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Xringer · 06-01-10, 04:02 PM

They look pretty good for 'used' resistors. Had to dig around for a few 1/4|20 nuts and washers,
but all the measurements came out very close to 40 ohms.

In parallel, these will be 10 ohms, and should be a good match to the (series) panels.

The plan is to mount these on an aluminum plate (maybe 11x5x0.5 inches)
and epoxy the plate onto the top of my boiler.
I wonder if I can find some cheap heat-conducting epoxy. I'm not sure how well JB Weld would work..

Just to the right of that clean spot..

I will need to make a sheet metal cover to fit over the heater array,
it will be insulated to keep the heat inside, so it can be absorbed
downwards, into the boilerplate and into the water near the top.

Each resistor is rated at 250 watts, so the total dissipation is going to be 1KW.
So, driving them with just 500 watts of PV, should allow them to last at least 30 years..

I've been trying to tweak the tracker to less sensitivity to clouds etc.
And I think maybe the array is picking RFI. We live a few within a few
miles of a powerful AM station. I tried adding a small ground rod..
But a thunderstorm this afternoon reminded me that I need a real
ground rod and some heavy connection cable..

I'm considering using RG8 type coax for routing the power.

And, I'm starting to think that PL-259/SO-239 connections
might be better (and cheaper) than N-connectors..
I think the PL-259 (also called UHF connectors) would handle current
better, since it has a much larger center pin. With more contact area.

Using this kind of cable, means that I would have the negative side
of the panels at earth ground, and run the + on the center conductor.

This should allow me to build a grounded bulkhead plate to install at the entry point to the basement.
This one of the old standard Ham Radio types of lightning protection.
(Double Female S0-239)

06-01-10, 04:02 PM	#66
Xringer Lex Parsimoniae Join Date: Feb 2009 Location: Woburn, MA Posts: 4,918 Thanks: 114 Thanked 250 Times in 230 Posts	The resistors came in.. They look pretty good for 'used' resistors. Had to dig around for a few 1/4\|20 nuts and washers, but all the measurements came out very close to 40 ohms. In parallel, these will be 10 ohms, and should be a good match to the (series) panels. The plan is to mount these on an aluminum plate (maybe 11x5x0.5 inches) and epoxy the plate onto the top of my boiler. I wonder if I can find some cheap heat-conducting epoxy. I'm not sure how well JB Weld would work.. Just to the right of that clean spot.. I will need to make a sheet metal cover to fit over the heater array, it will be insulated to keep the heat inside, so it can be absorbed downwards, into the boilerplate and into the water near the top. Each resistor is rated at 250 watts, so the total dissipation is going to be 1KW. So, driving them with just 500 watts of PV, should allow them to last at least 30 years.. I've been trying to tweak the tracker to less sensitivity to clouds etc. And I think maybe the array is picking RFI. We live a few within a few miles of a powerful AM station. I tried adding a small ground rod.. But a thunderstorm this afternoon reminded me that I need a real ground rod and some heavy connection cable.. I'm considering using RG8 type coax for routing the power. And, I'm starting to think that PL-259/SO-239 connections might be better (and cheaper) than N-connectors.. I think the PL-259 (also called UHF connectors) would handle current better, since it has a much larger center pin. With more contact area. Using this kind of cable, means that I would have the negative side of the panels at earth ground, and run the + on the center conductor. This should allow me to build a grounded bulkhead plate to install at the entry point to the basement. This one of the old standard Ham Radio types of lightning protection. (Double Female S0-239) Last edited by Xringer; 06-01-10 at 05:55 PM..