Insta-Hot??

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jahilliard

Senior Member
I have been asked to help with the installation of an insta-hot water heater in a customers home. The scenario is that this is about a 3000 sq ft home with a 200 Amp service. There have been a few upgrades and remodels done over the years. There is currently 2 30 Amp water heaters supplying the house and the home owner is wanting to replace atleast one, possibly both water heaters with insta-hots. The plumber explained today that just to replace one of them will take a 120 total amp insta-hot (3-40A elements). My question is if this would be a practical application with the current available service. I know these insta hots draw full name plate amperage while in use. I feel like there needs to be a service upgrade in order to practically install 1 OR 2 of these. I have seen lights in a house flicker throughout after one of these being installed under similar circumstances, just wanting some feed back from everyone possible before I go back to the customer suggesting an expensive service change to a 400 Amp service. Thanks a lot for any info!
 

mcclary's electrical

Senior Member
Location
VA
I have been asked to help with the installation of an insta-hot water heater in a customers home. The scenario is that this is about a 3000 sq ft home with a 200 Amp service. There have been a few upgrades and remodels done over the years. There is currently 2 30 Amp water heaters supplying the house and the home owner is wanting to replace atleast one, possibly both water heaters with insta-hots. The plumber explained today that just to replace one of them will take a 120 total amp insta-hot (3-40A elements). My question is if this would be a practical application with the current available service. I know these insta hots draw full name plate amperage while in use. I feel like there needs to be a service upgrade in order to practically install 1 OR 2 of these. I have seen lights in a house flicker throughout after one of these being installed under similar circumstances, just wanting some feed back from everyone possible before I go back to the customer suggesting an expensive service change to a 400 Amp service. Thanks a lot for any info!




I very rarely get to do insta hots except for new work because of this very reason. It many times pushes the service over it's limit, and most of the time when the owner finds out the cost of installation, they decide against it.
 

Cavie

Senior Member
Location
SW Florida
Do a load calc as Chris said. A seat of the pants guess based on 40 years experiance tells me that a 3000 sq ft 200 amp fully electric house would need 70 amps at any given time. Add the 120 WH load and you just maxed out the service. Doable? yes. Recomended No.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I'd recommend the 320/400a upgrade, adding a second 200a panel for just the water heaters; 100a for one.

That frees up four spaces in the existing panel, and minimizes flickering, if the POCO upsixes the drop/lateral.

I haven't installed more electric tankless heaters than I have installed, for just these reasons. I suggest gas.
 
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Volta

Senior Member
Location
Columbus, Ohio
I'd recommend the 320/400a upgrade, adding a second 200a panel for just the water heaters; 100a for one.

That frees up four spaces in the existing panel, and minimizes flickering, if the POCO upsixes the drop/lateral.
Good idea.
I haven't installed more electric tankless heaters than I have installed, for just these reasons. I suggest gas.

I haven't installed more electric tankless heaters than I have installed either, but for completely different reasons :grin:.
 

Chamuit

Grumpy Old Man
Location
Texas
Occupation
Electrician
I have a load calc of a 3026 ft? home total electric (16560VA heating/cooling load). No pools or spas. Calculated load on it is 160A. If I delete the one water and add the 120A (28800VA) insta hot I get an even 200A.

Like Cavie said, "Doable? yes. Recomended No."
 
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Volta

Senior Member
Location
Columbus, Ohio
I have a load calc of a 3026 ft? home total electric (16560VA heating/cooling load). No pools or spas. Calculated load on it is 160A. If I delete the one water and add the 120A (28800VA) insta hot I get an even 200A.

Like Cavie said, "Doable? yes. Recomended No."

The existing storage-type water heater is 64 amps?
 

kwired

Electron manager
Location
NE Nebraska
i have a load calc of a 3026 ft? home total electric (16560va heating/cooling load). No pools or spas. Calculated load on it is 160a. If i delete the one water and add the 120a (28800va) insta hot i get an even 200a.

Like cavie said, "doable? Yes. Recomended no."

the existing storage-type water heater is 64 amps?

? ? ?
The existing water heater was 4500va (18.75a). If i took out the old h20 htr 4500va, and added in the instahot 28800va (120a).


160-18.75+120=200?
 

jahilliard

Senior Member
in this house there are two 4500VA WH's currently. HO is wanting to install atleast one 120A insta-hot and possibly a second to replace the other original tank WH. A few years ago we did an 8000 sq ft house that had 3 of these installed. 400A service. When the water heaters were on the lights would flicker....in about 4 houses on the same transformer....POCO came out and charged 10K$ plus for a new xfmr....GC just put whatever the HO wanted without researching...and Yes...I did give him the heads up to contact the POCO frist in writing so he couldn't blame me!!! Those GC's know everything!!:D
 

eric7379

Member
Location
IL
I very much agree. I am not really sold on the gas ones either. If they offer an energy saving it is pretty much gone after the first service call to remove scale plus the efficiency loss leading up to it.


I have a gas one and I love it. I have had it for about a year and a half and have not had any problems with it. The newer ones (a.k.a "more expensive") ones are so efficient that you can run the exhaust in PVC just like a high efficiency furnace. The downside is that these ones run around 2 grand.
 

kwired

Electron manager
Location
NE Nebraska
I have a gas one and I love it. I have had it for about a year and a half and have not had any problems with it. The newer ones (a.k.a "more expensive") ones are so efficient that you can run the exhaust in PVC just like a high efficiency furnace. The downside is that these ones run around 2 grand.

How long is your estimated return on investment?

Remember that heat lost from a tank style heater during heating season is not lost entirely, it puts that much less load on your heating system.
 

hockeyoligist2

Senior Member
Update

Update

We are in the middle of installing one at work. No one asked the electricians opinions.... Most of the building is 277-480. The transformer is too small to handle the extra load.

Finished the installation today! Total cost of a new transformer, conduit, wire, ETC. Not including labor, Almost $3,000! The only thing it supply's is a bathroom with showers that is used maybe 2 times a year. But they got another notch in their "green hat"!

Sorry, I'm just getting a little tired of the "green" movement. It looks good to say" We are going green!" But, but, Naaahhh, I will shut up......
 
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