Willis solarsyphon

[Northbridge]

Cheer up. like other persons posting, it is an opinion, but one based on experience.

I havent said that they will not work at all, rather it is obvious what the shortcomings are.

[Brandon]

Me? - I'd sooner wait for the independent test results from the setup at Navitron HQ before leaping to possibly uninformed and plain wrong conclusions

 not wishing to accelerate myself towards the point at which I have out-stayed my welcome in these parts, but

           

...independent .. results ...from Navitron...

They are flogging these things pretty hard, check your inbox for the evidence!

I first put one of these in one of our in-house systems about a year ago, and I too wanted them to work, but they are not the magical answer, it has since been replaced with (if I remember correctly) about £40 worth of PHE and this works as well if not better.

[Ivan]

Personally, I'd prefer a twin coil cylinder, but I certainly wouldn't write off the Willis system.

Like the retrofit coil, it will produce a small amount of hot water when there is only a little sunshine, whereas twin coil systems will just heat the bottom of the tank slightly (ie to lukewarm or less).Twin coil tank is highest efficiency on heat transfer, but Willis/retrofit coil systems will give more useable heat....as long as they are used with vacuum tube systems.

The installation is important with Willis - fit it wrong and it will perform badly - probably the cause of some or all of the bad reports.

I wouldn't say we're biased - yes we're selling willis solasyphons, but we're also selling twin coil cylinders!

So I wouldn't call them second rate, but definitely cheaper systems - which means payback will be sooner. Our Navitron demo system should be running soon, so we'll be able to compare the different heating methods (and we've included as many as we can think of!).

P.S Check out Paul's reports on his retrofit coil system performance - very impressive at this time of year.

[wookey]

I actually think the most interesting question is how does willis device compare with equivalent side-arm PHE - where both nominally do exactly the same thing, but the latter is a lot cheaper (at least for DIYing).

I don't think the 'second-rate' comment is fair at all. The considerations are somewhat different for commercial installs from DIY installs (commercial more interested in reducing time, DIYers cost, and commercial keener to avoid 'non-standard' (in general)). But if you want to maximise no-boiler hot water then PHE/willis is almost certainly better. If you are going to use boiler anyway, and reasonable proportion of hot water generated, then coil is better. For some situation in between it's probably a tie. if heating is involved too then there are a lot more variables. But the idea that all solutions other than a standard (in the UK) twin-coil tank are inferior is just wrong.

[Brandon]

Please do not get me wrong, i am not writing them off all together, but the claims seem rather grand when set against the performance that i have witnessed, and set against the cost then it is harder to justify.

[Flamethrower_]

I have to agree with Wookey, in September I fitted two solar collectors to existing Megaflow unvented cylinders by the use of Willis Solar syphons (rather than having to replace with twin coil stainless steel unvented cylinders really expensive!)

Customers are well impressed with the production of solar hot water in December  
 
(The installations were 50 miles north of Inverness !)

By the way these were my first installations using the Willis solar syphon and I will say that YOU MUST FOLLOW THE INSTALLATION  INSTRUCTIONS RELATING TO THE NEED OF CORRECTLY POSITIONING THE INJECTOR TEE WHEN FITTING TO A UNVENTED CYLINDER as I found out to my cost.......! Otherwise all you will get is cold mains pressured water

[mick]

Hi all,

Any fellow installers got actual performance figures for the Willis's they have installed, preferably along with similar non-Willis set ups they've done. I am particularly interested, as were we all, in winter performance - we all agreed that the Willis would be fine in summer with a cool cylinder to work on. Nothing grand just brief installation details and upper, lower cylinder figures for a cold sunny day.

Thanks,

Mick.

[Ivan]

The Navitron showroom system is almost finished...

[paddylen]

Come on fellas - it's now May - any results yet?

[welshboy]

Bump - any update ?

[peater]

Hi Guys

Well over a year since this subject was bouncing in the air. What is the now the general opinion of the 'experts', as many of us from the Heath Robinson Club, look for expert guidance. Has anyone any hard evidence of performance, as no one has posted such information (applogies if posted elsewhere), it may could be construed as a poor performance. 

In Planning, Vaillant unvented vantage 200L storage, 2 x Worcester Bosch Green Skies panels, TDS10 controller, Resol pump.
Is it a Wallis and Gromet, or retro fit echanger coil (these tanks have the emersion boss at the bottom of the tank).     Anyone with a similar setup? 

THANKS

[climber]

Any results from the Navitron demo systems Ivan?

[ericw]

Some published test results

http://www.willis-renewables.com/pdf/Performance_Evaluation_Willis_Solasyphon.pdf

[wookey]

Hi Guys

Well over a year since this subject was bouncing in the air. What is the now the general opinion of the 'experts', as many of us from the Heath Robinson Club, look for expert guidance. Has anyone any hard evidence of performance, as no one has posted such information (applogies if posted elsewhere), it may could be construed as a poor performance. 

I've published plenty of evidence of performance (of a PHE, not a willis). It works very well indeed for us. I would do it this way again in a new house. I can't publish comparitive PHE/bottom coil results because I've only got one system. I wouldn't recommend it to everyone as the optimum system, because it does depend on which parameter you are trying to maximise. (max kWh off roof or max time with boiler turned off)

I never did get proper kWh/day numbers out of the system mustly due to laziness. And now my flowmeter seems to have died. Still I know how fast it was going, and I guess it hasn't changed so I could post-process my data to get real kWh/day. I'll put it on my list :-) (got an extension to detail right now).

[dhaslam]

Why does the Willis and  plate heat exchangers need  a pump?    I had a Willis electric heater in the  last house  (until it set the house on fire)  and it didn't need a pump, or at least not until it shorted and overheated.