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How cold can it get....


CC45

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This weekends fun & games was adding more loft insulation, we went from 100mm to 450mm and it was a pain to do with very little working space.  The cold snap has prompted me to do this.  The digital thermometer (positioned upstairs) in the house has been varying between ~ 5 to 10deg over the last month or so, this is around 1 or 2 degrees more than the thermostat on the Wunda ufh manifold suggests (downstairs)..  The house does not have any heating - thats due to come in January.  Today (with the loft hatch open - for the insulation) with 2 oil filled rads + a fan heater running (~ 5kw in total) the temp rose upstairs to 7deg (started at ~ 6) and up to 8 after an hour with the loft hatch shut but this is obviously air temp.  I measured the slap temps at between 4 & 5deg.  The ufh pipe in 70mm below surface, on top of 225mm of celotex on top of a b&b floor.

 

With up to minus 10 predicted around here for tomorrow night - how concerned do I need to be about the ufh freezing?  I am planning on leaving the oil filled rads on overnight (3kw).   Not too sure I can do a lot else.  With the temps then predicted to rise hopefully ther wont be any damage.  Right to worry or not?

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18 minutes ago, NSS said:

Do you not have any glycol in the UFH pipes?

Most typically don't pressure test with any antifreeze, and it's already been discussed on here that the likelihood of the below ground pipes ever freezing is pretty much zilch. It's the pipework that's above ground that's the issue, but a simple heater and a desk fan to blow it around a bit will be ample. 

 

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8 hours ago, CC45 said:

This weekends fun & games was adding more loft insulation, we went from 100mm to 450mm and it was a pain to do with very little working space.  The cold snap has prompted me to do this.  The digital thermometer (positioned upstairs) in the house has been varying between ~ 5 to 10deg over the last month or so, this is around 1 or 2 degrees more than the thermostat on the Wunda ufh manifold suggests (downstairs)..  The house does not have any heating - thats due to come in January.  Today (with the loft hatch open - for the insulation) with 2 oil filled rads + a fan heater running (~ 5kw in total) the temp rose upstairs to 7deg (started at ~ 6) and up to 8 after an hour with the loft hatch shut but this is obviously air temp.  I measured the slap temps at between 4 & 5deg.  The ufh pipe in 70mm below surface, on top of 225mm of celotex on top of a b&b floor.

 

With up to minus 10 predicted around here for tomorrow night - how concerned do I need to be about the ufh freezing?  I am planning on leaving the oil filled rads on overnight (3kw).   Not too sure I can do a lot else.  With the temps then predicted to rise hopefully ther wont be any damage.  Right to worry or not?

I had an issue with one UFH company insisting the heating must be commissioned prior to the cold weather

Cadmams were of the same opinion as Nick Very unlikely to freeze below ground

But agreed to pump five bar of air in just in case 

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Thanks for responses - going to get some heaters going in there, no time to rig willis heater & not likely to get hold of a plumber with such short notice.  Why couldnt the cold wait until Feb?  Lesson learnt - get some crude heating mechanism in before winter next time.

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@CC45 Best of luck with all this.

 

Screwfix have a couple of OK inpexensive compact fan heaters, with thermostats, if you are after one

 

This fixed one for £11.99, reduced from £20. I paid £20 as a drying heater and it was fine. This one is "Trade Rated". I will pick up a coupel of these for future needs I think at that price:

https://www.screwfix.com/p/portable-fan-heater-2000w/2963P

 

This oscillating one at £20:

https://www.screwfix.com/p/portable-oscillating-fan-heater-2000w/2147P

 

 

15 minutes ago, CC45 said:

Why couldnt the cold wait until Feb?

 

I think we all know the answer to that one. If you had been fully prepared now, it would have waited until you had stepped the prep back down :-o .

 

Ferdinand

Edited by Ferdinand
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@Ferdinand got one of the oscillating ones - its good but as @ProDave says I dont trust them enough to just leave on unattended. Been using it when I'm in there working.  Bought two oil filled ones last week and I will leave these on tonight.  Its going to be cold but at least its not days and days of it.  Normal weather due Wed.  Lets hope.

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11 hours ago, Nickfromwales said:

Buy a.Willis heater and get the chill off ;). You can get some heat into the slab and it's pretty straightforward to link to the manifold, prob only a few hours work to Heath Robinson one in. 

Or go nuts and buy 2 :)

 

This is exactly what I have right now, the 3kW willis is running flat out 24/7 but is keeping the slab at about 10oC with outside air temp between -2 and 5. Costing £££ in leccy, but its stopping any UFH freezing, and also dries up any water on top of the slab. Otherwise, it would be like an ice rink in there.

 

The Willis cost me ~£40 on eBay, and I used the old CH header tank just above the manifold to rig up something till I get the new boiler in.

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@chrisb any chance of a cheeky picture?  I've had 3kw of oil filled heaters going flat out since 10am and the air temp has lifted by 2deg, not too bad considering its been freezing all day.  Up to 7.2deg inside when I left tonight cf to -4deg outside, hopefully they will keep on top of the job tonight - better weather tomorrow.  Slab is cooler than this.  Hopefully before the next cold snap we will have heating sorted!

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5a2f0565a4f3f_manifoldwillis.thumb.jpeg.306a573caeda5535351564f969013e23.jpeg

 

5a2f8c82b1f4e_ufhheader.thumb.jpg.d0a44186b647c5239143aa490fabab30.jpg

Both the feed and return pipes are attached with tank connectors low down in the side of the tank. I filled it with a hosepipe and check the level every couple of days. The Willis thermostat is set to 25oC and the TMV set to the hottest setting. The Willis never turns off, well certainly not yet, anyway.

 

I wired the willis and the pump to their own 13A plugs (yes, I know about them not being continuously rated for 13A), which connect to a pair of single 13A sockets connected with a length of 2.5mm2 T&E run from a 16A MCB in the consumer unit on the other side of the wall. The plugs are in free air, and I have checked after several hours of operation and the heater one is only slightly warm. I'm satisfied that the fire risk is low, unlike the 2kw fan heater which stopped 'fanning' and turned into a melted lump of plastic pretty quickly, and the convector heater which has a very hot plug if run on the 3kW setting.

Edited by chrisb
Added a photo of the tank
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  • 6 months later...

thought I'd close this one off...

 

the heating system is now in and complete.  Mains gas boiler feeds a 90l buffer that then feeds two Wunda manifolds - ufh down stairs & rads upstairs.  All individual room stats.  A bit of cable management needs to happen but otherwise I'm pleased.  Its taken Q a bit of work but all good learning.  Its a @Nickfromwales design :)

 

IMG_2901.thumb.JPG.b291e51f92641818742422637e349068.JPG

 

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Looking good.

9/10 though I'm afraid.........

If you follow the expansion vessel back to the buffer, you can see it could be isolated from the heating system should the right hand manifold be fully isolated and left so for any duration ;) The expansion vessel should be connected independently to the buffer, BEFORE the isolation valves, as its to protect the vessel more than anything. Ultimately if its your house and nobodys going to work on it other than you then you can sleep easy, but the rule is that you never have an isolation, or any other valve, between the EV and the cylinder / heat source.

Im such a killjoy :ph34r: 

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bugger.  This is the second one on the heating system (1st one is in the system boiler) - just added it because I thought it would give a bit more slack.  If I shut off the valve then the system boilers own ev will still be plumbed in.  So the 24kw system boilers ev does the UFH (~100l) and this one does the rads.  Once we move in - I may go back and tweak this so my fellow Welshman can up the mark to 10/10 :D

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ps @Nickfromwales - I've left the PRV on the tank as well - I will pop a container under it (don't want to take it outside - it will impact on my airtight barrier) just in case it blows.  There's another one on the boiler.

 

Having typed all this I now feel a bit better!

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22 minutes ago, Nickfromwales said:

Im such a killjo

Yep - but we will still stand back and look on in awe at the tidiness of the job and it's  so much better than the one the gentlemen numpties who did the original @newhome system managed.

Edited by MikeSharp01
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23 minutes ago, CC45 said:

ps @Nickfromwales - I've left the PRV on the tank as well - I will pop a container under it (don't want to take it outside - it will impact on my airtight barrier) just in case it blows.  There's another one on the boiler.

 

Having typed all this I now feel a bit better!

You have to keep that T&PRV on the buffer so you're covered for the terminal failure scenario, which is all the isolations shut off and the immersion heater on and its stat to have failed. Its that situation that dictates the T&PRV's location ( and the fact that its factory fitted with half a tub of thread lock so its near impossible to remove ). 

Just put a 15L container under it and you'll be fine as the PRV on the boiler should be a lower setting. The buffer one is 5 bar IIRC and the boiler one will be 3 bar. 

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1 hour ago, CC45 said:

thought I'd close this one off...

 

the heating system is now in and complete.  Mains gas boiler feeds a 90l buffer that then feeds two Wunda manifolds - ufh down stairs & rads upstairs.  All individual room stats.  A bit of cable management needs to happen but otherwise I'm pleased.  Its taken Q a bit of work but all good learning.  Its a @Nickfromwales design 

 

IMG_2901.thumb.JPG.b291e51f92641818742422637e349068.JPG

 

 

It's like CAD come to life! ?

 

A few cable ties wouldn't go amiss...just make sure you get them all the same way around...

Edited by Onoff
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6 hours ago, Onoff said:

 

It's like CAD come to life! ?

 

A few cable ties wouldn't go amiss...just make sure you get them all the same way around...

 

I stay off plumbing, but what is the right way round for a cable tie if I want them all to line up?

 

?

Edited by Ferdinand
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1 hour ago, Ferdinand said:

 

I stay off plumbing, but what is the right way round for a cable tie if I want them all to line up?

 

?

 

Copy the first one pretty much! :)

Equispacing them looks good. Take a bit of time figuring how the bunched cables will lay too. I usually point the tail down or in whatever direction it's easier to get the snips in. You might be modding wiring in a tight panel for instance.

 

Snip off the potentially eye poking excess tail too.

 

However...beware the sharp ends that can still be present if you cut them off flush. End cutting pliers are quick and easy and many people cut them flush to the block with a Stanley thereafter. 

 

I actually use a pair of toe nail clippers, leaves a nice rounded edge. I've been told off before though as they're non insulated! :ph34r:

 

Or buy a zip tie gun. Tbh I don't even know where mine are.

 

 

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