Not stable netsupply.

[Peterphuket]

Oh, it go's wrong after a few hours....the safe-t-cut switch off and it doesn't matter wich eartleak current choice the safe-t-cut will not work, so I bypass the AVR and will take a look tomorrow what's going wrong.

I have to mention, today I got an new AC/DC adapter output 12V 6A, to feed my outdoor burgle safetycamera's and at the same time it cut off and is also not working anymore (made in China)

[Crossy]

11 hours ago, farmerjo said:

Can you explain that for us laymen Crossy????.

Are you saying the mains cable will get extremely hot back to meter?

 

Firstly, provided your wiring and breakers are correctly sized there's certainly no danger caused by feeding your water heaters via the AVR.

 

But here are some reasons why you may think about not doing it.

 

Water heater don't need a regulated supply, they work just fine (with a lower heat output) on a reduced supply voltage, that's a significant load that you don't need to size the AVR for ($$$ saving).

 

Now some sums ????

 

Let's make some assumptions:-

• 3.5kW water heater.
• A supply that drops by 1V for each Amp drawn (not too silly considering what some members are reporting) so a supply impedance of about 1 ohm.
• Supply is 210V with a nominal load.

A water heater is essentially a resistor which gets hot when current passes through it. Our 3500W, 220V heater will have a resistance of about 13.8 ohms (Ohm's Law).

 

Without an AVR

When we turn our heater on its resistance forms a potential divider with the supply impedance resulting in the heater getting about 195V. At this voltage our heater is developing about 2.7kW and drawing around 14A.

 

Now lets an AVR feeding the heater

The heater is now happily seeing a constant 220V so it is developing the full 3.5kW and you are enjoying a nice hot shower ????

 

Meanwhile the AVR is correcting for any supply dips and is therefore pulling the full 3.5kW from the supply regardless of the voltage.

When you first turn on the heater it pulls about 16A from our already 210V supply.

The supply falls to 194V.

The AVR corrects the fall in voltage so we are drawing 3.5kW @ 194V = 18A.

Of course our supply now falls to 192V.

The AVR corrects the fall in voltage so we are drawing 3.5kW @ 192V = 18.5A.

At this point we can probably say that things will become stable ????

 

Nothing is going to blow up or explode, but we are pulling 4.5A more from the supply than we would with the heater unregulated. That's about 4.5V extra drop.

 

Now turn on your 12000 BTU aircon, that's about 1.2kW from the supply.

So we are now drawing 3.5 +1.2kW @ 192V =  25A

The supply now drops further to 185V and is corrected by the AVR resulting in a current of 25.5A.

Stability again ????

 

Small heater, small-ish home no real issues on 15/45 meter and a 10kVA AVR ????

 

=========

 

Now your neighbour (who has no AVR) takes a shower and pulls the incoming supply down to 194V before you turn on your shower and aircon.

 

I won't go through all the working again but your incoming supply is now going to be (with shower and aircon) about 165V. This is the minimum voltage that many AVRs will accept, some just continue trying and the output voltage falls, others (like ours) turn off the output and plunge you into darkness.

 

If your heater wasn't on the regulated side you would have that extra 4.5V and would still be in the light ????

 

Then your neighbour buys a 6kW water heater and an AVR

 

=========

 

Of course if your supply is already much worse than 1V drop per Amp then things may go dark sooner.

 

In reality, suck it and see. I tried it with our 6kW heater on the regulated side and didn't like the supply current I was seeing, hence my suggestion that, if possible, don't regulate the heater supply ????

 

 

 

 

 

[Crossy]

12 hours ago, Peterphuket said:

Oh, it go's wrong after a few hours....the safe-t-cut switch off and it doesn't matter wich eartleak current choice the safe-t-cut will not work, so I bypass the AVR and will take a look tomorrow what's going wrong.

 

Oh dear ????

 

I hope it's nothing serious. With the AVR bypassed the Safe-T-Cut stays on ok?

 

Please check again that you have L and N correct at the AVR (the N usually goes direct from in to out inside the box so verify the labelling is correct too).

 

EDIT Also try with just the AVR connected (output disconnected).

 

[Peterphuket]

First I switch the AVR to bypass, and the problem was still there, it was dark so it was not possible to do anything and I bypass the safe-t-cut to get electric.

 

This morning I start again, it was a false alarm, luckily, it was the Safe-T-Cut yes, after pushing a few times the test-button, everything is okay.

Strange, but it is now for more then 1 hour good working.

To be honestly the sensitivityswitch is never possible to set lower then 25mA, but that is as long as I stay here (>10 years) I can live with that.

 

I think the whole problem was triggered with the new Powersupply 12V 6A, I connect yesterday and go's wrong after an hour or so.

Soon or late it go's always wrong with this switching powersupplys, I hate that stuff. But transformers....rthey are so heavy, the AVR is 70KG,

Edited January 8, 2020 by Peterphuket

[farmerjo]

2 hours ago, Crossy said:

 

Firstly, provided your wiring and breakers are correctly sized there's certainly no danger caused by feeding your water heaters via the AVR.

 

But here are some reasons why you may think about not doing it.

 

Water heater don't need a regulated supply, they work just fine (with a lower heat output) on a reduced supply voltage, that's a significant load that you don't need to size the AVR for ($$$ saving).

 

Now some sums ????

 

Let's make some assumptions:-

• 3.5kW water heater.
• A supply that drops by 1V for each Amp drawn (not too silly considering what some members are reporting) so a supply impedance of about 1 ohm.
• Supply is 210V with a nominal load.

A water heater is essentially a resistor which gets hot when current passes through it. Our 3500W, 220V heater will have a resistance of about 13.8 ohms (Ohm's Law).

 

Without an AVR

When we turn our heater on its resistance forms a potential divider with the supply impedance resulting in the heater getting about 195V. At this voltage our heater is developing about 2.7kW and drawing around 14A.

 

Now lets an AVR feeding the heater

The heater is now happily seeing a constant 220V so it is developing the full 3.5kW and you are enjoying a nice hot shower ????

 

Meanwhile the AVR is correcting for any supply dips and is therefore pulling the full 3.5kW from the supply regardless of the voltage.

When you first turn on the heater it pulls about 16A from our already 210V supply.

The supply falls to 194V.

The AVR corrects the fall in voltage so we are drawing 3.5kW @ 194V = 18A.

Of course our supply now falls to 192V.

The AVR corrects the fall in voltage so we are drawing 3.5kW @ 192V = 18.5A.

At this point we can probably say that things will become stable ????

 

Nothing is going to blow up or explode, but we are pulling 4.5A more from the supply than we would with the heater unregulated. That's about 4.5V extra drop.

 

Now turn on your 12000 BTU aircon, that's about 1.2kW from the supply.

So we are now drawing 3.5 +1.2kW @ 192V =  25A

The supply now drops further to 185V and is corrected by the AVR resulting in a current of 25.5A.

Stability again ????

 

Small heater, small-ish home no real issues on 15/45 meter and a 10kVA AVR ????

 

=========

 

Now your neighbour (who has no AVR) takes a shower and pulls the incoming supply down to 194V before you turn on your shower and aircon.

 

I won't go through all the working again but your incoming supply is now going to be (with shower and aircon) about 165V. This is the minimum voltage that many AVRs will accept, some just continue trying and the output voltage falls, others (like ours) turn off the output and plunge you into darkness.

 

If your heater wasn't on the regulated side you would have that extra 4.5V and would still be in the light ????

 

Then your neighbour buys a 6kW water heater and an AVR

 

=========

 

Of course if your supply is already much worse than 1V drop per Amp then things may go dark sooner.

 

In reality, suck it and see. I tried it with our 6kW heater on the regulated side and didn't like the supply current I was seeing, hence my suggestion that, if possible, don't regulate the heater supply ????

 

 

 

 

 

Thanks Crossy,great detailed reply for my better understanding.????

[farmerjo]

31 minutes ago, Peterphuket said:

First I switch the AVR to bypass, and the problem was still there, it was dark so it was not possible to do anything and I bypass the safe-t-cut to get electric.

 

This morning I start again, it was a false alarm, luckily, it was the Safe-T-Cut yes, after pushing a few times the test-button, everything is okay.

Strange, but it is now for more then 1 hour good working.

To be honestly the sensitivityswitch is never possible to set lower then 25mA, but that is as long as I stay here (>10 years) I can live with that.

 

I think the whole problem was triggered with the new Powersupply 12V 6A, I connect yesterday and go's wrong after an hour or so.

Soon or late it go's always wrong with this switching powersupplys, I hate that stuff. But transformers....rthey are so heavy, the AVR is 70KG,

If you bought the the cbc model in the picture,i have the same.

You can ring cbc in Thailand and they have english speaking engineers who can help if your not sure.

[Peterphuket]

23 minutes ago, farmerjo said:

If you bought the the cbc model in the picture,i have the same.

You can ring cbc in Thailand and they have english speaking engineers who can help if your not sure.

That will be nice in case of....

Thanks for your advice.

[Crossy]

2 hours ago, Peterphuket said:

This morning I start again, it was a false alarm, luckily, it was the Safe-T-Cut yes, after pushing a few times the test-button, everything is okay.

 

How old is the Safe-T-Cut?

 

If it's misbehaving it may be time to replace it, you don't want it not tripping when it should.

[Peterphuket]

Oh? It is as long I have this house, about 10-11 year.

Please will you explaine me why I have to replace.

I supposed a coordinated current f.e. 45 mA triggering a device (relay) who's switching off the power isn't?

[Crossy]

52 minutes ago, Peterphuket said:

Please will you explaine me why I have to replace.

 

Any safety device which behaves in an "odd" manner is suspect.

 

You said yourself that it needed a few operation of the toggle and test button to make it stay "On".

 

So now it's on what's to say it won't stay on when it should be off.

 

Does it trip correctly on the "Test" button?

[Peterphuket]

5 hours ago, Crossy said:

 

Any safety device which behaves in an "odd" manner is suspect.

 

You said yourself that it needed a few operation of the toggle and test button to make it stay "On".

 

So now it's on what's to say it won't stay on when it should be off.

 

Does it trip correctly on the "Test" button?

You are right, I have to check it a few times more, and maybe change when it refuse 1 time.