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Minimum Amps Required For Simple RIMS Setup

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A multimeter won't work.  You need an amp meter to check how much load a circuit has.  Some multimeters have an amp meter, but they are typically for teeny loads.  The easiest way to check the loads on a circuit is to turn it off and see what was connected to it by looking for inoperative stuff. 

Another thing, you said you are going to use a 1500w element?  That rating is based on 240v operation, so the current loading at 120v is much lower.  As pointed out above, a 4500w element operated at 120v has a much lower draw.  I think my old RIMS used a 4500w low density element and I never had a problem with over-current.  My new RIMS is run at 240v and all the circuitry was designed for a 50a max load.  That handles 5500w and 4500w elements operating together.   

Pawtucket Patriot:
I'll have to look at my multimeter to see if it even measures amps.

So would the wattage difference between running a 1500w element at 120v be proportional to the voltage difference?  In other words, would running the element at 120v use a maximum 750w?  If so, then I think I should be fine with using a standard 15A outlet.

First, find element resistance:

Resistance = (Voltage x Voltage) / Wattage 

In the case of most water heater elements, the voltage at which their power is rated is 220 to 240 volts (its usually 240v).  For a 1500w element, its resistance is therefore between 32 and 38 ohms.

Second, find the current draw at the new voltage:

Current (in amps) = Voltage / Resistance

In the case of a 1500w element operating with 120v, the current is: 3.75 to 3.15 amps. 

You should now see that a 1500w element is no problem for a 15a circuit.  I would upsize to at least 4500w (9.4a @ 120v) and you could also go with a 5500w (11.4a @ 120v) element.  They should be low or ultra-low density elements to reduce any chance at wort scorching, although scorching is unlikely if a PID is used and setup properly.


Pawtucket Patriot:
Thanks a lot, Martin.  This is very helpful!!

I would check the specs on the 1500W element.  1500W is PROBABLY a 120v element.


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