Unsteady Voltage Regulator

[Barns]

I run a small ecolodge in rural Laos and have a floating restaurant down on the river with several fridges. Being where we are, the electricity supply is patchy at best. It works nearly all of the time but the voltage rises and falls constantly.

As a result, I invested in a small 3000 VA voltage regulator for the floating restaurant which has two tall upright fridges (bottom part fridge, top part freezer), one ice cream freezer and a small regular fridge plus basics such as lights, a TV, DVD player, amp and toaster. I mainly bought the voltage regulator since the brand new beer fridge I bought wouldn't get cold. The fan and light worked but the compressor wouldn't fire up and I was told that this was because the incoming power to that fridge with everything plugged in hovered between 200 and 210 V which wasn't enough for such a tall fridge and it needed to be a constant 220V.

I wired the voltage regulator in correctly (although I'm certainly not a qualified electrician it was just simple connections) but it will run perfectly for about ten minutes at 220 V and about 2 amps or even less but will then suddenly drop down to about 110-140 V while the amps will shoot up to about 20 amps (Which should trip the 15A breaker on the unit, no?). The lights dim, the fan slows, the fridge compressors stop etc and it will stay like that for a few minutes before you can hear the voltage regulator kick in again and everything will be back to normal. However, this cycle continues constantly.

The incoming power to the voltage regulator hovers around 220 V according to my multimeter and the rest of the resort, which is all powered from the same breaker box, doesn't have the same problem

The wire from the main breaker box down to the restaurant is VAF 2 x 2.5 sq. mm 300V. Is that maybe too small? Another thought I had was that the small section of wire from the voltage regulator to the restaurant breakers is a bit smaller than the main cable I mentioned before. Could that be a bottleneck? Would something like that cause the situation I mentioned?

Any assistance gladly welcome. There are no reliable electricians around here in rural Laos unless you just want a light bulb fitted so I have to do it myself.

Thanks.

 

[Pete999]

Difficult one mate, being so far away, my immediate thoughts 3000va is a bit small for all that gear, only a thought though.

 

[Barns]

If the 3000VA was too little for the fridges etc would that cause the regulator to cycle like that? I can probably go and pay an extra £40 and change it for a 5000VA and I'm happy to do so if I know that too low a wattage would cause the unit to do this. However, I don't really want to go and spend the money if too low a wattage wouldn't cause this problem.

While I'm here, can I just clarify that when UPS' and voltage regulators etc have a VA rating that is exactly the same thing as wattage since volts x amps = watts. Or am I completely wrong?

How many watts/VA would one standard fridge usually require? And why would three of them work and not the fourth?

 

[Pete999]

va in an AC environment represents "apparent power" as opposed to the "true power" as a rule of thumb, and this is just that, you can multiply the va figure by 0.6 , so 60% of power being delivered. So in answer to your question "yes you are wrong" there are too many other thing to take into consideration when purchasing UPs or Voltage regulators, one example is the reactance of the circuits involved. It would be wrong of me to say "yes just bung in a larger VR, can you not get someone locally to size up the installation for you? sorry can't be of any more help

 

[Badged01]

While I'm here, can I just clarify that when UPS' and voltage regulators etc have a VA rating that is exactly the same thing as wattage since volts x amps = watts. Or am I completely wrong?

As above - VA is the "apparent" power supplied to the equipment and Watts represents the "true" power being used by the equipment. In laymans terms, your equipment only needs the true power (resistive) to work. But because of reactance (inductance/capacitance) in the equipment fighting against the current being drawn, you end up needing more current to get the true power. So you pay for apparent power but only actually use true power! -- apparent power being greater than true power. The difference between the two being the power factor --- the rule of thumb 60% mentioned above

How many watts/VA would one standard fridge usually require?

They all vary but an around 800W wont be far off the mark!

And why would three of them work and not the fourth?

Cant help you there without actually seeing things in action so to speak!

 

[Barns]

Yes, sorry, I do realise it's difficult to diagnose a problem when you can't see it hands (eyes?) on but there are only two Western electricians in Vientiane, Laos' capital, that I know of and, as a result, they are constantly busy and to get one of them to travel 20 miles out of town is hard so I just have to work it all out myself. That's why I've come to Internet forums!

What I now need to know is whether having too low a VA rating on the voltage regulator could cause it to fluctuate like it does? If this is possible then I'll try to swap it for a bigger one next time I'm in town.

I can see that 800W x 4 far exceeds 60% of 3KW so it does seem likely. I wondered why an 800 VA UPS was unable to keep my PC going in the office when it only has a 650W power supply. Thanks for clarifying!

However, 60% of 5KW is 3KW so even that may not be enough for 4 fridges plus the other general electrics. When you say about 800W for a fridge/freezer, are you talking about the big tall ones, standard little ones or a chest freezer? Or is that just an average and the bigger ones would need a lot more than 800W?

I presume they usually have a plate on them somewhere saying what wattage they are? I'll have a look tomorrow!

Thanks ever so much for trying to help.

 

[Pete999]

how long does the UPs last at 650 watts loading?

 

[shanky887614]

that pc will not be pulling 650watts.

for example ive got a 750watt psu in mine but realistically it cant draw more than 450watts at the moment. thats with core i5 and 7970 gpu and other stuff

that spec is way over office spec machines unless it is a workstation spec machine

 

[Pete999]

I'll rephrase the question then, how long does the UPs last when the power fails?

 

[Richard Burns]

Your voltage regulator may have a minimum voltage that it can work with and if your outside supply drops below this minimum voltage then the regulator may cut out once the supply goes up again the voltage regulator then restarts.

Similarly if your voltage regulator is overloaded (which sounds like it may be the case) then it could be overheating and a safety cut out comes in that stops the voltage regulator working, then when it has cooled down it restarts.

This is all supposition because we cannot see the item in question or measure any parameters.

The reading you have given that the voltage regulator is only delivering 2 amps when thing s are working normally does not soudn right.
Admittedly if the fridges are all cold and the compressor does not need to run then this value could be correct and it may be that when a fridge starts up this cuts out the voltage regulator.
However 20A sounds a bit high unless all the fridges started together, then again it may be that the voltage regulator starts up on a test basis that is limiting the current flow to set the correct voltage once it set itself up then it delivers a sufficient voltage to allow the fridges to start that then causes it to cut out.

Using 2.5mm² VAf cable would just about be OK for the loading you want but a larger cable size would be preferable, if noting else a small cable taking the maximum current will cause a voltage drop that will only make the situation worse.

A 15 A breaker will not trip for a long time (some hours, if at all) if it is taking 20A.

Fridges and freezers contain motors that can take a high current on starting up and will also take a higher than rated amount of power from the supply as stated above. It may be worth trying to run one or two fridges until they reach the set temperature and the compressors stop and then turn on the other two fridges, this will (at least initially) take the motors starts out of syncronisation so that they are not all starting at once.

As a reference this below is a list that I found somewhere that gives approximate values for power ratings for common appliances.
You can see from the first part of the list where the reactive power is given that items with motors in can take a lot more from the supply than the steady running rating suggests.
It may be worth calculating your total power demand from this list and this will give a you a general idea of what power voltage regulator you may require.
Again this is all very rough and ready and may well not give you the results you need. Only some one on site could give you more reliable information.
(and also some one more familiar with the power supply arrangements in Laos!)

Good luck.

Sorry the table has not formatted very clearly, hope you can make it out.
Appliances Resistive Load (Watts) Reactive Load (watts)
Blender 375 500
Clock Radio 5 ---
Coffee Maker 1,700 ---
Computer - PC 300 ---
Cuisinart 450 650
Deep Fryer 1,800 ---
Electric Blanket 400 ---
Electric Curlers 300 ---
Frying Pan 1,250 ---
Hair Dryer 1,875 ---
Iron 1,200 ---
Incandecant Light Bulbs as rating
Microwave 1,050-2,500 ---
Washing Machine 1,150 2,200
Water Heater 4,000 ---
TV - Color 300 ---
Air Compressor (1hp) 1,500 4,500
Cultivator 700 1,400
Freezer 800 2,100
Furnace Fan 875-1,200 2,200
Garage Door Opener (1/4 hp) 550 1,000
Grinder, Bench 1,400 2,450
Heater, Kerosene (90,000 BTU) 500 725
Sump Pump (1/3 hp) 800 1,250
Well Pump (1/2 hp) 150 1,950
Saw, Band 1,100 1,350
Table Saw (10 inch) 1,750 4,250
Coffee maker 800
Toaster 800-1500
Popcorn popper 250
Blender 300
Microwave 600-1500
Waffle iron 1200
Hot plate 1200
Frying pan 1200
Dishwaher 1200-1500
Gbg. disposal 450
Washing machine…
automatic 500
manual 300
Vaccuum…
upright 200-700
handheld 100
Sewing Machine 100
Iron 1000
Clothes dryer…
electric (n/a) 4000
gas heated 300-400
Heater (n/a)…
engine block 150-1000
portable 1500
waterbed 400
stock tank 100
Furnace blower 300-1000
Air Conditioner (n/a)…
room 1000
central 2000-5000
Electric mower (n/a) 1500
Ceiling fan 10-50
Table fan 10-25
Electric blanket 200
Blow dryer 1000
Shaver 15
Water Pik 100
Computer…
laptop 20-50
desktop 80-150
printer 100
Typewriter 80-200
TV (25" color) 150
TV (19" color) 70
TV (12" B&W) 20
VCR 40
CD player 35
Portable stereo 10-30
Clock radio 1
Car stereo 8
Sattelite dish 30
CB radio 5
Electric clock 3
Radio telephone…
receive 5
transmit 40-150
Lights…
100w incan. 100
25w CF 28
50w DC incan. 50
40w DC halogen 40
20w CF 22
Compact Fluorescent (CF)
vs. Incandescent Wattage*
40 watt incan. 11 watt CF
60 watt incan. 16 watt CF
75 watt incan. 20 watt CF
100 watt incan. 30 watt CF
Hedge trimmer 450
Weed eater 500
1/4" drill 250
1/2" drill 750
1" drill 1000
9" disc sander 1200
3" belt sander 1000
12" chain saw 1100
14" band saw 1100
7 1/4" circ. saw 900
8 1/4" circ. saw 1400
Refrig./Freezer Conventional
20 cubic feet 540
16 cubic feet 475
Sun Frost Refrig./Freezer (DC*)…
16 cubic feet 112
12 cubic feet 70
Vestfrost Refrig./Freezer…
10.5 cubic feet 60
Freezer Conventional
14 cubic feet FF 440
14 cubic feet 350
Sun Frost Freezer (DC)…
19 cubic feet 112
Vestfrost Freezer…
7.5 cubic feet 50

 

[Marvo]

I run a small ecolodge in rural Laos and have a floating restaurant down on the river with several fridges. Being where we are, the electricity supply is patchy at best. It works nearly all of the time but the voltage rises and falls constantly.

As a result, I invested in a small 3000 VA voltage regulator for the floating restaurant which has two tall upright fridges (bottom part fridge, top part freezer), one ice cream freezer and a small regular fridge plus basics such as lights, a TV, DVD player, amp and toaster. I mainly bought the voltage regulator since the brand new beer fridge I bought wouldn't get cold. The fan and light worked but the compressor wouldn't fire up and I was told that this was because the incoming power to that fridge with everything plugged in hovered between 200 and 210 V which wasn't enough for such a tall fridge and it needed to be a constant 220V.

I also live in a country where the supply voltage can drop as low as 200v, most refrigerators don't have a problem until around 190-195v when their compressor often fails to start.

I wired the voltage regulator in correctly (although I'm certainly not a qualified electrician it was just simple connections) but it will run perfectly for about ten minutes at 220 V and about 2 amps or even less

When acompressor starts you get a very brief large current flowing whilst it starts running then the normal run current will be pretty stable, it will then gradually reduce over a period of several minutes as the evaporating temp comes down (head pressure reduces) and it gets colder inside.

but will then suddenly drop down to about 110-140 V while the amps will shoot up to about 20 amps (Which should trip the 15A breaker on the unit, no?). The lights dim, the fan slows, the fridge compressors stop etc and it will stay like that for a few minutes before you can hear the voltage regulator kick in again and everything will be back to normal. However, this cycle continues constantly.

It sounds like one of the fridge compressors is stalling. When a compressor stalls it will draw a much larger current (maybe 5 x the run current) for several seconds and possibly up to half a minute until the thermal protection on the compressor disconnects the power automatically. This protector will auto reset in 3-15 minutes usually. This high current would almost certainly cause your 3000VA regulator to trip so all the other fridges would stop. The stalling could be due to several reasons but if the voltage is stable and remains above 210v up to the point of stall then there's most likely a fault on one of the fridges that's causing it.

I'd attempt to run the system with one of the fridges unplugged. If the fault persists then plug that fridge back in and try disconnecting another one. Do this until you figure out which fridge is the rogue one by deduction.

It's also worth noting that if a fridge is restarted quickly after it's been running and has stopped then it will restart or attempt to restart before the gas system has equalised. This load on the compressor, especially domestic fridge compressors will prevent it from starting and again high current draw until the thermal protection causes disconnection. This attempting to rapidly restart may be compounding your problems. It would be a wise move to add some kind of timer to your regulator so if it trips it doesn't reset and reapply power for a period of a few minutes. Similarly it would be advisable to try come up with a system that avoids having all compressors starting simultaneously when power is applied or reapplied because the combination of all the compressor start currents simultaneously would be very high and possibly cause the regulator to trip.

The incoming power to the voltage regulator hovers around 220 V according to my multimeter and the rest of the resort, which is all powered from the same breaker box, doesn't have the same problem

The wire from the main breaker box down to the restaurant is VAF 2 x 2.5 sq. mm 300V. Is that maybe too small?

Depends on the total current and the cable length but undersized cables are your worst enemy if you already have low voltage problems.

Another thought I had was that the small section of wire from the voltage regulator to the restaurant breakers is a bit smaller than the main cable I mentioned before. Could that be a bottleneck? Would something like that cause the situation I mentioned?

Definitely not ideal, splash out on a cable at least the same size or larger.

Some photos of the general setup, the regulator and the fridges would be helpful if you can attach some to your next reply.

 

[Barns]

how long does the UPs last at 650 watts loading?

The PC would immediately restart every time the incoming voltage from the mains dropped suddenly (which happens a lot here...) despite the presence of the UPS. It's quite a high-powered PC and the UPS also had the monitor plugged in to it. However, that's a separate issue which I solved by buying a 1,100 VA UPS. I now understand that real wattage is 60% of the VA rating...dunno why they don't just put the wattage on the box rather than the VA value but still...

Anyway, the pressing issue at the moment is the fridges and whether it's a good bet to exchange the 3000VA voltage regulator for a 5000VA one or whether I'll just be throwing good money after bad? I think the next highest I saw in the shop was 10,000 VA which would be overkill and probably prohibitively expensive.

Thanks.

 

[Barns]

@Richard Burns & Marvo

Firstly, the regulator is rated 90V-250V and the power doesn't drop as low as 90V so I think we can rule that one out.

According to your list (using the higher values since I don't know the difference between resistive and reactive loads...) I have:

Big Fridge x 2 = 540 W
Small Fridge x 1 = 475 W
Freezer x 1 = 440 W
TV x 1 = 300 W
14W bulbs x 10 = 140 W
DVD Player x 1 = 50 W (I guessed this one as being a bit higher than a CD player since I couldn't see it on your list)
Toaster = 1,500 W (Do toasters really take this much?? I never would have guessed!)

That makes a total of 3,985 W of "true power" needed so 6,641 W of "apparent power" needed from the voltage regulator which exceeds the 5,000 VA unit I was planning on.

However, without the toaster, I only need 2,485 W true power so 4,141 W of apparent power which would fit nicely.

We use the toaster very, very rarely so do I really need to include it in the calculations? Or would the fridge compressors just switch off for the 5 minutes when it's on?

I'll take some photos later as asked and stick them up but don't laugh at our wonky SE Asian wiring!

 

[Marvo]

I would plug the toasters into the supply without the regulator, just use the regulated supply for voltage sensitive items.

 

[Barns]

There is only one wire coming down the bank to the floating restaurant and that goes directly into the regulator to provide power for everything, including the plug sockets, so I haven't got a spare socket for it unfortunately.

I'll exchange the regulator for a bigger one when I'm in town on Wednesday and try that. If it still doesn't work we can examine other possibilities.

 

[Badged01]

.....using the higher values since I don't know the difference between resistive and reactive loads...

The higher value is the "apparent power" (reactive) which is what you will be drawing -- i.e. use that for your current calcs not the lower "true power" (resistive) value. You dont need to apply any power factor correction to the higher values (reactive) .......

 

[Barns]

So reactive and resistive are just the technical terms for apparent and true power. I understand now. Thanks Badged01.

Another question before I go and buy a bigger regulator:

If I invested in much bigger wire and replaced the connection between the breaker box and the restaurant (it varies in length between about 20 metres and 50 metres depending on the height of the river) would I actually need a voltage regulator in the first place? Does a voltage regulator actually increase the wattage available? Or, if there's not enough to start with, then it won't work anyway?

Thanks in advance.

 

[Badged01]

So reactive and resistive are just the technical terms for apparent and true power.

Not quite but for what you are doing I think helps explains it in sort of laymans terms!

Does a voltage regulator actually increase the wattage available?

Nope, it does what it says on the time and regulates the voltage to supposedly give a steady voltage. It will not increase your power!

 

[Barns]

I'm confused. Why would the cable coming directly from the breaker box to the restaurant (with no regulator in between) then not provide enough power for the four fridges and other stuff when there is 220V reaching the restaurant according to my multimeter?

Would a bigger cable increase the wattage reaching the restaurant? I can buy and wire up proper big black power line cable the same as we use for the three phases and neutral lines from the main road (black plastic with big silver wires twisted together inside...the size of one we use is 35 locally if that helps although I don't know 35 of what...although looking at it the diameter of the silver wires twisted together could be 35 mm but looks more to me). Would this make any difference?