So I have the luck( or misfortune ) to have 3-phase service at my apartment. It would be great if I had some heavy industrial equipment to power, but I don’t. Instead I have an electric water heater designed for 240VAC operating with 208VAC for a heating capacity 75% of rated power. My stove suffers the same way by taking much longer to boil water and not being able to keep up while frying.
I’ve been shopping for an Inductive stove and all the ones I have found are rated 220-240VAC. It sounds as if it would not work well in my home.
Short of getting a transformer to convert my 3-phase 208VAC to 1-phase 240VAC, (big sucker, probably in the 10KVA range) are there any other ideas on how to correct this?
And while I’m thinking about this, does anybody know if the BC Hydro Smart Meters are able to compensate for this difference?
yes, only two phases are going to the water heater, another pair is going to the stove and the remaining pair goes to the dryer.
I’m trying to wrap my head around how this would take place, since my device would see V = ABS(Va - Vb) assuming that it’s connected to phases A and B, with Va being the voltage at phase A and Vb being the voltage at phase B. And the current I = Ia = Ib (it’s a purely resistive element). There is no neutral connection going to the water heater.
VA for my device then would be VA = ABS(Va - Vb) * Ia. However, the smart meter does not know that the device is attached to phases A and B, so the meter only knows Va, Ia, Vb, and Ib. How do you get ABS(Va - Vb) * Ia from Va * Ia, and Vb * Ib?
Expanding the formula gets VA = ABS( ( Va * Ia ) - ( Vb * Ib ) ) (remember that Ia = Ib). The smart meter would need to know that the power consumed in my home is VA = (Va * Ia) + (Vb * Ib) + (Vc * Ic), but because Va and Vb are not 180 degrees in phase, then … aaaaah my head hurts
I’m not sure I understand your confusion. If you consider the BC Hydro meter as measuring all three phases independently, why would the sum of real power not equal the actual real power?
I think your confusion might be coming from your assumption that Ia = Ib. This is not correct. Ia + Ib = 0. So what you’re measuring is simply P = (Va * Ia) + (Vb * Ib). Ib will always equal -Ia, so this simplifies to P = (Va * Ia) + (-Vb * Ia) or P = Ia(Va - Vb). Adding the abs() only makes sense for resistive loads, and isn’t necessary, since if Vb > Va, then Ia will be negative in that case. For reactive loads, measuring the correct sign is important.
I’d be surprised if you actually had a 3 phase panel (as they are more costly than single phase) as it’s more likely just 2 of the phases and a neutral…
Does your main breaker have 2 or 3 poles?
Aaah, that makes sense. Thanks, This does clear up my confusion.
Well, this is where it gets funny. When I first moved in, a friend who is an electrician pointed out that my breaker panel does not have a main breaker. The only “main breaker” I have seen is downstairs in the electrical room, there is a lever on the side of the box that is attached to the meter for my unit. I know there are 3 thick cables going into the breaker in my suite. Could be the 2 live + 1 neutral like you indicate.
I guess there is no easy solution to solve my need for 240VAC for an induction cook top, or to increase the heating capacity of my water heater (the dishwasher alone is able to drain the hot water to the point where it’s lukewarm. It’s a 3 year old tank and the plumber has checked it and said there is nothing wrong with the tank).
Take a look at your hot water tank label. It should show both a 240V rating and a 208V rating (naturally this will be roughly 85% of the 240V. When running on 208 it will not have the recovery of the 240 it should still heat water to the correct temperature.
Unless your hw tank is really really small then it should be able to handle a dishwasher. Some thoughts below but be aware that you will need to open the panels on the hw tank and run the risk of letting out the magic smoke in you if you touch live wires. Don’t do any of these if you are not confident working around electricity.
You mat want to:
Check the temperature setting on the hw tank. If it is too low then you will run out quicker. When my kid was young I kept it at 120F as this is below scalding. However I now keep it at 125F (still won’t scald right away but will hurt) as he is old enough to not be a worry… You will need to measure the water coming out of the tap rather than trust the dial on the hw tank thermostat. The higher the temperature the more warm water you get to use before draining the tank as the hot water is mixed with cold water at the tap to get the temp you want. An issue is that higher temps have a higher standby loss so that can cost you more $$
You may want to check the line voltage actually getting to the hw tank to make sure a bad connection isn’t limiting the power to the elements. Mebbe there is a bad connection
Typically hw tanks have two elements, a lower one that is normally used for heating the water and an upper one that only comes on if the tank is running out of water (as it only heats the top part of the tank). Only one can run at a time. If your lower element is broken then you are dependent on the upper one and you will not get much hot water.
Yikes! The label says “VOLTAGE: 240 1-PHASE AC ONLY” Maybe I should call the plumber and find out, as this tells me the tank is operating outside it’s certified mode.
177 Litres ( 47 Gallons)
My multimeter says 206V AC (It’s an old Fluke 77, so it doesn’t have true-RMS, not sure if that means anything).
Tested this before, both elements work (one at a time). I measured this by checking the voltage across each element as the tank empties. First the lower one turns on, and once the tank starts getting empty, the top one turns on.
Running the hot water tap for about 5 minutes shows 135 F.
Oh well, thanks everyone, I guess I just have to live with my 208V and the reality that we use a lot of hot water. ( P.S. Never tell your spouse that they are using too much hot water, unless you want to pick a fight )