drained my hot water heater to replace my electric heating elements

[robphelan]

how long til I get hot water back?

it's ~60 gallons w/2 electric heating elements - 4500 W each.

11/03/08
something is tripping the breaker... and I can't understand why...

my existing elements both looked like this.

I went for a double loop like this.

they're the same 4500W as the ones I had before... could it be that the new ones are pulling more volts causing the breaker to trip?

EDIT: yes, I see your point about not having to drain - but my WH is in my garage & I don't need 50 gallons of water swishing around my floor.

 

[LS8]

4 hours (no real idea).

 

[BoomerD]

SHOULDN'T take more than an hour...if everything was hooked back up right...the water turned back on, and the water heater turned back on.

 

[rudeguy]

fill the tank back up BEFORE you turn power back on to the heater!!!!!!!!!!!!!!!

 

[robphelan]

yeah, it turned back on.. made all sorts of scary noises while filling up.

real easy to do - unplug, drain, unscrew heating elements, replace, refill & plug back in.

the most time consuming part was draining.. i opened the release valve and opened up a faucet.. but it still took a long time.

 

[robphelan]

Originally posted by: rudeguy
fill the tank back up BEFORE you turn power back on to the heater!!!!!!!!!!!!!!!

uh oh.

i don't think I let it fill all the way before plugging back in.

 

[Chaotic42]

What we know:

60 gallons = 227.124707 liters
227.124707 liters of water = 227.124707 kg of water
Specific heat of water = 4.186 Joules per Gram-°C
140°F = 60°C
4500W * 2 = 9KW


Let's say your water started out at 15°C. You need to heat ~227kg of water a total of 45°C. So you need 227,125 * 45 * 4.186 Joules = 42,783,536.2 Joules

42,783,536.2 Joules / 9KW = 1.32047951 hours or 1 hour 19 minutes 13.7 seconds assuming 100% efficiency.

I'd give it two hours to be safe.

 

[robphelan]

Originally posted by: Chaotic42
What we know:

60 gallons = 227.124707 liters
227.124707 liters of water = 227.124707 kg of water
Specific heat of water = 4.186 Joules per Gram-°C
140°F = 60°C
4500W * 2 = 9KW


Let's say your water started out at 15°C. You need to heat ~227kg of water a total of 45°C. So you need 227,125 * 45 * 4.186 Joules = 42,783,536.2 Joules

42,783,536.2 Joules / 9KW = 1.32047951 hours or 1 hour 19 minutes 13.7 seconds assuming 100% efficiency.

I'd give it two hours to be safe.

you see, this is why I come here... super geeks at home on a Sat night.

 

[BoomerD]

You'd better hope you had filled it all the way before you turned it on. It doesn't take much exposure to the air for the elements to burn out...and you'd get to do this all over again...

 

[LS8]

If only he had some of that "geek" knowledge.

 

[Chaotic42]

Originally posted by: robphelan
you see, this is why I come here... super geeks at home on a Sat night.

Hell, my math could be wrong. This is all stretching back a ways.

 

[rudeguy]

Originally posted by: BoomerD
You'd better hope you had filled it all the way before you turned it on. It doesn't take much exposure to the air for the elements to burn out...and you'd get to do this all over again...

I learned this lesson the hard way.

 

[robphelan]

crap.. anyone know how to use a multimeter to check the connection?

 

[FP]

Multimeter? Pssssssh...

You have two hands and a tank full of water. You don't need much else to check the connection.

 

[robphelan]

ok, found the problem... at some point, i must have tripped the breaker.. reset it.. will have to check in a little while to see if it's heating.

 

[rudeguy]

Originally posted by: robphelan
ok, found the problem... at some point, i must have tripped the breaker.. reset it.. will have to check in a little while to see if it's heating.

Ruh roh...

That could either be a very good thing or the breaker got tripped when the elements burned out from being exposed.

I really hope its the first option.

 

[robphelan]

Originally posted by: rudeguy

Originally posted by: robphelan
ok, found the problem... at some point, i must have tripped the breaker.. reset it.. will have to check in a little while to see if it's heating.

Ruh roh...

That could either be a very good thing or the breaker got tripped when the elements burned out from being exposed.

I really hope its the first option.

yeah me, too. it's certainly getting power now. i'll report back in 30 mins or so - hopefully I'll come back with a report of warm water

 

[drinkmorejava]

Originally posted by: Chaotic42

Originally posted by: robphelan
you see, this is why I come here... super geeks at home on a Sat night.

Hell, my math could be wrong. This is all stretching back a ways.

Math is right. I don't know who keeps their heater at 140F though. I thought it was more like 160-70

 

[Toastedlightly]

Originally posted by: Chaotic42
What we know:

60 gallons = 227.124707 liters
227.124707 liters of water = 227.124707 kg of water
Specific heat of water = 4.186 Joules per Gram-°C
140°F = 60°C
4500W * 2 = 9KW


Let's say your water started out at 15°C. You need to heat ~227kg of water a total of 45°C. So you need 227,125 * 45 * 4.186 Joules = 42,783,536.2 Joules

42,783,536.2 Joules / 9KW = 1.32047951 hours or 1 hour 19 minutes 13.7 seconds assuming 100% efficiency.

I'd give it two hours to be safe.

That is assuming a constant specifc heat. Now, if you want to integrate some 5th order polynomials... include a little heat loss (as we know that the heater is not 100% isolated...)

 

[FP]

Originally posted by: Toastedlightly

Originally posted by: Chaotic42
What we know:

60 gallons = 227.124707 liters
227.124707 liters of water = 227.124707 kg of water
Specific heat of water = 4.186 Joules per Gram-°C
140°F = 60°C
4500W * 2 = 9KW


Let's say your water started out at 15°C. You need to heat ~227kg of water a total of 45°C. So you need 227,125 * 45 * 4.186 Joules = 42,783,536.2 Joules

42,783,536.2 Joules / 9KW = 1.32047951 hours or 1 hour 19 minutes 13.7 seconds assuming 100% efficiency.

I'd give it two hours to be safe.

That is assuming a constant specifc heat. Now, if you want to integrate some 5th order polynomials... include a little heat loss (as we know that the heater is not 100% isolated...)

NERDS!!!

 

[BoomerD]

Originally posted by: drinkmorejava

Originally posted by: Chaotic42

Originally posted by: robphelan
you see, this is why I come here... super geeks at home on a Sat night.

Hell, my math could be wrong. This is all stretching back a ways.

Math is right. I don't know who keeps their heater at 140F though. I thought it was more like 160-70

Water temps that high are asking for burns...

ACTUAL recommendations are all over the place though:


Especially if you have small children, your hot water tank should be set to about 120 F to prevent scalding.

HOWEVER, if your dishwasher doesn't have a booster heater...then 140 is recommended.

http://apps1.eere.energy.gov/c...ndex.cfm/mytopic=13090


http://pge.com/myhome/saveener...avingstips/index.shtml

"Set the water heater thermostat at 140 degrees or "normal." If you have a dishwasher. Otherwise, set it at 120 degrees or "low." Check your dishwasher to see if you can use 120 degree water. Follow the manufacturer's direction on yearly maintenance to extend the life of your unit."


There is of course, the issue of bacteria...all kinds of nasty stuff...that can grow in the hot water tank if the temp is too low...That's where the 140 recommendation comes in.

http://www.naturalhandyman.com...eater/infwhadjust.html

"According to the US Department of Energy, a temperature of 120 degrees at the tap is adequate for most household chores with a minimal danger of scalding and maximal energy efficiency. However, that is the temperature at the tap, not in the tank. Tank temperature should be no less than 130 degrees to prevent bacterial growth, such as Legionnaires disease."




Seems like a "Dammed if you do, dammed if you don't sort of thing.
"don't set your tank too high, your kids can scald themselves badly, but don't set it too low, or you'll grow nasties in the tank and it can make you VERY sick."

 

[NoShangriLa]

Originally posted by: Chaotic42
What we know:

60 gallons = 227.124707 liters
227.124707 liters of water = 227.124707 kg of water
Specific heat of water = 4.186 Joules per Gram-°C
140°F = 60°C
4500W * 2 = 9KW


Let's say your water started out at 15°C. You need to heat ~227kg of water a total of 45°C. So you need 227,125 * 45 * 4.186 Joules = 42,783,536.2 Joules

42,783,536.2 Joules / 9KW = 1.32047951 hours or 1 hour 19 minutes 13.7 seconds assuming 100% efficiency.

I'd give it two hours to be safe.

Street water temperature is between 40-45 F

Hot water tank default setting is 140 F

1 W = 3.413 Btu

1 Btu heat 1 lbs of water 1 F degree

1 gallon of water = 8.33 lbs

(60 gal * 8.33 lbs) * (140 F ? 40 F) / (4500 W * 2 elements * 3.413 Btuh) = 1.627 h

It will take exactly 1 hour 37 minutes & 37.6 second if there is no heat lost.

The calculation is the recovery rate of the water tank, useable water is on the top 1/3 of the tank (20 gallon, or around 35-40 minutes).

The exact time till useable water can be calculate if flow rate of the fiture is provided.

Where is my cookie?

[add]

PS. drain the tank isn't a requirement for element replacement.

 

[flxnimprtmscl]

I'm not sure if anyone has mentioned this but you need to bleed the air out of your water heater any time you drain it. There should be a valve at the top of your heater which is connected to a pipe that runs down to the floor. Open that valve until water comes out the pipe and then close it.

 

[Loreena]

The calcs are wrong. You can run only ONE 4500W sandhog at a time. The input is NOT 9000W but one OR the other. 30A circuit, 10/3 AWG guys.

Oh and since this is a "hot water heater" [sic], it should take no time as you already have hot water!

 

[Lounatik]

Okay, so you have a hot water heater. Have you ever received workmens comp? Its a freakin' WATER HEATER!!!!!!

/insane rant.


Peace


Lounatik