Bringing a derelict UFH system into service.

[daiking]

Cast your minds back to ebuild and June 2015. I had a 40sq m concrete slab poured and put in 3x 75m (approx.)  loops  16mm pert-al-pert ufh piping (via Wunda). Also got all the parts to go with it. I did my best to connect up the manifold to pressure test the piping after noticeably denting one pipe during the install. It didn’t keep a seal during the pressure test on any of the 3 loops, not just the suspect one.

 

At least they had water in them for the concrete pour. I later found out that for the pipe connections to seal they must be straight. Mine weren’t so the connections were stressed during the test so I’m hoping that’s why they failed.

 

As for the concrete, no idea if the concrete had fibres but it did have a mesh that that the pipes were attached to. And I wasn’t around for the pour itself so no idea if it all floated or they wrecked the pipes during the pour. No bother as the concrete later got dry screed on top. Leaving a nominal 100mm concrete slab + 50mm concrete screed. Could be more could be less, who knows? Do I really want to heat that sort of thickness in a poor thermal spec house? House is brick/block, 100mm boggo cavity batts.

 

I later added an extra (shorter) loop for a section of suspended floor. I insulated as best I could but it was the tilers who screwed the final boards over the top so the integrity of this loop is unknown. This pipe was in spreader trays to give it any chance and I understood the issue of having this loop in the same single zone as my slab loop (lower temp). that’s ok, this was only a small section.

 

So now I have a place in the utility room where I have 8 loose pipe ends – 6 through the floor and 2 through the wall. Nearby is sort of random fused spur outlet – possibly put in for the UFH pump. The gas boiler is a 2015 Baxi duo-tec 33 that runs a conventional radiator system and is wall mounted on the other side of the room, approx. 3m away. The heating piping runs along the base of the wall adjacent to the presumed manifold location. The slab pipes still have the water in them from the abortive pressure test.

 

The floor finish over the UFH is tiles. The tiler insisted we use a decoupling membrane because of the UFH. We didn’t have a liquid screed which is also a bonus. I can’t actually remember what went on top of the suspended bit. It was 18mm ply at least followed by something else, possibly wedi or hardie?

 

So there we are, warts and all

 

- At the very least all the pipe work will need a pressure test and a good flush.

 

- I’m concerned that there are a couple of hollow sounding floor tiles and whether the UFH would affect these or others. Nightmare if more tiles lifted.

 

- When I told the builder that I was putting the pipes in the slab I didn’t expect there to be another 50 mm (min) screed going on top. Is the UFH even worth bother with now? I bet its thicker in places.

 

- Insulation wise I have 100mm EPS and 100mm PIR under the slab but there’s bound to be a few voids and the perimeter insulation was not great, 25mm PIR where present on the exterior walls. At the 3m wide bi fold door, he took the slab up to the outer face bricks. Not so much a cold bridge as a cold multi-lane super highway. And I don’t think I there was any on the edge that went up against the existing house wall either.

 

- Wisely, due to the problems with getting the UFH all fitted we had 2 feature radiators put into the space – 40 sq m fairly low ceiling. Most of the winter they are cranked open to max and we get by but it was pretty cold the either week during the cold snap. this space is our day space, cooking/eating etc. We go to the TV lounge at night or when its cold and crank up the gas fire. Considering how mediocre-ly everything is built, I’m surprised how modest the house running costs are for the 4 of us. Given that I’m already using the boiler to heat 10 radiators I hoping that the UFH will be able to top up the existing rads in this space to make things pleasant without adding a massive demand for heat from the boiler. I try to keep the boiler to below 60 degrees for the heating anyway as any higher and the towel rads in the bathrooms become dangerously hot.

 

- As above with the plumbing and electrics, there needs some thoughts on how to connect it up.

 

First play in this match is to get the manifold out, clean it up and sort an installation position to be able to connect it all up for a proper pressure test and take it from there.

[Nickfromwales]

The ufh would surpass the output of the feature radiators. They'd become ornamental tbh, or you'd likely overheat the space the rads and ufh share. 

I need to know what type of UFH manifold you bought. If its Wunda, and from back in the day, then it may be one like this, noting the curly capillary wire from a TRV type control knob  that is hidden behind the black cable, rather than one like this which is a true thermostatic blending valve with the rotary control knob inbuilt into the TMV. 

[Onoff]

I DREAM of UFH! 

[Guest Alphonsox]

2 hours ago, daiking said:

- When I told the builder that I was putting the pipes in the slab I didn’t expect there to be another 50 mm (min) screed going on top. Is the UFH even worth bother with now? I bet its thicker in places.

 

What you have there is a world class storage heater - We have much the same. Heat it up to the desired temperature and it pretty much stays there all day. Wev'e got the earlier type of Wunda noted bu @Nickfromwales above and it works fine.

[daiking]

4 hours ago, Nickfromwales said:

The ufh would surpass the output of the feature radiators. They'd become ornamental tbh, or you'd likely overheat the space the rads and ufh share. 

I need to know what type of UFH manifold you bought. If its Wunda, and from back in the day, then it may be one like this, noting the curly capillary wire from a TRV type control knob  that is hidden behind the black cable, rather than one like this which is a true thermostatic blending valve with the rotary control knob inbuilt into the TMV. 

 

Similar but different to first one.

[daiking]

Still in cellophane, never opened. Possibly not needed if just running off the central heating timer and setting temp with TRV.

Edited March 27, 2018 by daiking

[daiking]

3 hours ago, Alphonsox said:

 

What you have there is a world class storage heater - We have much the same. Heat it up to the desired temperature and it pretty much stays there all day. Wev'e got the earlier type of Wunda noted bu @Nickfromwales above and it works fine.

 

But I don’t have world class insulation 

 

Obviously I’m running a traditional GCH set up, ‘on’ for 2 hours in the morning and then 6 hours in the evening with stat at a set temp. Manually put it on outside those hours. If someone is cold and feeling it. Which wouldn’t suit a slab UFH so it prob will need extra controlling.

Edited March 27, 2018 by daiking

[MikeSharp01]

3 hours ago, Onoff said:

 

I DREAM of UFH

 

Is this the very definition of asymmetric fantasy. You dream of UFH ozing warmth while she dreams of bathrooms with tight / pert little taps, and that oh so heavenly toilet paper holder in chrome. 

[daiking]

 

15 hours ago, MikeSharp01 said:

Is this the very definition of asymmetric fantasy. You dream of UFH ozing warmth while she dreams of bathrooms with tight / pert little taps, and that oh so heavenly toilet paper holder in chrome. 

 

Perchance?

[Onoff]

53 minutes ago, daiking said:

 

 

Perchance?

 

SWMBO would bring her dinner up looking at that...as would I.

 

She'll be happy with the magazine fed loo roll holder in stainless steel! 

 

As for tight and pert.....two kids put paid to that!

[daiking]

Looks like I’ll be bumping the UFH of Doom thread.

[daiking]

So...

 

The verdict is in. Someone who seems to know what he’s doing is reluctant to bother  doing it. 

 

His problem is the seemly too thick slab. The UFH piping went in the 100mm concrete reinforced slab but we then ended up with another concrete screedy thing that is probably another 50-60mm on top. Then there’s the generic ditra mat and tiles on top. He thinks it’s just too deep and will take too much heat input to offer anything. I have absolutely no handle on how much extra energy this will take for any gain in comfort. Looking for thoughts?

 

Info should be in OP ( maybe I should read it to remind myself ?) but it’s a minimum standard extension to an old build. Only real upgrade is the 100mm EPS + 100mm PIR under the slab. The space (approx 40m2) has a couple of vertical rads which have heated it for the 3 winters it’s been built and it’s ok. Never toasty, cosy but a long way from having to put an extra jumper on. I set the boiler to about 60deg otherwise the bathroom rads can burn so turn the boiler up temporarily if it’s really cold and we’re staying in the extension all night. Obvs cooking and stuff adds enough extra heat normally anyway. So... utilisation of the UFH is only to supplement the existing rads not to replace. Don’t suppose I need a high ufh temp in the ufh like you normally would in a poorly insulated property and the lower delta will help lessen losses (he hopes) but who knows.

[newhome]

My UFH pipes aren't in the slab but they are in the screed on top and then Ditra mat and tiles on top and it works fine (think the UFH temp is a bit higher than a passive standard slab but not crazy amounts higher). You have better insulation than here too so not sure why it wouldn't work. 

 

[daiking]

19 minutes ago, newhome said:

My UFH pipes aren't in the slab but they are in the screed on top and then Ditra mat and tiles on top and it works fine (think the UFH temp is a bit higher than a passive standard slab but not crazy amounts higher). You have better insulation than here too so not sure why it wouldn't work. 

 

 

Thats the issue, my pipes are in too deep and it will take too long to get the heat to the surface.

 

Should have added typical central heating behaviour for the household is to have the central heating on in the morning half 6 to half 8 then again in the afternoon from half 4 to half 10. To be honest, half of the rads in the house are TRV’d down low except the bathroom/en-suite/toilet towel rads not on TRVs and these extension rads always cranked open to Max Power. Although my wife has been using the heating more in the day time for when she has guests round.

 

Ideally there needs to be a longer window of operation to usefully heat the slab but not wastefully heat the rest of the house. Which will need something a little bit more complicated than the kit I currently have for it.

 

 

[daiking]

On 29/04/2019 at 21:31, daiking said:

So...

 

The verdict is in. Someone who seems to know what he’s doing is reluctant to bother  doing it. 

 

His problem is the seemly too thick slab. The UFH piping went in the 100mm concrete reinforced slab but we then ended up with another concrete screedy thing that is probably another 50-60mm on top. Then there’s the generic ditra mat and tiles on top. He thinks it’s just too deep and will take too much heat input to offer anything. I have absolutely no handle on how much extra energy this will take for any gain in comfort. Looking for thoughts?

 

Info should be in OP ( maybe I should read it to remind myself ?) but it’s a minimum standard extension to an old build. Only real upgrade is the 100mm EPS + 100mm PIR under the slab. The space (approx 40m2) has a couple of vertical rads which have heated it for the 3 winters it’s been built and it’s ok. Never toasty, cosy but a long way from having to put an extra jumper on. I set the boiler to about 60deg otherwise the bathroom rads can burn so turn the boiler up temporarily if it’s really cold and we’re staying in the extension all night. Obvs cooking and stuff adds enough extra heat normally anyway. So... utilisation of the UFH is only to supplement the existing rads not to replace. Don’t suppose I need a high ufh temp in the ufh like you normally would in a poorly insulated property and the lower delta will help lessen losses (he hopes) but who knows.

 

bump for @Nickfromwales  and  @JSHarrisattention.

 

UFH in too thick slab of poorly insulated house?

Edited May 7, 2019 by daiking

[Jeremy Harris]

Sorry, missed this earlier.

 

All that will happen with the thicker slab is that the time taken for the UFH to have any effect on heating the room will be a bit longer, as the additional volume of concrete will need to be heated first.  Overall I think it should work OK, especially as the UFH is supplementary heating.  The UFH will act to keep the floor comfortable and provide background heating and the rads should be able to respond quickly if there's a boost needed.

[daiking]

1 hour ago, JSHarris said:

Sorry, missed this earlier.

 

All that will happen with the thicker slab is that the time taken for the UFH to have any effect on heating the room will be a bit longer, as the additional volume of concrete will need to be heated first.  Overall I think it should work OK, especially as the UFH is supplementary heating.  The UFH will act to keep the floor comfortable and provide background heating and the rads should be able to respond quickly if there's a boost needed.

 

This is what I’m expecting to happen but I’m trying to assess how that will work in practice. I know you favour starting at first principles to determine heating requirements but we’re way past that and as you’ve seen, looking for part of a heating system not a single solution in itself. I'm accepting of burning a bit more gas to use the UFH but not using a load more gas if the slab needs heating for so much longer. I’d like to have an idea of how long will it really take to heat up? 4 hours? 8 hours? Longer?

 

Nominally the 2 radiators we have there (vertical tubular style) are rated at 6500btu/1.9kW each although most of the time the boiler is set for a heating water temp of 60 ish deg and those rads were added at the end of the circuits so they will not be that hot and are clearly not putting out their rated output. I don’t know what the rating are based on, 75deg water in the rad? Either way they make the extension bearable most of the time (i.e. when outside temps are above 0 deg. The inland, sheltered, sub-urban, low altitude location means conditions are quite gentle). In the winter when its near zero overnight the Honeywell boiler stat will be showing about 13 deg in the morning compared to 18-19 deg 7-8 hours before when the heating goes off at night. So whilst this is better than any other house I’ve lived in, its not very good.  

 

So… if we assume that I'm looking for a 40W/m2 from approx. 30m2 of UFH to gain an extra 1.2kW, what sort of water temperature should the UFH thermostat be set at? Or do I have to supply the max sort of temp you should, 35deg? and I get that fixed heat output whether I want it or not? I think I laid it out with a 200mm piping pitch, reverse serpentine or whatever its called. Is it possible to make a guess on cost from this? Temp of water and time on?  Is that tweakable for best efficiency overall?

 

The longer warm up time will mean having the heating on longer but I don’t want to waste gas by unnecessarily warming the rest of the house. This is where Nick might be able to help me, how do I want the 2 parts controlled if I have a very slow warming slab? The original idea was just to have the single UFH zone as a low temp radiator on the existing rad circuit but clearly this won’t work and I will need extra kit. Also been informed that I need some 22mm tails of the existing pipework, not the 15mm tails that were left. I hear that 60deg* is a low setting for a conventional house and GCH. Could I run the modern boiler at a lower temperature to improve the system efficiency? The radiators have all been fitted in the past 4 years, so they're all modern panelled and finned items and he seems to like fitting oversized items.

 

*This is based on nothing more than some comments I read on here/ebuild but, to be honest, any higher and I think the towel rads in the bathrooms are dangerous. Even at 60 deg you get quite a zap if you brush past with something delicate.

 

Apropos nothing to do with the UFH but just general GCH management and how it could be adjusted to be more efficient or maybe integrate with UFH, the radiators in the house fall into 3 basic operating regimes –

 

1. Bathrooms/WC have 3 x towel rads with no TRV, always scalding hot.

2. Bedrooms/Lounge – TRV set low, don’t usually need much heat.

3. Extension/Hall/’Salon’ – always set to max.  

 

Unfortunately, we’re running the heating for the Salon room more and more in the daytime which means that we’re heating a lot of the rest of the house for no reason.  I need a better solution for this room including retrofitting insulation under the suspended floor.

[Jeremy Harris]

6 minutes ago, daiking said:

So… if we assume that I'm looking for a 40W/m2 from approx. 30m2 of UFH to gain an extra 1.2kW, what sort of water temperature should the UFH thermostat be set at? Or do I have to supply the max sort of temp you should, 35deg? and I get that fixed heat output whether I want it or not? I think I laid it out with a 200mm piping pitch, reverse serpentine or whatever its called. Is it possible to make a guess on cost from this? Temp of water and time on?  Is that tweakable for best efficiency overall?

 

At  rough guess I'd say that once the floor has been initially heated it will probably only take a couple of hours at the most to heat up, less if the flow temperature is increased a bit (although that does run a small risk of overshooting the set temperature, might not be a significant problem though).

 

To deliver 40 W/m² to a room at 21°C needs a floor surface temperature of about 25°C, so a flow temperature of around 30 to 35°C would seem about right (start low, see how it behaves and wind it up if you want a faster response).

 

Guessing the running cost is tough, as it depends very much on the total heat loss, but I'd be surprised if you find that you really need 40 W/m² all the time, or even most of the time.  I suspect that you'll need less than half this most of the time, so you can have a guess at the cost from the area and heat output.  30 x 20 = 600 W, so if the heating is on for 15 hours a day, the boiler is 85% efficient and the gas costs around 5p/kWh then roughly 50p/day, perhaps.

 

Re: the boiler, if it's a modern condensing boiler then they work best with a return temperature of around 55°C or so, so a flow temperature of around 60°C, perhaps a bit higher.  I used to run ours at the old house at around 58°C flow and found that was pretty efficient, as the return was normally just a bit over 50°C, and the boiler was condensing properly most of the time.

[daiking]

6 minutes ago, JSHarris said:

 

At  rough guess I'd say that once the floor has been initially heated it will probably only take a couple of hours at the most to heat up, less if the flow temperature is increased a bit (although that does run a small risk of overshooting the set temperature, might not be a significant problem though).

 

To deliver 40 W/m² to a room at 21°C needs a floor surface temperature of about 25°C, so a flow temperature of around 30 to 35°C would seem about right (start low, see how it behaves and wind it up if you want a faster response).

 

Guessing the running cost is tough, as it depends very much on the total heat loss, but I'd be surprised if you find that you really need 40 W/m² all the time, or even most of the time.  I suspect that you'll need less than half this most of the time, so you can have a guess at the cost from the area and heat output.  30 x 20 = 600 W, so if the heating is on for 15 hours a day, the boiler is 85% efficient and the gas costs around 5p/kWh then roughly 50p/day, perhaps.

 

Re: the boiler, if it's a modern condensing boiler then they work best with a return temperature of around 55°C or so, so a flow temperature of around 60°C, perhaps a bit higher.  I used to run ours at the old house at around 58°C flow and found that was pretty efficient, as the return was normally just a bit over 50°C, and the boiler was condensing properly most of the time.

 

Thanks that's very helpful in putting some of these issues into context. The 50p a day I could easily live with for the added comfort but the UFH will definitely need splitting from the GCH.

[Nickfromwales]

Hi @daiking

The 15mm feeds will suffice, you'll just need to put a manual bypass ( standard £5 gate valve ) across flow and return at the manifold, immediately prior to the pipes being connected to it. It'll make almost no difference whatsoever to the running of it, like near zero, and would only really impact the heating up when you want to warm it from cold ( and then TBH you'd not really suffer as 15mm flow and return will still keep a 2600 x 700mm K2 double radiator blasting ) so tell your plumber to have a chill pill and just connect to the 15mm ones you already have.

The only time the boiler will 'suffer' ( short cycle excessively ) is when the UFH is used on its own, so I'd try to never have a system configured where that would be the rule, or the exception TBH. When the UFH is up to temp it will require less than the boilers minimum output even at max modulation ( you have a Baxi Duotec IIRC? ) therefore will be a design load that is outside of it's 'happy place'. Running the bathroom towel rads simultaneously at the bare minimum will help the boiler out no end, so at least one of those should stay on manual ( bypass ) radiator valves, but the other 2 (?) certainly should have TRV's fitted. Leave the one in your ensuite on bypass valves and change the others to TRV's so visitors / kiddies are less likely to come into contact with them  Plumbers ( on their mothers side ) do this in bathrooms ( leave out TRV's ) as a knee-jerk action, and are bell-ends for doing so. Get those done asap for comfort and safety.

The blending valve on the UFH manifold will allow you ( as in you personally ) to adjust the flow temp of the UFH loops to whatever you want, so once plumbed in and commissioned you can tweak this daily. You can get two set points marked with Tippex and change the temp a little 'seasonally' for selecting between the shoulder months and deepest winter for eg, same way folk with boilers turn the flow temp up a bit when the weather becomes a bit sharp. You would do it at the manifold and not the boiler so as to not affect the flow ( surface ) temp of those emitters, again promoting comfort / safety.

Connecting this lot up is a doddle, so don't let anyone start tearing pages out of the Problematic Plumbers Bible, simply do as above, connect up the flow and return to the manifold, and get the slab warmed. Remember the 50p per day is only due when you need to heat the slab, so no banks are going to be broken here, and I reckon you'll only need to provide a bit of background heat from the slab to make a huge difference in the house. UFH via a slab is a bloody good way of getting 'comfort' heat into a space, so try it low first and go from there.

As far as controls are concerned, run with what you've got and just put a simple £1 1g1w light switch as an on/off switch so you can remove / introduce the UFH as required. Start off cheap and cheerful, and add complexity later if you find it's necessary   

"Proceed" 

  

[newhome]

So your set up re the floor slab isn’t really a million miles away from mine even if not exactly the same. The guys above have said all of the tech stuff so this is just my experience using the UFH daily. I tend to have the UFH come on once a day and it takes circa 2 hours to heat the floor up to temperature (20 degrees) in the largest room downstairs. The boiler doesn’t run at max for all that time though so the running costs aren’t enormous even with electric that I imagine costs twice as much as gas. The floor then retains the heat enough not to bother running it again for another 24 hours. Sometimes when it’s baltic outside I have it switch on earlier in the day but mostly every 24 hours is fine, and I don’t have any other heating. My losses will be higher than yours too as your insulation is better. Clearly if you’ve been away and the floor is brass monkeys it will take longer to heat up but the floor retains a surprising amount over the course of 24 hours. 

 

[daiking]

6 hours ago, Nickfromwales said:

Hi @daiking

The 15mm feeds will suffice, you'll just need to put a manual bypass ( standard £5 gate valve ) across flow and return at the manifold, immediately prior to the pipes being connected to it. It'll make almost no difference whatsoever to the running of it, like near zero, and would only really impact the heating up when you want to warm it from cold ( and then TBH you'd not really suffer as 15mm flow and return will still keep a 2600 x 700mm K2 double radiator blasting ) so tell your plumber to have a chill pill and just connect to the 15mm ones you already have.

The only time the boiler will 'suffer' ( short cycle excessively ) is when the UFH is used on its own, so I'd try to never have a system configured where that would be the rule, or the exception TBH. When the UFH is up to temp it will require less than the boilers minimum output even at max modulation ( you have a Baxi Duotec IIRC? ) therefore will be a design load that is outside of it's 'happy place'. Running the bathroom towel rads simultaneously at the bare minimum will help the boiler out no end, so at least one of those should stay on manual ( bypass ) radiator valves, but the other 2 (?) certainly should have TRV's fitted. Leave the one in your ensuite on bypass valves and change the others to TRV's so visitors / kiddies are less likely to come into contact with them  Plumbers ( on their mothers side ) do this in bathrooms ( leave out TRV's ) as a knee-jerk action, and are bell-ends for doing so. Get those done asap for comfort and safety.

The blending valve on the UFH manifold will allow you ( as in you personally ) to adjust the flow temp of the UFH loops to whatever you want, so once plumbed in and commissioned you can tweak this daily. You can get two set points marked with Tippex and change the temp a little 'seasonally' for selecting between the shoulder months and deepest winter for eg, same way folk with boilers turn the flow temp up a bit when the weather becomes a bit sharp. You would do it at the manifold and not the boiler so as to not affect the flow ( surface ) temp of those emitters, again promoting comfort / safety.

Connecting this lot up is a doddle, so don't let anyone start tearing pages out of the Problematic Plumbers Bible, simply do as above, connect up the flow and return to the manifold, and get the slab warmed. Remember the 50p per day is only due when you need to heat the slab, so no banks are going to be broken here, and I reckon you'll only need to provide a bit of background heat from the slab to make a huge difference in the house. UFH via a slab is a bloody good way of getting 'comfort' heat into a space, so try it low first and go from there.

As far as controls are concerned, run with what you've got and just put a simple £1 1g1w light switch as an on/off switch so you can remove / introduce the UFH as required. Start off cheap and cheerful, and add complexity later if you find it's necessary   

"Proceed" 

  

As well as upgrading the feeds to 22mm he said he had to control the UFH with a room stat to "meet building regs". So it sounds like he does want UFH and Rads to run independently and allow the UFH to only be heated when its below the trigger point rather than as you're suggesting just have it on all the time.

 

He said he could do it but it would cost at least £1000, I'm waiting for the worked out quote which is normally +20% round here.

 

 

5 hours ago, newhome said:

So your set up re the floor slab isn’t really a million miles away from mine even if not exactly the same. The guys above have said all of the tech stuff so this is just my experience using the UFH daily. I tend to have the UFH come on once a day and it takes circa 2 hours to heat the floor up to temperature (20 degrees) in the largest room downstairs. The boiler doesn’t run at max for all that time though so the running costs aren’t enormous even with electric that I imagine costs twice as much as gas. The floor then retains the heat enough not to bother running it again for another 24 hours. Sometimes when it’s baltic outside I have it switch on earlier in the day but mostly every 24 hours is fine, and I don’t have any other heating. My losses will be higher than yours too as your insulation is better. Clearly if you’ve been away and the floor is brass monkeys it will take longer to heat up but the floor retains a surprising amount over the course of 24 hours. 

 

 

Its not all gravy on the insulation front, detailing is poor, there are bridging issues and the above structure is also poor.

[daiking]

On ‎08‎/‎05‎/‎2019 at 06:53, Nickfromwales said:

Hi @daiking

The 15mm feeds will suffice, you'll just need to put a manual bypass ( standard £5 gate valve ) across flow and return at the manifold, immediately prior to the pipes being connected to it. It'll make almost no difference whatsoever to the running of it, like near zero, and would only really impact the heating up when you want to warm it from cold ( and then TBH you'd not really suffer as 15mm flow and return will still keep a 2600 x 700mm K2 double radiator blasting ) so tell your plumber to have a chill pill and just connect to the 15mm ones you already have.

The only time the boiler will 'suffer' ( short cycle excessively ) is when the UFH is used on its own, so I'd try to never have a system configured where that would be the rule, or the exception TBH. When the UFH is up to temp it will require less than the boilers minimum output even at max modulation ( you have a Baxi Duotec IIRC? ) therefore will be a design load that is outside of it's 'happy place'. Running the bathroom towel rads simultaneously at the bare minimum will help the boiler out no end, so at least one of those should stay on manual ( bypass ) radiator valves, but the other 2 (?) certainly should have TRV's fitted. Leave the one in your ensuite on bypass valves and change the others to TRV's so visitors / kiddies are less likely to come into contact with them  Plumbers ( on their mothers side ) do this in bathrooms ( leave out TRV's ) as a knee-jerk action, and are bell-ends for doing so. Get those done asap for comfort and safety.

The blending valve on the UFH manifold will allow you ( as in you personally ) to adjust the flow temp of the UFH loops to whatever you want, so once plumbed in and commissioned you can tweak this daily. You can get two set points marked with Tippex and change the temp a little 'seasonally' for selecting between the shoulder months and deepest winter for eg, same way folk with boilers turn the flow temp up a bit when the weather becomes a bit sharp. You would do it at the manifold and not the boiler so as to not affect the flow ( surface ) temp of those emitters, again promoting comfort / safety.

Connecting this lot up is a doddle, so don't let anyone start tearing pages out of the Problematic Plumbers Bible, simply do as above, connect up the flow and return to the manifold, and get the slab warmed. Remember the 50p per day is only due when you need to heat the slab, so no banks are going to be broken here, and I reckon you'll only need to provide a bit of background heat from the slab to make a huge difference in the house. UFH via a slab is a bloody good way of getting 'comfort' heat into a space, so try it low first and go from there.

As far as controls are concerned, run with what you've got and just put a simple £1 1g1w light switch as an on/off switch so you can remove / introduce the UFH as required. Start off cheap and cheerful, and add complexity later if you find it's necessary   

"Proceed" 

  

 

I'm looking at paying £1150 for this before "extras". There is still talk of a bypass valve being required.

 

Easy money for anyone who wants it.

 

(this work is now hold up the fitting out of my utility room)

[daiking]

Next up, will an 8-port manifold (4 loops) and pump setup with associated plumbing fit within the confines of a 500 wide kitchen base unit?

 

If not, how much space will it need? And,

 

Can you still use some of the space in the cupboard?

 

Do you need to provide any ventilation for it? Hopefully passive if at all

 

@PeterW @Nickfromwales

[daiking]

In this post:

The UFH stuff would be in the base unit adjacent to the tall larder unit.

 

As it stands in the picture that unit is actually a 600mm door on a blind corner unit going up to the corner. But I would like to swap the blind corner unit to the back wall and put a 500 wide base unit next to the tall larder unit with the UFH stuff at the back of it instead.

 

The blind corner unit will be difficult to access as it is - and I'm happy with that for seldom used stuff but don't want to hinder access further with the plumbing for the UFH.

 

The knock on effect is the sink bowl needs to fit in a 500mm unit but that's for another day.