I am having trouble with a commercial hot water heater,it is rated for 208v most of the time power coming in is 200v to 198v FLA on my contactor is 40 that is split between 3 elements through monitoring the power my volts somtime drop as low as 185, this unit is rated for 208v, 12,000 watts my problem is the contactor has seized up on me twice now i know that a drop in voltz will= larger current could this be what is seizing my contactor
cold water
- Thread starter ROD BAKER
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winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
For a resistance heater, reduced supply voltage means _reduced_ current draw. A heater is _not_ a constant power load; rather the load changes with the applied voltage.
-Jon
-Jon
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
ROD BAKER said:
What do you mean by "seized up"? Do you mean it came on and would not go off?
Is it possible the contactor coil is a 120V coil and you wired it into a 208V circuit?
DanZ
Senior Member
Are you using a 3 phase water heater with a single phase power source? Or vise versa.
Have you called the manufacturer tech support number? It's possible you have defective parts in the water heater itself.
Have you called the manufacturer tech support number? It's possible you have defective parts in the water heater itself.
cschmid
Senior Member
- Location
- Northern cold country
Rod I have several of these types of water heaters..May I ask how long this has been in service??If it is new the scenario does not apply but if it is old then it does apply..what happens is after years of service and not that many either..the contactor has seen several hours of heat and the plastic distorts and starts to become tighter so when the contactor is hot the plastic swells and sticks together then when it cools down it works properly again..Just replace the contactor and you will be fine..Yours is kind of small ours are 120amps..
the units are 2 months old and seemed to work very well four three weeks until the rest of the unit was powered up whitch inclued 13 HVAC units and 12 washers & dryers my thinking is that when all are in operation that the load drops too much (185v) that the 40amp four leg contactor is over drawing and burning up in this situation is this somthing that could be happening or is my thinking going the wrong direction please help
BackInTheHabit
Senior Member
- Location
- Lexington, Kentucky
ROD BAKER said:
Why are you heating hot water?:-?
Not picking a fight here. I know, most people say "hot water heater" anyway. But it is just a "water heater".
cadpoint
Senior Member
- Location
- Durham, NC
U have to love the rest of the story!
This is America, it sounds tired and worn out, replace accordingly!
If new, you wired it wrong or the person before you did!
How one can obtain that low a voltage on 208 service? Sounds like you answered your own question!
This is America, it sounds tired and worn out, replace accordingly!
If new, you wired it wrong or the person before you did!
How one can obtain that low a voltage on 208 service? Sounds like you answered your own question!
these are commercial water heaters 65 gallon with 3 elements on one 4 pole contactor and two 200 gallon storage tanks on a circulature pump that is circulating and heating which is drawing power most of the time to keep the water at a constant temp if you can imagine that which is why i believe there is resistance on the contact when voltage flucuates
Strahan
Senior Member
- Location
- Watsontown, PA
Dealing with a purely resistive load will not cause current to increase when voltage decreases. Using a 4 pole contactor it looks like you are sharing two poles for each leg meaning current draw should not exceed the 40amp rating of the contactor. You are saying these water heaters worked fine until the load was increased on the supply transformers. What type of coil is on this contactor is it a 208v coil or are you using something smaller with a control transformer. It may be possible that the contacts are chattering during this voltage dip if it is longer than a few cycles.
Strahan
Senior Member
- Location
- Watsontown, PA
Is the circulating motor wired to a seperate contactor ( I hope so) and if it is does this contactor have similiar problems? I believe the question is why is the 208 service droping so low (due to increased load without proper sizing adjustments). Sounds like this problem started with the voltage sags. If the motor is experiencing similiar problems than the statement would be true decrease in voltage increase in current.
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