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4000W at 120V


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9 replies to this topic

#1 ladylaz

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Posted 28 October 2009 - 12:09 PM

OK,
Chastize me for this, but I have a question regarding heating
elements. I used to have a water heater with a "quick recovery"
upper element and a standard lower element (220V). I loved
it until my power went out, the well turned off, and I lost the
top element.

Now this...and it is a water heating question...not your standard
variety...I have a 240V 4000W element running at 120V, which
puts out 1000W under about an 8A load. Would I be better off
with a true 1000W 120V element if I wanted to heat the water
faster? The 4000W element might be more durable and last
forever but it seems to heat very slugglishly, I assume due to
the extra resistance.

It is a water heating component of a bath/spa and I have a chance
to swap it for nothing right now because the manufacturer slipped
this in without anyone noticing and I caught it. PLEASE give me an expert's angle on this (I know this is not a standard hot water heating question, but it really is)...is the difference negligible, i.e., should I keep the
4000W...I can't convert to 220V there?

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#2 RegUS_PatOff

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Posted 28 October 2009 - 01:15 PM

The current one :) you have would work the same as a 1000w at 120v

(same resistance)

Why / where are you that you don't have 220v entering the Fuse / Breaker Box ?

P=E2/R


 

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#3 ladylaz

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Posted 29 October 2009 - 06:41 AM

Dear [user=3641]RegUS_PatOff[/user]:

You are so helpful in so many ways!

It is at the end of a 120V 20A run with plugs and switches
in between. I thought of making two hot wires out of it,
putting in 220V breaker,  and fusing the outlets and switch,
but the house panel it runs off
is teetering on the edge of overload. It is only a 125V panel
that is fed by a 100A breaker on the main external panel,
and has 200A+ worth of breakers in it already. I was
already edgy about the usage on 120V.

I could run it off another panel but I'd need to dig a 120 ft.
trench through caliche, and a trencher would probably kill
my mature pecan orchard.

Makes me wonder what that old "quick recovery element"
I used to have was. I always assumed it was some low
resistance less-coiled element...at least that's what it
looked like fried.

I used to have tub further North like this one that would
actually heat, in the snow, with a 1000W element, so I
thought that might be the difference. This one cannot
recover temperature uncovered. I assumed "bigger/
more surface area interacting with cold water"  =
"same output but slower to heat and slower to cool."

#4 RegUS_PatOff

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Posted 29 October 2009 - 07:38 AM

[user=30761]ladylaz[/user] wrote:

... fed by a 100A breaker on the main external panel,
and has 200A+ worth of breakers in it already...

I'm not an an expert, but it shouldn't matter how many total breakers are in the panel,
just matters how much total amps you'd be using at any one time...

If total draws more than the 100A main, it'll do it's job.,
but if you're not home, that may cause problems if some electrical devices need to stay powered.

The 220v Water Heater could be powered by a (2 wire & bare ground wire).


if you have a Harbor Freight Store near you

sometimes on sale... bring print-out to store 
 

click on picture 96308   $ 12.99
Posted Image


click on picture 95683   $ 19.99

 
Posted Image



click on picture 95652 $ 19.99  sale $ 11.99

 
Posted Image

 

click on picture 42397   $ 19.99
Posted Image




link Harbor Freight Digital Clamp Meters

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one of my video productions: “Easter Seals: Walk With Me”

every day is Down Syndrome Awareness Day
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#5 ladylaz

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Posted 29 October 2009 - 07:12 PM

OK.
I bought this one:
http://www.harborfre...temnumber=95683
With my coupons it was 11 bucks (I am real good with coupons).

There's the whole rest of the house on this box, including another water heater,
fridges, freezers, whole automated kitchen, so forth. I'd like to get this to
work with 120V as the bozos at the BIG box store advertised.

They say "switch to 220V" (a spec not provided before purchase).

This unit came with its own 15A GFCI plug, so I actually REPLACED a perfectly good
outdoor GFCI outlet with a regular one so it wouldn't trip.

Put  the inductive ammeter on the cord overnight and it was real touchy to get a reading...had to play with it...then it came up 11.5A on the max hold reading.
The heater only comes on when the 1.5HP pump is in low mode: mfg claims
pump draw is 4A...so remainder is 7.5A for the heater (almost right) for 1000W.

My problem is this was bought for a very special case: medical accessibility for
therapy. And it lasts just a couple minutes, loses heat, and never recovers: like it
loses temperature once under body temp unless covered---even in 80+ tropical
conditions.

So now I'm doing math:
How many degrees F can a 1000W heater raise 240 US gallons in one hour?

240 US Gallons = 240*8.34*453.6=907,925.76 grams of water

There are 60*60 = 3600 seconds in one hour

1 Watt = 1 joule/sec. and 1000 Watts = 1000 Joules/sec. or 1000*3600 = 3600000 joules.

1 joule = .239 calorie, so the tub receives 3600000*.239 = 860400 calories of heat.

Remember that a calorie is the amount of heat (energy) required to raise one gram of water one degree C.


Therefore the water will increase: 860400/907925.76 = .9475 C, or .9475*1.8 = 1.70 F
XXXXXXXXXXXXXXXXXXXXXXXXXX

Except IT LOSES HEAT, probably due to poor efficiency of the element or the surface area of the water. It does not recover, and if the air temp is lower it just continues to heat and drop. My old tub in the Ozark snow would gain on the coldest night. Seems like I'm not getting 7.5A worth of output from the element (?how would I know?)...and this ammeter won't inductively measure ohms.

#6 RegUS_PatOff

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Posted 29 October 2009 - 10:47 PM

[user=30761]ladylaz[/user] wrote:

.. I'd like to get this to work with 120V as the bozos at the BIG box store advertised.

Put  the inductive ammeter on the cord

The heater only comes on when the 1.5HP pump is in low mode: mfg claims
pump draw is 4A....

... How many degrees F can a 1000W heater raise 240 US gallons in one hour?

..this ammeter won't inductively measure ohms.


120v advertised ?  OR verbally mentioned ?

ammeter must be on only one wire, not the pair

is the Pump 120v ?

1000w = 3400 BTU's

1 BTU will raise the temperature of (1) pound of water 1F in one hour

240 gal = 240 x 8.35 # = about 2000 pounds

at 3400 BTU'su you'll get 1.7 degree per hour
(edited calulations) 

don't need inductive OHMs for heating element reading...

(edited calculations)
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#7 ladylaz

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Posted 30 October 2009 - 05:04 AM

HERE is what I bought. (Hope that link embedded). It says: "Plugs into any 120 Volt/15 amp outlet with built in 15 ft. GFCI protected cord". It also says: "Features a 1000 Watt heater" . After they told me to convert to 220V they said I should have noticed the ad said "220V convertible",  which they now admit it doesn't (at least not yet). Yes, it has a 1.5HP 120V two-stage pump they claim draws 4A on low and cuts off heat on high. The terminals on the heating element are not in a friendly spot. If I could get a probe to both of them I assume you you are saying I could measure resistance. If it was leaking to ground wouldn't the GFCI have tripped? They factory rewired this with a GFCI plug right into the internal housing so finding a single wire would be from the controller to the heater (big bare live copper in a hard-to-access confined space is not a favorite of mine). I need help with your figures: 3400BTU/2000lbs. = 1.7 F/hr. like I did in metric. How did 80% efficient get it down to .5F/hr.? Wouldn't that be 1.36F/hr. ? Anyway, here is the sad reality: this thing heats when covered, then loses heat so fast it is under body temperature in just minutes. The manufacturer response: don't use any jets or convert to 220V. For instance, it loses temperature with low jets (necessary for heating mode) in 85F+ air. In fact, it loses so much I have yet to measure if it EVER recovers even one degree above air temperature. I have asked if this is a normal "benchmarked behavior" or if I have a weak element and need a service call...they say it should heat without a cover. I agreed to take some more measurements. But I must be missing something...my old tub with a 1000W heater reheated as snow fell into it, but this one doesn't make it in a tropical climate.

#8 RegUS_PatOff

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Posted 30 October 2009 - 05:48 AM

You're right... it is 1.7F/hr

I was using the wrong figures ...

I was dividing 1000w by 2000 #

Corrected to 3400 BTU 2000 #

I don't see how 1000w will heat that much water ...

Are you sure you old tub had only a 1000w Heater

and did it have 240 gallons ?

You could find a single wire in the Circuit Breaker Box to measure,

OR this AC Line Splitter

 
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one of my video productions: “Easter Seals: Walk With Me”

every day is Down Syndrome Awareness Day
"A Child Is Waiting" . Burt Lancaster . Judy Garland . 1962

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#9 ladylaz

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Posted 30 October 2009 - 06:52 AM

Yep. My old tub (which is still working on a snowy mountainside up there) was
120V and 1000W heater (which I replaced once, after 10 years...naturally soft
well water there). It was almost identical in size. I installed a GFCI breaker
in the box for it that also needed replacing at one point. I oversized the run
with 10 gauge armored romex (buried). Cost next to nothing to operate.

If I put a wire splitter between the wall plug and the GFCI plug will it trip
the GFCI?

Is 80% a good rule of thumb for elements?

You make a good point about the gallonage. Even at 100% efficiency and zero
heat loss it would be impossible to heat even 400 gallons AT ALL. This product
is over halfway there, and with evaporative loss is below the threshold where it will heat without a cover on. The trouble is the cover makes it hard to sit in.

BTW, is Indian Head Black and White hatuey with Guiness head?

#10 RegUS_PatOff

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Posted 30 October 2009 - 10:22 AM

The GFCI won't be affected as long as the Hot & Neutral are still connected ...
ground is still connected, but isn't actually needed for the GFCI to function normally

The 80% efficiency value I was using is for a tank water heater, which I thought, at first,  you were using


Indian Head. Black & White ... just a good sounding name that fits the avatar picture
 

 

 
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one of my video productions: “Easter Seals: Walk With Me”

every day is Down Syndrome Awareness Day
"A Child Is Waiting" . Burt Lancaster . Judy Garland . 1962

RegUS_PatOff > www.youtube.com/watch?v=oPAY2LsKVEw




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