installing an 8,000 watt water heater

[mahjongguy]

This Mazuma product specifies VAF wiring at 6 to 10 mm2. A similar product from Mex specifies VAF or individual wires.

 

Does it matter if I use or don't use what we Yanks call Romex?  How could it matter?

[KannikaP]

6 minutes ago, mahjongguy said:

This Mazuma product specifies VAF wiring at 6 to 10 mm2. A similar product from Mex specifies VAF or individual wires.

 

Does it matter if I use or don't use what we Yanks call Romex?  How could it matter?

As long as the cable used can take 8000/220 = about 35 amps, and a suitable breaker, it shouldn't matter. 

[mahjongguy]

It will be on a 40 amp RCBO.

[KannikaP]

5 hours ago, Yellowtail said:

 

Sorry, wrong post

 

 

[KannikaP]

7 minutes ago, mahjongguy said:

It will be on a 40 amp RCBO.

That's OK as long as the cable can take that current.

[OneMoreFarang]

13 minutes ago, mahjongguy said:

It will be on a 40 amp RCBO.

Then the cable should be able to handle 40A.

 

Please be aware that not only the cable must be good for 40A.

All connectors must be able to handle that current.

 

I.e. terminals like this are not able to handle 40A, even if the cable fits.

 

 

 

 

 

 

You need something like this with the correct rating. The A rating must be same of higher of the RCBO.

I.e. this: http://www.es.co.th/detail.asp?Prod=131200076

 

 

Edited July 11, 2023 by OneMoreFarang

[KhunLA]

I personally wouldn't buy a Mazuma product.  And why 8000w, as overkill.  Had 8k at the one house, and could easily brew tea/coffee with it.  

 

Bought it as it supplied whole house (3 facets), with 2 not exactly close to the unit.  And still put out hot water, even on cool NE mornings.

 

This brand, Stiebel Eltron, I think, and excellent unit.  I believe still going strong, 12 yrs on.

 

 

Edited July 11, 2023 by KhunLA

[mahjongguy]

- That's a good reminder about connectors. Happily, in this case the wiring will be a straight run from the heater to the breaker.

 

- This heater will be in the master bathroom. It will supply two sinks, two showers, and a good size bathtub. I was advised by the contractor's engineer to choose 8,000 watts rather than the usual 6,000.  

[marin]

20 minutes ago, mahjongguy said:

This heater will be in the master bathroom. It will supply two sinks, two showers, and a good size bathtub. I was advised by the contractor's engineer to choose 8,000 watts rather than the usual 6,000.  

All at the same time?  I have used Stiebel for 20 years a solid product. 

 

[lopburi3]

18 minutes ago, mahjongguy said:

It will supply two sinks, two showers, and a good size bathtub. I was advised by the contractor's engineer to choose 8,000 watts rather than the usual 6,000.  

Not sure why you would need that much heat - normal single point heater is 3.5 or 4.5k and provides enough heat for most locations.  High wattage units run into issues when trying to mix water with the normally almost hot "cold" water of Thailand in my experience.

[bamboozled]

1 hour ago, OneMoreFarang said:

Then the cable should be able to handle 40A.

 

Please be aware that not only the cable must be good for 40A.

All connectors must be able to handle that current.

 

I.e. terminals like this are not able to handle 40A, even if the cable fits.

 

 

 

 

 

 

You need something like this with the correct rating. The A rating must be same of higher of the RCBO.

I.e. this: http://www.es.co.th/detail.asp?Prod=131200076

 

 

Good call. I had to rewire the power cord in my vacuum (circumventing the retractable cord feature as it broke) and the connectors I used completely melted. Luckily, the vacuum just stopped working and when I opened it up I saw the melted blob. Lesson hopefully learned. The unknown unknowns....

[TimeMachine]

Before wiring,  i would run  test.  Hook up with the wire size you want to use just for an initial short test and check the startup current. 

 

Sometimes the units are over specked to look good.  Ideal conditions and all that.

 

Once you see the highest current,  choose a cable size and match with breaker making sure breaker trip current is less than the cable can carry. 

 

With an instantaneuos water heater used for only short bursts like showering,  i personally would be ok using a cable size down.  Cable will heat up a bit but no harm done if you are aware of the dangers. 

[OneMoreFarang]

6 minutes ago, TimeMachine said:

With an instantaneuos water heater used for only short bursts like showering,  i personally would be ok using a cable size down.  Cable will heat up a bit but no harm done if you are aware of the dangers. 

Cable is not that expensive. Why save 1000B on something like that? 

[bluejets]

Mains large enough?

Meter appropriate size?

Long run from PEA transformer to your 8Kw electric muncher?

Time to start thinking oil burner.

[mahjongguy]

Slight topic drift: 

 

1)  I'm going to replace most of the 20A and 32A breakers that were installed by the builder in a Bticino QO-style cabinet with RCBOs. I can get Nano brand for about 500 baht, Chang brand for 700 baht, and real Schneiders for around 1,700 each. For a dozen breakers that's 6,000 or 8,400 or 20,400 baht. Any comments of the quality of Nano vs. Chang?

 

2)  I intend to replace the 3-pole 50A main breaker with a 63A model. Actually, since the mains are 16 mm2, I'm tempted to up the breaker size to 80A. That would allow me to feed 12A or more per phase to a 3-phase Juice Box. As best I can see from the Bticino catalogue, the installed cabinet is a 24 slot model 125A so it should be able to handle a 63A or 80A master. 

 

I am open to any and all questions, comments, and criticisms.

 

Cheers.

 

 

[Crossy]

12 hours ago, mahjongguy said:

Slight topic drift: 

 

1)  I'm going to replace most of the 20A and 32A breakers that were installed by the builder in a Bticino QO-style cabinet with RCBOs. I can get Nano brand for about 500 baht, Chang brand for 700 baht, and real Schneiders for around 1,700 each. For a dozen breakers that's 6,000 or 8,400 or 20,400 baht. Any comments of the quality of Nano vs. Chang?

 

2)  I intend to replace the 3-pole 50A main breaker with a 63A model. Actually, since the mains are 16 mm2, I'm tempted to up the breaker size to 80A. That would allow me to feed 12A or more per phase to a 3-phase Juice Box. As best I can see from the Bticino catalogue, the installed cabinet is a 24 slot model 125A so it should be able to handle a 63A or 80A master. 

 

I am open to any and all questions, comments, and criticisms.

 

Cheers.

 

 

 

1) For preference I would use the Bticino ones, around the same price as Schneider. These are the units guaranteed to fit and will maintain any type-approvals.

 

 

Nano and Chang are both low-cost alternatives, I've not used their plug-in units but the DIN ones are fine.

Schneider / Square-D are, of course, a well-known, decent quality brand.

 

2) Do you have your permanent supply meter? If not don't replace your incomer until the inspector has been and gone.

 

What size meter do you have? I wouldn't go over 65A on a 15/45, it's not going to explode but the accuracy falls off at high current, bet it won't read low!

 

Is your incoming cable copper or aluminium? 16mm2 copper should be good for 90A in free air, aluminium 70A.

 

As always, Up2U.

 

[mahjongguy]

Thanks for the well-considered reply.

 

1) Well, okay, I'll buy the most expensive brand.   ????

2) At the moment we have a mechanical 3-phase 15/45. In a few months PEA should finally process our contract application and put in a TOU meter. I don't know what the specs will be. 

3) The mains cables are strictly copper. They run about 15 meters, most of that distance underground in striped black hose.

 

[Crossy]

Consider which circuits really need an RCBO.

 

Don't worry: -

Inside lights

Inside outlets that aren't likely to feed stuff used outside (bedrooms etc.)

Aircons

 

Do worry: -

Outside lights

Outside outlets and inside outlets that might get garden tools etc. plugged in

Outlets in wet rooms and the kitchen (but consider having an "unprotected" circuit for the fridge / freezer)

Water heaters

The Shed

Pool stuff

 

[Crossy]

Your TOU when it comes will likely be an electronic meter, they are all 5/100 so no problem upping your incomer.

 

[mahjongguy]

2 hours ago, Crossy said:

Your TOU when it comes will likely be an electronic meter, they are all 5/100 so no problem upping your incomer.

 

That is excellent news.

[mahjongguy]

You think it unnecessary to put RCBO on aircon units? They are metal, they have 220 inside, often sit in wet areas. So I just assumed...

 

 

[bluejets]

Seems the one aspect of the install most forget is the importance of calculation of the voltage drop.

It's ok to waffle on about how one intends to replace this with that and "get more oomph" but one of the critical and just as important and often never given a thought to aspect is the aforementioned.

[Crossy]

16 hours ago, mahjongguy said:

You think it unnecessary to put RCBO on aircon units? They are metal, they have 220 inside, often sit in wet areas. So I just assumed...

 

If correctly installed and grounded there's no risk from an internal L-E short, the MCB will open. They are not portable so no trailing cable to cut.

 

This assumes your system is wired to the required TNC-S with MEN earthing (a N-E link in the distribution box).

 

If you are TT (no N-E link, just a rod) then everything needs earth leakage protection to be 100% safe.

 

 

[mahjongguy]

On 8/27/2023 at 8:29 AM, Crossy said:

This assumes your system is wired to the required TNC-S with MEN earthing (a N-E link in the distribution box).

 

Is it correct to say that the main reason to add MEN earthing to a TNC-S system is to avoid the dangers of PEN failure?

[Crossy]

6 minutes ago, mahjongguy said:

Is it correct to say that the main reason to add MEN earthing to a TNC-S system is to avoid the dangers of PEN failure?

 

It's right up there with the main reasons yes.