Switching AC off when EHU fails? How to? (1 Viewer)

sallylillian

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Oct 29, 2011
3,896
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Falmouth, Cornwall
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18,670
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Palace Liner 90LO
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2011
A bit of a preamble so those with the knowhow can understand the reasoning and those that don’t are provided with info to avoid unhelpful questions or comments

Our first RV was a Yankee with two humungous and efficient Coleman roof air cons. There were no Hekis, just 2 off Fantastic vents. This worked great, we only use the AC when the temperature is in excess of circa 30c. The RV had what was called load shedding and it would progressively switch off appliances in a pre-set order to maintain amp consumption at the set breaker size.

Fast forward. New Flair in specification in 2014. Look at those lovely panoramic Hekis, 2 please with the extra electric control and rain sensor. We thought their control would be as competent as the fantastic vents but they were not, that’s a different story, and fortunately we also had specified 2 more Fantastic vents as well. That aside the Hekis brought more cons than pros in our opinion. When its hot, the sun’s rays beat through, so a good percentage of the time we had the blackout blind in use to some degree, and when they were open the bug screen was very often in play. In cold weather the black out screen helped with insulation. Factor in the leaves, dust and crap we did not get much benefit.

So we decided that we would not have any Hekis on the Morelo, we would have 2 Freshlights AC units which have a built in dome and as this is somewhat raised and small we hope there is little heat transmission. We are also having 2 fantastic vents again. The theory is that the Fantastic vents and the Freshlights (using just its low powered fan) ventilation with no cooling will provide a comfortable environment, instead of opening a Heki.

Now to the problem. Morelo will connect the Freshlights to the inverter side of the inverter charger for me (with caveats) so that the fans can run even when not on EHU, and of course with 640ah of Lithium together with power assist I could even run one on Full AC for a short time on pure inversion or use them both on puny EHU without concern. But what if I want to leave one or two on Full AC whilst on EHU and we are away from the van for a few hours and the EHU goes during our absence. That will play merry hell with the batteries and the inverter. So what I need is some sort of relay that I can switch on and off so that when required it senses EHU failure it switches the Freshlights off if I choose to set it that is.

So how?
 
Apr 27, 2016
4,498
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Manchester
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Since the 80s
I can't think of an easy way to do exactly what you want automatically, but I think this is the next best thing. Have a manual switch on each of your Freshlight A/C units that switches between EHU power and inverter power. Then at least you know which power source it is using. If you use 3-position 'centre-off' switches, they could replace the on-off switches.

In case you're not familiar with the terminology, you want a DPDT (Double Pole Double Throw) switch. Centre-off, or sometimes called ON-OFF-ON. Make sure it's rated for 250VAC, and capable of switching at least 10 amps. Something like this:
https://uk.farnell.com/arcolectric/...UK-GEN-SHOPPING-2252075&CATCI=pla-41477300408

Connect the A/C to the 'Common' terminals, the EHU mains to one side, and the inverter mains to the other.
 
OP
sallylillian

sallylillian

LIFE MEMBER
Oct 29, 2011
3,896
4,951
Falmouth, Cornwall
Funster No
18,670
MH
Palace Liner 90LO
Exp
2011
I can't think of an easy way to do exactly what you want automatically, but I think this is the next best thing. Have a manual switch on each of your Freshlight A/C units that switches between EHU power and inverter power. Then at least you know which power source it is using. If you use 3-position 'centre-off' switches, they could replace the on-off switches.

In case you're not familiar with the terminology, you want a DPDT (Double Pole Double Throw) switch. Centre-off, or sometimes called ON-OFF-ON. Make sure it's rated for 250VAC, and capable of switching at least 10 amps. Something like this:
https://uk.farnell.com/arcolectric/...UK-GEN-SHOPPING-2252075&CATCI=pla-41477300408

Connect the A/C to the 'Common' terminals, the EHU mains to one side, and the inverter mains to the other.
Thanks, I was trying to overthink it... I think! Your suggestion would be ideal. A mate has suggested a relay which when switch to the circuit would disconnect invereted power when the EHU drops out. But your more analouge solution is possibly preferable and within my electrical understanding envelope!
Michael

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eddievanbitz

Trader - Funster
LIFE MEMBER
Oct 4, 2007
7,241
31,829
Taunton Somerset
Funster No
540
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RV
Exp
since 1989
A bit of a preamble so those with the knowhow can understand the reasoning and those that don’t are provided with info to avoid unhelpful questions or comments

Our first RV was a Yankee with two humungous and efficient Coleman roof air cons. There were no Hekis, just 2 off Fantastic vents. This worked great, we only use the AC when the temperature is in excess of circa 30c. The RV had what was called load shedding and it would progressively switch off appliances in a pre-set order to maintain amp consumption at the set breaker size.

Fast forward. New Flair in specification in 2014. Look at those lovely panoramic Hekis, 2 please with the extra electric control and rain sensor. We thought their control would be as competent as the fantastic vents but they were not, that’s a different story, and fortunately we also had specified 2 more Fantastic vents as well. That aside the Hekis brought more cons than pros in our opinion. When its hot, the sun’s rays beat through, so a good percentage of the time we had the blackout blind in use to some degree, and when they were open the bug screen was very often in play. In cold weather the black out screen helped with insulation. Factor in the leaves, dust and crap we did not get much benefit.

So we decided that we would not have any Hekis on the Morelo, we would have 2 Freshlights AC units which have a built in dome and as this is somewhat raised and small we hope there is little heat transmission. We are also having 2 fantastic vents again. The theory is that the Fantastic vents and the Freshlights (using just its low powered fan) ventilation with no cooling will provide a comfortable environment, instead of opening a Heki.

Now to the problem. Morelo will connect the Freshlights to the inverter side of the inverter charger for me (with caveats) so that the fans can run even when not on EHU, and of course with 640ah of Lithium together with power assist I could even run one on Full AC for a short time on pure inversion or use them both on puny EHU without concern. But what if I want to leave one or two on Full AC whilst on EHU and we are away from the van for a few hours and the EHU goes during our absence. That will play merry hell with the batteries and the inverter. So what I need is some sort of relay that I can switch on and off so that when required it senses EHU failure it switches the Freshlights off if I choose to set it that is.

So how?
GSM controlled switches, we use them with a built in temperature sensor so that people can monitor mains and temperature in the case where a pet is left in the camper

The mains fails you would get a message (having a dedicated "non invertered" 13amp socket) you send a GSM message and isolate the Freshlights
 
OP
sallylillian

sallylillian

LIFE MEMBER
Oct 29, 2011
3,896
4,951
Falmouth, Cornwall
Funster No
18,670
MH
Palace Liner 90LO
Exp
2011
GSM controlled switches, we use them with a built in temperature sensor so that people can monitor mains and temperature in the case where a pet is left in the camper

The mains fails you would get a message (having a dedicated "non invertered" 13amp socket) you send a GSM message and isolate the Freshlights
Thanks Eddie I will look at that too, having a message for 230vac failure would be good in its own right.
 

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