Fitting a Willis Immersion heater

tnegun

This is the one I'm using its for pumps and hot water cylinders also the Eddi's output limit is 16 amps which matches the EPHs.

Coln64

I would be nervous using this to switch an immersion heater, the datasheet says its use is for connecting to a pump or a valve, the load from an immersion is very different to the load on a pump or motorised valve. Its a tricky problem to solve and you have obviously got a good solution with your set up so far. The only thing I can think of is some clever amendment to the pipework above the willis to allow an immersion heater thermostat pocket to be created separately from the immersion heater and to use a proper dual immersion thermostat with set point and high limit controls. But that takes you back to the initial problem of immersion thermostats and their wide switching bands & hysteresis. Alternatively use your pipe stat to drive a relay to switch the current flow to the immersion: but if your Eddi is the same as my iBoost they are very clear about not installing additional switches or controls so even that may be more difficult than it seems.

Wearb

Any electricians care to comment on above.

I've seen pipe stats used to switch immersion heaters, of course that doesn't mean it correct.

My feeling is that if it's rated to switch that current it should be able to carry it, but I'm not an electrician.

John.G

The EPH stat can switch a 16A resistive load like up to a 3.68kw immersion or 4A inductive load, no problem in switching modern circulating pumps, some pipestats can switch 16A resistive but "only" 2A inductive.

Mutley123

Hi all

Thanks for the great thread.

I'm think of installing a Willis and was wondering where would be best to install the upper connection. I understand that some way up the vent pipe is good, but was wondering about the impact of two 90-degree bends (one where it exits the tank, and one where the pipe reaches the wall).

I've attached a photo - if anyone could provide advice one whether higher-up trumps two 90-degree bends I would appreciate it!

The Continental Op

I'd replace the rt angle joint where the pipe comes out of the cylinder with a T piece then put in another rt angle to connect to your Willis. However if that rt angle is a soldered joint it might be awkward, but if that joint isn't 3/4 inch (think it might be) then you could up the size of that pipe off the top of the cylinder to increase the flow. So largest diameter pipe possible at the top of the cylinder to a T to feed the existing pipe work and Willis. Others might disagree but thats my take on it.

Mutley123

https://www.boards.ie/discussion/comment/120191614#Comment_120191614

Yes, the existing joints are all soldered so that might be a step too far for my rudimentary plumbing skills. Pipes are 25mm (including the feed pipe from the tank) so I'd planned to use 25mm to 22mm reducing, then a 22mm to 15mm reducer to connect up the Willis heater.

The Continental Op

If you replace that hole section by cutting the pipe to the right of the rt angle bend thats a soldered joint you will only need a couple of short pieces of pipe and a straight connector to get the start of the set up for the Willis. Given the small amount of pressure exerted by the heat to move the hot water around the system I'd try and reduce the number of bends ruling out your connection to your highest arrow.

If you go for the lower arrow you are still going to need to remove the pipe coming off the tank to put in your T connection there so you are half way to my suggesting anyway.

TwmSionCati

This is indeed a fabulous thread, but there’s something I haven’t grasped, brought up by Mutley123’s “wondering where would be best to install the upper connection”, given his understanding that “some way up the vent pipe is good” [#186]. Why should that even be necessary?

I have a perfectly conventional DHW cylinder with a boiler-fed coil at the base and a 27” electric immersion-heater vertically mounted on the domed top. The element’s now died (short to earth), and can’t be dismounted because too close to the ceiling.

I could of course install a 14” replacement, mounted horizontally in the side of the cylinder, just above the coil, using an appropriate Essex flange.

Or I could install a Willis and direct its output into the cylinder, at roughly the same height, again using an appropriate Essex flange.

The upper connection would be far below the vent pipe: but what's wrong with that?

Regards to all, TSC

The Continental Op

https://www.boards.ie/discussion/comment/120217623#Comment_120217623

Willis heater doesn't work that way. Because the force created by the thermo syphon the Willis creates is quite small you need to get a reasonable difference in height between the top and the bottom.

The Willis doesn't heat the water in the same way as the internal immersion. With the Willis the water stratifies in the tank so in effect it heats the water at the top of the tank first and as the thermo syphon moves the water the tank continues to heat from the top down.

iwb

I learned a lot from reading this thread but went a different way about solving the same problem. Not everyone has a coil in their tank they can use but I did, so I tried this. I started a new thread rather than mess this one up. Any feedback greatly appreciated.

5500

Hi Guys, in the same boat with solar here and copper cylinder/bath immersion not heating the whole thing. Is adding a willis my best option to get the tank (200litre) full? Although from looking at diagrams I see that it looks to heat water from the top, the same as my current immersion, so how does it end up heating the whole tank as opposed to the current immersion?

Is there another option that would circulate water around the tank that might be more beneficial or is willis the only way to go with keeping the current tank?

The Continental Op

https://www.boards.ie/discussion/comment/120813289#Comment_120813289

Because its external and connected to the top and bottom of the tank it sets up a very low powered thermal syphon so it pushes hot water out the top while sucking cold(er) water in from the bottom. Provided the water coming in at the bottom will keep the thermostat below the level its set at it will keep heating the water. It should work no matter what the height of the element in the Wilis is in relation to the tank but the lower it is the better the thermosyphon will work so basically mount it a low as possible.

Ceedee22

Hi all, thanks for such a useful thread. I'm still at a bit of a loss on what is ideal in terms of fitting to the expansion pipe. My setup is similar to the previous in having 2 right angle bends but pretty tight in terms of what I can do due to distances to bends. If I fit higher up (30cm or more) on the expansion pipe do ye recon it would cause an issue, versus trying to remove soldered sections and adding a T?

The Continental Op

My understanding is fitting higher up will be fine and should improve the flow in the Willis. The down side is you are moving heated water through a greater distance of pipework outside the tank that is subject to heat loss so lag it well.

bawnBeag

Would this be a good alternative to a Willis? https://www.wrightpumps.co.uk/product/energy-storage-device/

Any thoughts on whether the hot water flow would be impacted?

Jonathan

https://www.boards.ie/discussion/comment/122389029#Comment_122389029

Haven't seen that before but it's just a destratification pump so no reason why it shouldn't work. Quite a nice design. And much safer than a Willis heater too.

ctlsleh

looking for some advice please……..

I have 2 electric showers at the moment, think one is going to go soon. I have a 40Gallon standard cylinder (about 25 years old), immersion is gone in it, an I have 7kW solar with 5kW battery.

I’m thinking of getting rid of the electric showers when they fail, upgrading the tank and maybe getting a Willis and running it off the solar? I don’t use that much hot water and I can only warm it through the central heating if I want hot water in the house oil boiler) but would like to have it warm at least, esp in winter.

Additionally I was thinking I could have just normal regulated showers and a central pump, although I’m concerned about the noise, as the cylinder is off my bedroom? Upstairs(2 story house, showers are also upstairs so not much gravity)

would I be better to replace the electric showers with individually pumped showers, is a Willis more efficient than an immersion? Would it be worth getting an eddi or just use a timer? What size tank? 2 adults, 2 college kids home at weekends. Approx price to upgrade? Is it worth it?

appreciate any ideas and sugggestions. Thanks in advance….

conor_mc

if you have an attic tank then your pressure is dictated by the head (gravity) of that tank, not your hot water tank. We have two pumped showers in a similar setup, works fine.

Re tank size, we bought a house with a down-sized tank for previous owner of about 120l, pain in the backside, stick with a decent family size tank (40 gal = 180 litres or so).

Don’t recommend an Eddy or other complicated electronics with solar feed-in tariff now available, fix up your immersion and get a timer switch to run it on cheap overnight electricity instead.

ctlsleh

https://www.boards.ie/discussion/comment/122488285#Comment_122488285

thanks, do the pumped showers provide good power, or the same as an electric shower?

conor_mc

better than an electric shower, particularly in winter when the incoming water is much colder. Mind you, you might have a similar problem with a Willis (as in, it’s also heating water on demand). The electric showers work best straight off pre-heated water from a tank.

John.G

https://www.boards.ie/discussion/comment/122513212#Comment_122513212

Triton sell a power shower, the Novel SR, which looks like the electric T90SR. The Novel SR can supply up to 14LPM at any temperature you like, say around 40C showering temperature, it has to be supplied with cold water from the CWSC and hot water from the (vented) HW cylinder and is only limited by the HW cylinder volume, a 200L cylinder heated to 60C will give 23/27 minutes winter/summer showering time at 40C and 14LPM, you can run it at any flow rate you like, 14LPM or less. The T90SR, a all electric 9.0 KW shower will "only" give 3.9/5.9 LPM winter/summer, some find this perfectly acceptable, others don't, all this has probably been posted before.

ctlsleh

https://www.boards.ie/discussion/comment/122513402#Comment_122513402

Thanks @ John.G very helpful

ctlsleh

good point @conor_mc regarding the Willis…….think I’ll go for a larger tank and immersion……and move to power showers when the electric ones die…….I assume Mira also do pumped showers, as my electric ones are Mira and I think they tend to have the same shape/size, so easier to replace