I have a ~50g Marathon water heater, in which I've installed a 1500W 120V element. At the base of the heater I've plumbed in a temperature gauge before a valve, so I can monitor internal temperature. I've left the heater plugged in for a half-hour at a time, and haven't seen the temp gauge budge. I've checked the circuit and verified that power is reaching the element, and even plugged it in with the tank empty (for about a minute) and removed the element, which was giving off heat.

How long should I expect it to take for 25 gallons (or so) of water to heat up?

From what I read the temperature gage is in the liquid in a location that has no circulation. This will not give you an accurate reading. The sensor should be in a circulation stream or in the middle of the heater. Wether it is in the top, middle, or bottom will not make a significant difference as the thermal currents in the tank will mix the fluid enough to have a fairly homogenous temperature in the tank.

Well, that leads to another question, I guess. HOW do I get the thermometer anywhere that has circulation? Or, do I just have to trust that the oil is heated to the appropriate temperature?

quote:

HOW do I get the thermometer anywhere that has circulation?

You would plumb it into the output line of the recirculation pump. Like I have.

Recirculation pump? I don't have recirculation in my design, nor have I seen it mentioned before now. How important is it?

quote:

Originally posted by brianm:
Recirculation pump? I don't have recirculation in my design, nor have I seen it mentioned before now. How important is it?

You are planning to make biodiesel in it, right? Using a pump to circulate the mixture is the best way to mix it and assure a reaction, as well as the best way to introduce methanol to the hot oil.

Brian,
The appleseed design is based on using a pump to do the mixing of the oil and the methanol. It is also used to fill the tank with the oil and methanol.
How did you get your oil into the tank?

The tank also needs to be modified a little in order to use it to make BD. You need to take out the dip tube and disable the upper heating element. You should look into getting these instructions http://www.b100supply.com/product_p/139.htm I think he has a way to download them, but I am not sure how. You should contact Rick for the easiest way to get them. They are a great resource.
You should not go any further until you know for sure that your appleseed is designed properly and will function properly.
To answer your original question the thermometer needs to plumbed in the circulation stream. I have put them both before the pump and after the pump and they both seem to work. It is a little easier to see if you mount it on the top.
But please make sure your system is designed properly before you proceed.
You can also find some pictures here http://www.biodieselpictures.com/
DD

I had to be gone for a few hrs, and came back to read the reply from Dandy Don,and old300d and they are "spot on" seems as though you are on the right track now LOL>

I used the diagram at http://www.biodieselcommunity.org/appleseedprocessor/ to build my processor. I'm not done yet (haven't installed the pump), and had put in water from my garden hose to verify that the element was working. Once I do install the pump, having it run while processing won't be a problem. I just didn't know that it was part of the process. (Glad I found out!)