Another DHW / DCW / UFH design

[jack]

34 minutes ago, JSHarris said:

I agree with all of that, but find the boiling water tap recommendation a bit odd.  

 

As did we!  There was nothing in the instructions about this, so I called the manufacturer just to confirm softened water was okay before the plumber plumbed it in.  They left me on hold while they spoke to their tech department.  The answer (best I recall) was something like "We don't recommend the use of softened water because the boiler hasn't been tested with it.  We suspect it would be okay but you won't be covered by our warranty if you supply it with softened water".

[TerryE]

On 24/01/2017 at 19:08, JSHarris said:

I bought a Wiltec stainless brazed PHE, from Germany, the 20 plate, 44kW version, here: Wiltec shop.  The reason for getting a 44kW, even though at most it's delivering only a few kW, was to allow for the difference between the higher temperature difference used testing.  I wanted as low a temperature difference as possible, and as the 44kW one was only around £50 inc postage.

 

In fact Wiltec also sell these through Amazon.  Incidentally the Wiltec datasheet gives the pressure drop at 15ltr/min as ~1.5kPa or 0.015 bar which is two shades of bugger all.  My only dilemma is whether to defer fitting this until after the BInsp visit since it isn't WRAS approved.  

 

So I can get this for 47.29 € +  13€ shipping from Wiltec direct and the exchange rate is 1.17 or £49.24 + £11.00 UK delivery via Amazon. Go figure that one.

 

As far as the water treatment goes, Janny and I had a long discussion about that one and we decided that our local water supply isn't really hard enough to bother.  (We descale the kettle about 4 times a year but we could get away with less).

[Jeremy Harris]

7 minutes ago, TerryE said:

 

In fact Wiltec also sell these through Amazon.  Incidentally the Wiltec datasheet gives the pressure drop at 15ltr/min as ~1.5kPa or 0.015 bar which is two shades of bugger all.  My only dilemma is whether to defer fitting this until after the BInsp visit since it isn't WRAS approved.  

 

So I can get this for 47.29 € +  13€ shipping from Wiltec direct and the exchange rate is 1.17 or £49.24 + £11.00 UK delivery via Amazon. Go figure that one.

 

 

Not being WRAS approved isn't a biggie, as the thing has to be enclosed in insulation, anyway, so will be well out of sight.  Plus, my experience was that the BI didn't check anything for approval on the water side, even the jobsworth interim bloke who went on and on about meeting the water consumption regs.  Those PHEs are made in exactly the way the ones in a combi are made - stainless steel plates copper brazed together, so they would get WRAS approval easily, it's just that, being German, they don't need too.

 

Yes, the pressure drop is negligible.  Our whole system runs at between 2.5 and 3.5 bar (2.5 bar is the borehole pump cut-in pressure, 3.5 bar is the pump cut-off pressure) and there is masses of flow available on the hot side.

Edited February 11, 2017 by JSHarris
typos

[TerryE]

OK, guys.  It's manifold time, and this Q is addressed to those who are wizards and / or have been through this with an MBC frame, such as @Nickfromwales, @JSHarris, @jack, @Calvinmiddle, though PeterW always seems to be very informed on this stuff..  I'll be putting in a basic 3-port system such as this 3 Port Complete Manifold Assembly from the The Floor Heating Warehouse (and this looks very like the one that Jeremy used, BTW).

 

I'll need a pump, but I will probably get a Gunfoss Temperature Controller and Pump Assembly.  OK, in my case using an inline heater or as with Jeff using his ASHP unbuffered, the mixer regulator is probably redundant.  Even so, part of me says that if something does go totally ape-shit with the heating system then I'd rather keep the problems / damage above the slab where the repair costs are relatively minor, so having the built-in TMV to limit the slab temp to 35 °C is probably a sensible safety back-stop.

 

Finding the water heater that I want hasn't been going well. What I want is essentially a 3 kW immersion element in a tube.  I'll be pumping water through it pretty fast, say 20 ltr/min, so it's only going to raise the flow by a few degrees and the water will never be hotter than 30 °C.  About the best that I've found so far is something like the Stiebel-Eltron Mini Instantaneous Water Heaters, but these are really designed to lift very low flow rates by ~30°C.  If anyone has any suggestions here, I'd be very grateful.  Thanks.

 

 

[Nickfromwales]

Something like this any good?

Link

[Jeremy Harris]

What you want as a water heater is a 3kW immersion in a tube.  They are an Irish thing, invented by a chap years ago over there, to go on the side of a conventional tank that doesn't have an immersion heater port.  They are known as Willis heaters, see here: https://www.stevensonplumbing.co.uk/willis-complete-3kw.html

Edited February 11, 2017 by JSHarris
typo - "as" when I meant "is"

[Onoff]

2 minutes ago, JSHarris said:

What you want as a water heater is a 3kW immersion in a tube.  They are an Irish thing, invented by a chap years ago over there, to go on the side of a conventional tank that doesn't have an immersion heater port.  They are known as Willis heaters, see here: https://www.stevensonplumbing.co.uk/willis-complete-3kw.html

 

That's rather clever. How does it get insulated? 

[TerryE]

How do you buggers know this stuff?  You do know that you are going to get a man-hug when we meet.

[Gone West]

2 minutes ago, JSHarris said:

What you want as a water heater is a 3kW immersion in a tube.  They are an Irish thing, invented by a chap years ago over there, to go on the side of a conventional tank that doesn't have an immersion heater port.  They are known as Willis heaters, see here: https://www.stevensonplumbing.co.uk/willis-complete-3kw.html

I always thought they were a good idea because they put the hot water into the top of the tank and heat the tank downwards. They also did the solarsyphon.

[Jeremy Harris]

1 minute ago, Onoff said:

 

That's rather clever. How does it get insulated? 

 

Back when Willis invented them, decades ago, insulation was unknown.................

 

They were originally invented to allow an immersion to be fitted without changing the cylinder, back in the days when not all cylinders had an immersion port.  As Peter S says, they have some advantages over a conventional immersion as they only feed hot water to the top of the tank, so the tank stratifies well and they allow you to heat just a part of the tank if you only want a small amount of hot water.

 

Should be easy enough to insulate with some PIR and expanding foam, as long as the immersion head is left free from insulation.

[Jeremy Harris]

6 minutes ago, TerryE said:

How do you buggers know this stuff?  You do know that you are going to get a man-hug when we meet.

 

Insatiable curiosity, Terry, and like the cat, it invariably gets me into trouble from time to time......................

 

PS: it helps being part-Irish, and having a load of Irish relatives who have all manner of bodged-up systems in their houses, some of which are really ingenious.

 

Edited February 11, 2017 by JSHarris

[TerryE]

One issue is that these Willis heaters are spec'ed for a vented system.  I'll be running my UFH at roughly 1-bar with pressure relief valve and ½ ltr expansion but technically this isn't unvented.  Needs more thought.

[Jeremy Harris]

Vented systems are usually specced for 1.5 bar max working pressure, to allow for say, a three storey house with the cold tank in the loft and the cylinder on the ground floor, or even in a basement, so it'll be fine at 1 bar.

 

Edited to add:

 

Just checked, Terry, vented cylinders are either rated at 1 bar, 1.5 bar or 2.5 bar working pressure.  Gledhill have info here: http://www.gledhill.net/pdf/Spec 115 Vented Cylinders.pdf

 

I know for sure that the Willis is good for over 1 bar, as I've seen one fitted to a cylinder in a hot press on the ground floor of a three storey Victorian house, where the head must have been way over 10m.

 

Our buffer is just a vented cylinder from Newark, and came with a 1.5 bar max working pressure sticker on the side.  I run it at around 0.5 bar, but with a 1.5 bar PRV, in a sealed system and the BI was fine with it.

 

Edited again:

 

I've found the spec for the Willis heater, it's rated at 10 bar TP!  Here's the spec:

Quote

Shell height 300mm
Shell diameter 75mm
Water content 0.96 litre
Water connections 2x15mm compression
Tested 10 BAR
Elements Copper Clad – Rod Type
Loading 3kw at 240v
Voltage range 230/250v 1 phase
Weight 1.5kg empty
Weight 2.5kg including water

 

Edited February 11, 2017 by JSHarris
added the "working pressure" bit, for clarity and again for more info

[Nickfromwales]

1 hour ago, Onoff said:

 

That's rather clever. How does it get insulated? 

This

[TerryE]

1 hour ago, Onoff said:

That's rather clever. How does it get insulated? 

 

In this case the output will never get above about 25°C so there isn't a lot of point.

 

On a different tack, the two SunAmp PVs have internal PRelVs and the UFH will also have one so am I correct saying that the easiest way to deal with all three is just to have a row of 3 tundishes all draining off into a HepVO and back into the stack?

[Jeremy Harris]

11 minutes ago, TerryE said:

 

In this case the output will never get above about 25°C so there isn't a lot of point.

 

On a different tack, the two SunAmp PVs have internal PRelVs and the UFH will also have one so am I correct saying that the easiest way to deal with all three is just to have a row of 3 tundishes all draining off into a HepVO and back into the stack?

 

 

Pretty much what I have.  There are two tundishes draining into 1 1/2" waste pipes that then drops vertically down to the ground floor and across to the foul drain, via a U bend trap fitted at the ground floor level.  The condensate drain from the MVHR and the 10mm waste pipe from the water softener also connect to this, so the trap is always kept full of water, negating the need for the HepVO.  You can't get a high temperature discharge from this system, anyway, so it's fine to run it into a big enough waste pipe, unlike something like a UVC with an immersion or solid fuel appliance, where you could have very hot water discharging.

 

 

[PeterW]

5 hours ago, Onoff said:

 

That's rather clever. How does it get insulated? 

 

Willis tubes can be insulated with rigid rock wool - you can get a standard size to fit - or just use Armaflex sheet glued to the can. 

 

This one even comes pre-insulated. Willis Heater

 

 

[Calvinmiddle]

On 2/11/2017 at 15:52, TerryE said:

OK, guys.  It's manifold time, and this Q is addressed to those who are wizards and / or have been through this with an MBC frame, such as @Nickfromwales, @JSHarris, @jack, @Calvinmiddle, though PeterW always seems to be very informed on this stuff..  I'll be putting in a basic 3-port system such as this 3 Port Complete Manifold Assembly from the The Floor Heating Warehouse (and this looks very like the one that Jeremy used, BTW).

 

 

I just got most of my stuff from the Wunda store   http://www.wundatrade.co.uk/

 

We had a Willis heater at home when I was growing up, it had the advantage that you could turn the immersion on and if you ran the water slow enough (about pencil thick) you got instant hot water - even if the cylinder was cold

[TerryE]

@Calvinmiddle David,  I should have asked the guys when they laid the slab, but looking at the pipe it is 16 mm PexAlPex or PertAlPert, so you go for the 16mm Pert-Al-Pert adaptors on the manifold?

[jack]

I went the same way (wundatrade).  From memory, MBC uses 16mm pex-al-pex, and the wundatrade stuff connected directly to that without the need for special adaptors.

 

I did ring the supplier before I ordered to confirm compatibility.

[Jeremy Harris]

I can confirm that the pipe MBC uses fits the Wunda 16mm UFH manifold fittings just fine. 

[TerryE]

@jack @JSHarris Thanks guys, it's nice to have this confirmed.  I'll be ordering al this kit in the next 24 hrs.  

[Calvinmiddle]

What they said

 

I also had to get a pipe reamer as the plumber didn't have one as he does do much UFH

http://www.wundatrade.co.uk/tools-accessories/461-pipe-reamer.html

[jack]

Worth having the cutters too. They aren't expensive and they do make the job easier.

[Jeremy Harris]

If you have an old lathe centre knocking around, then I found that warming that up and pushing the cone into the end of the UFH pipe flared the end just enough to slide over the O rings on the fitting without snagging.  If you don't flare the cut ends of the pipe slightly you risk damaging the very thin O rings.  Ask me how I know this........................