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

[Jeffrey346]

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..

[stubuzz]

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?

[worgeordie]

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 

[NanLaew]

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

[richard_smith237]

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. 

 

 

[RichCor]

...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?

 

 

 

[uncleP]

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.

[Crossy]

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.

 

 

 

[sometimewoodworker]

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.

[Jeffrey346]

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.

 

 

 

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?

[Jeffrey346]

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.

[Jeffrey346]

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.

[Jeffrey346]

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

[Crossy]

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 ...

[Jeffrey346]

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.

[Oldie]

Seems to be a typical Thai installation. They are used to maximum 6 kW. My ex girlfriend got one installed like this for a 9 kW heater. The breaker always switched off and then the guy told her that the heater has a problem. Then she contacted me. And I told her that this can't work. And even worse. Her house connection with 4 aircons wasn't not strong enough too. If anybody needs an unused Stiebel Eltron heater in Pattaya please contact me...

 

[Jeffrey346]

3 minutes ago, Crossy said:

 

That's going to make your 8kW heater into a 6.5kW heater to begin with ???? 

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?

Set on high #3

 

How far are you from the transformer?

My guess.. about 150m

 

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

About 10m

 

 

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

I'll try to check it out.

 

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

15/45 meter

[Crossy]

Volt drop seems high for being that close to the transformer, but as I said it's within the 10% allowed.

 

Everything else looks OK but do see if you can see the wire size although only 10m probably won't matter.

 

Have you tried the heater on #2? That's likely the equivalent of the 6kW heater anyway. 

[Jeffrey346]

7 minutes ago, Crossy said:

Volt drop seems high for being that close to the transformer, but as I said it's within the 10% allowed.

 

Everything else looks OK but do see if you can see the wire size although only 10m probably won't matter.

 

Have you tried the heater on #2? That's likely the equivalent of the 6kW heater anyway. 

The wire at the pole says Bangkok Cable 700v. Can't see the rest of what's printed.

I just tried the unit on #2. No blink in lights or fan speed but the water is just warm.

 

[lopburi3]

As one who has never found equipment of that brand name to work well here am not a fan - do understand it has more to do with electric and installations than the equipment itself.  We find no need for hot water in kitchen (have dish washer which makes its own) and in bathroom just pull the shower point of use to fill sink for a shave.

 

Using the lower wattage unit might help to keep voltage high enough to provide hot water if you can not lessen the drop (can you change from single phase to three phase power perhaps?).  

[Crossy]

10 minutes ago, Jeffrey346 said:

I just tried the unit on #2. No blink in lights or fan speed but the water is just warm.

 

Reduce the flow or use a low flow shower head.

 

I'm not convinced that replacing the heater with 6kW is going to help but if it's a free swap ...

 

EDIT If you do go for the swap ask the tech to check the voltage at the heater (heater on) before he swaps it out. If it's significantly lower than the voltage at the board then that needs looking at first.

 

Our 6kW Mazuma makes the water too hot for me at present (northern BKK so it's not really chilly) it only really gets used on full power on the cool winter mornings.

[Jeffrey346]

2 minutes ago, Crossy said:

 

Reduce the flow or use a low flow shower head.

 

I'm not convinced that replacing the heater with 6kW is going to help but if it's a free swap ...

 

Our 6kW Mazuma makes the water too hot for me at present (northern BKK so it's not really chilly) it only really gets used on full power on the cool winder mornings.

The unit only feeds the sink. I had the water reduced and got much better results but the Steibel Tech said the pressure sensor may shut down the heater. 

[Crossy]

9 minutes ago, Jeffrey346 said:

The unit only feeds the sink. I had the water reduced and got much better results but the Steibel Tech said the pressure sensor may shut down the heater. 

 

I'll bet that it's the flow that's the real issue, it would probably be the overheat that shuts down the heater unless you go really slow. Sinks do usually "need" hotter water but 8kW still seems over the top.

 

Restrict your hot flow so the water is how you like it then see if the heater cuts out.

 

 

[Jeffrey346]

25 minutes ago, Crossy said:

 

 

 

EDIT If you do go for the swap ask the tech to check the voltage at the heater (heater on) before he swaps it out. If it's significantly lower than the voltage at the board then that needs looking at first.

 

 

He checked the voltage at the water heater and it was 204 with the heater running on #3

[Jeffrey346]

1 minute ago, Crossy said:

 

I'll bet that it's the flow that's the real issue, it would probably be the overheat that shuts down the heater unless you go really slow. Sinks do usually "need" hotter water but 8kW still seems over the top.

 

Restrict your hot flow so the water is how you like it then see if the heater cuts out.

 

 

Great minds think alike as I just did that. The heater does not shut down but the water isn't as hot as it should be.. Quite a dilemma..  

[lopburi3]

1 minute ago, Jeffrey346 said:

Great minds think alike as I just did that. The heater does not shut down but the water isn't as hot as it should be.. Quite a dilemma..  

This is the issue I have seen in those units used in hospitals and hotels here - just about impossible to balance flow to get temp you want without cutting out or burning up.  Do you have constant water pressure at good PSI/BAR?

[Crossy]

3 minutes ago, Jeffrey346 said:

Great minds think alike as I just did that. The heater does not shut down but the water isn't as hot as it should be.. Quite a dilemma..  

 

How hot is "should be"? How hot is it? What's the flow rate? Incoming water temperature?

 

We're getting into the realms of physics now. There's only so much energy your heater can add to the water.

 

[Jeffrey346]

3 minutes ago, lopburi3 said:

This is the issue I have seen in those units used in hospitals and hotels here - just about impossible to balance flow to get temp you want without cutting out or burning up.  Do you have constant water pressure at good PSI/BAR?

 

3 minutes ago, Crossy said:

 

How hot is "should be"? How hot is it? What's the flow rate? Incoming water temperature?

 

We're getting into the realms of physics now. There's only so much energy your heater can add to the water.

 

My water pressure comes from a 350W water pump. I know I have one but can't find my thermometer anywhere in the house.

The 6000w Panasonic shower heaters puts out very hot water. I can't understand why the Stiebel is not.

It kills me to go from 8000w to 6000w as I paid for 8000. 

[lopburi3]

3 minutes ago, Jeffrey346 said:

My water pressure comes from a 350W water pump.

That is not a large pump and if of the well tank type varies greatly between high and low pressure so could be causing heater flow cut off to activate on and off or having an issue remaining on.

[Jeffrey346]

43 minutes ago, lopburi3 said:

That is not a large pump and if of the well tank type varies greatly between high and low pressure so could be causing heater flow cut off to activate on and off or having an issue remaining on.

I don't have a well it's city water