I have recently been involved in helping a new home owner have her contractor upgrade her service panel from a 200 amp to a 400 amp due to it being overloaded !! Once getting the code office involved we achieved that goal.. But what we are faced with now is the water heater is a 37kw water heater which requires 4 double pole 40 amp breakers .. Two of these breakers are coming out of the service panel and two are coming from a sub panel next to the service panel that is being fed from the service panel. To me I would think for the safety of the plumber that would possibly be working on this unit in the future all four of these breakers would need to be coming out of the same panel so they would be identified To be feeding one common water heater.. To me this is just a common sense thing but is there any code to back this up .. Any help would be greatly appreciated I have looked as much as I can at the moment I have just been too busy to go into depth ..
Tankless water heater!!
- Thread starter Petemoran
- Start date
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texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
Appliances with multiple circuits feeding them such as this require the disconnects to be grouped. If they are not within sight of the appliance they will need to be lockable and grouped. See 422.30 and 422.31(B).
One way to fix this may be to install 4, 60 amp non-fusible pull outs at the water heater. That way you would not have to worry about the source breakers being grouped.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
IMO in an adjacent panel is about as grouped as all of them in same panel but one with say 60 spaces - is about as easy either way to miss one or more of them if you are the plumber wanting to shut it all off.
That said is it really worth all the cost to upgrade things to supply this kind of water heater vs cost of what energy might be saved over next 5-8 years? Tankless gas unit, might be more worth installing. - JMO.
That said is it really worth all the cost to upgrade things to supply this kind of water heater vs cost of what energy might be saved over next 5-8 years? Tankless gas unit, might be more worth installing. - JMO.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
You should do what I did when I upgraded a service from 200 to 400 amps for a tankless water heater: I put in a second 200a panel that supplies only the water heater and contains only the four 40a breakers. In fact, this new panel's feeder doesn't even include a neutral, only an EGC.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
though there isn't a lot of capacity left, I'd probably still run a neutral, someone might add a 120 volt circuit to it. Would be code compliant to run a #6 copper for 200 amp feeder or #4 copper/#2 aluminum if it is service conductors supplying it, as you sort of only have about 46 amps left to utilize for other loads after supplying the water heater.
Thankless
Thankless
To clarify this isn’t for me to fix i am helping a friend out with her house that she doesn’t even have a Certificate of occupancy for .. We are trying to have everything corrected before she makes final payment.. And on the grouping my thought is that if they are all in one panel grouped together they can be all labeled water heater with even a bracket drawn on the side indicating one appliance .. To me someone could easily open one panel see hot water heater and turn off all the breakers that indicate hot water heater and could easily be hurt .. Of course they should properly check volatage but we all know that isn’t the always the case especially with an inexperienced plumber .. So my thought on grouped would be the same panel .. Thank you for the location in the code book .. And also thank you for other comment and opinions ..
Thankless
To clarify this isn’t for me to fix i am helping a friend out with her house that she doesn’t even have a Certificate of occupancy for .. We are trying to have everything corrected before she makes final payment.. And on the grouping my thought is that if they are all in one panel grouped together they can be all labeled water heater with even a bracket drawn on the side indicating one appliance .. To me someone could easily open one panel see hot water heater and turn off all the breakers that indicate hot water heater and could easily be hurt .. Of course they should properly check volatage but we all know that isn’t the always the case especially with an inexperienced plumber .. So my thought on grouped would be the same panel .. Thank you for the location in the code book .. And also thank you for other comment and opinions ..
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Whether in same panel or not I myself would maybe rather see "Water heater 1 of 4, Water heater 2 of 4..."
Even if all in same panel, say you had a 60 circuit panel, not impossible these days, and had two near the top and two near the bottom, it could be easier to miss some of them.
hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
Sounds to me like this is a train wreck from the beginning. I assume that the tankless water heater was existing and now, because of the sale the violations have to be corrected in order for the purchaser to get a C of O?
How about just replacing it with a conventional water heater? That certainly wouldn't entail the expense of upgrading the service and the long term cost of using that thing. Costly to use, costly to maintain and costly to replace. Somebody gave her bad advice.
-Hal
How about just replacing it with a conventional water heater? That certainly wouldn't entail the expense of upgrading the service and the long term cost of using that thing. Costly to use, costly to maintain and costly to replace. Somebody gave her bad advice.
-Hal
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
The cost difference between SE and SER for 60' is one reason. Avoiding the addition of 120v loads is another.
The original panel, now relieved of the original water-heater load, is where any new circuits should be landed.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
In my example, with two teenagers in the house, the tank hot-water duration limitation was their main concern.
No sir it is a bran new home that they are doing the final check off on , originally it was supposed to be a conventional water heater but with the suggestion of the home builder they used that area for a bathroom/sink room .. And following the recommendations of the builder they went and bought the 37kw water heater he suggested .. Once i checked amperage draw and got the code office involved they were forced to upgrade to a 400 amp service .. The breakers located in diff panels is just another thing I didn’t feel like was save or correct.. I believe the biggest problem is the code has not evolved to meet the demands of these new water heaters.. If u calculate the load of this house using the optional method its meets a 200 amp service all day long but when I pulled up to test her load she was washing and drying cloths the heat was on i asked her to turn the stove on as if she was cooking a full meal and to run both shower heads and the service was drawing 248 amps now this is with no TVs , microwave, fridge, or any other appliances being used as they are not living in the house yet .. So i think the tankless water heaters should not be able to be included In the deducted load area.. I built my own house last year and its pretty much identical to this ladies as far as size and appliances besides her electric stove and she has a 37kw W/H and i have a 27kw tankless with a gas stove .. With a 200 amp service .. and even with a gas stove I would have went with a 320 amp service if i was to have used a 37kw W/H.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Possibly a second tank style heater or a 80-120 gallon should be sufficient, if they use all the reserve on that - they are spending too much time in shower and need it to get cold to force them out.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
I won't say NEC maybe needs to consider some change in demand factor for these particular water heaters, but at same time the rate of flow and amount of temp rise needed is what should determine how much load they draw. If you are only drawing a trickle of water, you certainly don't need all 37 kw, and the thing is probably going to boil the water if it turned on all 37 kw. Those should turn heat on in stages as needed for demand. So the question on figuring a demand factor would involve figuring how likely it is they will draw full rating and for how long? You could come up with different figures for northern places then you come up for southern places as well as amount of temp rise needed will likely be greater.
I am still convinced that one should at least have a conventional tank heater and preheat water to at least around room temp or even as much as 85-90 degrees, then maybe put instant water heater to bring it to user temp on demand, it won't need as big of a heater to raise it 20-35 degrees as it needs to raise it 60-70 degrees, and the tank won't lose that significant amount of heat if only at or a little above room temp. Winter months any heat loss is just reducing your heating system demand a little, it is when you are running cooling that heat loss from a water heater into the conditioned space is pretty much a complete loss, plus you now need to spend some more energy removing that heat via your cooling system.
romex jockey
Senior Member
- Location
- Vermont
- Occupation
- electrician
A few years ago we did a tankless install for a 9 unit place , 200A 4-40's. The manufacturer had convinced the landlord via ROI. The poco changed out the 15KV to a 50KV pole pig. The thing ran constantly, the poco billage tipped into and stayed in 'commercial rate'.:slaphead:
The 'heating guys' determined storage tanks as remedy.....
~RJ~
The 'heating guys' determined storage tanks as remedy.....
~RJ~
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Seems it could easily be undersized for 9 units, depending on how much temp rise was necessary. ROI can be convincing, but is based on energy used and cost of the unit, usually they don't factor in installation and especially the need for larger service/distribution gear to be able to handle it.
Why did it run constantly? Had to be some water flow for it to do that or else you are going to boil the water in the unit, and even then has to be pretty good flow rate if you get all 37 or so kW running.
romex jockey
Senior Member
- Location
- Vermont
- Occupation
- electrician
The maufacturer sized it, sold the landlord on the ROI, it ran constantly , any actual 'savings' became a fairytale when the place clicked over to commercial rates
:happyno:
Pretty much summed up my 'lectric is the most $$$ fuel' spiel i give everyone on my turf kwired
~RJ~
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Did it get replaced with tank style electric or gas? Was there demand metering? I could see demand metering factoring into commercial rates.
If replaced with electric tank style total energy used shouldn't go down if hot water usage remained the same, you are raising same amount of water same temperature - watthours needed to do that don't change. But if the tankless constantly ran, I don't see that tank style heaters will necessarily be able to keep up with demand either, or there will need to be significant number or higher than typical 4500 watt units, because hot water demand is still going to take a certain amount of watt hours to keep up with.
Right now gas is cheaper even in places with some of the lowest electric rates. Wasn't always that way.
growler
Senior Member
- Location
- Atlanta,GA
Sounds like the cheap and simple solution to me.
gadfly56
Senior Member
- Location
- New Jersey
- Occupation
- Professional Engineer, Fire & Life Safety
Junk the electric and install gas. They'll probably still save money.
ramsy
NoFixNoPay Electric
- Location
- LA basin, CA
- Occupation
- Service Electrician 2020 NEC
Yes, if exhaust-riser vent is practical, a gas tank-less would allow more room for future expansion in fuse box.
Home buyer only needs an estimate to negotiate final purchase price.
- Status