Kentish RenoExtension

10 minutes ago, dpmiller said:

tee it into A or B

 

 

Was hoping that's what somebody would suggest. Thanks!

 

 

B is the 3/4” female union that the expansion vessel screws into.....

A is the pipe that you want to tee into. 

1 hour ago, Nickfromwales said:

B is the 3/4” female union that the expansion vessel screws into.....

 

 

Yes Nick, I had figured that one out!! ?

 

But I'll be back soon for more amateur plumbing questions!

Not sure if this helps or not, but I've just taken a couple of photos of our UFH expansion vessel:

 

 

The bit with the cap on at the front is the fill loop connection.  I've added red and blue max and min markers on the pressure gauge, just so I can see at a glance if it's in the right zone.  The fill loop is the flexi that can be seen at the bottom (I use the same flexi to fill the UFH and the buffer tank, they are separate).  The feed down to the UFH is the copper pipe right at the back.  The bit of grey pipe is the overflow from the PRV, OK in this case as the maximum temperature is restricted by the ASHP, so plastic is OK in this case.  If there is a risk that the temperature could get very high then the overflow needs to be in copper.  The black plastic tundish can just be seen at the bottom of the pic.  Here's another view showing the tundish fitted to the waste pipe:

 

 

The drain from the tundish feeds down to a large diameter drain that runs through a trap downstairs.  This trap is kept topped up by the water that is drained from the water softener, so cannot dry out.  The same drain is also used for the PRV outlet on the buffer tank (that one is set to 1.5 bar, because of the tank limit) and again plastic is OK as the buffer cannot ever exceed the ASHP maximum temperature (the ASHP cannot ever get hotter than about 60°C even under fault conditions).  For Willis heaters I think you would have to assume that, under fault conditions, the water could exceed 100°C (because of the pressure) and so make sure that the overflow, tundish and drain followed the requirements in the regs for the safe discharge of boiling water and steam.  Details are in Part G3:

 

 

 

Thanks @Jeremy Harris ! Will have to take worst case scenario with the willis setup i.e. copper all the way. What I don't get is how some of these 2-in-1 (dry trap and a tundish combined) tundish products state that you can plumb them in "allowing water to be safely discharged to a soil or waste pipe" i.e. no need for external drain. If the water is near enough to 100C, then that tundish isn't going to reduce that temperature down by much or at least down to a level where the plastic waste pipe isn't going to get impacted.

It comes down to the maximum volume of water in the unit/system, I think.  I'll see if I can dig out the relevant bit of the regs later, it'll be buried away in Part G somewhere.

 

Edited to add:

 

Found it.  The regs are relaxed for systems with a total water volume of less than 15 litres, which is how the boiling water taps etc can get away with not having to run vent pipes as shown above (I think the boiler on ours holds about 5 litres, or thereabouts).  A UFH system with a couple of Willis heaters is probably going to be over 15 litres.  As a rough guide, 100m of 16mm UFH pipe holds about 11.3 litres of water.  Not sure what the volume of a Willis heater is, but the chances are that you've got more than 133m of UFH pipe, anyway, so will be over 15 litres system volume.

Edited February 20, 2020 by Jeremy Harris

Yes, it’s time / volume / temp that dictates the permissible discharge regs. 
Also, iirc, all modern plastics can tolerate high temp for quite long durations. That’s how communal UVC’s ( dozens of them ) can be connected to a foul water riser without issue. 

 

Some more pics of a sealed / expansion setup. PRV yet to be connected. That’s the port at the rear of the angled brass union with the small red cap 

 

 

@Nickfromwales - stop showing off. You win on the neatness front!

 

Okay, so have tee'd off and this is what I have:

 

T = Tundish position (15mm in /22mm out)

W = pipe from willis set up.

 

 

Fill loop will be disconnected and valve shut off so that willis feeds into expansion vessel. I'll also have a check valve on the incoming water mains that the fill loop is connected to so there's no contamination.

 

FYI - Pipe from tee going up is only to illustrate set up - that will be replaced after I find the pipe bender!

 

 

 

 

2 minutes ago, oranjeboom said:

@Nickfromwales - stop showing off. You win on the neatness front!

 

Just you wait till he rubs all the pencil marks off and paints the wall!

I hate compressions! Think you've tightened each little weep, then come back a day later and find it weeping again or find another drip in a new location that seemed fine before. Think it's behaving now.

 

So compression vessel with tundish (will go to overflow pipe in the room next door) - thanks for the info @Jeremy Harris, @Nickfromwales above!

 

 

So plan is to have the blending valve on manifold set to fully open so that the UFH pump will hopefully pump the water around the willis circuit without too much burden.

 

 

As a failsafe, I was thinking about adding on a temperature control switch that would switch off the willis heaters if their thermostats fail and they go over 75c. Would something like this work??

 

 

https://www.amazon.co.uk/dp/B00NBT0Q10/ref=psdc_1938192031_t1_B0796RSMRW

 

Insert probe into this 'open' tee piece where I was going to use my temperature guage

 

Could that be wired into the 20A DP switch outlets which? I'll have one DP switch for each willis heater. I just need it to be KISS!! I could go with @TerryE's DS18B20 approach, but no time to configure all of that right now.

 

There will already be a resettable over-temperature cut-out built in to the immersion heaters, in all probability.  It's been pretty standard to include such a device for some time now, I think, as a fail safe in the event that the thermostat sticks shut..

I liberally smear compression fittings with Jet Blue Plus. They do up better, smoother and with none of that nasty brass on brass squeak. I don't use PTFE anymore. No weeping and going green and crusty after a few years either. Just my humble opinion. 

1 hour ago, Jeremy Harris said:

There will already be a resettable over-temperature cut-out built in to the immersion heaters, in all probability.  It's been pretty standard to include such a device for some time now, I think, as a fail safe in the event that the thermostat sticks shut..

 

Yes Jeremy, there is a safety cut out that pops out if temp exceeds 70oC:

 

 

I'm just concerned if that were to fail also, then I could have some serious high temps going into the slab! Blending valve on UFH will be set to fully open (70oC) though so if that works as intended, the +70oC water should flow back into the willis circuit? I'm just wary of multiple equipment failure.

Edited February 25, 2020 by oranjeboom

TBH, I think you're pretty well covered with the thermostat and the back up safety cut-out.  Any additional safety cut-out you add would need to be as least as well-proven as the certified one in the immersion to be useful, I think.  I can only once recall having an immersion "run away" and boil a tank, and that was over 40 years ago, before they were fitted with safety over-temperature cut outs.    My experience since has been that, if anything, the safety cut-outs tend to operate when there isn't really a problem, as they seem to err on the side of being safe.

2 hours ago, Jeremy Harris said:

There will already be a resettable over-temperature cut-out built in to the immersion heaters, in all probability.  It's been pretty standard to include such a device for some time now, I think, as a fail safe in the event that the thermostat sticks shut..

many years ago, before these devises, I had an immersion stick on, it had heated the plastic header tank above it to the point the header tank was about to melt (it was wobbling) which would have flooded the house .

9 minutes ago, joe90 said:

many years ago, before these devises, I had an immersion stick on, it had heated the plastic header tank above it to the point the header tank was about to melt (it was wobbling) which would have flooded the house .

 

 

When my tank boiled, years ago, the noise was enough to wake the dead!  I didn't think to clamber up in the loft and see what was going on, didn't occur to me at the time that it would cause a potential problem up there.  In my case it would have been the cold water tank that was taking the overflow, so if that was plastic it may well have caused a major problem.  I suspect it may well have been a galvanised tank, though, given the age of the house.

7 minutes ago, Jeremy Harris said:

When my tank boiled, years ago, the noise was enough to wake the dead!

that’s what caught my attention when I returned home from work and made me look.

29 minutes ago, joe90 said:

many years ago, before these devises, I had an immersion stick on, it had heated the plastic header tank above it to the point the header tank was about to melt (it was wobbling) which would have flooded the house .

It was sadly such an incident that resulted in a child in bed, getting drenched with scalding water when the tank did burst, that led to the introduction of the safety cut outs.

You don’t really need the tundish as it’s not potable. 
Change it to a waterless trap if you’re getting draughts coming up   

3 minutes ago, Nickfromwales said:

You don’t really need the tundish as it’s not potable. 
Change it to a waterless trap if you’re getting draughts coming up   

 

 

I thought that the tundish was a requirement in order to provide a visible indication of the PRV letting by?

1 hour ago, Jeremy Harris said:

 

 

I thought that the tundish was a requirement in order to provide a visible indication of the PRV letting by?

On an UVC always, but, you can get away without one on primary circuits as it’s just the volume of expansion to get rid of. BCO’s never chase on that but are all over D1 & D2 on potable as it’s drinking quality water being ‘lost’.

There are several waterless traps ( sealed ) which are transparent, so you can use one of those if a visible discharge is required internally.  
Where it runs to an outside wall you can rely on that as means of visible discharge. 
 

7 minutes ago, Nickfromwales said:

On an UVC always, but, you can get away without one on primary circuits as it’s just the volume of expansion to get rid of. BCO’s never chase on that but are all over D1 & D2 on potable as it’s drinking quality water being ‘lost’.

 

On the new build I am on I noted today, that the D2 pipe has 9 bends or elbows in it. 22mm pipe.  That would reduce it's allowable length to just 1.8 metres.  but it must be at least 6 metres long.

 

What's the betting BC never notice.  The plumber is not always right.

1 hour ago, ProDave said:

On the new build I am on I noted today, that the D2 pipe has 9 bends or elbows in it. 22mm pipe.  That would reduce it's allowable length to just 1.8 metres.  but it must be at least 6 metres long.

 

What's the betting BC never notice.  The plumber is not always right.

I always go to 28mm if there’s anywhere near that many bends. In honesty I can only recall a couple, where they were 22mm for a couple of metres and straight out, where I didn’t upsize. 

Okay, so no further failsafe is deemed required. Most likely I will be in the house whenever the willis heaters are on as I'll just be dumping heat into the slab gradually via manual on/off means. If it turns out that I don't go down the heat pump route, I'll wire them up via room thermostat.

 

So next question is what cable to bring in from the fuse cupboard to the willis heaters bearing in mind I will have two of them? They will each have a 20A DP switch outlets.

Erwin, I gave a couple of very useful links in my Plumbing Design – Part I blog entry, and I found John Heartield's pages very useful.  John's widow let me know that he passed away some years ago, but she has kept his pages online in his memory.   

 

Pressure drop over a few m of 15mm pipe isn't really going to be an issue, but you want to keep the flow rate in 15mm pipe under 2 m/s otherwise the flow will be audible, especially with those tight 90°s.  With both Willis's on you will be putting ~6 kW into a flow rate of say 8 l/min. Do the maths, or now that you've got the real system to test you could just run it and do a subjective check, but you might find it better to do the main loop in 22mm if it is too noisy. 

 

BTW, the max O/P temp logged  from my Willis in 2½ years running is 37.8°c  and the max (out - return) del T has been 4.6 °C.  Because perhaps 40%  of my flow  is diverted through a PHE preheat form my DHW (redundant history) the delta T across the Willis is higher: 7.7 °C.  Plugging the 4.6 number into the spec heat formula for water gives an overall flow rate of  0.32 ltr/s through my manifolds which is 0.8 m/s for a 22mm loop (or 2.2 m/s if I'd used a 15mm pipe, and 2 Willis heaters would require 4.4 m/s unless I raised the delta T).  This Del T gives a drop of ~ 0.05 °C/m in my pipe at loop flow rate of ~ 0.7 m/s in the UFH pipes.

 

I used the per loop return temps to balance my three loops, Since we run the UFH as a single logic zone,  we laid out our three loops to be roughly the same length (all +/- 10% of 95m), so balancing was easy in our case.   The maximum difference in return temps between any 2 circuits across a typical 24hr heating cycle is about ¼°c in our case.  You've got 9 loops, no doubt of varying lengths and heat output requirements, so balancing in your case is going to be hard, but in the first instance I suggest that you do the same and trim the flow rates so the return temps after 3 hrs heating are roughly the same.

 

As to DS18B20s etc., IMO you don't need lots of these, but they do make understanding and tuning the system a lot easier.  I bought a load of the waterproof ones from ebay at ~£1 ea if you buy then in 10s.  I just tape mine along the pipe under the sleave logging.  As JSH will point these are almost certainly not the pukka Maxim parts but Chinese clones, so you do need to calibrate them. I dropped batches of 10 into an open thermos-style mug with H/W starting at ~40°C and plotted the logged temp against batch average overnight at the water dropped to room temp..  I rejected maybe 1 or 2 per batch if their reading slope was off or the offset was more than 0.4°C IIRC, and also recorded the per device address offset for using in my logging calcs.  You can plug these direct into an RPi and use a Python or NodeRED routine to analyse / log them.   There are simple worked examples online to tell you how to do this..  No ESPs or Arduinos are needed.

 

I have been thinking about simplifying my current system and dropping my front-end ESPs to run then entire HW / CH system from a single RPi using NodeRED, keeping simple as possible, just in case shit happens and I need one of my kids to do the system maintenance for Jan.