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Change 3 phase Steam Boiler to 3 phase Hot Water Boiler?

tinrat

Nov 21, 2021
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Hello all! I would like to “slow down” a 3 phase Steam Boiler so that i can utilize the 3 phase elements to only create hot water. I have taken single phase 220 elements and ran 110 through them to cut the wattage and heat created in a previous project. But I can’t grasp how I might lower the power to elements in a 3 phase setup. Can this be done using resistance? Or capacitors? Or a combination of both? And if so, would some sort of heat sink be needed to help cool any of the items restricting the energy? Any thoughts on this would be greatly appreciated. Thanks,
Don tinrat
 

Harald Kapp

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Nov 17, 2011
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Use a bang-bang controller:
Measure the temperature of the water with a sensor. Turn power off when the water temperature you want has been reached. Turn power on again when the water cools down. Add a bit of hysteresis, say 2 ° for example to rapid switching (oscillations).
This way you make optimal use of the heating elements.
 

tinrat

Nov 21, 2021
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So how would you wire this into a three phase circuit to reduce the power to the three elements that create enough heat to make steam in a chamber? I am not very smart on electrical. I don’t understand how this can be wired into the 3 legs?
 

Harald Kapp

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I don’t understand how this can be wired into the 3 legs?
You will need a 3-phase thermostat. This is essentially the bang-bang controller I mentioned. The single phase controller depicted in post #3 will not work.
In some forums you will read that people often use a single phase thermostat instead plus a 3 phase contactor. The thermostat then controls the contactor which in turn switches the power side (heaters) in all 3 phases.

So how would you wire this into a three phase circuit to reduce the power to the three elements that create enough heat to make steam in a chamber?
Power is reduced by varying the ratio of on-time to off-time (duty cycle) of the heater.
The water will not instantly turn into steam when the heater is turned on. Instead the temperature of the water will rise slowly. When you turn of the heater once the correct water temperature has been reached, the water will no longer continue to heat up (apart from what energy it picks up that is stored within the heating elements).
 

tinrat

Nov 21, 2021
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Harold,
Is this “ bang-bang controller” switching applied to each leg separately? Would one need to attach three thermostats such as the one Bluejets has posted? I think I see the concept. But I don’t understand how to apply this switching to this 3 phase circuit.
 

Harald Kapp

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I don't think using separate controllers for each phase is a good idea. The controllers will not all switch at identical times. Use a dedicated 3 phase controller or the controller plus contactor circuit.

I am not very smart on electrical.
You're dealing with potentially lethal power levels (voltage, amperage) here. You should leave this to a qualified electrician.
 

tinrat

Nov 21, 2021
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Harold,
Sorry, it seams that you are answering many of the questions while I’m still asking more questions! I now see your answer and have a better understanding. I will see if I can find a 3phase thermostat that I can place in the system. Thank you very much. I appreciate your ability to explain this as now i have a better understanding of how to proceed. This was a project that has been “back- burnered” for some time. I will try to work on it soon and will post to you my results. Thank you again.
Don
 

Bluejets

Oct 5, 2014
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The single phase controller depicted in post #3 will not work.

Yes it will.
Use the thermostat shown to operate a contactor , 3 phases in and assuming 415v, star the three 240v elements together, done.
Thermostat shown also has an overtemp cut out which will work in conjunction with the rest of the layout just explained.
 

flippineck

Sep 8, 2013
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Possible to just use one phase on one, single phase, thermostat if there is a supply neutral available? Just leave the other two phases disconnected, unless it causes uneven heating in the chamber?

Second thoughts, it might leave live terminal(s) inside the connection box that don't appear at first glance to be live. That could end up causing someone a problem in the future.

Is it worth researching the make of boiler, to see if there's an easily changeable, lower powered / single phase element easily available at an economic price?

A single-phase thermostat controlling a high-current 3-pole contactor (relay) may be cheaper.
- I'd be following that advice
 
Last edited:

tinrat

Nov 21, 2021
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Hello all! I would like to “slow down” a 3 phase Steam Boiler so that i can utilize the 3 phase elements to only create hot water. I have taken single phase 220 elements and ran 110 through them to cut the wattage and heat created in a previous project. But I can’t grasp how I might lower the power to elements in a 3 phase setup. Can this be done using resistance? Or capacitors? Or a combination of both? And if so, would some sort of heat sink be needed to help cool any of the items restricting the energy? Any thoughts on this would be greatly appreciated. Thanks,
Don tinrat
 

tinrat

Nov 21, 2021
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Does this help? I am still confused.
 

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tinrat

Nov 21, 2021
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It took me an hour to figure out how to post these. File sizes were too big. Hope othets can still see the detail enoug.
 

tinrat

Nov 21, 2021
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A single-phase thermostat controlling a high-current 3-pole contactor (relay) may be cheaper.
Ok I see the idea here. I have quite a few starters off different pieces taken out of operation. I wonder if the “speed” the large 29kw boiler elements would heat up might be a problem to my contactor/starter? I may be in way over my head as i really don’t have a working understanding of how to wire such relays. I have received great answers to my question but am starting to realize that I lack the intellect to apply a lot of the information you gentlemen have so graciously provided. I apologize for
 
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