SimonD

I have this question as an issue I've been kicking down the road. Building Regulations says either into a drain (by whatever means) or soakaway. My first BCO was happy with a french drain out onto the sloping ground in front of the house (but this wasn't followed up in writing). Now I'm being asked to either have it into drain or soakaway. A customer recently had an extension done to their house and they used a drainage channel to get to the foul drain. I might do the same if I can.

Very true -it's like the ones who call to book in a service because the boiler isn't working right. They say they're surprise as it was only done recently while the paperwork says 7 years ago!

It's quite funny you say this. In three years I have only been asked once for an unvented service and that turned out to be because the bubble needed to be recharged on a MegaFlow, queue twiddling my thumbs for 45 minutes listening to bubbles in the cylinder and a customer repeatedly asking me if I was okay. When I service a boiler and they have an unvented cylinder I always tell the customer that it needs an annual service and they shrug because they don't even want to pay for the boiler to be serviced. They don't even ask me how much the unvented service would cost.

Oh, I see! There was me being a bit dopey. A thread sealing compound will do it - I always use Loctite 55 myself - your PTFE liquid should do the job.

Can you share a photo?

None, you should just have a nice little rubber (epdm) washer in there on the flat face.

As @joth says, there are other factors to consider in how the system will work with solar gain with plenty of ways to mitigate the problem without zoning that shuts down flow to a specific area. The zoning proposal is more likely to increase your costs, not the other way round. Okay, so you will have received a design from the installer. So what are the individual room loss the installer calculated? And how do these each match up with the UFH design? And what flow temperature is being proposed. What has the installer calculated the existing UFH output to be at design temperatures? Additionally, when doing a heat loss calculation without blower test results, a lot of assumptions have to be made, including with ACH and MVHR. Also, because heat loss calculations are fundamentally based on SAP too, there are further adustments that can be made for thermal bridging, which can have a big impact on the overall heat loos calculation. In addition to this, and something that is often overlooked is that loss through the floor and therefore the floor's U-value, varies depending on the floor dimensions and the specific arrangement of the room and external walls - a lot of designers don't know this and put a single figure in because it isn't specifically covered in the design training, not even in Heat Geek training. Here's a specific example regarding my house: MCS Umbrella does a heat loss calcuation using my given U-values and floor plans - heat loss about 7.5kW My heat loss calculation - 4.83kW This is the difference between a 9kW heat pump and a 6.5kW heat pump by the chosen manufacturer. Now, the other night, at -6 to retain a steady state of about 21.5C indoors my heat pump had to produce 3.8kW for 2 hours and for the rest of the time knocked itself back to 3.1kW. So even my heat loss calcuation taking into consideration thermal bridging and careful calculation of ventilation rates is slightly high, but I dread to think what things would be like if I'd put in a 9kW unit. Now, your installer may have covered all this, but I'm not so sure given the first design using buffers etc. My other question has to be why no one, including your architect, has suggested waiting until you've completed your blower tests before doing the heat pump design?

A lot of them are nowadays - even ones set up by merchants charge a hefty 1000-1500 for the privilege. Some will also send someone to site to complete the commissioning costing another 400-500

Here we go again. In some ways he's correct. In others he isn't. MIS 3005-D provides a basic procedure that must be followed. The Standard for heat load calculations and the correct method is defined by BS EN1283-1 2017 which is also covered in the CIBSE Domestic Heating Design Guide. Lots of designers and installers falsely believe it's prescriptive, but it isn't, especially where building details are known. The outputs aren't defined by the procedure/standard/methods, but fundamentally by the inputs. Again, this is kind of correct. The changes were implemented in June this year according to the standard BS EN1283-1 2017. This provides two methods of ventilation calculations. one based on actual door blower tests and the other based on a simplified method, which isn't too many miles off the old one. It's also based upon the designer's perspective on the building. The standard also includes infiltration losses based on the building height and exposure. What was his basis for telling you this? Is this installer MCS certified or using an MCS umbrella? What heating qualifications does the installer hold above the basics? I'd really be wanting to use someone who has at the very least done extra training by some recognised provider in hydronics. So in terms of calculated heat loss what are the figures being used for reference for all their design?

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With a flow return 35/30 something like DT50 output of 1985. Have a look and play with the attached spreadsheet. What I've generally found with radiators is that as soon as you get into the 35 and below flow temp and DT5 the sizes start to get quite ridiculous, especially with warmer rooms - e.g. with this one the conversion factor is 0.115 bathroom rad size estimate.ods

Neither! It's a good room-by-room heat loss calculation that must come first which you then use to size the heat source, followed by the emitter design. Then you look at flow rate, velocity and pressure loss through your pipework.

Nice floor then! 😁 What are you planning mean water temp wise v air temp as at 26 you'll need to have a very small DT?

Why as low as 24? Most of my commissioning of wooden floors over ufh say max 27C floor temperature and on gas systems this has sometimes required floor temp sensors.

I'm all on radiators. Hindsight since getting the heat pump tells me UFH would have been a good idea and I could have run much lower flow temp. But isn't that self-build and learning for you? The rads aren't too intrusive thankfully. Quite pleased though as my calculated theoretical flow temp at -3 was 37C.