New Water heater circuit too small

[Tulsa Electrician]

I ran the numbers in 125 rated running on 6 v drop. Still good?

 

[brother]

@brother how sure are you that the water heater is 120v and not 240V

I'm 100% sure. I saw the name plate and its brand new.

 

[kwired]

A 3000 watt heater at 120 volts is about 25 amps. It should surprise no one that it ran all these years without any issues on a 20 amp ocpd.

Bottom line. It does not meet code. If whomever is footing the bill wants it to meet code, it is going to cost some money.

I don't know how you can claim that it's a 3-hour heat up time because you don't know what the temperature of the water coming in is or what the setting is.

The calculation is simple. It takes 1 btu to raise the temperature of 1 pounds of water 1 degrees F. 3000 Watts is a little over 10,000 btu per hour. Three hours would be about 30,000 btu. Thirty gallons of water is about 250 pounds so in three hours you could raise the temp of the water by about 120 degrees.

That is if you don't replace any that water, now factor in water usage and you have new incoming water that needs heated up, and should you be using it fast enough you eventually get to a point your water outlet temp drops too low to still be considered "hot water". Tank type electric water heaters never really have the ability to keep up with demand once the heat is depleted. They size them assuming demand will end before hot water runs out and gives the thing a chance to recover for the next use.

 

[kwired]

I think the watt rating is at 125 volts too so at 114 volts you are looking at about 21 amps.

My best guess is the rating is either at 120 or 115 volts.

 

[kwired]

I ran the numbers in 125 rated running on 6 v drop. Still good?

Depends on who this matters to. Resistive load still works you lose a little power in the conductors but performance wise you won't notice any difference unless taking some rather precise measurements. If this is a 25 amp heater and you are losing 6 volts then you are losing 150 watts in the conductors. Lets say the circuit is 50 feet one way which ultimately is 100 feet out and back = 1.5 watts lost per foot per conductor so actually 3 watts per foot in a two wire cable. That will be noticeably warm if you let it run for very long I would think.

 

[petersonra]

My best guess is the rating is either at 120 or 115 volts.

I looked at a couple manuals. It seems to be 120 V. For some reason small appliances are typically rated at 125 V. Don't know why.

 

[Barbqranch]

I would be tempted to put a buck/boost transformer on it to reduce the volt and the current.

 

[petersonra]

I would be tempted to put a buck/boost transformer on it to reduce the volt and the current.

I am not sure that fixes anything. If the label says 120 Volts how are you in compliance by supplying a much lower voltage. I am thinking about 75 volts to get it down to 16 amps.

 

[kwired]

I would be tempted to put a buck/boost transformer on it to reduce the volt and the current.

Lower capacity element cost a lot less. If recovery time is any kind of issue you make it longer way if you lessen output watts in any way.

getting a 240 volt heater instead of 120 volt might not cost less but is probably the better investment

 

[PaulMmn]

Liter? What's a liter?

A Liter is what you buy soda in-- 1 or 2 liter bottles. Been that way a LONG time!

 

[kwired]

A Liter is what you buy soda in-- 1 or 2 liter bottles. Been that way a LONG time!

Pretty much since they went to plastic bottles, though 20 oz is fairly common.

I remember 16 oz glass bottles, and the 16 oz returnable glass bottles as well. Used to have to handle those (full as well as the returns) when I worked in grocery store while still in high school.