SimonD

I've got a retired electrical engineer doing the 2nd fix electrics with me but passed me on to another guy to install an ev charger in our remote garage. Unfortunately, this one has disappeared into one of those trades black holes and just doesn't get back to me. I have a problem because I've got open trenches partly used for national grid to install my permanent supply, but also to take the cabling down to the garage. So, my plan is to just install this with the retired electrical engineer and then get it covered with the part p inspection. question is, what stuff do I need to install the infrastructure now and for the future? I'm putting in 25mm cable and the sparky who was supposed to do the job mentioned its useful to have a control cable, but I don't know what this is? Can someone here list everything I need from my meter tails to the ev charger, so I can get these trenches filled in and stop getting hassled by my wife about getting a proper charger instead of the wall plug? Thanks!

Yup, this drives me mental. I did an instal (natural gas) a while back where the owner was doing a deep refurbishment. I put in the boiler with modulating controls etc. and said she should call me when it's time for the ufh. However, the guy doing the floors, ripping them out and properly insulating them etc. never called me and did it himself with some other plumbing/heating muppet. Then winter came and the customer called me to say house wouldn't get hot. its a tiny cottage and they'd zoned it all up, then thrown away the brand new modulating controls for cheap shite relay ones and the system constantly short cycled. The circle completed with me tearing all their crap out and putting back modulation. Hey presto no short cycling. Makes my blood boil...

TBH the installers could have made their life easier by just using a heatmiser UH-8 as that can also control rad ch and dhw, and then no need for the abovementioned Navien wiring centre which I assume is just like the widely used Honeywell and Drayton standard wiring centres. It would also be a lot tidier I think.

Yes this. I'm really confused. The installation manual clearly shows switched live from wiring centre to boiler terminal 4 on CONM4. This is connected to the two orange switched lives that come from dhw and ch 2-ports, which is standard in the wiring centre. So to add ufh, there will be a switched live from the ufh 8 zone wiring Centre, which is sometimes volt free and just needs a bridge to com on the wiring Centre itself, and Bob's your uncle. Given the thread, this seems too simple. Or am I missing something? Some electricians too 😉 A customer of mine had new ufh installed while I was away last summer and then emailed me when i got back to say that neither the heating engineer nor his very competent electrician could get the ufh calling for heat to the boiler. It took 10 minutes 😁 I was tempted to say it was a very complicated and expensive call out but went easy on the electrician, who was there when I sorted it 😀

It could just be the fan. When you switch on ufh fan speed increases slightly to compensate for addition load.

Yes. Like the figures I posted earlier, this provides the best output. Radiator manufacturer figures are usually based on Top and Bottom Same End. But remember that rad output depends on the air temperature differential too. So for example with a flow temp of 70 with return of 50 you have a mean water temp (mwt) of 60. Mean water - air temp differential is then mwt - air temp so output differences between 21 degrees and 16 degrees are as follows: 60-21 = 39 60-16 = 44 To get the actual radiator output you then divide this by the manufactures delta, usually 50 so: 39/50=0.78 44/50=0.88 This means that with a room temp of 21 the radiator output is 78% of catalogue and with 16 degrees it's 88% Which clearly shows that even just 5 degrees has a big impact on output. You then take these results and multiply by the connector emissions factor which for TBOE is 1.05 or 0.96 for BOE Plus there are other factors used for the whole calculation.

Yes, but is it useful to believe its all down to delta T, even for general public and enthusiasts without also understanding the implications this has on heat output and mass flow rate and how this impacts the function of the system as a whole? By definition a lower delta T distributes less heat and therefore requires higher flow rates for the same output, some of which are impractical. And then with radiators heat transfer is based on Mean Water Temp to Air Temp differential as shown by the spreadsheet above so many radiator systems just won't work at low flow temperatures. Yep, maybe it's a sheesh post......😉

yes, they must be, but like most Heatgeek blogs, the nuance of all factors required to get a heating system working are missing, giving what I think is a misleadingly simplistic account, even if the principles are fairly simple. A lot of the figures above simply won't work very well with radiator systems without impractical modifications.

Sounds like the system needs purging which could also account for poor flow through some of the loops. Then a need to balance the loops. If this is a new/ish system is there a technical manual showing the theoretical flow rate through each loop? Setting them to this would be a great start.

Doesn't instill much confidence, does it? But yes, Opentherm is supported with the 050-W and 100-W which are plusbus, weather comp or opentherm, or relay. With the 200-W it's plusbus or canbus and you'd probably go weather comp. You can even add opentherm to many older 100-W with an X21 wiring harness for less than £10.

I can't speak for ATAG but you'd be far better off with a Viessmann 100-W or 200-W than a Worcester. 4 pipe out of the box PDHW with directly connected cylinder stat. then you just have to worry about heating control. They're also 12 year warranty out of the box if registered through the Viessmann installer portal. Too many fudges and system compromises (as well as unnecessary costs) doing it with a Worcester, whose system control implementation strategy is terrible IMHO. Edit: BTW poor system control, heating not working very well in new and newish builds with Worcesters installed with UVC and combined rads/ufh is one of my common jobs to sort out!

What we're you using for Opentherm control? This is entirely possible within the protocol - the master simply asks for relevant flow temp from boiler when the dhw cylinder calls for heat and you wire in a relay for any external valves.

yes, Opentherm does work in reality, but like all things heating, it depends on the boiler and or controller implementation as well as the heating system overall. The Opentherm protocol specifies a certain amount of information to be available but quite a bit of it is optional. Boiler cycling again depends on the setup. I'just installed Opentherm on an Ideal Vogue Max 18kW system boiler. House has a calculated heat loss of 7.35kW and the size of boiler was selected for DHW reheat times. The controller has a default minimum flow temperature of 45 C on opentherm. At this temp, even on a fairly cold day like today, the boiler will short cycle, and even worse with minimum flow temp set to 40C, which is what I set it to first. As soon as I increased this to 50, with a 55C max flow temp, the boiler ran constantly for well over an hour, with an almost constant return temp of 39.5C, increasing and then maintaining room temp nicely. On another recent install with a Viessmann 100-W into a very large, very old place with a very old heating system, I had to set the max flow temp to 80C and minimum at 45C. With Opentherm the boiler would run at 80 to get towards target but then ramp down as it got closer, so when I checked, it had dialled back to 53C to maintain temp at setpoint. It certainly can be used with UFH and rads. I work mainly with gas systems so always use mixers with ufh. In terms of controls, I like EPH because I have access to set max/min flow temps together with dhw temperature and its also possible to run pdhw on an s-plan system with these controls. I've even done this succesfully with Worcester boilers using the Nefit opentherm ems converter. Savings wise, research suggests between 10-15% although Tado in Germany has at some point suggested 25% iirc. Whilst it is two way, when I've had discussions with Viessmann technical when fault finding control problems, they confirm that the boiler becomes slave to opentherm and just passes info to the controller. However, the boiler doesn't necessarily pass all info across and will continue to manage some aspects like pump modulation relative to fan speeds etc. These will be managed by the boiler when it is simply responding to Opentherm's instruction for flow temp. HTH.

Yes, I saw that. Good modification you made. Something I warn all my customers about when they buy them but most don't listen.

You would have thought since we moved over to metric over 40 years ago but go onto sites like screwfix and they're all listed in BTU. One of my suppliers and radiator manufacturer recently republished their catalogue in BTU changing it from kW - I phoned the manufacturer up to ask what was going on and they replied as if I had gone mad! So I asked them what unit is used to complete heat loss calcs and they still were blank. It's just bonkers....