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Temporary heat source for UFH: Willis heaters

oranjeboom

Entry posted by oranjeboom

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After various delays, the time has come to get some heat into the house, and as there have been a few on BH that have gone down the route of Willis, thought I would give it a go as well. Hopefully others will find the blog entry also.

 

Background:

  • Renovated (3G passiv-rated windows, 120mm EPS EWI, 400mm loft insul, MVHR - not tested air leakiness yet) / extended (175mm SIPs) south facing detached house, East Kent
  • 156sqm of wet UFH in 100mm concrete (with circa 300-375mm EPS insulation)
  • 130L in UFH
  • Wunda 12 port manifold (The heating valve on the manifold operates in the range of 30-70oC)
  • Wunda wired room thermostats for each room (but probably won't use for this temporary setup now)
  • 12Kw eDual for DHW (not to be included as part of Willis setup)
  • 12Kw Sunamp for DHW/UFH (not to be included as part of Willis setup)
  • 3.8Kw PV (potentially have further DIY grid implemented later on)

 

Not looking to cater for worst case low temps as at these times will just plug in some extra heaters:

 

image.thumb.png.295847607acdac4392e32785661847d1.png

 

 

image.thumb.png.c4678aa7fe5231b1bb4fc06732888055.png

 

I originally ordered 2x 12Kw heat batteries for DHW and UFH. Total reliance on the PV in summer and then off-peak grid in the winter. An all electric approach initially without ASHP. Not keen to spend £8-10k on an MCS installed heat pump to get back an estimated / possible £8-10k. Installers seem very vague on the RHI returns and if I have read correctly, I will have to be metered in order to qualify in any case (as have not lived in the property previously). Since the house will be far above buildreg stds (but below PH level), I simply won't be using the amount of expected input that the installers calculate - hence I won't be getting back the cost of the ASHP supply and fit install. So most likely won't go down the MCS route, and if I were to install an ASHP, it would be a cheapy from fleabay.

 

Having excluded using an ASHP, I learnt that Sunamp were testing various units late 2019. But typically with Sunamp, after continued confusion on their part as to what ASHPs they may have tested/not tested/will be testing soon, I've made the decision that I can't want any longer on their input. So for now I will leave the ASHP option until later on and perhaps consider a propane unit (e.g. Vaillant ) when they come online on a non-RHI basis if I can get a decent install cost.

 

 

 

Willis Heater approach

So therefore looking to heat the UFH with 2x 3Kw willis heaters in order to progress with the internal house work. Thought I'd add some info on here as a lot of people like myself aren't familiar what they are. They originated out of Ireland and still much in use over there. They're essentially external immersion coils and instead of sitting inside a tank are simple external electric units - AKA "Willis jacket", "standard sleeved immersion heater"," inline electric heater". Googling should get you something like this:

Willis Immersion Heater | Shell & 3kW Element

 

Item Weight 1.15 Kg
Product Dimensions

30 x 9 x 9 cm

 

I have tried to get plumbers interested in rigging this up, but they're either not interested or have told me it's not possible/don;t know what a willis heater is. I've managed to plumb in all the Hep2o in the house, so hopefully this won't be too much of a bodge.

 

@TerryE has kindly discussed his set up which is pretty impressive with his DS18B20s set into the walls etc. I'm no programmer and my javscript is mainly simple web stuff and wanting to get heat into the place ASAP, I just want a KISS approach for now. Perhaps later I will think about having some of it programmed using Terry's Node Red option which makes for interesting possibilities. Get a feel for Terry's approach here: 

 

But as I've said, I'm after a bog standard dummies approach to this - seriously KISS:

 

So rather than wiring up room thermostats to the wiring centre, I will for now simply use the Willis inbuilt thermostat and set that to gradual increasing temps from 10oC up to a max of 25oC. A gradual heat increase seems safer in my mind. My only concern is if the Willis thermostat fails and carries on beyond 25oC - up to max temp. Obviously I will have the manifold mixing/blending valve that should restrict temp flow into the UFH also, but is there a further failsafe to consider?

 

Dummies layout.

Eventual Sunamp units (for DHW) will be located on left of manifold so having to locate Willis heaters to right  and expansion vessel top right:

 

1909803810_willissetup2.JPG.ac25b07edcc1b69892d4d33a3c4e984b.JPG

FYI: The immersions need to be turned the other way (so colder water enters the side)

 

Parts list:

  • 15mm copper pipe. The Willis heaters are 15mm so I presume plumbing them into the manifold with 15mm would be okay?
  • 15mm plastic pipe for cold return should suffice I presume?
  • Bottle vents - automatically release any trapped air (like this one). Do I need any and if so where do I place them?
  • Willis heater (ebay has the cheapest)
  • Expansion vessel - 8litres sufficient for total UFH volume of 130L? (like this one) 
  • 20A DP switch outlet (for each willis) from a 16A MCB (like this one)  . Probably one for each willis
  • Immersion timer (like this one) to be added possibly when I change over to E7 low tarriff rates

 

Will get an electrician to wire it all in for me!

 

Be grateful for comments, suggestions and any answers to above questions!

 

 

FYI: I'm no way the first person to install a Willis, so here's a list of other users on BH that have gone the Willis way and will know more than I do:

 

@dpmiller: photo / details here

@TerryE

@vivienz

@CC45

@chrisb here

@Gav_P - here (Any pics?)

 

Willis instructions:

 

schematic

 

20200117_104153.thumb.jpg.1021a23b20f869bf8516fe2b44605ab9.jpg

 

 

 

 

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Jeremy Harris

When we bought the house in Portpatrick that had a genuine Willis heater (an "Economiser") the installation instructions were left behind by the previous owner.  This would have been around 1994.  The diagram was a line drawing that was identical to that diagram posted above.

 

As mentioned before, I think the issue is that these things are now made by several different companies, and it doesn't even look as if Willis Heating still make them.  The companies that are now making them seem to assume that people will know how to fit them, probably not that sensible given that some are now using them for purposes that Willis never intended back when they first designed them.

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Triassic
On 23/01/2020 at 13:29, Nickfromwales said:

On our permanent installs they’re exactly as you say. Contractor fed so cannot be run dry

Does anyone have an electrical diagram using contractors? My electrician starts in few weeks time so would like to give him something.

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dpmiller

Correct fitment is indeed terminal box down. I don't think I've ever heard of one failing ever but I do know that the housing is light-gauge copper and the chances of unscrewing the element out of an elderly one are small. Hence some now being sold as a soldered-up unit.

 

interesting note also that in their normal application- from the bottom to the top of the DHW cylinder- running the heater for a minute or two to get hot water moving means that you can then open a tap to a low flow rate and have continuous hot water. The willis basically bypasses the tank...

  • Thanks 1
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oranjeboom

Question for the experts. Can I use a flexi braided steel tap type connector to join up the copper to the manifold? Most of the flexi's I have seen will operate up to 10Bar and temps of 85 degrees. The willis setup is most likely going to be a temporary set up ( and likely will be used as a backup if ASHP is out of action) so be handy if I could just disconnect the whol willis side of things by using flexi's. With the current arrangement it's also a pain in the backside to solder and place all the copper, only for me to have to cut the pipework later on again for ASHP connections.

 

20200123_164645.thumb.jpg.64e1a85a2fb6c3c8d2cf4571ea477301.jpg

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dpmiller

Yep. I was able to mod my manifold to get flow out into the Willis, but only because a. it had a bypass and b. said bypass pointed at the return of the Willis. And I have the Willis underneath the manifold so have the chance of convective flow anyway.

 

You'll need a pump...

 

unless... where does the braided hose at the far right go? Tee into that and connect to the bottom of the Willis, and go from the top of the heater to the supply into the manifold. Cap the return. Sme of your flow will be diverted through the heater and the mixer will then sup heated water.

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oranjeboom

Bugger! Wish someone had spotted that at the beginning.

 

Will see where I can squeeze the pump in. 

13 minutes ago, dpmiller said:

unless... where does the braided hose at the far right go?

 

That's a filling loop connected to the mains -  I will need purge all the loops of air. Also need to get a bit of copper in there still to the expansion vessel (out of shot). 

 

So what pump should I be looking at? 

 

 

 

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epsilonGreedy
55 minutes ago, Jeremy Harris said:

The manifold pump only pumps around the loops though.  You'll need a pump to push water through the heaters as well.

 

If the OP upgrades to an ASHP later would this come with its own pump and make the second pump just mentioned redundant.

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Triassic
1 hour ago, oranjeboom said:

Was going to rely on the UFH manifold pump.

So was I. Can’t see why you would need a second pump in a closed system?

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Jeremy Harris
1 hour ago, epsilonGreedy said:

 

If the OP upgrades to an ASHP later would this come with its own pump and make the second pump just mentioned redundant.

 

 

Some do and some seem to need an external pump.  Not sure why some ASHPs don't have an internal circulation pump, but then perhaps that's no different to boilers, some of them have internal circulation pumps and some don't.

 

1 hour ago, Triassic said:

So was I. Can’t see why you would need a second pump in a closed system?

 

Because the UFH pump only pushes water around the UFH loops, it doesn't normally push water around the primary pipe loop.  The primary loop can be shut down or restricted and the UFH pump can continue to push water around the loops.  I use this feature to equalise heat around the floor, by running the pump when the ASHP is off.  It works well to even out the floor temperature, by drawing heat from areas of the floor than might get warm from solar gain and moving it to areas of the floor that are cooler.

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oranjeboom

Right then, so adding a pump on the feed pipe into manifold, just above the willis heaters:

 

image.png.7799c566e3c47b1d836aff23b97543dc.png

 

Would that work? It's the only bit of spare pipe I could tap into really.

 

And there's a Wilo glandless circulating pump going at a decent price at BNQ. Will that do the job?

 

Brand Wilo
Energy rating A++
Flow volume 3.5m³/h
IP rating IPX2D
Power output 40 W
Voltage 230 V
Pack quantity 1
Model Yonos PICO 25/1-6-130
Product code 4048482758480
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Triassic

If you get rid of the mixing /blending valve and manifold pump you could revert to just having one pump. According to what others have said the Willis heaters should regulate the temperature, doing away with need to blend?

 

PS - Ive just ordered bare manifolds and will connect these up directly to the Willis heater and use a standard recirculating pump set up. Ill set a low temperature on the Willis and see how it works.

Edited by Triassic
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redtop

this seems like the obvious easy solution.  I guess you could also, with a bit of fancy wiring, also run the pump without the heaters (As Jeremy has done) petty easily.  Having two pumps could surely cause issues if one was operating at a different flow rate to the other, even if only slightly...

2 hours ago, Triassic said:

If you get rid of the mixing /blending valve and manifold pump you could revert to just having one pump. According to what others have said the Willis heaters should regulate the temperature, doing away with need to blend?

 

PS - Ive just ordered bare manifolds and will connect these up directly to the Willis heater and use a standard recirculating pump set up. Ill set a low temperature on the Willis and see how it works.

 

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TerryE
23 hours ago, Jeremy Harris said:

The manifold pump only pumps around the loops though.  You'll need a pump to push water through the heaters as well.

 

Jeremy, there's absolutely nothing stopping anyone putting the Willis heaters in the manifold loop apart from preconceptions. See my set up. In this configuration you aren't using the manifold TMV for mix down, and I have mine cranked fully open.  The only reason that it's there is because it came with the kit and acts as a connector.

 

This isn't the case if you have buffer tank and a heating system that can output more heat that the UFH can sink and stay within design ratings -- such as a 20kW gas boiler, but this isn't the case here.

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Pete
13 hours ago, TerryE said:

 

Jeremy, there's absolutely nothing stopping anyone putting the Willis heaters in the manifold loop apart from preconceptions. See my set up. In this configuration you aren't using the manifold TMV for mix down, and I have mine cranked fully open.  The only reason that it's there is because it came with the kit and acts as a connector.

 

This isn't the case if you have buffer tank and a heating system that can output more heat that the UFH can sink and stay within design ratings -- such as a 20kW gas boiler, but this isn't the case here.

Hi Terry, have you a drawing of your set up?

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oranjeboom

Right, almost done here with this willis setup. Just need to plumb in the expansion vessel. Have 15mm pipe tee'd off from the willis return pipe. But bit stumped on what to do with the expansion vessel. Fill loop is obviously a temporary connection (A), pressure vessel on top (B) pressure gauge (C) on the opposite side and pressure relief valve at bottom. So I presume I need to add a bit of pipe from here  (D) that will act as discharge pipe? So where does the 15mm from willis setup get plumbed into? Confused....

 

image.thumb.png.a35600474b41f6f1a6369296dfa38efa.png

 

 

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Onoff
2 minutes ago, oranjeboom said:

Right, almost done here with this willis setup. Just need to plumb in the expansion vessel. Have 15mm pipe tee'd off from the willis return pipe. But bit stumped on what to do with the expansion vessel. Fill loop is obviously a temporary connection (A), pressure vessel on top (B) pressure gauge (C) on the opposite side and pressure relief valve at bottom. So I presume I need to add a bit of pipe from here  (D) that will act as discharge pipe? So where does the 15mm from willis setup get plumbed into? Confused....

 

image.thumb.png.a35600474b41f6f1a6369296dfa38efa.png

 

 

 

...so have you got a sealed system?

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oranjeboom
5 minutes ago, Onoff said:

 

...so have you got a sealed system?

 

Yes. This is for my UFH willis setup, not for DHW:

 

1909803810_willissetup2.JPG.ac25b07edcc1b69892d4d33a3c4e984b.JPG

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