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Solar Collector


dax021

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Hi learned forumites, found these drawings on some forum and was wondering which would be the best solution.  I have been given a lekker flat panel collector and want to connect to an old geyser as a holding tank, then feed into my small 6lt/min gas geyser.  I don't have Eksdom.  Thanks in advance.

Peter

Solar Geyser Connection.jpg

Solar Preheater for Gas Geyser.jpg

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1st two will both work, 3rd one will not get hot water from the "collection box" back into the "holding tank" because the hot water will not flow down into the top of the "holding tank" - that simply means that the "holding tank's" water will never be heated by the "collection box". The input "from street" into the "holding tank" should also be at the bottom of the tank, not at the top. Like hot air, hot water rises and you have to keep that in mind when you route the piping and when you mount the solar collector and where the water enters and exits the "tank" / geyser.

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Don't as yet have a geyser, but am on the lookout for one.  At this stage any geyser should do and I'll just orientate it to make the best use of available ports.  It will basically just be an insulated holding tank.  TP, from what I understand, you are actually suggesting that I use the top picture layout, as the 2 cold feeds are on the same level and therefore the same as a tee of the cold supply.

Out of interest, I plumbed cold water into my collector with a stopcock on the outlet and by 16:00 on a sunny day the water was too hot to hold my hand under it.  At 16:00 today, after no sun the whole day, the water was luke warm.  I could probably just plumb it straight into my gas geyser and just make sure I shower before 19:00 each day.  By the next day the collector is obviously cold, but still not as cold as the water coming from my holding tanks 

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13 hours ago, dax021 said:

Out of interest, I plumbed cold water into my collector with a stopcock on the outlet and by 16:00 on a sunny day the water was too hot to hold my hand under it.  At 16:00 today, after no sun the whole day, the water was luke warm.  I could probably just plumb it straight into my gas geyser and just make sure I shower before 19:00 each day.  By the next day the collector is obviously cold, but still not as cold as the water coming from my holding tanks 

Keep in mind that the collector only holds 1 or 2 litres of water depending on the type and size. If you feed the gas geyser directly from the collector, without having storage, you will use the hot water from the collector within the first few seconds while you shower.

Or do you have a solar collector with an integrated storage tank at the top?

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I'm sure that with that type of collector then your plan to feed your gas heater will work. Incidentally, do you know if you gas heater modulates? ie, reduces it's flame if the required delta T is small. 

Yes, looking at your pictures again, you are correct, the top one is the same as what I advised. I was just thinking of what brand of geyser would work with that set-up. I haven't seen one with the ports available like in the top pic but a HeatTec is similar to the middle pic. 

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I doubt that my geyser modulates, as in it is an ancient Junkers with pilot light.  On the other hand, who knows, as when I open the hot tap it seems to flame up to half, then wait a second or two and then flame up full.  Maybe this is just a pressure or gas test.  Hopefully, I'll be able to regulate the flame by manipulating gas and water flow controls.  If the collector is hot enough my plan is to just close the gas valve completely.  I have tested this and closing the gas doesn't make any difference to water flow.

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On 7/22/2016 at 6:12 PM, dax021 said:

Luckily my collector is a "Sundome" which has two integral 50Lt tubes, making 100Lt of storage.  Not insulated though, so cools down overnight. 

OK, totally different story.  You can then feed the gas geyser directly since you already have storage.

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Thanks all for helping me get my head around this.  I will plumb it straight to the gas geyser in the meantime while I wait for the right AC geyser (insulated reservoir) to come along.  Adding insulated storage should enable me to have hot (solar) water all night too.

(PS. Integrated tanks are actually 55Lt each. I see)

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Sounds good. I am thinking forward to your control of the flame. If it is a permanent pilot type heater then by closing the gas valve when you don't require the heat then you will have to relight the pilot before use the next time. Would it not be better to plumb in a bypass of the heater? I'm sure that once you have a insulated storage vessel you won't be using the gas as much (especially in the summer) in which case periodically having to light the pilot might not be a big issue.  

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Just a question @Transcape Plumber. I have a very similar setup with a permanent pilot Bosch geyser. I have an electric geyser which uses excess PV energy to heat/preheat the water going to the geyser. Does hot water damage the diaphragm of the geyser? Under normal circumstances the first part of the gas geyser only has to deal with cold water and in the reticulation only once the water has been through the heat exchange and burners do you have hot water.

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Hi Chris, I hope it is not too cold there in Graaffies. We share many acquaintances. I went to Union at the same time as Dave Stern, Jason Jacobs etc. I was in Jennifer's class. My name is Russell Collett.

I would need to have the model number to get a concrete answer from the agents but - They recommend not feeding the gas geyser with very hot water. They are usually fed by solar heated systems and in that case, you would always install a thermostatic mixing valve after the solar, before the gas heater. I guess, as long as you set the thermostat on the electric thermostat to around 50 then it will be fine. It seems a pain to waste that free energy though so maybe installing a mixing valve after the pre heat is a better idea. 

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Hi Russell There is a bypass valve that leaks a bit so I have decommission it. My old man mounted it flush with the wall like a shower tap and I can see the damp causing the cement to bubble so perhaps I need to fix and recommission it.

I know Norman, Sincs, Alan and Hugh and Dave Collett was at school with me.

 

 

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Nah someone was recently warning against the crossover skills of a plumber and a sparky (politely called a Jack of all trades). Us farmers pride ourselves in excelling at this. So Russell is going to watch from afar as I cock this up and then say I told you so.

Russell your Dad was with us in March with the birdclub.

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