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Hot water cylinder - Not on boat


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So what's a good HWC brad?

 

We're putting in a solar hot water system, and have been offered choice of SolarMaster or Peter Crocks.

 

One is copper inner 1mm the other 2mm stainless.

 

I'm normally a copper man. 

 

Anyone have opinions on which way to turn?

 

R

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I'm no expert but I would have thought copper would have been the most durable, I would have thought SS would 'work harden' with heat cycles and water hammer 

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Not a lot of sales pitch going on. System is for solar with wetback additional.

 

There's nothing in the price but normally the stainless ones are more expensive and quoted as being the "rolls royce" of cylinders.

 

It does seem strange to me, though, to have a stainless heat exchange coil for the wetback... 

 

Also mixing of metals like that...I can't see it ending well with copper fittings and stainless systems - heating and cooling contraction etc.

 

Bu ti might be limited as to brands and suppliers as the solar system has a bunch of probes etc.

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My father in law was telling me about a stainless one he had, mixing of metals would cause a standard element to quit unless than a week. So if choosing ss, make sure all compatible.

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use of SS and hot conditions look no further than our Dairy industry, lots of boiling water, steam, acids etc. go through them every day they are in operation. I would look for a heating element taht is compatible with SS though. Or if there isn't going to be any mains power input,  the heating coil from the engine / generator exhaust will be all you need.

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I missed the non boat use!!!

Copper had / has been the only option until the 1970's and has been more than adequate for the job. Copper does slowly erode with use. What is now a 5 year guarantee used to be 15 years and before that 25 years. The problem today is the thickness of the copper or lack of it!  It is a finite resource and is getting harder to extract therefore the  price has gone up and is continuing to go up,  Hence the reduction in the thickness of the copper sheet used to make the cylinder and keeps the profit margin up.  The thickness of copper products also show itself in the reduction in the wall thickness of copper tubing and the pin hole leaks that are showing up with greater frequency in (boat) refrigerator / freezer installations.

I have a neighbour who installed an Marshal heater ( wood fired) with a SS header tank 25 years ago, It has never given any cause for concern, the only problem he ever had was the installer using compressed air to pressure test it. He ended up with a larger tank than he started out with. An SS cylinder from  a known supplier would be my recommendation.

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our house cyl started leaking last year

 

was an old copper one and according to the label was 20 gallons

 

so probably 40? years old and still had scrap value 

 

we went copper again

 

couldn't justify the extra expense of the ss

 

(i guess the new copper isn't as thick as the old

 

but i bet the ss is as thin as possible too)

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I think the copper coil V's SS coil as per the above link is as stated. 

The issue here is the tank being either copper  or SS, all standard electric heating cylinders used in NZ do not have a wet back heating coil installed and rely on an electric element to do the heating therefore the link isn't relevant.

Anything with a coil fitted would be a one off special.

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Stainless. 

 

My cowsheds all have LOTS of stainless which gets heated to 85 degrees twice every day. The 40 year old one is still perfectly fine. Stainless comes in several flavors. I have never, ever had any stainless fail in a cowshed.

 

I have many Peter Cocks ones, none have given any problem at all. 

 

If your water is a little aggressive, get Incaloy elements fitted. Thats what spa pools use and they are very durable.

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