hot water flow sensor

[jessey]

Hi Darrel & SteveB,

Thanks for all the info and the links. I'm now waiting for a friend to return my plasma cutter and as soon as I get it back I'll be starting my project. I think I'll use a copper tubing (for better thermal conductivity) for the DS1820. I enquired to the link that you sent me SteveB for a good thermo substance, I described my application and just got an email back today suggesting to use Artic Silver Adhesive and also got a phone number for arctic silver so I'll call them tomorrow to see what they have to say.

Could anyone here suggest an alternative heat transfer compound (maybe not the best but something that will work to try) that is widely available and easy to get just in case I have to wait for the artic silver adhesive as I live in Canada and sometimes I have to wait a few weeks for some stuff to clear customs. If Active Electronics carry it then I shouldn't have to wait too long.

Its hard to tell in a lot of the pictures of the electric on demand water heaters in the sites that I visited but I would assume that the enclosures for the heater elements are round with convex ends (like a hot water holding tank) so I think my flat design will have to be beefed up somewhat to withstand the extra stresses especially if the water pressure is high. A friend suggested drilling multiple holes in between the length of the elements and using solid round stalk inserted into the holes and welded on each side of the tank to beef it up, a good idea that I think I'll employ. What is the shape of your tank for the heating elements Darrel? Looking at the pictorial drawing of SteveB's non metal polymer tanks, it looks like they are round as well which I think results in less psi stresses overall.

I think I'll put the solar thing on hold and just try and get the heaters working with the code that I posted for now then if I get it working good then I'll consider it. Green is good.

Anyways, thanks for your help and I'll keep you informed on my progress, maybe with some pictures later on.

Thanks
jessey

[Darrel Taylor]

Round here too.

Here's a model that's similar, except ours has a relay, instead of triac.
http://eemax.com/operations%20manual...SP%20instr.ppt

Like I said, it's small.

DT

[air1kdf]

Cool project.

DIY solar setups can be very inexpensive, check out ebay.

I am setting up a solar panel system to heat my 30,000 gallon pool. There are systems like Goldline that make and sell differential temp systems to optimize the heating. They also use 10k thermisistors that sense temperature. There are many sensors that can be placed inside or outside of your setup.

If it was me, I would use 2 sensors. 1 going in, 1 going out. Make sure to add code for circuit failure(like no temp reading, and invalid readings).

I would also forget about limiting flow. It would prove to be more complex than it needs to be, expensive for the control valve and actuator, and a PITA for the end user.

The thermal grease that you mentioned is great for putting a fan on a CPU. But it is a grease and not an epoxy.

FYI a 4x10 ft panel made 20 years ago can boil water in 5 minutes.

[BobP]

Hi,

This may be a simple and cheap solution. When I installed my power shower I was surprised to notice that the flow sensor on the outlets of the pump were no more than a magnet and reed switch positioned on opposite sides of each of the 2 plastic outlet pipes.
I can only assume as the water flow starts the magnetic field changes releasing the reed switch.

It is simple and cheap enough to try?

It has worked faultlessly on the pump for over 2 years now.

Hope this helps,
BobP