contactor is required, or one with two sets of NO and NC contacts.
When not energised, heater is connected to the output of the solar diverter.
When contactor is energised by the ASHP controls, heater is connected directly to the supply.

Contactor needs to have a 230V AC coil. Other wiring is the same as it is now - the wires to A1 and A2 on the existing contactor go to A1 and A2 on the new one. The thin blue / brown wires connected to the input side of the existing contactor connect to the L&N terminals connected to the supply.


View attachment 279229

Does there not have to be more to it than that?
What I see there is (assuming the switch is set to 'auto') is the heater running on solar but the ASHP will change it over to mains regardless of what it's doing on solar.
Should the Solar not be taking priority?

 

[rangorgubbins]

@SUNRAY
Couldn't i put the ASHP on the N/O connection, and the solar on the N/C?
Then the ASHP would have priority but the solar diverter would take over when there was electricity coming through.

 

[flameport]

What I see there is (assuming the switch is set to 'auto') is the heater running on solar but the ASHP will change it over to mains regardless of what it's doing on solar.

That is correct.

Heater on solar most of the time, which means the power to the heater will be varied according to how much solar is available. Hot water for free.

When the ASHP system needs to heat the water for the anti-legionella thing, which is typically once a week or whatever, the heater is switched on at full power for a set time regardless of solar to ensure it reaches the required temperature.
If there happens to be some surplus solar available at the time, then that will be used. If there isn't, then it just uses grid power for some/all of that function.

 

[rangorgubbins]

Unfortunately that has 4 NO contacts so not suitable.

Wiring as below - changeover relay or contactor is required, or one with two sets of NO and NC contacts.
When not energised, heater is connected to the output of the solar diverter.
When contactor is energised by the ASHP controls, heater is connected directly to the supply.

Contactor needs to have a 230V AC coil. Other wiring is the same as it is now - the wires to A1 and A2 on the existing contactor go to A1 and A2 on the new one. The thin blue / brown wires connected to the input side of the existing contactor connect to the L&N terminals connected to the supply.

Many thanks for the info and diagram. That makes sense.
I'll look for a like-for-like contactor i can swap out the old N/O only one with one that has both N/C and N/O.
Looking through some of the Eaton info it seems that accessories can be added to these mini contactors, which *i think* can add in N/C connections. Might not be a good solution though as i don't think there's space in the box for an accessory.

 

[rangorgubbins]

@flameport
This would do the job wouldn't it?

20A Contactor 4 Pole 2 Normally Open and 2 Normaly Closed Contacts 240V Coil AC1

Miniature contactor with auxiliary contact for inductive and resistive loads

www.cef.co.uk

240v, 20A loads for each N/C and N/O, plus the A1 and A2 for the ASHP control.

 

[flameport]

Yes. Just link each pair of contacts on one side (where the heater connects) which makes it 2x changeover contacts.

 

[rangorgubbins]

I ordered the schneider LC1K09008U7 '20A contactor 4 pole 2 NO and 2 NC contacts 240V coil' as in the link above.
There aren't any clear instructions that i can find, but apparently R1/R2 and R3/R4 are the Normally Closed contacts, and 1/2 and 3/4 are the Normally open contacts.
So, i guess that the ASHP supply should be on 1 and 3 (NO) contacts.
The solar diverter supply should be on R1 and R3 (NC) contacts
And then 2 and R2 are linked, and 4 and R4 are linked, and these go to the DHW immersion heater.

I'm not quite sure what i need to do with the wires from the separate 3 way 'Auto, On, Off' switch. On the original contactor there are 2 pairs of wires, one pair into A1 and A2, and the other pair into L1 and 13. I guess I only need the pair of wires for the 'Auto' position on the switch (which allows the ASHP controller to turn on the immersion when needed). So i think i need to identify which pair is for the auto position and wire those into A1 and A2 on the new 4 pole contactor. I guess there is no place for the other pair of switch wires.
I've sketched out how i think i should be wiring it. Does this look right?

 

[rangorgubbins]

If anyone familiar with wiring contactor relays can confirm whether my proposed wiring is correct or not, that would be really helpful.
Many thanks

 

[flameport]

On the original contactor there are 2 pairs of wires, one pair into A1 and A2, and the other pair into L1 and 13.

Same connections on the new one.
The wires to 1 and 13 on the existing are connected to 1 and 3 on the new one. They are the power supply to the 3 position switch, without those it will do nothing.

The rest of it is correct.

 

[rangorgubbins]

Thanks Flameport.
Just to confirm (I want to make sure i get this right!), on the new contactor, connection 1 will have two wires in it, which are from positions 1 and L1 on the old contactor. And likewise, on the new contactor, connection 3 will have two wires in it, which are from positions 13 and NO on the old contactor?

 

[flameport]

Yes.