4- 36v 305 watt panels in parallel directly wired to 36v 1200 watt heating element

Toptownjoe

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I have Amp meter wired in line and it reads open voltage of 37-42 depending on time o day. But it reads 0 amps and 0 watts. Heating element not producing any heat. See attachments for photos of Amp meter and dc heating element.

Anyone know why this isn't working? Much appreciated
 

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efficientPV

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These only read current in one direction. I suspect it is connected backwards. Do me a favor, make a chart of voltage and current every half hour to see what this is producing. I'd like to compare your results in direct connect to what could be produced with a power point system.
 

Toptownjoe

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The Amp meter is marked with load and source and wired respectively to that. So I believe it's wired the correct way.

Th panels wired directly to HE did not make the HE heat.

The HE is one that has 2 different elements and the connections just bridge them. I need to make sure those connections are not just on one loop each or else it would just be a open circuit like the Amp meter is reading. Just thought of this so I'll have to check
 

efficientPV

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There is no need to pass current thru the red wire. Doing so will only add more internal heat to the unit and more resistive loss. Just connect one red wire to the positive. The most common failure of this unit is one of the black wires becoming unsoldered because the current shunt got too hot.
 

Toptownjoe

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Found the issue.... I had it in the top of my outside wood boiler and apparently it was working fine at some point and I'm guessing water level dropped and it burned up when only exposed to air
 

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DThames

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Found the issue.... I had it in the top of my outside wood boiler and apparently it was working fine at some point and I'm guessing water level dropped and it burned up when only exposed to air
So, open circuit.
 

DThames

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Have you used the thermostat that the heater vendor is also selling? Just curious.
 

GLC

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I have Amp meter wired in line and it reads open voltage of 37-42 depending on time o day. But it reads 0 amps and 0 watts. Heating element not producing any heat. See attachments for photos of Amp meter and dc heating element.

Anyone know why this isn't working? Much appreciated
I am doing basically the same thing but with a 36 volt/ 2400 watt element. I have tried different scenarios with panel sizes and number of panels. I have the same heating element but split the contacts to only use 1/2 of it per panel string. Best combination that I found was 3 - 305 watt panels wired in parallel. which gave me appx 36 volts and 23 amps. 3 panels on the south east of my house and 3 panels on the west side. Two strings wired to the same element but with the element not tied together on the posts. Pulls solar from about 9am to about 7 pm in the summer. Both sets of panels (connected to different sides of the element) produce 600 watts each + when the sun is at best angle. This DC element is in the bottom of our regular hot water heater tank. Still have the upper element wired with grid tie. Thermostat set at 120 but the upper element is on a timer to come on at 5 am till 7 for early showers. And then back on at 5 to 10 pm if needed on cloudy days. Currently no thermostat on the DC element just direct connect. On sunny days it has no problem at all getting to 150 degrees even with my wife washing clothes or cleaning during the day. I have a temp probe on the tank to set off an alarm if it hits 155-160 so we can disconnect the panels with a 20 amp blade style breaker. I tried a few different dc thermostat type devices but they all failed. In the last week I found a 30 amp DC thermostat switch that can handle the amps and voltage and it is on the way. It is from a heating system in a tractor trailer heating rig.
 
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DThames

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Nov 22, 2019
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I am doing basically the same thing but I have tried different scenarios with panel sizes and number of panels. I have the same heating element but split the contacts to only use 1/2 of it per panel string. Best combination that I found was 3 - 305 watt panels wired in parallel. which gave me appx 36 volts and 23 amps. 3 panels on the south east of my house and 3 panels on the west side. Two strings wired to the same element but with the element not tied together on the posts. Pulls solar from about 9am to about 7 pm in the summer. Both sets of panels (connected to different sides of the element) produce 600 watts each + when the sun is at best angle. This DC element is in the bottom of our regular hot water heater tank. Still have the upper element wired with grid tie. Thermostat set at 120 but the upper element is on a timer to come on at 5 am till 7 for early showers. And then back on at 5 to 10 pm if needed on cloudy days. Currently no thermostat on the DC element just direct connect. On sunny days it has no problem at all getting to 150 degrees even with my wife washing clothes or cleaning during the day. I have a temp probe on the tank to set off an alarm if it hits 155-160 so we can disconnect the panels with a 20 amp blade style breaker. I tried a few different dc thermostat type devices but they all failed. In the last week I found a 30 amp DC thermostat switch that can handle the amps and voltage and it is on the way. It is from a heating system in a tractor trailer heating rig.
Have you considered a solidstate relay controlled by a t'stat, where basically you have FETs switching the DC power? I have thought that might be a good solution but I have not tested it.
 
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