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Author Topic: Willis Immersion  (Read 3235 times)
langstroth3
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« on: July 21, 2019, 11:29:10 AM »

Hi - it's been quite a while since I posted, great to see forum sill going strong. My Navitron Solar EV tubes are still operating really well after about 7+ years of operation. Wasn't quite sure whether to post this here in Solar Thermal or PV so apologies if wrong.

Since I also have PV, I'm looking to augment the water heating using surplus PV energy (for those spring/autumn/winter marginal days). Was looking at the Willis Immersion arrangement as an easy retrofit (the tank doesn't have a spare immersion hole).

Anyone got experience of this type of set up? The one thing I don't quite understand is how you don't end up drawing cold water through the willis immersion loop rather than pulling hot water from the hot water tank when someone turns on a hot water tap. My sketchy diagram below tries to illustrate what I'm head scratching about. The Willis type arrangement works by convection.





* Willis.png (40.54 KB, 800x600 - viewed 216 times.)
« Last Edit: July 21, 2019, 11:35:33 AM by langstroth3 » Logged

Solar Thermal = Navitron 40 (20 x 47mm) Evacuated Tubes.
Solar PV = 4kWp, 16 x 250w znshine; sb4000tl inverter
Tinbum
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« Reply #1 on: July 21, 2019, 01:06:05 PM »

Take a look at the instructions. The bottom tee is not just a simple T if I rightly remember.
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85no 58mm solar thermal tubes, 28.5Kw PV, 3 x Sunny Backup 5048, 3x Sunny Island 5048, 2795 Ah (135kWh) (c20) Rolls batteries 48v, Atmos wood gasification boiler, Brosley wood burner, 2000lt buffer tank and 250lt DHW
langstroth3
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« Reply #2 on: July 21, 2019, 01:27:16 PM »

Hi Tinbum, sorry not sure what you mean - I've not bought anything yet so don't have any instructions...
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Solar Thermal = Navitron 40 (20 x 47mm) Evacuated Tubes.
Solar PV = 4kWp, 16 x 250w znshine; sb4000tl inverter
Tinbum
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« Reply #3 on: July 21, 2019, 01:30:36 PM »

Go to their website.
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85no 58mm solar thermal tubes, 28.5Kw PV, 3 x Sunny Backup 5048, 3x Sunny Island 5048, 2795 Ah (135kWh) (c20) Rolls batteries 48v, Atmos wood gasification boiler, Brosley wood burner, 2000lt buffer tank and 250lt DHW
langstroth3
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« Reply #4 on: July 21, 2019, 01:55:18 PM »

...okay...but I've googled Willis of course already - a few places selling the external jacketed immersion, but no website I could find with instructions. (The original Willis company website is all about plumbing services). If you have a website in mind, would you share thanks.

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Solar Thermal = Navitron 40 (20 x 47mm) Evacuated Tubes.
Solar PV = 4kWp, 16 x 250w znshine; sb4000tl inverter
Tinbum
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« Reply #5 on: July 21, 2019, 04:40:28 PM »

I can't find them either now. I seem to remember its a 22mmm 15mm 22mm T piece but the 22mm cold water in is reduced to 15mm on the inlet side and goes through the T and extends into the 22mm outlet.

Its called an injector T.
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85no 58mm solar thermal tubes, 28.5Kw PV, 3 x Sunny Backup 5048, 3x Sunny Island 5048, 2795 Ah (135kWh) (c20) Rolls batteries 48v, Atmos wood gasification boiler, Brosley wood burner, 2000lt buffer tank and 250lt DHW
JohnS
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« Reply #6 on: July 21, 2019, 05:48:49 PM »

Available here
http://www.injector-tee.co.uk/compression.html
or make your own
http://diy.torrens.org/HowTo/Injector/

Amazing what can be found using Google.
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Philip R
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« Reply #7 on: July 21, 2019, 08:20:02 PM »

You do not need and injector Tee.
Does your cylinder have a drain cock independent of the cold feed connection? If so use this connection tee-ed to a drain valve of course. That way the cylinder will not be shorted circuited by the solar syphon when DHW is drawn.

The way the system is drawn on the diagram will part short circuit the cylinder and you risk drawing tepid water from the hot taps, even when the cylinder is hot.

Philip R
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langstroth3
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« Reply #8 on: July 21, 2019, 08:54:57 PM »

Thanks for confirming - having done some more googling on "Injector T's" it doesn't appear to be the right solution as you say, seems more aimed at ensuring a pumped circuit works with/doesn't stop a gravity circuit. It was good to have the "keyword - Injector T" to google for - it's all in knowing the right keyword to search for, then google is great.

Unfortunately my cylinder doesn't have a drain cock, however there is a section of pipework that t's off the cold inlet left from a previous install, I wonder if that will help as it means the route via the willis will be longer than through the cylinder, and through 15mm pipe rather than 22mm. These two things combined might help stop any significant short circuiting, I hope.   



* Willis.png (45.22 KB, 800x600 - viewed 168 times.)
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Solar Thermal = Navitron 40 (20 x 47mm) Evacuated Tubes.
Solar PV = 4kWp, 16 x 250w znshine; sb4000tl inverter
vantheman
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« Reply #9 on: July 22, 2019, 08:05:58 AM »

Just purchased a Willis Immersion to add an additional immersion to a thermal store.

Before purchaseI I  found it difficult to find any installation instructions or directions online,

Therefore when I received the immersion I was surprised to find the instructions completely
counter intuitive,

These showed the unit mounted inverted with the immersion facing downwards towards the ground
the complete reverse of normal installation practice and allowing any leakage from the riser to access the
electrical connections.

Futhermore mounting it adjacent to the base of the tank means that the complete tank needs to be drained
to just change the element .

I was hoping to to install this in the same position and aspect as a conventional top mounted immersion, parallel but adjacent
to the tank.

I wonder if anyone who has any experience of these would like to comment

 

   
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Iain
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« Reply #10 on: July 22, 2019, 11:50:49 AM »

Hi
Quote
.Futhermore mounting it adjacent to the base of the tank means that the complete tank needs to be drained
to just change the element .


Just put a couple of full bore valves to allow isolation. gate valve or ball valve.

Iain
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freddyuk
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« Reply #11 on: July 22, 2019, 12:44:46 PM »

Why not install a double element immersion to the full extent of the cylinder. These are available. Or you can have a long one and a short one for "top loading".
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vantheman
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« Reply #12 on: July 22, 2019, 05:37:15 PM »

Diy 800 litre thermal store .

 I am looking to utilise excess PV. but there is no way to fit internal immersions retrospectively. 

The Willis appears to be just a small cylinder housing an immersion element with inlet and outlet connections at each end.
with no NRV or  restriction between the two outlets .

I have not found any explanation as to why this should be installed pointing upwards and aligned with the bottom of the tank
although the instructions do relate specifically to a syphonic DHW system

I am trying to graft this on to a pumped heating system containing inhibitor.

In this situation it seems tthe logical way to do this is to align the Willis with the top of the Thermal store with the
element facing downwards as normal.  The orientation of the Willis outlets also lend themselves to this configuration.
I will isolate with gate valves to ensure no impeded flow.

I have decided the only way to determine if this will work is to suck it and see and will report back
.
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Countrypaul
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« Reply #13 on: July 22, 2019, 06:03:57 PM »

Can I ask why you believe the Wills should be aligned with the top of the thermal store? I would have thought having the Willis lower would allow a larger volume of heated water above it and therefore better circulation, as the circulation will depend on densities and hotter water is less dense.

I have no experience wth a Willis, and ask out of curiosity more than anything else since I am unlikely to install one as far as I can see.
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vantheman
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« Reply #14 on: July 22, 2019, 09:00:20 PM »

Thanks for the interest Countrypaul.

I had reasoned that by connecting directly the 15mm outlet from the Willis to the existing  22mm CH flow outlet nearly at the top of the tank,.
under non pumped conditions heat from the immersion would syphon straight into the large volume of the tank.
under pumped conditions the heat would be redirected into the CH circuit. 

If the willis was oriented as per the installation instructions towards the bottom of th tank with elements facing upwards I fear
that the water may siphon in the 15mm riser too slowly.causing the thermostat to cycle on and off too frequently.
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