Help Needed Balancing 3-Phase House System

Consider altering the distribution board connections so that the loads are more equally balanced across the phases. Whichever one that is top-left at the dis board is usually the one carrying the highest current; electricians work that way.

Yeah, the problem is my house has tens if not hundreds of loads, and they aren't all on or off at the same time.

For example, I am allowed 20kW total across the 3 phases, so about 7kW on each.

The hot water heater is 6kW, but it is only used for a few minutes in a day and for a few days in a month, so if I manually balance the loads across the 3 phases, I am using up capacity without using it, if that makes sense.

[by the way, thanks for the very speedy response ;) ]

You could create a spreadsheet.....(to autocalulate sums) figure out what all of your known loads are and figure out how to spread them across each phase.

You know the max on each one...but totals can be higher if the loads are intermittant as it might be difficult to balance for a worst case situation where everything is on at once. And once you caluclate that....you can make the appropriate changes in your breaker panel to suit.

Its going to take some work...but thats the best Idea I can come up with at the moment.

Yeah, thanks for the idea but that's not really going to help.

The problem is when we use a high load item and another one kicks in either on auto, or timer, or because someone in the house doesn't know.

example would be water heater and underfloor heating. Both are heavy load, but set on thermostats.

I need a circuit that sits between the loads and the supply and automatically routes the power through the phases equally. so if we are pulling 15kw, it pulls 5kW from each phase.

I didn't think this would be something I'd get from the local hardware store, but you never know?! ;0)

I did some searching before I gave that answer and for a house sized load, I couldn't find anything.....I had thought of a 3 phase to one phase converter which should automatically balance everything, but found nothing in the size you would be needing.

Not saying they don't exist....they must. I just couldn't find anything.

The problem with switching between phases...is the phases are not in sync with each other (as in the phases are different). A smooth transition would not be possible as a result

aha, ok thanks.

I guess the next step is to hack the govt. box and up the size of the fuses!!

Before you hack something up...give this thread a few days....there will be other and likely even better answers by people that haven't seen the thread yet.

Well, the fuses are there to protect the wiring. So, don't mess with their sizing otherwise there will be a decreasing popularity trend amongst domestic fire insurance companies.

It sounds like your primary power loads are water and under-floor heating. If other loads are relatively small, consider three water heaters at 2.5 KW, one on each phase and a single three-phase contactor on the thermostat. Divide the under-floor heaters in a similar fashion. Might work.

QL

A motor generator will provide a balanced draw from the mains regardless of unbalanced loads.

Thanks for that but I have no idea what you mean ;)

An electric three phase motor would be connected to your incoming power mains. The motor output shaft is coupled to a generator, which would provide power to your unbalanced loads.

OK, thanks for clarifying.

I was hoping to find a zero maintenance, plugin solution.

That sounds like it would require maintenance, generate noise, need a fair bit of space and cost a lot ;)

I know I want to have my cake and eat it. Maybe I'm stretching.

Still, I do appreciate your feedback, and it is something to consider.

Best

RT

I have had this same problem many times. I recommend a solution that exactly meets the stated goals only to have new conditions added. Oh well, fortunately this time it didn't cost anybody anything.

Thats what I was thinking. Maybe, something with a microcontroller (PIC, Stamp, etc,) that could measure the current load on each phase and connect the large loads to the lightest loaded phase when thier thermostats indicate they are ready to turn on. Not really plug and play but, real fun for a tinkerer like me.

If the OP is not interested in going that route, I would suggest doing a load profile and moving the largest loads around to balance the phases as much as possible. If you have to put a couple of large loads on the same phase, you could come up with a way to deactivate one or the other at different times of day. Say, if you had to put the electric stove and water heater on the same circuit and you always cook dinner around five, have the water heater turn off at 4:45, so you can cook dinner, then turn it back on at 6:30 so the water will be hot for showers and dishes. You would have to experiment with the times so they correspond to your lifestyle. I'm not sure what is available in your country, but here in North America they make timer panels. They are made specifically for water heaters, but should work for any load that has similar current ratings. They also have a manual overide if you ever have to deviate from your normal schedule. (Such as baking a cake or the Christmas Turkey for several hours during the day)

uC are fun but very complicated for something that simple, relay logic would be the best choice. It could be maintained by most electrician once he sells his house.

The only thing I can think of is a relay arrangement where non time critical high loads like the HWS, dryer are prohibited from switching on while other higher priority loads eg cooking are active.

Hi Roger

A simple solution but it comes with an inconvenience you could put some change over switches in so that if you want to use the oven you select the oven on the change over switch this will disable the water heating if you want hot water you switch the change over switch again and you get hot water but no oven.

I know that this is not the best of ideas, but it would be very cheap to install.

Other ideas that could be implemented are essential and non essential power circuits controlled through some form of micro controller that has been designed with piroity programming, but this would have a cost attached to it

Cheers

Joe

What country are you in?

Thanks everyone for your input. What a great community ;0)

I'm in Slovenia btw.

I think a cheap idea whilst I ponder the cost of the more advanced solutions would be to put a timer circuit on the water heater to come on only during sleeping hours, as the tank should keep the water hot all day anyway.

The water heater is usually the culprit that trips stuff out.

Don't know why I didn't think of this obvious fix myself, but that's what friends are for eh?

Thanks again.

Sorry to here of your plight with your country and its' stupid way of controlling the power. Actually, here in the USA, we have what is known as the National Electrical Code, a.k.a. NEC, you can find sollutions online at the NEC site. The NEC goes into detail in balancing solutions for power distribution, it is one of the requirements to pass and be certified as a master electrician in this country. Yes, as mentioned before, an electrical motor on a generator will actually be your best solution.

With a generator, a transformer, and a seperate distribution panel away from your incoming feeds, will grant you the freedom to not worry about being cut off by your country's power police. The price to pay at first will give you freedom for life.

Maximo

Roger,

Other solution could be to replace heater element with a 2KW element. Since this is probably a storage heater, it would not matter. It will only take a little longer to heat.

you might have a closer look at the water heater, there are generally 2 heating elements

you may be able to connect using a contactor [relay] to two different phases, assuming they are connected in parallel, the in floor heating probably also has several sections connected in parallel

I think this is on the right track. If it's his water heater that is the main problem, he would just need one of these to power that. The rest of the house could stay as is.

Does anybody manufacture a three phase water heater or oven? That would be the optimal balanced load. i.e. spread it evenly across all three phases to drop the current in any given phase.

Consider 3 phase loads for the higher loads, if available.