Joethemechanic
Senior Member
- Location
- Hazleton Pa
- Occupation
- Electro-Mechanical Technician. Industrial machinery
44.11/38.22 = 86.64%
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277 Volt single phase water heater on 240 volts
- Thread starter g-and-h_electric
- Start date
44.11/38.22 = 86.64%
ptonsparky
Tom
- Occupation
- EC - retired
or if I needed to make it work for a couple days.
fastline
Senior Member
- Location
- midwest usa
- Occupation
- Engineer
We must have attended different schools together!
ptonsparky
Tom
- Occupation
- EC - retired
FWIW, I get 1.5 ohms difference from ambient air measurement of 64.1 ohms to 65.6 ohms after 115 volt is removed from a 200-watt, 115-volt heating element.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
How about at 75% power?
The few simultaneous water heater's I have seen all use two circuits. I remember because of how confused I was as to why two 10/2's would be going to the waterheater thinking someone mad a mistake.
Joethemechanic
Senior Member
- Location
- Hazleton Pa
- Occupation
- Electro-Mechanical Technician. Industrial machinery
We bought 5 R Model Mack tractors off of either Matlack, or Chemical Leaman Tank Lines back in the day. So I never noticed they had 240 volt block heaters until it got cold out. All the rest of our trucks and equipment had the same 1500 watt block heaters, but they were 120.
So the garage and yard were all set up to run the 120 V heaters and I'm in a pinch for time. (Trucks are delivering structural steel to a job in Manhattan)
They were just like my toy here with the plug mounted in a socket next to the headlight.
So I just changed the guts in the plugs and ran them on 120
They ran right around 6 amps and 325 watts on 120. The stuff with the 120 volt elements ran about 12 amps and 1500 watts. The trucks started fine, It was Philly, some were in the building, some outside, but even the yard had big buildings on 3 sides, so not much wind.
Now everybody has to ask permission to do anything. I drove from Port Richmond, to Mack over by Grant and the Blvd, bought the plugs, drove back and installed them in like 2 or 3 hours. How much time does the permission asking/granting process take? And you know that some guy that is afraid of electrocution by his car battery because it's 1000CCA and "It's the amps that kill you" has inserted himself into the process.
Sounds like a day in Manhattan with a crane there, and a bunch of ironworkers all drinking coffee on the clock
Over my 50 years I have wired in /replaced hundreds of mostly immersion heaters from 120 volt for boning room knife sterilizers , 240 & 480 vole single & three phase. Some were in colder rooms around 40 degrees & others in hot rooms over 100 degrees. I always took ampere readings and even with a 80 degree temperature difference the ampere readings were identical especially once heater came up to operating temperature. We were having trouble with immersion heaters having a short live span when used to heat thick mineral oil. Nice people at Chromalox told me that that most immersion heaters are designed for only heating water.We installed a much higher wattage heater rated for 240 volts and ran it on 120 volts and it did a good job. ( halve the applied voltage = 25% wattage ).
Once the heater is up to temperature room temperature has absolutely no affect on resistance, especially on PID temperature controllers.
Joethemechanic
Senior Member
- Location
- Hazleton Pa
- Occupation
- Electro-Mechanical Technician. Industrial machinery
Yeah, oil is hard to do with immersion. Moves a lot less heat than water does.
Lot of problems keeping the oil lines hot at the KitKat Factory. Water jacketed but old, but then they switched from Palm Kernel Oil to Palm Oil. Not to mention installing a hot jacket water heating scheme that was open to air because it's all hoses and stainless (or so they thought). They couldn't do immersion because it's food, but there were all kinds of heating blankets wrapped around stuff for quite a while
fastline
Senior Member
- Location
- midwest usa
- Occupation
- Engineer
Honestly, I can't believe there is 4 pages talking about hooking up a water heater. As someone that has done design work with immersion heaters, I might bring up a few things.
Many of these heaters use a Nichrome wire element. Nothing can be definite unless you actually know the wire size and arrangement but it is without question that part of the design IS the operating temp, as that is a function of the wire resistance, thus current! However, it is NOT as simple as other mention because what actually matters is the running temp of the heating wire, and that is a thermal transfer function based on delta T and thermal conductivity, and even the ceramic wire insulation casting.
But to say the resistance does not change? That is BS! But the reality is as the delta T increases with higher current, so does the BTU transfer! This is why it sort of "self regulates".
But Nichrome wire, even in air, does a bit of self regulation as you run it hot and it's resistance is largely affected.
Many of these heaters use a Nichrome wire element. Nothing can be definite unless you actually know the wire size and arrangement but it is without question that part of the design IS the operating temp, as that is a function of the wire resistance, thus current! However, it is NOT as simple as other mention because what actually matters is the running temp of the heating wire, and that is a thermal transfer function based on delta T and thermal conductivity, and even the ceramic wire insulation casting.
But to say the resistance does not change? That is BS! But the reality is as the delta T increases with higher current, so does the BTU transfer! This is why it sort of "self regulates".
But Nichrome wire, even in air, does a bit of self regulation as you run it hot and it's resistance is largely affected.
Joethemechanic
Senior Member
- Location
- Hazleton Pa
- Occupation
- Electro-Mechanical Technician. Industrial machinery
ptonsparky
Tom
- Occupation
- EC - retired
It went from ambient resistance of 64.3 to 65.5.
99.7 volts at 1.51 amps.
Joethemechanic
Senior Member
- Location
- Hazleton Pa
- Occupation
- Electro-Mechanical Technician. Industrial machinery
so like 1% change in resistance
So off of a pair of elements that present 6.28 ohms to the line we are talking about 0.06 ohms change
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fastline
Senior Member
- Location
- midwest usa
- Occupation
- Engineer
It does not math like that.
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I meant to compare resistance at both operating temperatures; ambient isn't relevant here.
Yes, heating oil requires an element with low watt density. Not only willcan element designed for water fail prematurely, as you saw, the surface temp of the element can be high enough to cause the oil to breakdown.
Worked at a large candy plant years ago and they had double walled stainless steel tubing. Inside the 2" tubing milk & dark chocolate ran thru and outer 3" tubing had temperature controlled water. Milk chocolate froze around 89 degrees.On short runs from a tempering tank to depositers I had it down pretty good. They purchased 500' rolls of a blue heat trace tape that ever 18" was a new connection point. To keep keep black schedule 40 pipe at a good temperature might install 6 turns every foot of pipe. Too many turns and they complained chocolate or pink, green, or white coating mixture was too hot. VP from the lab told us that candy coatings made with Palm oil should be avoided if your cholesterol is high. Saw that you have transformer oil listed. Just curious that I have not seen a new oil filled transformer for voltages under 15KV in 30 years. ( forget about the utility oil filled transformers that run so hot the gray paint turns dark ). At my first job we had halve a dozen oil filled transformers that were tested and usually at least two required running oil thru a press to reduce moisture content. Had GE 13,200 transformers and crack GE service department contaimaned one of the transformers with PCB'S when they used two long PCB oil filled hoses to reach transformer.
Joethemechanic
Senior Member
- Location
- Hazleton Pa
- Occupation
- Electro-Mechanical Technician. Industrial machinery
Do you believe that the 6.28 ohm combined heating elements are going to change by like 1.2 ohms or something. Of course it works by percentages.
This is all basic electrical theory taught in 8th grade. The numbers are all so small as to be insignificant. and if it isn't as hot the resistance will be lower so it will draw more current, but not enough in this application to mean anything.f it was a manufacturing tolerance it woukl
I'll bet manufacturing tolerances are wider than what difference is caused by the small temperature changes in the element cause.
Hell it's so small a difference in percentage of resistance it'd be in the gold
For all of the heaters that I came across wired in troubleshoot etc for just heating water in food or even injection molding machines ( 500 ton plastic presses might have up to 8 or 10 heater bands on long nozzle. Even a two or three % change in resistance would not have any affect the PID or thermostat would keep temperature at set point. Yea thermostats are not as accurate.