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Phil
Phil, Mechanical Engineer
Category: Home Improvement
Satisfied Customers: 5942
Experience:  Retired contractor, 51 years experience
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Hi, We are building our new house and our electrician wants to instal

Resolved Question:

Hi,

We are building our new house and our electrician wants to install 2 single phase 60 amp lines to our property. He says our electrical requirements will need extra power.

I've listed the main power draw items.

2 Pyrolytic Ovens 30A
Fridge 1.3A
Dishwasher 10A
Heat Pump A 10.9A
Heat Pump B 4.4A
Lights 6A
Pool pump 2.4A
Sewer Pump 4.3A

There will be other stuff running the house e.g. computers and washing machine, but it is highly unlikely they will all be run at the same time. I think a SINGLE 60A supply with load sharing will be sufficient.

What do you think?
Submitted: 1 year ago.
Category: Home Improvement
Expert:  Phil replied 1 year ago.
Welcome to Just Answer!

If all of those appliances are 230 volt rated (approximately) then one 60 amp panel would get you by, but just barely... two 60 amp panels allows you the luxury of many more separate circuits.

There is another factor... any electric motor driven appliance draws roughly 3 times as much power during its 2 second start phase as it draws for running amps

Please tell me where you are in the world, nearest city so I can assess the power available in the region, and tell me the voltage of the appliances.

We can go from there tomorrow, I am off to bed right now, its 3 am here.

Phil
Customer: replied 1 year ago.

Hi, I'm in Auckland, New Zealand.


 


Are you saying a 2400 watt fan heater will draw over 30 amps on start up?

Expert:  Phil replied 1 year ago.

Thanks for the data.... take your electricians advice, he knows what he is doing, you won't regret it later.

 

The fan heater is largely a *resistance load, not a motor load, so will not draw 30 amps on start up... just the heat pumps and the sewage pump etc will draw 3x the running amps on start up.

I will be back in 8 hours if you need more elaboration.

Phil

Customer: replied 1 year ago.

Thanks for your help. We'd like to have the extra power but it we cannot afford it, hence my question on whether 60A will be sufficient.


 


I am hopeful load sharing resolves this issue e.g. put heat pumps and ovens on same line. I think a bit of common sense should ensure we don't blow the load per say.

Expert:  Phil replied 1 year ago.
Hello again, if the only loads you have are listed, then 'load sharing' called 'diversity' in this business would work quite well.

However most homes have several 10 amp rated wall receptacle circuits that you have not listed.

Each of these major appliances needs to be on its own circuit however... putting them on the same circuit is not load sharing, and will have no beneficial effect.

You have not listed a water heater... if the reason for that is that the water heater is gas fired, and you have not purchased your ovens yet, you can buy at least one gas oven to replace that 30 amp load... that would come real close to making just one 60 amp panel viable.

Let me know about all that, we can go from there.

Phil

Customer: replied 1 year ago.

Hi, yes water heating is via gas hence I did not mention it. Unfortunately we have already purchased the ovens and we cannot change this.


 


Also the 30 amps is a bit misleading for the ovens. They are pyrolytic ones and they each draw a maximum of 15 amps when used in pyrolytic mode. In normal operation I suspect they'll both be working at a max of around 10 amps like similar ovens.


 


The only other appliance I have not considered is a washing machine but again a bit of common sense will ensure we don't use it when we're running the ovens.

Expert:  Phil replied 1 year ago.
Hello again,

Using only one 60 amp main service panel would likely work with only an occasional over load.

Its a close call if the city will allow it or not.

Tell the electrician that if he can get just one 60 amp panel approved, with all of your loads listed you would like to install it that way because you are running out of money or whatever the case is.

You really do need the higher amperage service however. What is the difference in price?

Phil





Customer: replied 1 year ago.

The difference in price is substantial. We are staring down the barrel of between $1500 - $3000, depending on how much work the power company and electrician need to do to enable the extra power to our place.

Expert:  Phil replied 1 year ago.
Hello again, you could leave one or both of the 15 amp rated ovens off of the plans, ask the electrician to just 'rough in' the power to where an electric oven(s) 'will be installed later', and ask them to not connect it at the panel.

Tell them to set the job up so that you can add the additional electric service later. lets see what this does to their diversity calculations.

The city may have a rule that demands a certain minimum electrical service to a home depending on the size of the house, in addition to what loads are connected.... such rules are intended to prevent fires due to electrical service and circuits being installed that later get over loaded.

Let me know what you can discover, we can go from there.


Phil









Phil






That would leave you operating with just the smaller oven..
Customer: replied 1 year ago.

Hi, I just got an email from my electrician where's reworked the numbers and now feels comfortable that a 60A supply will be sufficient.


 


He said that there is a chance where you could trip the circuit if you use too many appliances at the same time but that is perfectly safe.


 


I think a bit of common sense will ensure we don't cause an overload.


 


Again, thanks for your help.

Expert:  Phil replied 1 year ago.
Hello again! Your persistence paid off!

I will put the ratings box up now, I do this work on my own time and a my own expense, the company pays me a portion of your deposit only if you rate my assistance positively!

Thanks!

Phil
Phil, Mechanical Engineer
Category: Home Improvement
Satisfied Customers: 5942
Experience: Retired contractor, 51 years experience
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Phil
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Retired contractor, 51 years experience