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Restive load on UK supply

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malc-c:
Thanks again for the suggestions.  The thermostat is quite responsive using DS18B20 digital sensors.  My concern was really the impact of running these 12w / foot heaters at four times their rated power.

I have since found a manufacture of similar heat strip but made to run on 230 / 240v and meet EU requirements.  Just waiting on a reply to my enquiry to have 30' shipped to the UK for use in my new hatchling rack.  Failing that the use of a 240v to 120v transformer seems a logical approach.

Thanks again for the suggestions...

jeroen79:

--- Quote from: malc-c on July 02, 2019, 12:16:16 pm ---Never thought about that.  Obviously it becomes twice as expensive, and fitting two strips would prove challenging as its doubling the area, but I guess its worth experimenting with

Thanks

--- End quote ---
It would not be twice as expensive.
You would need x Watt of heat and thus x/12 feet of heat strip.
At 120V you connect the strip as it is.
At 240V you cut the strip in half and wire the halves in series.

dzseki:
What is actually stopping you to get heater cables those were already designed for 230-240V operation? We had such for turtles...

malc-c:

--- Quote from: jeroen79 on July 02, 2019, 01:47:57 pm ---
It would not be twice as expensive.
You would need x Watt of heat and thus x/12 feet of heat strip.
At 120V you connect the strip as it is.
At 240V you cut the strip in half and wire the halves in series.

--- End quote ---

I would have thought that I would need to use 2 x 12w 120v strips in series on 240v.  If i had a single 12w strip and cut it in half, effectively making 2 x 6W strips and wired them in series would it not equate to the same as a single 12" 12w strip as the resistance would still be the same ?


--- Quote from: dzseki on July 02, 2019, 02:05:43 pm ---What is actually stopping you to get heater cables those were already designed for 230-240V operation? We had such for turtles...

--- End quote ---

In the UK these rolls of heat strip are not available.  You can get ready made 6" wide strips up to 47" in length, but are very expensive.  The heat strips on a roll are around $2.50 per foot.  As posted above, I've found a manufacture in the US that supplied the same product but at 230/40 volt rating.

jeroen79:

--- Quote from: malc-c on July 02, 2019, 02:42:05 pm ---
--- Quote from: jeroen79 on July 02, 2019, 01:47:57 pm ---
It would not be twice as expensive.
You would need x Watt of heat and thus x/12 feet of heat strip.
At 120V you connect the strip as it is.
At 240V you cut the strip in half and wire the halves in series.

--- End quote ---

I would have thought that I would need to use 2 x 12w 120v strips in series on 240v.  If i had a single 12w strip and cut it in half, effectively making 2 x 6W strips and wired them in series would it not equate to the same as a single 12" 12w strip as the resistance would still be the same ?

--- End quote ---
No.
Think of the strip as two resistance in parallel.
At 120V each draws 6W (50mA @ 120V).
If you cut them apart and connect them in series each will have half the voltage across it.
At 240V, each will still have 120V and each will still draw 6W.

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