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Posted: Sat Jan 02, 2010 5:26pm

Post Subject: Sterling Charger/Inverter

I have a Sterling Combi (Pure Sine Wave) Charger Inverter fitted. I believe when connected to the 240v landline it acts purely as a charger, however I have noticed that when my wife uses a hair dryer the unit starts to "buzz" as the Inverter should not be active in this situation what could be the cause of the noise? No other 240v appliance appears to give rise to this sound. Has anyone had a similar issue?

Tony-B
Tony-B

Posted: Sat Jan 02, 2010 6:47pm

Post Subject: Sterling Charger/Inverter

Dear Duncan, unless this is a 12 volt hair dryer then the inverter may well work depending upon how the maximum draw from the mains has been set. Many combi-units have a facility to make the inverter supplement the mains when the current required exceeds a set level. This is needed because many/some marinas may only have 5 amp outlets. Many domestic hairdryers are rated at over 2kW (2000 watts) which indicates a current draw of over 8.5 amps. As you do not specify what the other appliances are I can not comment but 2kW is a lot and is only likely to be equalled by an electric kettle or other heating device. Tony Brooks

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Posted: Sun Jan 03, 2010 1:23pm

Post Subject: Sterling Charger/Inverter

Tony, It is a strange phenomenom in that on half power 800w you get the "hum" however on full power 1600w it disappears!?

Tony-B
Tony-B

Posted: Sun Jan 03, 2010 5:55pm

Post Subject: Sterling Charger/Inverter

I would suggest that you consult Sterling about this because 800 Watts equates to about 3.5 amps and I would expect (but can not be sure)the shoreline to cope with this without requiring inverter assistance.It is possible that the dryer achieves half power by half wave rectifying the AC supply which could well cause any change over relays or even sheet metal or other components and such like to resonate in the inverter. Tony Brooks

Tony-B
Tony-B

Posted: Mon Jan 04, 2010 10:55am

Post Subject: Sterling Charger/Inverter

I realised I should have explained half wave rectification. Many small domestic appliances achieve half power by fitting a diode in the supply line and for full power bypassing it with a switch. When the switch is open the mains AC electricity has to pass through the diode which then "chops" off (say) the negative half of the wave form. This means the appliance only receives half the power but in pulses about 100th of a second apart. For the other 100th of a second no power flows. (well in your case it probably does through the motor unless the hair dryer slows down. It is perfectly possible for these pulses to set up resonance in equipment which is what I suspect you are hearing. Tony Brooks

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Posted: Mon Jan 04, 2010 12:04pm

Post Subject: Sterling Charger/Inverter

Tony, Thanks for that explanation. It sounds very likely, as we had another hairdryer (same power) and it did the same. I have run a TV and a Vacuum Cleaner and had no issue. I will still have a word with Sterling. I should have mentioned that this unit has already been replaced once because of this issue. I would add that both units were fitted by a very competent electrician who works primarily with Sterling equipment. Thank for the help when I get to the bottom of the issue I will let you know the outcome. Duncan

Tony-B
Tony-B

Posted: Mon Jan 04, 2010 3:28pm

Post Subject: Sterling Charger/Inverter

See if the vacuum has a half speed switch on it, we had a Hoover with one. I never used half poser and I doubt most people do so if you have one try it ans see if you get the buzz. If so I suspect we've cracked it. Tony Brooks

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Posted: Mon Jan 04, 2010 4:23pm

Post Subject: Sterling Charger/Inverter

It will be a few weeks before I am back on the boat, however I will try it. Spoke with Syerling, not totally impressed with their comment "sounds like it is a thyristor issue (half power control as you suggested), just ignore it, if it blows up let us know and we will sort it out"!!

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