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Stiebel Eltron Tells Me I Need # 10 Wire and A 40A Breaker or A Free Exchange


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Firstly let me start by saying Stiebel Eltron is an amazing company and a pleasure to deal with.

 

I recently had a new house built and purchased Stiebel Eltron DDH 8 EC 8000W water heaters to feed kitchen and bathroom sinks only. No tubs no showers.

From the day one, I have not been happy with the  way these units have been performing. I knew I should be getting much hotter water.

Last week one of the units only worked sometimes. Turned the unit on and off but just got cold water. An hour later it seemed to work fine.

I found Stiebel on Facebook and sent them a message. Couldn't have been more than 10 minutes and they replied. They said as the units are under warranty, they will have their Tech call for an appointment to check out the units. A few hours passed and the Tech was on the phone. He said he could be at my home on Sunday at 1PM. Sure enough he showed up today at 12:30 with a box of new parts.

He changed just about ever thing in the unit but it just didn't help. Then he checked the power and said it doesn't look right. He went to the breaker box. He got on the phone and called Stiebel. I was surprised someone answered on a Sunday.

He handed me the phone. The Stiebel person who spoke perfect English said the following.

 

She said the 8,000W unit requires #10 wire and a 40A breaker. She continued to say that I had #6 wire and a 32A breaker. She said this is why the unit is not operating properly.

Now here is the shocker. She said it's expensive to change the wiring and breakers and offered to swap the units for their 6000W units. She said they will work fine. In my 13 years here in Thailand, no company has ever come close to resolving any issues.

 

OK now here is my delimah. I checked the unit specs on the Stiebel website that states the 8000W unit requires #6 or 8 wiring and a 40A breaker. Do I just change the breakers which could be costly. Or allow them to swap the units which will cost me nothing and hope that I am satisfied with 6000W Units.

 

Would appreciate your advise..

Edited by Jeffrey346
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That is quite probably the problem. I can pull the supply voltage down from 227V to 200V  by putting a 40A load on it, others have reported even greater drops. So your only option maybe to get the sma

A 6000w heater should be adequate for kitchen and bathroom sinks.    Note that the cable size can come in two measurements... either mm2 (i.e. the cross sectional area of the cable) or as AW

...if you aren't getting hot water now with an 8000W unit (that isn't popping the breaker) then I'm not sure how going with a 6000W unit would help.    Questions: Have you put a handhe

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The breaker protects the wire. Changing it will not make the heater any better or any worse.

 

Change the wire or use a lower wattage heater. How long is the wire run from the consumer unit to the heater?

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Maybe you should have chosen Solar water heating, no electric, maybe more expensive

in the beginning ,but the savings over the years,the weather here is perfect for solar.

regards worgeordie 

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I would opt for the lower wattage heater but maybe check what the price difference is and get some cashback?

Edited by NanLaew
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A 6000w heater should be adequate for kitchen and bathroom sinks. 

 

Note that the cable size can come in two measurements... either mm2 (i.e. the cross sectional area of the cable) or as AWG (‘gauge’ measurement) 

 

Thus: knowing whether the cable is 8mm2 or 8 AWG is important. 

 

Stable Eltron being a German company is likely to use mm2 as their measurement. 

 

 

https://1xtechnologies.com/mm-to-awg/

 

 

We had similar issues in our Condo about 10 years ago - the MD of Stable Eltron turned up with an Electrician - they found the problem. 

The mains electrical cable 10mm2 was not quite long enough (Thai electrics eh !) thus the electrician we employed to install the heater simply used a 4mm2 cable to ‘extend’ the electrical cable so it could reach the 8000w heater. 

The 4mm2 cable burnt out. 

 

Stable Eltron fixed the issue and somehow managed to ‘work’ some more of the 10mm2 cable through the interior wall conduit to provide sufficient length and rewired the heater. 

 

Summary: Let the Stable Eltron guys get on with it - they know what they are doing. 

 

 

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...if you aren't getting hot water now with an 8000W unit (that isn't popping the breaker) then I'm not sure how going with a 6000W unit would help. 

 

Questions:

  1. Have you put a handheld digital ampere meter on the live wire feeding the Stiebel Eltron DDH 8 EC 8000W water heater to see what current it's drawing when heating? (ref 220-240V 36.6-39.6A)
  2. is the electrical pvc feedline jacket to the Stiebel hot to the touch when it's been on and heating?
  3. What, of the three available power level adjustments is the unit currently set to use?
  4. Are you experiencing any light dimming or fan rpm speed changes in the house that might indicate your mains electrical feed from the pole isn't up to snuff?
  5. Are the waterlines to the sinks insulated (without a recycle system the initial water that's sitting in the line uninsulated can be cooler than desired)? ...and
  6. Do you have a temperature thermometer, what is the COLD water temperature and the HOT water temperature at the nearest and farthest tap?

 

 

 

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We have used 6kw steible Eltron water heaters for years. We have never had them full on.  No2   about half way is the maximum for us. Great water heaters.

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I'm assuming you have 6mm2 cable and Stiebel suggest 10mm2.

 

6mm2 THW is good for 48A in free air your 8kW heater will pull about 36A - no issue there unless your cable run is very long when volt-drop may become an issue.

 

The 32A breaker, if it's not opening is marginal but OK. Breakers are inexpensive so you could swap it for a 40A unit but I would expect it to make no difference.

 

BUT

 

As others have noted it's quite possible that your house supply voltage is dropping off significantly when the heater is operating. We're not far from the transformer but the voltage at our distribution board drops by about 20V when we run the 8kW heater. A 10% drop in supply voltage will give about a 20% drop in heater output (power is related to V2).

 

Get a cheap multimeter and measure your incoming supply voltage at the board without the heater then with it running. Publish the results here.

 

It's also possible that there is a poor joint in the 6mm2 between your board and the heater (which is possibly what the man noticed) checking the voltage at the heater with it off and then running and comparing with the voltages at the board will give you an idea.

 

For interest here is a graph of heater power vs supply voltage.

 

Heater.jpg

 

 

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1 hour ago, Crossy said:

As others have noted it's quite possible that your house supply voltage is dropping off significantly when the heater is operating.

That is quite probably the problem. I can pull the supply voltage down from 227V to 200V  by putting a 40A load on it, others have reported even greater drops. So your only option maybe to get the smaller heaters.

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2 hours ago, Crossy said:

I'm assuming you have 6mm2 cable and Stiebel suggest 10mm2.

 

6mm2 THW is good for 48A in free air your 8kW heater will pull about 36A - no issue there unless your cable run is very long when volt-drop may become an issue.

 

The 32A breaker, if it's not opening is marginal but OK. Breakers are inexpensive so you could swap it for a 40A unit but I would expect it to make no difference.

 

BUT

 

As others have noted it's quite possible that your house supply voltage is dropping off significantly when the heater is operating. We're not far from the transformer but the voltage at our distribution board drops by about 20V when we run the 8kW heater. A 10% drop in supply voltage will give about a 20% drop in heater output (power is related to V2).

 

Get a cheap multimeter and measure your incoming supply voltage at the board without the heater then with it running. Publish the results here.

 

It's also possible that there is a poor joint in the 6mm2 between your board and the heater (which is possibly what the man noticed) checking the voltage at the heater with it off and then running and comparing with the voltages at the board will give you an idea.

 

For interest here is a graph of heater power vs supply voltage.

 

Heater.jpg

 

 

Thanks for the reply.. Yes the cable is 6mm2. The heater is about 8m from the circuit box.

The Tech measured the volts at the box which was 220. He measured the volts at the box with heater off 220v.. with heater on it dropped to 204v.

I do notice that when I turn the hot water on the lights in the bathroom dim and the fan sloes down as well. 

Could this be a result of the power coming into the house?

IYO, do you think I should allow Srieble to install 6000w units, OR change the breaker and check the results?

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10 hours ago, stubuzz said:

The breaker protects the wire. Changing it will not make the heater any better or any worse.

 

Change the wire or use a lower wattage heater. How long is the wire run from the consumer unit to the heater?

About 8 meters from the box to the heater.

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10 hours ago, NanLaew said:

I would opt for the lower wattage heater but maybe check what the price difference is and get some cashback?

I am grateful that Stiebel will do the swap at NC. Not looking for cash back.

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10 hours ago, richard_smith237 said:

A 6000w heater should be adequate for kitchen and bathroom sinks. 

 

Note that the cable size can come in two measurements... either mm2 (i.e. the cross sectional area of the cable) or as AWG (‘gauge’ measurement) 

 

Thus: knowing whether the cable is 8mm2 or 8 AWG is important. 

 

Stable Eltron being a German company is likely to use mm2 as their measurement. 

 

 

https://1xtechnologies.com/mm-to-awg/

 

 

We had similar issues in our Condo about 10 years ago - the MD of Stable Eltron turned up with an Electrician - they found the problem. 

The mains electrical cable 10mm2 was not quite long enough (Thai electrics eh !) thus the electrician we employed to install the heater simply used a 4mm2 cable to ‘extend’ the electrical cable so it could reach the 8000w heater. 

The 4mm2 cable burnt out. 

 

Stable Eltron fixed the issue and somehow managed to ‘work’ some more of the 10mm2 cable through the interior wall conduit to provide sufficient length and rewired the heater. 

 

Summary: Let the Stable Eltron guys get on with it - they know what they are doing. 

 

 

Thanks for the response. The cable is 6mm2

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16 minutes ago, Jeffrey346 said:

The Tech measured the volts at the box which was 220. He measured the volts at the box with heater off 220v.. with heater on it dropped to 204v.

 

That's going to make your 8kW heater into a 6.5kW heater to begin with 😞  but it's still within the 10% variation allowed so PEA are not going to do anything about it.

How far are you from the transformer?

How far from the pole with the meter to the house?

Can you see the cable size that's coming from the meter?

What meter do you have (5/15, 15/45, 30/100)?

 

Did he also check at the heater? 8m of 6mm2 shouldn't give much in the way of volt drop, about 3V @ 40A, so it's worth checking what you are actually getting.

 

How are things with the heater set on the middle heat?

 

EDIT Do you have a multimeter? It may be an idea to go and buy one, they're not expensive and even Tesco sell them.

 

EDIT 2 You may consider going for a gas heater. Not expensive and 10kW units are readily available. Careful instalation / ventilation is needed but if you like lashings of hot water ...

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7 hours ago, RichCor said:

...if you aren't getting hot water now with an 8000W unit (that isn't popping the breaker) then I'm not sure how going with a 6000W unit would help. 

 

Questions:

  1. Have you put a handheld digital ampere meter on the live wire feeding the Stiebel Eltron DDH 8 EC 8000W water heater to see what current it's drawing when heating? (ref 220-240V 36.6-39.6A)
  2. is the electrical pvc feedline jacket to the Stiebel hot to the touch when it's been on and heating?
  3. What, of the three available power level adjustments is the unit currently set to use?
  4. Are you experiencing any light dimming or fan rpm speed changes in the house that might indicate your mains electrical feed from the pole isn't up to snuff?
  5. Are the waterlines to the sinks insulated (without a recycle system the initial water that's sitting in the line uninsulated can be cooler than desired)? ...and
  6. Do you have a temperature thermometer, what is the COLD water temperature and the HOT water temperature at the nearest and farthest tap?

 

 

 

Thanks for the response.

 

1. The current was 204 with the heater on.

2. The wire is NOT hot.

3.The unit is set to #3. Please note I am getting hot water but not hot enough.

4. Yes, I am getting lights dimming and fan slowing.

5. The water line from the heater to the sings are hot water rated.

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