john0wingnut

Hi all Im after a bit of a sense check on my UFH system pump setup / flow rate. System: ASHP is a 12kw Nibe F2040. SMO 20 controller 100L Buffer, plumbed as a 3 port. Wilo Yonos PARA pump with max 6m head supplying 2x manifolds. 175 sqm of UFH slab 17 loops, now fully de-zoned Heatloss from my calcs is 8.3kw at -3/20 dT5 Flow rate would thus be 1.41m3/hr or 23.6l/min I fully opened all the flow meters on all 17 loops, put the Wilo pump on max and then totalled all the flow rates up on each flow meter and got a total of 34l/min, which i then converted to 2.04m3/hr. Reading that max flow rate off of the Wilo Yonos Constant pressure pump graph at max setting gives a head of 3.5. https://www.ufht.co.uk/wp-content/uploads/2018/03/yonos-manual.pdf page 14 I then put the red dial on constant pressure no. 3 and got a total of 24.7l/min Is this then the correct setting for the UFH pump? Many thanks John

Found this thread interesting, as I am currently tinkering with my setup and also not hitting delta T of 7 on my UFH. I have Salus auto balance actuators, 2 manifolds - 12 and a 5. 180Sqm slab, 11 zones. I have turned the stats all to max, so they stay on / open and act as one zone to let weather compensation do its thing. Weather compensation curve is asking for 25.9 degs flow temp currently. Just now, flow to UFH heating is 27.7 and return is 25 degs. This morning, when I checked, flow was 26.9 and return was 24.1 UFH pump is a Wilo Yonos Para 25/6, set to constant pressure on setting 3 of 6, which is a 3m head. Flow rates vs designed vary across the loops. eg my lounge has 2 loops of 85m with a 1.3l/m flow rate, and this is bang on. Ensuite is 50m single loop and should be 0.9l by with the Salus ABA its sitting at 2l/min. Heatpump is putting out 28.4 with a return of 24.5. Very similar this morning. Looks to work to a dT of 4 or 5, which is modulated via the the charge pump speed. All rooms are maintaining 21 degrees +/- 0.2 degrees, except the lounge which is about 0.5 degs lower.

Thanks Dan I had a look at that, but from what I can tell, thats not to do with flow and return temps. In that menu it would appear you are setting min and max frequencies at a particular outdoor temperature. Page 37, 5.1.3 allows you to set the max flow differential, which by default is 10 degs, so in essence, the heatpump can overshoot the calculated flow temp by 10 degs. I have reduce this to 2 degs, and this has actually caused me more short cycling, as it reaches required temp quicker and thus cuts out the heat pump. Page 38, 5.1.14 is an interesting one. dT at DOT. My DOT is set to -2.0, but i cannot seem to find where one can actually tweak the dT that the heat pump works to. John

Hi Luke How do you do that in the SMO controller. Mine constantly overshoots the target by about 7 degrees. Would rather it stay on longer as per your view John

If you have a leaky house, you will be losing heat through air leakage and thus this is not recovered by MVHR

Hi all I just want to check that I am on the right track with my plans, which I have attached, to this post, and I have a few questions: 1) Have I interpreted the part F regs properly? I have taken the m2 of habitable rooms only. Is that correct or should it be the overall floor space including kitchens, bathrooms etc? 2) As my kitchen, diner, seating area and lounge are all open plan (seating area / lounge has a double sided brick fire hearth between it and open walk way as shown), I have put an extract in the kitchen above the sink / dish washer area, a supply in the diner area, and supply in the lounge, BUT, Im not sure how to treat the seating area. Should that have a supply or extract? 3) Hallway and porch I have treated as transfer zones, so I have zero'd out and then re-profiled overall flow rates to the other supply rooms. 4) MVHR (purple square on my plan) will be in the loft above the utility, which is near the north facing gable end. Plan is to build an insulated box for it out of PIR. 5) Supply / Extract manifolds are shown as green / red square on the plan. I assume closer to the MVHR unit, the better? 6) Should I go with 75mm or 90mm duct given the flow rates shown in my table 7) If opting for 90mm, is one duct to bathrooms / shower rooms ok? and should the longer runs to Master Bed / Lounge be double up, or would that only be needed for 75mm duct Thanks in advance John MVHR Calculations v4.xlsx

Your rooms with 29.16m3/h should that translate to 1.7m/s with 90/78 radial pipe, rather than 1.27m/s

As per dpmiller, it looks like you have put the diameter in, rather than the radius, so you would need to use 34mm

Not sure if it’s me having a moment here, but, taking your snug as an example - 21.87m3/h through a 68mm ID pipe would be 1.67 m/s via my maths: 21.87 m3/h / (Pi*0.034m^2) = 1.67 m/s John

Im working through the motions, planning my retrofit, which will go in the loft. Biggest problem for me currently is - I need a unit in the 400-500 m3/h range and most of them are bigger than my loft hatch, which is 500mm wide (1000mm length isnt a problem). For the pipes off the unit I'm going to use something like this: https://heatpex.pl/en/new-insulated-mass-flow-duct-work/ or https://www.phstore.co.uk/zehnder-comfopipe/zehnder-comfopipe-plus as its already insulated, the later has 43mm of insulation. Unit wise, I have been looking for ones purely made from EPP, to minimise the risk of condensation in the winter, however slim pickings from what I can find. Still debating over whether all the radial ducting needs insulating too, although it will be under 300mm for glass wool.

Problem is, having looked into decentralised alternatives, for example ecostream prana, the costs are going to be very prohibitive, vs a centralised system. Its about £1k fitted per room.

What insulated ducting have you used?

Interested in this thread. I’m in a similar position mulling over MVHR. 1970s bungalow with a 2015 extension on it. Original house footprint has a standard cold pitched roof and newer extensions has a warm pitched roof with a central flat void bit. Interesting reading the report re MVHR being useful in fairly leaky houses, which has me saying yes, but, and the big but for me, is I have nowhere except the cold roof to put the unit and ducting which for me feels like the wrong thing to do, and will likely result in negligible heat recovery and points me back towards a dMEV route, and thus returns me to my on the fence position John

Thing is, this practice is everywhere, and is similar to limiting via software. Eg take Tesla - £1500 for acceleration increase. Everything is already in the car but limited via software. In the instance of Vallient Heatpumps, they have gone down the route of a resistor to do the same thing. Do they retail at a lesser cost than other brands with cooling fiction available as standard?

Only have the SMO20. What are the benefits of the SMO40

I have an F2040 12Kw and Luke in this thread has an F2040 8kw unit

What about NIBE? Ours has the function built in which you then turn on in the controller

Strange. Mine has run constantly for the last 15 hours. Was maintaining a 4 deg dT between flow and return which is about right given avg outdoor temp is 32 degs, but would not reach the set temp of 15 degrees. Maybe just too much heat to extract. in the heating settings it has the differential set to 10 degs dT.

What have you set your cooling dT too for the 20 and 40 degree settings? Default is 3 and 6 respectively which I find strange as I’m sure with heating the dT it tries to maintain between flow and return is 7-10 degrees C.

Mine did the same. Wouldnt work between around 13:00 - 16:00. set my flow temp to 15 degrees. strangely the degree minutes shot up to 120 and have not changed since. Usually once flow temp is reached it gets back to 0, shuts compressor down, then counts back up before reaching the threshold for inverter to come back on again.

Potentially looking at this window supplier. Also found eurocell home and supply only windows, but haven’t scoped them out properly yet. Modus system you can get 0.7 U value 3G windows.

My Bungalow is approx 180sqm, UFH with a 12Kw Heatpump. Insulation is 100mm walls and floors, 300 in the roof.

Luke Have you got both the Bt6 and Bt7 temp sensors fitted, so hot water top and hot water charging? John

I have got the F2040 12Kw version. Ive had it about 4 years I have recently started playing with settings myself, having read a few ASHP efficiency threads on here. I have my DWH set to 45 degrees from 10pm through to 4pm (next day), then have it from 4pm-10pm at 50 degrees, as this is when we all normally shower, but sometimes, my Wife will shower in the morning or mid morning. Seems to be working well. In terms of heating, I have just removed the weather compensation curve and set it at a flat heating curve of 30 degrees. The tech doc shows decent COP at 35 degrees. I have a 100l buffer, and with these settings its currently working well. I have also changed the minimum charge pump speed to 15%, down from 30% and also the degree minute settings from -60DM to -100DM

I have a NIBE. Are you using the the SMO 20? If so it alternates between 30 mins hot water and 30mins heating, when there is demand for both, so in your example where it starts heating the tank, its likely done it on 30 min cycles from 2:40, which could explain why its taken longer. John