Post by JohnV on Dec 15, 2022 0:05:37 GMT
As I said I would here is a run down of a very puzzling and annoying inverter issue.
Sabina H is almost all 240v electrics. Water pump, drainage pumps, bilge pumps and toilet which are all 24v
everything else lighting, cooking, fridgefreezer and central heating system is 240v
Originally during the long fit out based in Benfleet the majority of the time was on shore power or when on the occasional short jaunts using generator
cooking on the Rayburn and night time lighting with lamps but gradually as more things were added (SWIMBO's requirements) an investment was made in a 1.5 Kw
inverter .... the introduction of a washing machine caused an upgrade to a 2Kw inverter (from the same company) a couple of years later the addition of
dishwasher, tumble drier, electric hob and oven forced the change to a 3Kw inverter from the same company again.
The changeover from shore power to inverter was fully automatic so that in the event of the failure of shore power the inverter would run the freezer.
The heart of the unit was a double contactor the two halves being mechanically and electrically interlocked so that only one was capable of operating at a time
If the mains failed, the relay closed a pair of contacts operating the remote control of the inverter switching it on, at the same time the mains half of the contactor
would release disconnecting the mains side from the boat and releasing the mechanical lock on the second side and closing the interlock electrical connection.
As the inverter switched on it would operate the other half of the contactor and connect the inverter to the boat, mechanically and electrically locking out the mains half.
If the mains was restored the relay operated switching off the inverter, when the supply to the contactor opened removing the connection between inverter and boat
Sabina H is almost all 240v electrics. Water pump, drainage pumps, bilge pumps and toilet which are all 24v
everything else lighting, cooking, fridgefreezer and central heating system is 240v
Originally during the long fit out based in Benfleet the majority of the time was on shore power or when on the occasional short jaunts using generator
cooking on the Rayburn and night time lighting with lamps but gradually as more things were added (SWIMBO's requirements) an investment was made in a 1.5 Kw
inverter .... the introduction of a washing machine caused an upgrade to a 2Kw inverter (from the same company) a couple of years later the addition of
dishwasher, tumble drier, electric hob and oven forced the change to a 3Kw inverter from the same company again.
At each increase the replaced unit was kept installed as an emergence unit.
As I was making a major re-vamp of the electrical system and having no further room to add anything to the elecrical board which had just ..... grewed
I decided I might as well upgrade the inverter at the same time so I bought a 4Kw unit, yet again from the same company.
Duly installed with a new upgraded circuit breaker, I changed the output plug over to the new unit went through into the accomodation
and turned the shore power off, lights all came back on although I did notice the red overload light came on momentarily as it started but didn't
really think much about it. It was quite sunny that day and later on I noticed the batteries were quite high
I decided to run on them for the night so I switched off the mains. It went dark .......... and stayed dark !!!
Switching the shore power back on I went into the engine room to check ........ The inverter was dead, gone to meet it's maker, snuffed it.
No blown fuses no smell of magic smoke escaping ....... muttering imprecations about poor quality control I plugged the old 3Kw model in.
I went back to the corridor, turned the shore power off ..... lights came back on everything showing normal.
Next morning on the phone to the company, they were good as gold "terribly sorry new one will be sent out today"
two days later, courier arrives, hands me the new one and picks up the old one. This was Thursday afternoon ...... I unpack the unit
and fit it onto the panel, connect the leads, out of the engine room into the accomodation switch off the mains ..... lights come on.
Again I did notice the red light coming on briefly, anyway switched it on and off again .... still fine.
Friday afternoon was doing some welding so was running the generator
(which runs through the same changeover system just switched from shore to gennie) I finished the job turned it back to shore power
Then decided to run on batteries for the night again so switched off the mains ......
the red light on the inverter panel flashed and then everything went dark .......... this time swearing profusely went into the engine room
and switched back to the old 3Kw inverter.
Straight onto the telephone to the technical department of the company and got a voicemail.
by this time it was about 4.30 so I hadn't been very hopeful for a reply.
Went back into the engine room and checked, double checked and treble checked everything ..... I mean what the hell could be wrong
It works fine with all the other models and the only difference is the size of the fuse (200 amp instead of 120Amp) and cables (50mm instead of 35mm)
everything else is exactly the same, the output is on a plug ..... and there is only the one plug which has to be moved from one unit to the other.
The changeover from shore power to inverter was fully automatic so that in the event of the failure of shore power the inverter would run the freezer.
The heart of the unit was a double contactor the two halves being mechanically and electrically interlocked so that only one was capable of operating at a time
A fairly basic, common system used industrially for such things as motor reversal or star delta starters
.
When there was shore power it would operate a relay which signalled the inverter and one half of the contactor and connect the shore mains to the boat.If the mains failed, the relay closed a pair of contacts operating the remote control of the inverter switching it on, at the same time the mains half of the contactor
would release disconnecting the mains side from the boat and releasing the mechanical lock on the second side and closing the interlock electrical connection.
As the inverter switched on it would operate the other half of the contactor and connect the inverter to the boat, mechanically and electrically locking out the mains half.
If the mains was restored the relay operated switching off the inverter, when the supply to the contactor opened removing the connection between inverter and boat
it also closed the electrical interlock and released the mechanical interlock, the shore power side then pulls in re-connecting shore power to the boat
On the Monday I tried most of the day to get the technical department and in the end phoned sales, explained the problem.
They said they would send a note down to him to call me. Just to save time I emailed photos of the installation and a circuit diagram.
On Tuesday morning getting my Mr Angry hat ready to start if he didn't call before the deadline I had set when not much before that I got the call.
He'd seen the photos and the changeover circuitry and we had a long talk about possibilities ..... the upshot was he gave me three options.
Another inverter that he would give a full checkover and a long test before dispatch, a different model 4Kw inverter or my money back.
To my question of what if you can't blow it up but I can ? the answer was, no problem you still have two more choices.
To be honest it was doing my head in as to what it could be, ok it's theoretically possible that I was unlucky and got two units with the same fault.
I decided to take another one the same as i really wanted to find out if there was something about my set up.
Friday the new unit arrived but I decided that I wouldn't do anything until the next day.
Saturday morningI re-connected the older 2Kw model onto the panel and by switching off the control circuit fuse on the changeover unit
operated the changeover with me in the engine room next to the units, loud clunk as relay pulled in and the lights came back on .... fine
now plugged in the 3Kw unit .......switched off, loud clunk and lights back on. Took the 2Kw unit off the panel and mounted the 4Kw up
switched the power off, this time very loud buzzing and chattering noise followed by a clunk as the contactor eventually pulled in with the red
overload light showing momentarily !!! If I had been in the accomodation I wouldn't have heard it.
They have changed the switch on spec of the 4Kw unit from the earlier models, the 240v ramps up quite slowly maybe half a second to reach 240v
Because the coil of the contactor is not getting enough voltage to pull in it is acting the same way as a stalled electric motor, it's inductance
in that state is much lower so that although the voltage is lower the current is massively higher !!!
For me there is a simple answer, let the inverter build up to full voltage before connecting the main contactor.
In my junk box I have a small contactor and a couple of the old fashioned vacuum operated delay switch modules.
First job, see if the inverter disliked operating a smaller contactor from start up ..... it did, much less than the big one but you could still hear it
One of the time modules was quick open slow close so that installed on the mains side keeps the contactor coil on the inverter side disconnected
for 0.5 sec after the switching on of the inverter.
For me that is the problem solved but the technical director of the company now has a headache !!!
That kind of loading is probably very unusual ...... but it is definitely a flaw in this model !!!
Sent him a long email about my findings.
He's going to speak with the manufacturers urgently to see what they can do and has promised to keep me in the loop
Although I'm glad it's solved, I would have hated to have just got my money back and still been at a loss as to what was happening
but that still adds up to another two weeks of delays on this project ...... it seems every bit of it has been aggro
Anyway ........ if anybody reads right to the end of this long and convoluted post 
well done !!!
well done !!! 
