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#164059 - 05/24/07 02:55 AM Tankless Water Heater  
aldav53  Offline
Member
Joined: Aug 2001
Posts: 545
Chandler, AZ USA
Residential home - I'm wiring a tankless water heater that calls for 2 - 40 amp 240 volt ckts. It has 2 separate heaters. I was going to run 4-#8's and 1-#8 ground to a junction box on the flat roof (splice there) of the house then go in with 2-#8 NM's into the attic then down to 2 disconnects then to the tankless water heater.
Would it be legal to run 2-#4's instead to the junction box then split off with the 2-#8 NM's to the water heater (2 ckts). Probably be better to keep both cicuits separate all the way.


The Golden Rule - "The man with the gold makes the rule"

2017 / 2014 NEC & Related Books and Study Guides

#164060 - 05/24/07 03:39 AM Re: Tankless Water Heater [Re: aldav53]  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
It would be fine as long as you use fused disconnects at the taps.

I don't see much specific benefit to keeping them separate.

But I have no idea which way will work out better as far as costs.

By the way some power companies have rules regarding these units, it may come back to haunt the customer if their new water heater makes the neighbors lights flicker.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#164071 - 05/24/07 12:00 PM Re: Tankless Water Heater [Re: iwire]  
e57  Offline
Member
Joined: May 2003
Posts: 2,876
S.F.,CA USA
OCP(panel) or fused discos, otherwise it could be a tap rule violation. Depending on where the discos are. Why not go the whole distance as a feeder with a panel between them?


Mark Heller
"Well - I oughta....." -Jackie Gleason

#164096 - 05/24/07 09:22 PM Re: Tankless Water Heater [Re: e57]  
HotLine1  Offline


Member
Joined: Apr 2002
Posts: 6,853
Brick, NJ USA
I came upon a very confused resi guy a few weeks ago; he had a instant wtr heater that needed three (3) 40 amp 240 feeds! That poor boy was a lost soul!

Funny thing was...he did not have any mfg info, no book, no diagram, etc. The unit had one (1) 1-14 KO on the bottom, no place to punch any other KO's

John


John

#164104 - 05/25/07 12:44 AM Re: Tankless Water Heater [Re: HotLine1]  
aldav53  Offline
Member
Joined: Aug 2001
Posts: 545
Chandler, AZ USA
Its a 400 amp service. I fed it with 2 - 40 amp 240 volt breakers. The sub-panel on that side of the house was too small, so I just ran both circuits all the way from the main 400a panel. Fused at the panel plus 2 disc at the tankless WH area for convienience. Had to run the pipe across the roof, the only way to get there.


The Golden Rule - "The man with the gold makes the rule"

#164108 - 05/25/07 01:42 AM Re: Tankless Water Heater [Re: aldav53]  
mxslick  Offline
Member
Joined: Oct 2004
Posts: 803
Atomic City, ID USA
Sometimes being a sparky is a tankless job!! smile

I got lucky, just had to drop a single 120v, 20 amp to a gas-fired unit here at the apts. while helping the landlord.


Stupid should be painful.

#164137 - 05/26/07 12:24 AM Re: Tankless Water Heater [Re: mxslick]  
EV607797  Offline
Member
Joined: Oct 2006
Posts: 745
Fredericksburg, VA, USA
Yeah, but you got lucky because you are in Southern California where gas is the norm. You guys use gas for everything; I don't see how electricians make any money in Southern California. It's all dinky 15 or 20 amp circuits, maybe an occasional 30. Even 100 amp services that are practically unheard of in these parts!

Many other parts of the country don't have insane electricity rates that you guys have.

These tankless units are perfectly acceptable in many other areas of the country. Not to mention that many places don't have access to gas! Here were I live, gas is more expensive than electricity. My 3,000 SF house has a panel full of 30, 40, 50, 60 and 80 amp loads and my average electric bill is about $200.00.


---Ed---

"But the guy at Home Depot said it would work."

#164141 - 05/26/07 01:35 AM Re: Tankless Water Heater [Re: EV607797]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,099
Estero,Fl,usa
At my house, if it doesn't come from FPL we ain't got it, I don't even have a water bill (well) We still get by on $200 or less most of the year. This spring it has been in the $150 range. The A/C will bump that a bit


Greg Fretwell

#164240 - 05/28/07 10:22 PM Re: Tankless Water Heater [Re: gfretwell]  
EV607797  Offline
Member
Joined: Oct 2006
Posts: 745
Fredericksburg, VA, USA
Well, they do say that everything is insanely overpriced in California, Greg.

We have the same thing here; total electric costs about half of what using gas or propane costs. My house is also like you indicated, using well water, septic, etc. It's not so much the cost for electricity, but the lack of the need for gas or water/sewer cost. We have a few bumps during the extremely cold or hot swings in temperatures, but the average is still $200.00 for ALL utilities.

We are seeing a lot of conversions back to electric heat pump being done here where people made propane/NG conversions a few years ago. Propane costs as much as super unleaded gasoline! NG prices in the same ballpark and are too unstable.

My neighbor put in a pool at the end of the season last summer. They included a propane heater. After 1.5 months and $750.00 for propane, they shut it off and decided to let Mother Nature heat it.


---Ed---

"But the guy at Home Depot said it would work."

#164244 - 05/28/07 11:36 PM Re: Tankless Water Heater [Re: EV607797]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,099
Estero,Fl,usa
My wife got a propane heater for free but we have the same situation. It costs about $20 to bring the pool up 10 degrees and the bottom is still cold. I have done it 3 times in a year.
I use my solars and they work pretty well, virtually for free. If I had a cover they would work real well.

Home heat is such a rare thing that toaster wire is the norm. It is not worth the extra money to buy a heat pump for the 3 or 4 days a year we have the heat on. She will turn it on for a few minutes some mornings just to knock the chill off the house but I am not sure we ever use it all day.


Greg Fretwell

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