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Post by JohnV on Mar 10, 2017 15:48:29 GMT
just on 1Kw
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Post by JohnV on Mar 10, 2017 15:55:02 GMT
that sounds a neat out of the box idea ....... my panels are about 72v raw voltage the immersion is 3Kw so about 19.2 ohms so at 72v that's 270w at about 3.25A ........ Thinking about it, I don't see why I couldn't leave the solar controller connected. If I connect the immersion direct to the panels via a c/o relay operated by the dump power setting I could still use the immersion when on shore power/generator edit to add ..... you already said that ..... must learn to read properly !! I'd prefer a plug and socket arrangement, more straightforward (fule proof? than a relay with many terminals. How many watts of solar do you have btw? I think the thing that bugs me is seeing 75v at the panels with only half an amp @ 24v going to trickle the batteries. Probably the best thing will be to reduce the immersion to a 1Kw unit and run it from a el cheapo modified sq wave inverter when the dump load level has been reached. I don't particularly want to reduce the immersion though as when running on gennie it's nice and quick to heat up (6Kw gennie)
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Post by smileypete on Mar 10, 2017 16:50:39 GMT
1kW? Jeez! Best I can think of is a cheapo 1kW inverter 110V inverter to feed the 3kW immersion, should run at about 600W which is a useful amount. Or do some switcharoo with double pole changeover relays to put 4 panels in series to the immersion heater, should give about 120V, again for 600W heating. I guess you have 6 domestic panels in 2x3 series parallel so a couple could be left on the controller. With the latter it's a bit like those double pole contactors that let you start an engine with 24V then charge the pair of starting batts with 12V. Probably just one double pole relay would do it.
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Post by Deleted on Mar 10, 2017 17:20:45 GMT
Your idea about using the speed controller - do you think it would work to allow a 2.5kw heating element to run from a 700w generator? Would almost certainly kill an inverter genny! A low frequency inverter will have a gurt big transformer which protects the delicate and pricy mosfets. Do you have a Morco water heater or gas hob something like that? Gotta be cheaper than petrol for a genny.... I've got running hot water but I want to boil my clothes and my nice new clothes cooker has a 2.5kw element in it. Apologies for this being off topic.
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Post by tonyqj on Mar 10, 2017 18:55:39 GMT
I'd prefer a plug and socket arrangement, more straightforward (fule proof? than a relay with many terminals. How many watts of solar do you have btw? I think the thing that bugs me is seeing 75v at the panels with only half an amp @ 24v going to trickle the batteries. Probably the best thing will be to reduce the immersion to a 1Kw unit and run it from a el cheapo modified sq wave inverter when the dump load level has been reached. I don't particularly want to reduce the immersion though as when running on gennie it's nice and quick to heat up (6Kw gennie) Won't the dump load switch off almost immediately when you start drawing 100A from the batteries?
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Post by smileypete on Mar 10, 2017 19:20:38 GMT
Would almost certainly kill an inverter genny! A low frequency inverter will have a gurt big transformer which protects the delicate and pricy mosfets. Do you have a Morco water heater or gas hob something like that? Gotta be cheaper than petrol for a genny.... I've got running hot water but I want to boil my clothes and my nice new clothes cooker has a 2.5kw element in it. Apologies for this being off topic. Hmmm, don't think there's a cheap easy answer here if your geny only does 700w...
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Post by JohnV on Mar 10, 2017 19:31:02 GMT
I think the thing that bugs me is seeing 75v at the panels with only half an amp @ 24v going to trickle the batteries. Probably the best thing will be to reduce the immersion to a 1Kw unit and run it from a el cheapo modified sq wave inverter when the dump load level has been reached. I don't particularly want to reduce the immersion though as when running on gennie it's nice and quick to heat up (6Kw gennie) Won't the dump load switch off almost immediately when you start drawing 100A from the batteries? The Hysteresis of the dump load settings are presettable so they can be set to a suitable level ...... also remember it's a 24v system and we are talking about a 1Kw unit supplying approx 600 watts so the drain would only be of the order of 25A
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Post by quaysider on Mar 10, 2017 20:00:04 GMT
the max it can handle is 150v and the 3 panels get to about 125 give or take..
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Post by JohnV on Mar 11, 2017 9:24:18 GMT
1kW? Jeez! Best I can think of is a cheapo 1kW inverter 110V inverter to feed the 3kW immersion, should run at about 600W which is a useful amount. Or do some switcharoo with double pole changeover relays to put 4 panels in series to the immersion heater, should give about 120V, again for 600W heating. I guess you have 6 domestic panels in 2x3 series parallel so a couple could be left on the controller. With the latter it's a bit like those double pole contactors that let you start an engine with 24V then charge the pair of starting batts with 12V. Probably just one double pole relay would do it. I've been thinking long and hard about this. It will have to be put on the back burner for now, I have enough jobs that need doing over the next 6 weeks without adding another fairly time consuming task to the list. Your idea about switching the panels round to get the higher voltage for the existing immersion is interesting, I have 4 x 250w panels wired series parallel with each pair of series panels wired back individually to the engine room and a 4 pole isolator switch. in series this would give me about 140v about 1Kw if applied to the existing immersion ....... a sensible sort of performance !!! The parallelling being at the output of the isolator, this would obviously simplify any wiring changes. One possibility occurs to me is that the switching could series the panels and connect that to the immersion but leave the MPPT controller connected to just one of the pairs (the o/c volts of all four in series is above the max input volts of the unit) I do have in my junk box some delta star mechanically interlocked contactors (240v coils, but this voltage is available at all times on Sabina, shore/generator/battery and inverter) Certainly I could use them at least for a trial run ......... (not keen on spending money if I don't have to ) Definitely something I will investigate later on this year (I will probably have time to kill while waiting on drydocking) Lots of food for thought here. When I have tried it out I will post it up here Thanks for the ideas Pete
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Post by Deleted on Mar 11, 2017 10:49:08 GMT
Has anyone tried solar thermal water heating? Or would the small pump required negate any benefits?
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Post by Deleted on Mar 11, 2017 11:37:22 GMT
Has anyone tried solar thermal water heating? Or would the small pump required negate any benefits? I'm going to try a pool heating mat but I doubt it'll be feasible to pump hot water down to the calorifier - will need its own water tank on roof with it I expect. I started a thread about this yesterday
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Post by peterboat on Mar 12, 2017 23:12:15 GMT
I bought a 12 volt immersion from ebay a few years ago it was normal size 300 watts it worked ok and got water hotish but didnt last long so ended in failure! It ran from the dump side of my midnite controller so easy to wire in and only used what was waste power might try it again on the broads cruiser but look for a better immersion
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Post by quaysider on Mar 13, 2017 6:10:01 GMT
thanks for all the input here ... on reflection, I think I'll use the shower block in summer ;-) lol. Seriously though, that chap on ebay selling the reducing flanges and one of his 12 ones has to be worth a try - I've even got Mick on the boat behind researching the topic now as he's keen to have a go.... not that you'd think he showers much if you get what I mean
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