# How many wattage is your bathroom electric heater actually?

The omni wattmeter can't show power factor. The US KillAWatt meter can? But it doesn't have 240v version so I'm stuck with the only wattmeter in my country.

YouTube video of the wattage measurement

https://youtu.be/mPzP-6Nqt9E

I need to determine maximum wattage that can be drawn because i'm migrating it to subpanel with total whole house GFCI breakers.

This is the heating elements:

Notice the last 2 were wired shorted. So are these one or two heating elements pair? How is it wired?

This is thermal scan of the heating elements a few seconds after turning on the faucet.

It shows all are energized.

This is the reading in the plug-in wattmeter showing 1278 Watts while the faucet is turned on and thermal scanner on.

This is top left side of heating elements showing the thermal cutoff fuse (once it tripped and the technician taught me how to push it to turn it back on):

This left side of it showing the wires from elements to the circuit:

This is front of it:

Zoomed out view:

What kind of usage that you can enable the entire 6000watts of heater element? I can't seem to get the wattage in my WattAMeter. Is it an overated heater? Based on the internal parts. Which one is the heating elements? I want to know how many there are. Also if it's really 6000watts/240v= 25A, the plug is only rated for 15A and could melt.

It's a Multipoint electric heater in bathroom. Since it has no EGC, it's connected to a GFCI breaker. I'm trying to estimate the wattage actually used. I plugged a KillAWatt meter to measure wattage consumption. It has at most only 1800 Watts maximum at all temperature which is about 1800/240v= 7A. Although it averages 1200 Watts most of the time. I have two of these exact units so it can't be both are defective. They heat well. But the specs of the heater says it is 6kW. Why is the meter showing smaller value of the wattage? Also the temperature setting is supposed to just control water flow, right? I used medium and maximum setting, the wattage didn't change. What wattage did you actually measure and what is the theoretical one that should come out?

This is its specs:

http://zetaorion.com/alpha-electric/product/vizz-98-e-ep/

click 98EM (M for Multipoint which I have)

• Try it again with Kill-a-Watt, and look at power factor (PF). Or you can compare VA to Watts. Plain electric heaters always have a PF of 1.00, or VA=watts. If power factor is other than 1.0, and especially if it changes with flow, that means there is electronic control of the heater going on, and it is drawing less than it is able . Feb 2, 2019 at 0:30
• Please see edited post for the youtube video showing possible pf. Is the RT 2.4% the pf?
– Jtl
Feb 2, 2019 at 0:42
• I found the manual of the omni wattmeter. It doesn't have PF (power factor). RT means Ratio of operating condition: 0 to 100% (see edited additional manual pic). Not related to PF. Is there other way to determine the PF?
– Jtl
Feb 2, 2019 at 1:40
• Not if the meter doesn't support it, no. But the fact of non-stepped electronic control explains everything, it is indeed electronically regulated, that is limiting the current. If the inlet temperature was lower, or if you flowed more water, it would draw up to the nameplate. Feb 2, 2019 at 4:58
• One of your photos suggests that you were blown out of your shoes. Did you accidentally touch a hot wire? Feb 2, 2019 at 7:10

I only see 1 heating element on that 6kw heater is there a second one in the back? I did notice one of the wires going through what may be a current transformer so the unit can detect the amount of power being used. With the temp control being electronic there may be some calibration settings since it has electronic control turn the temp knob all the way up and flow as much water through as possible. If your water is reaching temp it may not draw the full 25 amps that a 6kw heater can require. If your water is not reaching the correct temp and you are not drawing full amperage the control board(s) may be faulty, contact alpha. From looking on line this could be a common problem if less than a year old it should be under warranty and the comments on line were positive about alphas customer service.

• Ok there are 2 elements probably in parallel that's why they may look shorted to the untrained eye. Since your water is achieving its set point or two hot it sounds like the electronics are working properly. If the water was cool or not hot enough the heater would be drawing full current since the water is hot the electronics limit the power , if the electronics did not limit the power to the heater you would probably get scalded. I believe the system is working properly. Feb 2, 2019 at 17:14
• JTL, you have a heater that is controlled by electronics. The bar across the elements is probably putting them in parallel. The potentiometer controls the power to the elements as you have found because the heater is not currently drawing full load. For your new panel. Use 30 amps, this is what would be required in the US. You stated you have poor water pressure if you add a water tank and booster pump I am sure that heater will draw 25 amps or close with full listed flow at max temp. You are over thinking this, the water is hot, the heater is working. I am not so sure about your measurements Feb 3, 2019 at 8:42
• It is wrong to put a 25 amp device on a 60 amp breaker. You said you wanted to us the NEC. Code has a max breaker size of 1.5x the listing value and with electric heat code is more restrictive. Each heater should have a 30 amp breaker using #10awg wire. I tried to leave a longer comment in chat but it was not working. Your plug at 15 amps is a hazard waiting to happen, especially when using a 60 amp breaker. In the US these heaters usually do not provide enough heat or that is the major complaint. Since your water is making temp I would just set things up to the mfg requirements 6kw or a 30amp Feb 3, 2019 at 9:26
• Since the heater states 6kw in the photo I would believe it. With the power off you could measure the resistance of each element end to end and then do the math using ohms law. This would have been a much simpler question if asked that way. Feb 3, 2019 at 9:50
• With the power off measure the resistance of each element E squared / R = will provide the wattage or 57600/ 9.6= 6000 . Since there are 2 elements in parallel I would expect them to measure approx 18 ohms each maybe up to 20 putting 2 elements in parallel cuts the resistance in half you may see 9 or 10 ohms when measuring the elements depending on the electronics and how the power is controlled. Feb 4, 2019 at 14:19

I doubt anything drawing 8kW is going to have a plug, but if it did it would be a very large plug like an electric stove or clothes dryer. That said, these heaters typically have multiple heating elements. It's possible that not all the elements are turning on based on the water flow or that some of the elements are bad.

From what I could find on that product, it seems to be sold in Malaysia. If it was sold in the US, it would have a label or plate that listed the electrical requirements on the back or on the inside of the wiring cover. I'm not sure if that's true in your part of the world, but I would look for such a label rather than relying on information from the internet. For simple devices like a heater, those electrical requirement labels tend to be accurate.

Edit based on internals:

The large copper "tank" on the right is the heating unit, and there seems to be only one. The label indicates that it could use up to 6000 watts at 240v. The label in the bottom right also seems to indicate 6kW is required. To me, that indicates that the wiring going to the device should be rated to handle 6kW (25 Amps). If the plug it's going to is protected by a 15A breaker, then you wouldn't have to worry about melting wire - you would just trip the breaker if too much power was used.

The two tubes at the bottom would be the water inlet and outlet. There might be a flow sensor on the inlet side behind the bracket. The wires connected to the bottom of the heating unit look to be a high-temperature cutoff switch that's common on heating appliances - or even just a temperature sensor.

The copper stubs at the top of the tank are the ends of the heating elements. It's hard to tell, but it looks like there might be 4 stubs which would be the two ends of two heating elements. Because there are so many wires going to the top, there could be some multi-stage electronically controlled magic going on that only uses the current needed to heat the water to a set temperature. Incoming water temp and flow rate could determine the amount of power needed.

The black box with the two red wires on top of the heating element might be some type of high-pressure cutoff. I don't think you would need red, thick wires for a temperature or flow sensor.

• I can't see the label in the unit but I edited the post to share the exact specs of it. In the Philippines. All of our bathroom heaters use plugs right inside the bathroom outlets, without any EGC or GFCI. This was why I connect it directly to the GFCI breaker for protection since it's near the bathroom floor.
– Jtl
Feb 1, 2019 at 5:30
• That's one of the charts I found online, but on another product page there was a listing that said 3kW-8kW and another that said 3.6kW. I wasn't sure what to make of the discrepancies, so that's why I mentioned you might not be able to trust them. As long as your Kill-a-watt is made for 240v, it shouldn't be wrong on a simple heater. I would trust what it says, but I would also wonder about multiple heating elements as I mentioned. If the 3.6kW figure is accurate, 1800W could mean that one element is on (half of 3600). Feb 1, 2019 at 5:38
• I'm not sure, but I wouldn't be surprised if they existed. Yours might have one element - I'm just making assumptions based on other designs I've seen. In general, there seems to be a maximum wattage that designers use for single elements, so if the heater needs more power, they use multiple elements. I guess that the max wattage is determined by the wire size and physical size of the element. Multiple elements also make scaling up the device easier. Want more capacity? Add another element (with no more design money going into a bigger element)! Feb 1, 2019 at 6:05
• YouTube has several videos of the inside of "electric tankless water heaters" (what we call them in the US). We have "whole house" electric heaters that can use over 100 amps of power! In the US, one heater for the house is normal rather than smaller point-of-use devices. Feb 1, 2019 at 6:07
• Whole home heaters are more expensive and typically more advanced. For instance this model uses flow control and heater control to heat water as efficiently as possible. Flow control is used to make sure you get hot water even if its less flow than normal and the heater control makes sure the water doesn't get over-heated for lower flow applications. So, it's going to depend a lot on the model and how advanced (expensive) it is. Feb 1, 2019 at 6:32