ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
Recent Posts
by renosteinke - 01/27/23 09:52 PM
Does NEC 551.71 (F) apply to dwellings?
by BigB - 01/20/23 10:46 AM
Power submeter connections
by HotLine1 - 01/19/23 09:09 AM
AFDD's coming to the UK
by Texas_Ranger - 01/17/23 07:22 PM
New in the Gallery:
Burger King crown sillyness
Burger King crown sillyness
by wa2ise, December 11
240/208 to a house
240/208 to a house
by wa2ise, October 9
Who's Online Now
0 members (), 92 guests, and 12 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
Joined: Aug 2006
Posts: 11
sprynda Offline OP
Junior Member
Hello to all,
I have a customer that was thinking about a whole house instant hot water heater. I did some research and looked at the bosch and SEISCO units. The customer wants the electric unit not the gas unit. The thing that concerns me is that both units require 3 40 amp 220 circuits. The customer has a 200 amp service. The main panel is filled except for 4 slots with all 220 breaker for electric heat and includes a 100 breaker for one sub panel and one 60 amp for a second sub panel. I just feel that there is too much on the panel to add this type of devise. Has anyone ever used this type of heater and if so i would like some comments
thanks for the help

Joined: Apr 2002
Posts: 7,333
Likes: 7
Seems that a good load calculation is in order. Better may be installing a recorder for actual readings.

Gut feeling is....service upgrade

Joined: Jul 2004
Posts: 787
Whole house instant hot water heater? I thought Instant DHW heaters were point of use devices? How does a whole house become a point of use?

Larry C

Joined: Aug 2006
Posts: 11
sprynda Offline OP
Junior Member
these units are bigger that the point of use. i have installed several of those units in kitchens or baths, but then i foynd these whole house units. i just have not found anyone that hsa one to get feed back from

Joined: Feb 2003
Posts: 939

I allready install few whole house instat waterheater and unforetally most place where they have 200 amp service they useally really pushing pretty hard with the rating.

from my experince i genrally expain what will happend when they get the whole house instat waterheater i have to warn them they will have to hevey up to 400 amp service and the cost as well.

anyway few did have it hook up in few months later they asked me to remove it and get the standard electric waterheater or go with gas version of whole house instat waterheater

the other thing is that from my exerince i am sure few will ring in here as well

1] the lights will be more noticeable flicker when the IWHWH cycle [ just like turn on and off 3 electric range at the same time or run in stages ]

2] many POCO will get little ticked off becuase if this transfomer feed few homes and burn up the transformer. [ try that on very hot summer day when everyone crank up A/C and the IWHWH kick in with overloaded transformer]

3] the whole house instat waterheater is very senstive to the water flowage it can be anywhere from lukewarm to pretty hot [ if you have very cold water supply it will make it lukewarm ]

i will let other peoples fill in their experince with this as well

Merci , Marc

Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

Joined: Feb 2006
Posts: 144
I stayed in a small (5-room) hotel that had one of these on a 200 amp panel. The flickering lights were almost unbearable, as the unit turned on and off as each guest turned their water on and off. In my opinion, a 200 amp panel would be way too small.

Joined: Oct 2005
Posts: 40
We are installing some commercial grade three phase, tankless water heaters in some of our buildings. Check out this company, they make a nice product. I believe there are some units that can be fed with one 2pole breaker instead of three 2pole breakers. If you go with tankless water heaters, make sure they have replaceable elements. Some manufactuers sell some models where, if you blow an element, the whole unit has to be replaced. Just a nice company to check out. Thanks, Brian

Brian Gibbons
Joined: May 2007
Posts: 169
I haven't seen a whole house electric unit but from what I have seen of the point of use elements I wouldn't install any of them in my house, nor recommend them to a client.
I've installed a 30A and a 50A unit. The 30 was worthless above flow rates more than a trickle.
The fifty was installed where the ground water gets cold and the house had a loooong overhesd service drop.
Result was to pull the mains down about 9% while providing just enough rise in water temp at an almost tolerable flow rate to wash your hands. I checked out the one in a friends office restroom and it was the same story. 50A, dimming lights, poor rise in temp at any kind of flow rate.

I have wired a couple of houses that use gas whole house on demand units. Both houses were long kinda long in design.
Both houses have 2 units feeding the hot water line at opposite ends of the house. One of the units didn't even need the receptacle I installed for it because it used a flow powered generator for ignition. I was impressed with the performance of these systems and the homeowners seem happy with them.
If you can go gas and think about 2 units if you have long hot water pipes.

Joined: Jul 2002
Posts: 717
If you end up having to go with the electric whole house heater, MAKE the customer sign papers that clearly outline the forseen problems with the install and release you from any responsibility for any voltage drop problems on either side of the meter socket. After he signs the paper, go ahead and put it in and collect the check for the job. My bet is he will give in at that point and opt for gas.

Joined: Jan 2007
Posts: 59
I agree with doing a load calc.

Page 1 of 2 1 2

Link Copied to Clipboard

Tools for Electricians
Tools for Electricians

* * * * * * *
2023 National Electrical Code (NEC)
2023 NEC Now Available!
* * * * * * *

2020 Master Electrician Exam Preparation Combos
2020 NEC Electrician
Exam Prep Combos:
Master / Journeyman


Member Spotlight
Amish Country, PA
Posts: 46
Joined: March 2013
Top Posters(30 Days)
BigB 7
triple 3
Popular Topics(Views)
302,734 Are you busy
231,965 Re: Forum
216,683 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.5