[werdegast]

I am installing a water heater in an existing shop. The existing load center is not large enough and either a sub-panel will have to be installed or another load center. Would it be advisable to install another load center in between the existing center and the meter/service entrance?


M Meter
|
|
|----LC----WH New LC and water heater
|
|
|
|
|----LC Existing LC



My brother has a similar setup in his house but something about it seems off to me.

 

[TarheelTerp]

The existing load center is not large enough and either a sub-panel will have to be installed or another load center.

That's a very common situation. Happens everyday.

Would it be advisable to install another load center in between
the existing center and the meter/service entrance?

This is a building specific question.

The most common approach is to mount the additional panel near to if not
immediately next to the existing panel (using shorter lengths of bigger wire)... and then to run new/additional circuits from there (using longer lengths of smaller wire) as needed.

hth

 

[werdegast]

The existing WH is LP and will be replaced with the Tankless Electric (along with the new LC expansion).

If I use a sub-panel the current LC will need upgrading (100 amp). Adding the additional LC would be much easier.

The service into the building is 200 amp.

The water heater will be on the opposite side of the building (about 40') and I was going to add the new LC next to the WH. The power will come into the building and then branch into two for the separate LCs.

I hope that makes sense

 

[rrolleston]

What size tankless water heater. I have installed some and know that they are very few that are under the 100 amp range. Unless you live in a very warm area.

 

[werdegast]

It is an Ecosmart 18. According to the specs the max amp draw is 75 amps. It does require two 40 amp breakers. One for each heating element.

http://www.ecosmartus.com/products/electric-tankless/eco-18.aspx

 

[frenchelectrican]

Did you ever done a load demand caluations yet ?? those tankless electrique water heater can get pretty hard on the system and 18 KW is pretty good size heater and IMO the 200 amp service may barely hold on depending what ya got in the the house / shop.

That I will done in first place to make sure if your exsting service can handle the load of electrique tankless water heater.

Generally from my experince the 18 KW and larger tankless electrique water heater useally go with 320/400 amp service and that about only minuim service size can hold up without issue.

If you really want to keep the exsting 200 amp service there will be couple issue it will come up is.,

A) for sure you will need subpanel for this if you are pretty full in your breaker box.

B) expect lights to flicker when the unit cycle. ( this will get worst during summer time when you have Central Air running or couple window shakers )

C) some case you will either pop the POCO transfomer fuse or make smoke come out of the transfomer ( genrally they only put a transfomer large engough to handle the basic load but once you have tankless electrique water heater they will upsize the transfomer )

Merci,
Marc

 

[J. V.]

Just install a sub panel in a convenient location. Anywhere is the answer. It does not need to go in any special spot and trying to install it like you suggest is silly and hard to do. Why in between meter and existing Panel? You gonna make the new panel a service panel?
Search this forum using the keywords ( sub panel, garage sub panel) you see where I am going? Right?
There is more information on sub panels on this forum. It is by far along with 3 and 4 way switches the most hot topic here.

Now, read Marcs post above. French Electrician. Read and take his advice.

Do you mind if I ask why you decided on a tankless WH? I am curious.

The addition of a whole house system will require much power and it will require a qualified electrician to provide this power.

 

[AllanJ]

If the existing first main disconnect for the building is the master breaker in the first load center doesn't the second load center (also with a master breaker up top and if not a subpanel) have to be installed next to the first so both panels' master breakers can be flipped off together quickly?

In most cities, adding or replacing a load center (that is not a subpanel) or service entrance requires a separate permit.

Whereas a subpanel usually does not need a separate permit from the rest of the project i.e. the water heater per se.

You must do the load calculation per the NEC and do the possible service upgrades and permits related to that. You may not simply make your own judgment and live with planning what appliances you will use and when, and put up with the issues and dimming lights etc.

 

[rrolleston]

Our POCO did not upgrade the transformer unfortunately so everyone experiences a voltage drop I am sure I cook some oil. I would definitely make sure they understand the increased usage.

I think my problem was I bough this about 13 years ago and it was a rare item so they did not really understand what I was trying to tell them. Still very rare that anyone uses them. But I hopefully they have a better understanding now.

 

[werdegast]

Thanks for all the info.

I spoke to my utility and it would require a major overhaul of the shop electrical system to power a tankless heater. Instead of spending the big$$$ I will stick with LP.

If anyone is interested Ozark Border Electric Cooperative is a great power company.

 

[frenchelectrican]

Thanks for all the info.

I spoke to my utility and it would require a major overhaul of the shop electrical system to power a tankless heater. Instead of spending the big$$$ I will stick with LP.

If anyone is interested Ozark Border Electric Cooperative is a great power company.

I am glad you are making a right move to use the GLP ( Propane ) verison this will work alot better and will not affect the exsting electrique system however still there is a other gotcha instead of electrique system now we are dealing with gaz the GLP pipeing size it may need to be increase depending on the BTU of burner size.

This part will depending on gaz pipe size and distance to the tank and if you have primary ( high pressure ) and secondary regulatour ( low pressure ) ( if you have them that will help a bit )

Cost wise between the gaz and electrique verison is not very wide at all. but venting is the other item unless you have outdoor tankless heater it may be ok but not 100 % for sure depending on how cold it get in your area.

Merci,
Marc

 

[werdegast]

I am glad you are making a right move to use the GLP ( Propane ) verison this will work alot better and will not affect the exsting electrique system however still there is a other gotcha instead of electrique system now we are dealing with gaz the GLP pipeing size it may need to be increase depending on the BTU of burner size.

This part will depending on gaz pipe size and distance to the tank and if you have primary ( high pressure ) and secondary regulatour ( low pressure ) ( if you have them that will help a bit )

Cost wise between the gaz and electrique verison is not very wide at all. but venting is the other item unless you have outdoor tankless heater it may be ok but not 100 % for sure depending on how cold it get in your area.

Merci,
Marc

The heater is already in place and working. I was only thinking of replacing the existing WH with a new one.

It is used in a shop and only supports a shower, sink, and power washing bay.

 

[rrolleston]

I have though a few times about getting lp gas tankless so I can switch between electric and lp gas depending on what is cheaper. The time I installed the electric one I did not really care to do the huge size vent and upgrade all my gas lines and the propane soared to over 4 bucks a gallon the year we wanted to switch to tankless so that was our main reason in deciding. But it would be nice to have the gas for when that is cheap and when the power goes out.