Locating safety thermo switches on the head

[potter]

Also for fan control.

[bschwartz]

They only top out at 180 if you stop turning at the factory set point.   I use one turned a little past it on my cleaning centrifuge.  It works fine.

[Ronmar]

Ron, while I put in the larger radiator, I may redo the expansion tank.....
Do you have pictures of yours? (aside from your cute avatar)

Sure, here are a few, but my "cute" avitar is basically a scale drawing of my system:)  

Here is a pic from the front.  I drilled and tapped a hole in the top of that 90 degree elbow and threaded in a 1/4" hose barb fitting...



Here is one looking up past the pipe fitting that houses my 120F secondary loop thermostat.



The tank came from Napa, the P/N is 730-4514.  It is a good solid tank, you just need to drill up thru the cast in hose barb on the bottom to use it in this fashion.  I also have one on my tractor.  Surplus center has a bottom-fed one similar on their website for $3.95.  https://www.surpluscenter.com/item.asp?item=1-2848&catname=water  The napa one is easier to mount as it has tabs cast in for bulkhead mounting, where the surplus center one will need rails to bolt it down onto...  I also have one of the surplus center tanks I bought for another project, it is also a robust tank, and has a strainer/filter on the bottom outlet port...

[bschwartz]

Wow, that looks like a really big heat exchanger!!  What are it's approximate dimensions, and fittings?

[Ronmar]

The heatex is 5" X 12" with 10 plates, not real big at all.  It has 2.something SQ FT of transfer area if I recall correctly.  It has 1" male NPT ports, so it was a perfect match for thermosiphon with the 6/1's plumbing...

[potter]

I am using them with 12VDC and was scared that the arching would damage them  but so far so good, there have been thousands of cycles on the fan thermoswitch. This gives me hope that the overheat trip will work when needed with only two cycles so far.

   Potter

[Ronmar]

I am using them with 12VDC and was scared that the arching would damage them  but so far so good, there have been thousands of cycles on the fan thermoswitch. This gives me hope that the overheat trip will work when needed with only two cycles so far.

   Potter

Those switches are designed to switch the current on and off to a 240V, 4500W electric heating element.  Or put another way, they open and close on a live 18.75A load several times a day...  I think they will hold up alright with most anything esle you are going to throw at it using 12VDC:) 

[Crofter]

The current may not be the main issue. Breaking a DC flow without drawing an arc is more difficult than with AC which goes to Zero 120 times a second. DC inclination to pit points depends to a large extent on the nature of the load, inductive or not. Metal transfer contact to contact can occur and become a problem after a large number of cycles as it is always in one direction. This is the issue with ignition points and the inductive load of the coil. Might be a good idea to stick a capacitor parallel to the contacts in your temp switch.

I was in complete agreement with Ronmar in regard to the relative current consideration but Jens did sow the seed of doubt and brought back this bit of trivia.

[mobile_bob]

another option is use the temp switch contacts as pilot contacts to control a 12v automotive relay
they are cheap and can handle 30-40 amps dc for thousands of cycles, and they draw so little current
for their coils that the temp switch contacts should last nearly forever.

bob g