Country hotel - shower upgrades and voltage drops

[IDug]

Hello, I am looking for some help regarding our problems with guest-room showers.

 

Up until recently all our rooms had standard 3.5KW water heaters mounted on the inside walls of the bathrooms. These worked fine in normal weather and when used by Thailand residents who are familiar with them. In cold weather the units did not provide enough hot water for a good shower and international visitors often did not work out that by reducing the water flow they could get warmer water.

 

The reasons the heaters can not produce enough warm water include - too many heaters on one power supply (up to 5), long power cables to the meter on the road (up to 650m circuit), power cables too small (16mm), and probably some other factors I am not aware of.

 

We used to have highly variable voltages as the nearest transformer was almost 2km down the road, this has improved since the PEA put in a transformer just 150m down the road. We now have a fairly stable 240V until we turn on a heater.

 

We would not only like to improve the shower experience for the guests but also improve the appearance of the bathrooms. To this end we have recently changed the system in two adjoining rooms. We have taken the 3.5KW heaters out of the bathrooms and put 6KW water heaters on the outside walls with hot and cold water coming in to a mixer tap (which international guests are used to). This all looks much better but has not fixed the hot water problem.

 

With one shower going, there is plenty of hot water but with both going the voltage drop causes both heaters to struggle. The 240V supply drops to 210V with one heater on and 180V with both on.

 

The cable from the meter is about a 550m circuit and is 16mm aluminium. This cable not only serves these two rooms but also two more with the old 3.5KW heaters.

 

My question is - what are my options for fixing this issue? Install bigger/copper cable? Run extra cables from extra meters? Install some magical box near the rooms which reduces the voltage drop? Other?

 

I attach a schematic showing our current electrical system. The rooms we have put the new heaters in are 4 & 5 which run off meter 2.

 

If I can fix the problem in these rooms I would like to roll out the upgrade to all our rooms.

 

Side question - the 6KW multi-point heaters - If two showers are run off one heater will turning on the 2nd shower change the temp in the 1st shower or do these heaters have a system which gets around that?

 

 

Thanks for any help.

 

Baan Maka electricity map.pdf

[KannikaP]

If 2 x 3.5 Kw heaters were not enough, how can 6Kw/2 be better?

 

Sorry Woodworker, my mis-understanding. He put 2 x 6Kw heaters in.

[sometimewoodworker]

18 minutes ago, IDug said:

The cable from the meter is about a 550m circuit and is 16mm aluminium. This cable not only serves these two rooms but also two more with the old 3.5KW heaters.

The supply cables at ½ km long are way too small @crossy will be along soon to advise the size of cables you need to add. You can certainly keep the ones you have but will need to put in two more probably bigger than the ones you already have. Aluminium will be OK and a more affordable price.

 

FWIW. Your supply voltage at 240v is higher than normal.

[VocalNeal]

Maybe you would be better served with each room having a small storage tank. Then the instantaneous electric load is less. You'll have to replumb though for both hot and  cold water. Just do the sums!

 

Next question is where? Very common in Indonesia for the same problem you have.

 

 

[Crossy]

28 minutes ago, VocalNeal said:

Maybe you would be better served with each room having a small storage tank. Then the instantaneous electric load is less. You'll have to replumb though for both hot and  cold water. Just do the sums!

 

Next question is where? Very common in Indonesia for the same problem you have.

 

This is exactly what I was thinking, you can get away with 2kW or so and they won't all be on together (you can even arrange that they're not).

 

Or, you could use gas multipoint heaters, zero electrical load, just take care on the installation.

 

@IDug could you post a sketch plan of where everything is with approximate distances and the current cable routes so we can get an idea just what we are looking at. Also what size meter do you have, I'm assuming 3-phase but what amps?

 

[Whale]

To do any calculation you need to estimate the total diverse load of the complex at its incoming consumer unit and work from there. Its not something one could attempt with the info given. Your supply cabling is under-sized (and causing a voltage drop under non-diverse load conditions i.e. your peak load period) no question but what is the correct sizing (and therefore cost) needs to be calculated by someone competent who has inspected the facility. Theres also the question of what is the load on your area supply (the neighbours) before your first consumer unit. 

 

 

[IDug]

[IDug]

Thanks for the suggestion of a tank system. Does anyone know what size tank would be needed to provide a good shower to 2 people. I see the Siebel Eltron tanks can heat up to 75°C and an average shower uses about 80L of water at about 37°C. This would suggest that an 100L tank would be needed for each room. Does this sound about right? I would like to do some pricing, thanks.

[Crossy]

Do we assume all those meters are single-phase?

 

Are the meters spread between the three phases?

 

Each 15/45 is good for about 11kW down hill with the wind behind it.

 

Of course the largest load (meter 5) is on the longest run of the smallest cable - welcome to Thailand. That load @ about 300m from the road should be on something like 70mm² copper for 5% volt drop, might explain your issue.

 

For your tanks, 75C is VERY hot, serious scalding risk, so you will need pukka thermostatic mixers to avoid cooking your guests. Depending upon how cold your "cold" water is I would think a 100L tank heater at that temperature would easily do two rooms.

 

[VocalNeal]

6 hours ago, IDug said:

My question is - what are my options for fixing this issue?

 

Sitting at a mates house waiting for him to come back with beer and looking across the road.

 

How about some form of solar system to heat all the water in the resort? Toilets don't care if they get 20C+ water neither will wash basins of even the laundry and dish washer.

 

Just a thought!

[IDug]

Thanks for your ideas everyone.

 

To answer your questions Crossy - yes, all single phase meters. As far as I can see two of the four meters which are together are connected to one phase and the other two are connected to a second phase. The third phase is unused at this pole.

 

Here is a question for you Crossy, If I upgrade the 16mm cable, that currently goes to the two 6KW instant heaters I have already installed, to a 35mm aluminium cable, would I need to upgrade the meter from 15/45 to 30/100?

 

I've spent a bit more time on calculations for a hot water heater/tank system.

 

75C, as you say, is way too hot. max 50C is recommended at taps so we could set the water heaters to low 50s. The lowest temp the cold water ever gets to is 20C.

I tested the water flow rate at the showers. It is currently at about 3 litres per minute. I hope that with better plumbing and pumps to raise this to about 5 litres per minute. If two guests in a room take a ten minute shower each then that will use 100 litres. If they shower in 40C water then they will use 35 litres of cold water and 65 litres of hot water which suggests that I need an 80 litre tank for one room or a 150 litre tank for 2 rooms. As they are currently 12,000 Baht and 15,000 Baht respectively at Homepro it would make sense to have one 150 litre tank service two rooms.

 

Any further ideas/input would be greatly appreciated.

 

Thanks again.

[sometimewoodworker]

1 hour ago, IDug said:

Here is a question for you Crossy, If I upgrade the 16mm cable, that currently goes to the two 6KW instant heaters I have already installed, to a 35mm aluminium cable, would I need to upgrade the meter from 15/45 to 30/100?

The need to have a larger cable is to reduce the voltage drop you are getting because of your extremely long run of thin cable.
 

Changing the meter is only needed if you are regularly trying to use over 65A+80A for extended periods, if you are not doing that then changing the meter is of no significant benefit. You will probably have to install a smaller diameter pigtail anyway as 35mm cable is probably too big for the terminal block. Also you don’t need to have a single cable, you can add others in parallel, in which case you will definitely need pigtails.

 

while the two heaters, if pulling full power simultaneously,  will be around 50A they will be not be doing it for a long time and the 15/45 meter will have no problem with that.

[IDug]

23 minutes ago, sometimewoodworker said:

Changing the meter is only needed if you are regularly trying to use over 65A+80A for extended periods, if you are not doing that then changing the meter is of no significant benefit. You will probably have to install a smaller diameter pigtail anyway as 35mm cable is probably too big for the terminal block. Also you don’t need to have a single cable, you can add others in parallel, in which case you will definitely need pigtails.

Great, that not only answered that question but also one I had thought about but hadn't asked regarding parallel lines. Thanks. This means I can leave my 16mm lines up and add new lines as long as I don't overload the meter.

[Crossy]

1 hour ago, IDug said:

This means I can leave my 16mm lines up and add new lines as long as I don't overload the meter.

 

Indeed, and your 15/45 can easily do 100% overload for a short (an hour or so) time but it will lose accuracy (bet it won't read low).

 

Is the current cable copper or aluminium?

 

With Al being $$$ cheaper I would go for the biggest Al that budget allows, 32 will make a difference, 70 will be better. If you do go with the tank heaters you would likely get away with the existing cable.

 

You may also save by moving three of the meters to be one 3-phase supply (check the standing charges).

[IDug]

1 hour ago, Crossy said:

Is the current cable copper or aluminium?

16mm aluminium apart from the one to the kitchen which is 25mm aluminium.

[IDug]

1 hour ago, Crossy said:

You may also save by moving three of the meters to be one 3-phase supply (check the standing charges).

If I do this then would I put all three lines through the same meter? Wouldn't this likely overload the meter?

[IDug]

A follow up question. If I want to understand the existing voltage drop and estimate the voltage drop after cable upgrades then which cables should I include? Just from my side of the meter or all the way down the road to the nearest transformer. If the latter, then I can see that 10mm aluminium has been used from the street line down the pole down to the meter on the PEA side but any idea what the PEA runs down the street to the transformer?

[sometimewoodworker]

7 hours ago, IDug said:

I can see that 10mm aluminium has been used from the street line down the pole down to the meter on the PEA side

It’s extremely unlikely that they are using 10mm aluminium. I’m virtually sure it will be double insulated copper.

[PJHassselt]

According rules in many countries, (but I do not know if Thailand has rules about this) water temperature in storage tanks must be above 60 degrees to prevent legionella diverse.

 

Some hospitals even require that the hot water temperature at each tap point is once a week 60 degrees, to kill the bacteria.

 

Some hot water tanks have an outlet valve that mixes cold and hot water to reduce the outlet temperature for safety reasons.

[Led Lolly Yellow Lolly]

On 12/18/2020 at 12:33 AM, sometimewoodworker said:

It’s extremely unlikely that they are using 10mm aluminium. I’m virtually sure it will be double insulated copper.

 

Certainly if the PEA did the install their side it would be NYY copper, but it would be of absolutely no surprise whatsoever if someone NOT from the PEA have done their own 'upgrades'.

[Led Lolly Yellow Lolly]

On 12/15/2020 at 1:07 PM, IDug said:

With one shower going, there is plenty of hot water but with both going the voltage drop causes both heaters to struggle. The 240V supply drops to 210V with one heater on and 180V with both on.

 

The cable from the meter is about a 550m circuit and is 16mm aluminium. This cable not only serves these two rooms but also two more with the old 3.5KW heaters.

 

Sorry if I've missed this in another post somewhere, but what size are the cables between the individual consumers units to the shower units themselves? At 6 kW you'll get away with 4 sqm if the run is very short but if it's more than a hop and a skip from the CU to the shower this will be a significant contributor to voltage drop at full power and this will need 6 sqm to help mitigate that. Where are you measuring the voltage drop? I feel there is more going on than just the size of the cable outside. There are all manner of mechanisms that will cause voltage drops, including badly clamped supply side cables, with mixed metals and the galvanic corrosion involved with that, to name just a couple.

 

 

 

[IDug]

On 12/18/2020 at 12:33 AM, sometimewoodworker said:

It’s extremely unlikely that they are using 10mm aluminium. I’m virtually sure it will be double insulated copper.

Yes, sorry, my mistake. They are using 10mm copper wire.

[IDug]

19 hours ago, PJHassselt said:

According rules in many countries, (but I do not know if Thailand has rules about this) water temperature in storage tanks must be above 60 degrees to prevent legionella diverse.

Thanks, that's good advice. I think I will heat to 75C and then use a thermostatic mixer valve to take it down to about 45C before sending it through the wall to the shower mixer tap. This should minimise the size of the tank needed while fixing the legionella issue.

[IDug]

1 hour ago, NilSS said:

Sorry if I've missed this in another post somewhere, but what size are the cables between the individual consumers units to the shower units themselves?

As the heaters are now attached to the outside walls, they do not use the rooms internal wiring. Instead, we have new 6mm wiring going straight to the incoming 16mm cable.
It turns out that the first 105m of cable from the meter is 25mm aluminium with the next 180m being 16mm aluminium. Using the voltage drop calculators I can get very close to what is actually being recorded. For these two rooms I will run a new 50mm aluminium all the way. The new voltage drop will probably be from 240v to about 215v with both showers being used and although not perfect, there should be enough hot water for good showers. 

On another pair of rooms I will install a water tank heater system on existing wiring. I will then let them run for a few months and see what problems arise. At Thai Watsadu the staff were recommending AO Smith heaters as they come with a 5 year warrantee and onsite maintenance/servicing.

[Led Lolly Yellow Lolly]

2 hours ago, IDug said:

As the heaters are now attached to the outside walls, they do not use the rooms internal wiring. Instead, we have new 6mm wiring going straight to the incoming 16mm cable.
 

 

If I've understood this correctly this is an extremely hazardous situation and you need to stop what you're doing and get a qualified electrical engineer on site. The cables should NEVER bypass the Consumer Unit, EVER. I don't care if some local spark told you it's fine.

 

 

 

[IDug]

1 hour ago, NilSS said:

If I've understood this correctly this is an extremely hazardous situation and you need to stop what you're doing and get a qualified electrical engineer on site. The cables should NEVER bypass the Consumer Unit, EVER. I don't care if some local spark told you it's fine.

Is this true even if the wires go through a trip switch and the heaters are earthed? What other protection does the consumer unit give us?

[Led Lolly Yellow Lolly]

Everything must go back to the CU, including earth/ground. Do you know or even understand if the system is TT or TN-CS-MEN, for example? I don't wish to sound high handed, but it's a gross violation of good practice to bypass the CU. Sorry but I have to say it straight.

[VocalNeal]

12 minutes ago, IDug said:

Is this true even if the wires go through a trip switch

 

If the trip switch looks something like this with a "test"  button

 

 

My local electrical shop sells them. 450 baht (no excuse?) Made by Kyokuto. (Because that was in the other shower when we bought the house)

 

Here's another reference https://www.ie.co.th/circuit-breaker-698.html

 

Generally speaking no test button= No good.

 

Some shower heaters have integral breaker but I'm old fashoined.

 

Of course if the feed bypassed the main board then they have to be installed hot as you cannot turn off the feed. No my comfort zone. 

[IDug]

32 minutes ago, NilSS said:

Everything must go back to the CU, including earth/ground. Do you know or even understand if the system is TT or TN-CS-MEN, for example? I don't wish to sound high handed, but it's a gross violation of good practice to bypass the CU. Sorry but I have to say it straight.

No problem at all with you saying it straight. I will have a word with the electrician and either move the existing CU out of the bedroom or install a new one outside. Does that sound OK?

[Led Lolly Yellow Lolly]

I'm not going to say anything is OK without seeing it or installing it myself. One of the problems is you're dealing with a wet room, which should be an equipotentially bonded safe zone. Messing around with multiple ground rods or (multiple paths to ground) is just asking for trouble. 

 

Note that I am NOT a qualified electrician, so I make no warranty with anything I say here, nor should you trust anything you read on a forum. The reason I do everything myself in our hotel is because, as you are finding out, finding competent local electricians is pretty much impossible. We were also having problems with theft and corruption costing the company millions of Baht (I started checking invoices and cross referencing them with what we actually had, it was sure an eye opener).

We even had hundreds of our rooms fitted with fake/copy sockets, it took me a while to figure out why live and neutral were apparently reversed on all of them, even though they appeared to be wired correctly, turned out the wire holes on the back were mislabled, just fakes. We screwed the electrician over that debacle, he lost a lot of the money he stole from us. . .

So I've ended up swinging around on electricity pylons with my own set of hot sticks pulling out expulsion fuses on our own transformers, all the way down to wiring kettles and everything in between. As I said, I'm not qualified or certified, but I guarantee that anything I personally do is of an infinitely higher standard than ANYTHING I've seen in Thailand in 20 years.