Nelliekins

Heating system for an ICF house with UFH

Recommended Posts

2 hours ago, Nelliekins said:

Hmmm you have got me wondering now! There is definitely 2 for coil, 2 on opposite side (top and bottom) and vent out at top. 

Be good if you have as you'll have a separate flow tapping for the DHW PHE. With regards to sustain, I wouldn't worry about sapping the cylinder as the space heating wont even blink if its has an empty buffer for 30 mins or so. Only issue will be the useful temp cut-off point of ~40oC but if you set the cylinder set temp to ~65oC and try it I think you'll be fine. If your DHW usage is higher and you find yourself needing more 'capacity', just incrementally raise the set temp by 2oC and retry daily, adjusting accordingly as you go, until your happy. 

Share this post


Link to post
Share on other sites
1 hour ago, Nickfromwales said:

Be good if you have as you'll have a separate flow tapping for the DHW PHE. With regards to sustain, I wouldn't worry about sapping the cylinder as the space heating wont even blink if its has an empty buffer for 30 mins or so. Only issue will be the useful temp cut-off point of ~40oC but if you set the cylinder set temp to ~65oC and try it I think you'll be fine. If your DHW usage is higher and you find yourself needing more 'capacity', just incrementally raise the set temp by 2oC and retry daily, adjusting accordingly as you go, until your happy. 

 

I assumed the PHE flow would tee off the vent connection right at the top of the cylinder, next to the immersion port. The boiler would connect to the direct ports (top and bottom) on the opposite side of the tank to the coil ports. 

 

So would I tee the PHE return with the boiler return, or add a new flanged fitting at the bottom for the PHE return? 

 

Do you agree with @PeterW that the UFH buffer is probably not needed, and I can simply heat via the coil? Or am I better with a separate buffer tank, if only so I can use another immersion to assist with initial heating of the UFH? 

 

Share this post


Link to post
Share on other sites
3 hours ago, Nickfromwales said:

Just enough time to try all your frocks on :/

Images I cannot un-see :( 

 

Aw, I bet he looked cute 👗 with the stilettos 👠  on 😀

 

  • Sad 1

Share this post


Link to post
Share on other sites
9 hours ago, PeterW said:

You cannot wire the pump direct to the switch ..! Have to put a relay in as otherwise you will fry the contacts, irrespective of what the MIs say about current rating ..!

 

 

If you get the flow switch I used to circulate water through our PHE, then you can wire it direct to the pump, as it has a built in triac that can switch 3 amps: https://cpc.farnell.com/gentech-international/fs-01/flow-switch-noryl-ac/dp/SN36161

 

 

  • Thanks 1

Share this post


Link to post
Share on other sites
15 minutes ago, JSHarris said:

 

 

If you get the flow switch I used to circulate water through our PHE, then you can wire it direct to the pump, as it has a built in triac that can switch 3 amps: https://cpc.farnell.com/gentech-international/fs-01/flow-switch-noryl-ac/dp/SN36161

 

 

 

Thanks @JSHarris - I was referring to the one that @Nelliekins linked as that was the one we had issues with. Useful to know that there is one with a decent current control. 

Share this post


Link to post
Share on other sites
4 hours ago, newhome said:

 

Aw, I bet he looked cute 👗 with the stilettos 👠  on 😀

 

 

You don't want to know what @Nickfromwales was doing .... 👙👜 💄 

  • Confused 2

Share this post


Link to post
Share on other sites
1 hour ago, JSHarris said:

 

 

If you get the flow switch I used to circulate water through our PHE, then you can wire it direct to the pump, as it has a built in triac that can switch 3 amps: https://cpc.farnell.com/gentech-international/fs-01/flow-switch-noryl-ac/dp/SN36161

 

 

 

Thanks, @JSHarris - ordered!

 

Any recommendations on pumps - I see Wilo and Grundfos being used in most places, and wouldn't know how to choose between them. Is one brand longer lasting (ie higher MTBF)? Or quieter, I guess that might be nice? Or failing that, cheaper? 🙂

 

@PeterW and @Nickfromwales - one of you clearly needs to make the first move here. Be brave - BH is here for you! 🤣👨‍❤️‍👨💞💍🍾

Edited by Nelliekins
Auto correct corrections
  • Haha 1

Share this post


Link to post
Share on other sites

Wilo and Grundfoss are both recommended as they are reliable and quiet.

 

My UFH manifolds came with IBO pumps. Horrible noisy things.  I have changed one for a Wilo already and still have to get around to changing the other one.

 

The last thing you want with a heating system is a horrible droning whine all the time.

  • Like 1

Share this post


Link to post
Share on other sites

Wilo seem to be slightly quieter than Grundfos, based on our experience, although both are pretty quiet.  We have a Grundfos pump on the UFH manifold and a Wilo on the DHW preheat PHE circuit and the Wilo is definitely quieter, so much so that I've had to fit a light to show that the flow switch has turned the pump on, as I can't hear it running.

 

  • Like 1

Share this post


Link to post
Share on other sites

Can’t beat these Wilo Pico pumps for performance - virtually silent too. 

 

Best price seems to be Screwfix too 

  • Thanks 1

Share this post


Link to post
Share on other sites
14 minutes ago, PeterW said:

Can’t beat these Wilo Pico pumps for performance - virtually silent too. 

 

Best price seems to be Screwfix too 

 

Thanks @PeterW.

 

I presume I should put a set of gate valves either side of them, to make eventual replacement easier? 

Share this post


Link to post
Share on other sites

Yes you need pump valves either end. I would use Pegler ones. 

 

I also think this PHE and pump need to go across the tank input and output, not across the vent pipe and output. Reason being, the PHE and DHW need priority and tbh the tank won’t stratify as it’s too small -  if you use the vent pipe, there is a chance that the PHE pump will just pull the tank content rather than take the full heat of the  boiler which may result in lukewarm water. 

  • Thanks 1

Share this post


Link to post
Share on other sites
1 hour ago, PeterW said:

Yes you need pump valves either end. I would use Pegler ones. 

 

I also think this PHE and pump need to go across the tank input and output, not across the vent pipe and output. Reason being, the PHE and DHW need priority and tbh the tank won’t stratify as it’s too small -  if you use the vent pipe, there is a chance that the PHE pump will just pull the tank content rather than take the full heat of the  boiler which may result in lukewarm water. 

Yup. 

 

9 hours ago, Nelliekins said:

so I can use another immersion to assist with initial heating of the UFH? 

Definitely a waste of time and money. Your boiler will be chucking 30kW in and another immersion would only provide another 3, totally pointless. 

 

9 hours ago, Nelliekins said:

Do you agree with @PeterW that the UFH buffer is probably not needed, and I can simply heat via the coil?

100%, dress or no dress. 

Share this post


Link to post
Share on other sites

@PeterW

Any benefit from going out the top via a Sussex? It’ll be the hottest water after all. 

I’d be happy enough as long as the cyl stat is kept ( mounted ) low tbh. 

Share this post


Link to post
Share on other sites
1 hour ago, PeterW said:

Yes you need pump valves either end. I would use Pegler ones. 

 

I also think this PHE and pump need to go across the tank input and output, not across the vent pipe and output. Reason being, the PHE and DHW need priority and tbh the tank won’t stratify as it’s too small -  if you use the vent pipe, there is a chance that the PHE pump will just pull the tank content rather than take the full heat of the  boiler which may result in lukewarm water. 

 

OK, leave the vent as a vent, got it.

 

So would you suggest tee off both top and bottom (1 pair for boiler, 1 pair for PHE)? Or fit new flanges for the PHE?

Share this post


Link to post
Share on other sites
1 hour ago, Nickfromwales said:

@PeterW

Any benefit from going out the top via a Sussex? It’ll be the hottest water after all. 

I’d be happy enough as long as the cyl stat is kept ( mounted ) low tbh. 

 

Be about 15 usable litres above it - can’t see the point tbh. It’s purely as a buffer to stop the boiler firing every time it needs a bowl of water or someone washes their hands. When the showers kick in, you’ve probably got about 3-4 mins before the boiler kicks in and takes over providing heat to the PHE. 

 

I’d mount the stat about 6” above the bottom inlet directly opposite the outlet. It will probably be mid point of the coils for the UFH at that point too. 

 

1 hour ago, Nelliekins said:

 

OK, leave the vent as a vent, got it.

 

So would you suggest tee off both top and bottom (1 pair for boiler, 1 pair for PHE)? Or fit new flanges for the PHE?

 

Top inlet I would use a tee upright, boiler into the top, tee to the tank and bottom to the PHE. 

 

Bottom I would use tee horizontal with left to boiler return, top to PHE and right to tank. 

 

Pump below the PHE pumping downwards, maximize any convection through it. 

 

  • Thanks 1

Share this post


Link to post
Share on other sites
2 hours ago, PeterW said:

 

Be about 15 usable litres above it - can’t see the point tbh. It’s purely as a buffer to stop the boiler firing every time it needs a bowl of water or someone washes their hands. When the showers kick in, you’ve probably got about 3-4 mins before the boiler kicks in and takes over providing heat to the PHE. 

 

I’d mount the stat about 6” above the bottom inlet directly opposite the outlet. It will probably be mid point of the coils for the UFH at that point too. 

 

 

Top inlet I would use a tee upright, boiler into the top, tee to the tank and bottom to the PHE. 

 

Bottom I would use tee horizontal with left to boiler return, top to PHE and right to tank. 

 

Pump below the PHE pumping downwards, maximize any convection through it. 

 

 

That's fantastic, thanks @PeterW. Even a pillock like me can follow those instructions! 😁

 

Better head to screwfix tomorrow then! 

 

Share this post


Link to post
Share on other sites
4 hours ago, Nelliekins said:

Better head to screwfix tomorrow then! 

Best of British with that lol. 

  • Haha 1

Share this post


Link to post
Share on other sites
17 hours ago, Nelliekins said:

 

That's fantastic, thanks @PeterW. Even a pillock like me can follow those instructions! 😁

 

Better head to screwfix tomorrow then! 

 

 

So as they are all closed today... are you making a list ..?? 

 

Assuming  the PHE has threaded connections ..? Tank got 22mm compression ..?

 

Are you doing this in copper and compression or push fit..? 

Share this post


Link to post
Share on other sites
13 hours ago, PeterW said:

 

So as they are all closed today... are you making a list ..?? 

 

Assuming  the PHE has threaded connections ..? Tank got 22mm compression ..?

 

Are you doing this in copper and compression or push fit..? 

 

Sorry @PeterW I was at site all day, mainly fitting the UFH loop into the main bathroom, now that Kim has picked a bath at long last. I really don't like the stiff PEX pipe... Should have researched that more before I bought!

 

I am thinking of a mix tbh, with everything connected to boiler or tank in copper + compression, and everything else (eg the hot/cold/RWH manifolds) in push fit. The manifolds are being sited in the laundry alongside the upstairs UFH manifold and the tank, so central isolation of every outlet instead of individual stop taps everywhere... Allows me to commission stuff in stages, and simplify the "RWH backup from mains" side of things. 

 

I have about a dozen 22mm push fit elbows and half that number of Tee fittings. I also have a bag full of 15mm & 22mm compression fittings of various types. I tend to prefer push fit if it's all going to be serviceable / accessible, and solder or compression if not... Had 10 out of 12 Floplast push fit 15mm elbows leak in the first 2 weeks, replaced most with Speedfit fittings and a couple with compression and not so much as a drip in the 5 weeks since. Lesson learnt - you get what you pay for. 

 

Anyone know of a reason not to use 16mm PEX pipe for hot/cold/RWH feeds around the house? The fittings are only a couple of quid each to convert to 15mm COMPRESSION, and the PEX pipe has WRAS approval, and is good for upto 95C, and I have about 600m of the pipe left over from doing the UFH 🤔

Share this post


Link to post
Share on other sites
14 hours ago, PeterW said:

Assuming  the PHE has threaded connections ..? Tank got 22mm compression ..?

 

 

Sorry missed this. Yes to both. PHE is 1" BSPP and tank is all 22mm compression - they even supplied the olives! 👍

Share this post


Link to post
Share on other sites
20 minutes ago, Nelliekins said:

Anyone know of a reason not to use 16mm PEX pipe for hot/cold/RWH feeds around the house? The fittings are only a couple of quid each to convert to 15mm COMPRESSION, and the PEX pipe has WRAS approval, and is good for upto 95C, and I have about 600m of the pipe left over from doing the UFH

No reason not too at all, other than converting to 15mm. Done it a few times where the pipe was over-ordered.

  • Like 1

Share this post


Link to post
Share on other sites

PEX as water pipes is fine but also invest in some blue and red insulation tape and mark all the pipes as you go. 

  • Like 1

Share this post


Link to post
Share on other sites

Oh yeh - buy Hep2O next time too... 😉 Floplast push fits are made from recycled pot noodle tubs.... 

  • Like 1
  • Haha 1

Share this post


Link to post
Share on other sites
8 hours ago, PeterW said:

Oh yeh - buy Hep2O next time too... 😉 Floplast push fits are made from recycled pot noodle tubs.... 

 

The manifolds for hot /cold /RWH will be the Hep2O sectional units that screw together, so that I could get both 15mm and 22mm feeds off the same 3/4" input pipe. 

 

That said I do prefer Speedfit for elbows etc - no idea why but the twist lock seems to give me some comfort, and they've never let me down yet. 

8 hours ago, PeterW said:

PEX as water pipes is fine but also invest in some blue and red insulation tape and mark all the pipes as you go. 

 

And black/green stripy, since we are doing RWH as well! 🙂

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now