tankless water heater – power requiremen
My old water heater has recently failed and I am looking at installing a tankless water heater.
I have a question on the power requirements and my panel capacity.
I have 225 amp panel. I run two HVAC units (50a each) an elec drier (60 a), electric stove (gas rangetop), and two waterheaters (30a typ) as my major power draws. The waterheater that failed is the lower house unit. It only serves the washing machine, kitchen sink and dishwasher. We run the washer once a week on hot cycle and the dishwasher every other day.
We use so little hot water that a standard water heater is a waste IMHO.
With this in mind I am looking at the smaller Bosch system, but it still takes two 60 amp breakers.
Also, I ran a subpanel for my shop (for the 220 outlets) and this is runs probably 1 hr a year.
The question I have is will my panel handle the additional load.
Replies
What you need to do is to compute the actual electrical DEMAND.
And that is based on several requirments, but for things like the HVAC, dryers, stoves, dishwahsers, etc and the WH's you base it on ACTUAL NAMEPLATE RATINGS, not breaker size.
Go to FHB and then under the extras, or online articles (don't remembeer the exact name) under mechanical systems - How to size an Electrical SErvice.
It has the worksheet about how to do this.
One possible option, if you come up short, is to get someone to rig a box that will shed other loads when the tankless comes on. The AC and the other WH would be likely candidates.
Not sure how much it would cost to do this. There's probably no ready-made device, so you'd need a commercial/industrial electrician who can design the setup. Luckily, the AC units can be switched off with low voltage/current contacts, so it would probably just comprise a current relay (to sense when the WH kicks in) and a control relay (and maybe a time-delay relay to assure that the AC isn't cycled off/on too rapidly). A separate contactor would be needed for the other WH, if you decided to switch that too. 24V could be vampired off the AC.