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BANGKOK 16 November 2018 09:11
shaemus

Excessive voltage drop fixing solutions and costs

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Well its my turn to ask this Question.

 

Uptill now on my farm property i have't really had any high loads on my electrical system.

 

I am now getting to the stage of the build of the house 2nd fixings and finals. And i have just commissioned one of the hot water heaters (on demand 6Kw) with quite poor results,  water temperature wise. 

 

I  i have a 15/45A meter/connection single phase supply 16mm Alu

the O/H cable run Line side is 305m from the Transformer 30KVA to my Meter, the TF is 3.3KV-230V, i couldnt see any visible taps that could be changed to give me my required voltage

Voltage drops ffrom 230Vish down to 195V when under 6KW load 

Any voltage drop my side is negligible as i have installed 35mm copper running to the meter 

 

The HWS is on demand so the load is not constant, i didn't have any other loads on at all when i was measuring the Voltage

 

I did go and see the PEA a few years back and guy there was super helpful and said i could do what ever i wanted. Solar wind, whatever

 

So my options are as follows (maybe more)

  • find out if the PEA install meets regs and question the reason for the voltage drop if outside of range
  • Install a voltage regulator
  • Just install my own cabling on the poles (with permission) 
  • Install a HV transformer just for me.
  • Install a solar wind combo with some batteries to get me past suppy Authorities problems

 

Obviously i am hoping to find the cheapest solution, My experience in Australia with Grid connected PV systems is that the Inverters are looking at the supply voltage  and adding a Volt to get the power out if exporting, but the inverters were programmed for that region and the local regualtions so they would switch off if the grid failed of went over or under supply voltage allowances +10V - 6V based on 230V. I am not sure how the locally sold inverters are set up for this voltage failsafe. Obviously this is one of the many failsafes built in to safeguard the Supply authorities netwrok and protect their staff from danger 

 

To me, the Voltage regulator is just a band aid for a shit network, it would be great if the PEA, said yes whatever you want at no cost, but that is very unlikely to happen. 

 

again i dont need hot water all the time, they were selling gas units when i bought the units but i steered  away as i am in now way a gas fitter, nor is there anyone round here is remotely capable

 

 

your experiences and costs are what i am looking for 

 

Thanks in advance

 

Shameus

 

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First I would measure the voltage as near as possible to the transformer.

And if that is not what it should be contact the supplier.

I don't know if that will work but I think that should be the first step.

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1 hour ago, shaemus said:

Voltage drops ffrom 230Vish down to 195V when under 6KW load

Taking a simplistic view (easy sums), 6kW is about 27A @ 220V so a drop of 35V is a source impedance of 1.2 ohms. Certainly a bit (ok a lot) high, ours is about half that.

 

How long is the run from the meter to your home?

 

Certainly talk to PEA, the issue will be your off-load voltage is pretty high (220V +10% is about 240V), you want to avoid going outside limits at the high end.

 

Have a look at my pinned thread on installing an AVR (don't feed the heater from it).

 

  • Haha 1

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1 hour ago, Crossy said:

Taking a simplistic view (easy sums), 6kW is about 27A @ 220V so a drop of 35V is a source impedance of 1.2 ohms. Certainly a bit (ok a lot) high, ours is about half that.

 

How long is the run from the meter to your home?

 

Certainly talk to PEA, the issue will be your off-load voltage is pretty high (220V +10% is about 240V), you want to avoid going outside limits at the high end.

 

Have a look at my pinned thread on installing an AVR (don't feed the heater from it).

 

I have read the thread.. Its very informative.. Good on you to put it up. 

 

I am going to do a few calculations using cablecalc Pro and see what the cable size would be in Aus and the Uk. When. In Aus I used to deal with the networks a fair bit and generally they dispensated themselves into be able to do what they wanted. I'd assume the same goes here maybe more so or less need to dispensated as there is less litigation and I'd say less rules. 

 

I'll have a chat to the chaps at the PEA.. 

 

But if you could please send me the relevant page in the Thai electric standard you have it would be greatly appreciated. 

 

I am situated quite rurally and the distribution is set up to cope with the average farmers simple light and fridge in his hut. 

 

I'll Do they calcs And post the results.. All though the software is based on asnz. 3008. The the calcs are based on consumer mains rather than incomers. So it might not be relevant. 

 

The  fix is to up size the cable. I'd say of the top of my head 50mm or 70mm sq Al would be plenty. I have often considered 3 phase. Might be time to upgrade. Just 2 more cores and I'm away.. Ideally in an. ABC Config xlpe xlpe. 

 

I am quite sure this is not uncommon. The reason for the post was to get others experience of getting over it.. 

 

Thanks again for your help

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1 hour ago, OneMoreFarang said:

First I would measure the voltage as near as possible to the transformer.

And if that is not what it should be contact the supplier.

I don't know if that will work but I think that should be the first step.

I was looking around there today. There is a meter. At the bottom of the pole, I will take the cover off and test the voltage, I'll have to get someone to do the same at the load so we at least get a useable reading. 

 

Good idea and thank you

 

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I know the principal but I have not much experience with these transformers.

Does it have a label, maybe with some specs?

If not (or you can't find or read it) I would measure or estimate the dimensions of the transformer and check what a transformer of that size is supposed to be able to provide.

If that transformer is overloaded then some options like a voltage regulator don't make sense because you would still draw too much power.

 

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9 hours ago, shaemus said:

I was looking around there today. There is a meter. At the bottom of the pole, I will take the cover off and test the voltage, I'll have to get someone to do the same at the load so we at least get a useable reading. 

The meter is where PEA's responsibility stops, so taking off and on load readings there is a good idea. If it goes much over +- 10% of the PEA nominal 220V it's worth a word.

 

Try taking readings at various times of day, or build a data logger like mine :-

 

 

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13 hours ago, OneMoreFarang said:

I know the principal but I have not much experience with these transformers.

Does it have a label, maybe with some specs?

If not (or you can't find or read it) I would measure or estimate the dimensions of the transformer and check what a transformer of that size is supposed to be able to provide.

If that transformer is overloaded then some options like a voltage regulator don't make sense because you would still draw too much power.

 

there is a compliance plate on the back of the TF. It's about 5m in the air and a meter away from the HV overheads, i will see if i can zoom in with my camera and get a picture, As i mentioned before its a 30KVA and there is a very slim chance of it being overloaded as i can count the  qty of metered connections on one hand, each one is basically a farmers hut/shack with a light and a small fridge at most.

 

Going by crossy's info and advice on the Voltage reg, then its not going to assist me in heating my water

 

thanks again

 

Shaemus

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3 hours ago, Crossy said:

The meter is where PEA's responsibility stops, so taking off and on load readings there is a good idea. If it goes much over +- 10% of the PEA nominal 220V it's worth a word.

 

Try taking readings at various times of day, or build a data logger like mine :-

 

 

Thanks i have been considering a few items like the Audrino/raspberry PI.

 

Can you Send me the page in the regs about the voltage drop on the Supply side or share the names/ISBN of the books and i will get them and have a browse through.

 

The power logger is a good idea but in my mind i have diagnosed the problem, which is an undersized cable for my requirements.

 

ill get back to you with the calcs and what the PEA say. 

 

Thanks Again

 

Shaemus  

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Get a gas powered water heater and/or solar water helper which could even just be a big coil of black water hose put in the sun all day.

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2 minutes ago, johng said:

Get a gas powered water heater and/or solar water helper which could even just be a big coil of black water hose put in the sun all day.

Thanks i mentioned in my OP that Gas isn't an option i am considering. it still doesn't get rid of the voltage drop. When i did the measurements it was a cloudy day and not that hot. plus i am not going to start a new plumbing project now as i have made my choices and the tiling is finished etc etc.

 

A solar hot water heater is definitely an option in the future but currently quite an expense, the rheem heat exchanger types are very good and not all roof mounted.

 

Like alot of things in thailand they are imported and taxed heavily so the prices are exorbitant. a potential lack of a service network puts me off also.

 

thanks for your input

 

Shaemus

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2 hours ago, shaemus said:

there is a compliance plate on the back of the TF. It's about 5m in the air and a meter away from the HV overheads, i will see if i can zoom in with my camera and get a picture, As i mentioned before its a 30KVA and there is a very slim chance of it being overloaded as i can count the  qty of metered connections on one hand, each one is basically a farmers hut/shack with a light and a small fridge at most.

 

Going by crossy's info and advice on the Voltage reg, then its not going to assist me in heating my water

 

thanks again

 

Shaemus

Here is the Beast. i couldn't find any info on the web site of the manufacturer.http://www.charoenchai.com/Home.aspx

 

the images of the compliance plate show me that there is a tap setting, Standard is No. 3, the Overhead HV's from the rating would seem to be 22KV so there is even less chance of me going any where near it. 

 

This could be a very quick fix to my voltage drop problem, i might just ask the PEA man to  change it when he comes, if they want to change the cable then all the better, there is a blade/knife type fuse arrangement under the transformer housing so they could do it safely without a Load on the windings.

 

From my expericence with newtworks in Aus. when they were faced with a long run and lots of load so the end of the street have low volts. they would change the tap setting. the House at they start of the st would then get more volts the farther house would then get. but its far cheaper to do that than install a new transformer.

 

Shaemus

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