UFH newbie

[therealfronty]

Have you thought of going electric?

I thought about it for a few seconds but the running costs scared me off. The floor area is about 45m2, I just figured it would be too expensive.

[philchillbill]

Hello gents, I thought I'd revisit this post as my UFH will be installed soon. It's taken ages for the extension to be built, it's been very stop-start and the hot weather hasn't helped. The roof tiles are being done at the moment and the windows and doors are due to be installed next week I think.

I just wanted to double check I've got this correct, we are going to have a single zone as it's all open plan, so no need for any actuators or UFH controllers. It seems like the simplest solution is to install a third BDR91 and room stat and create a new zone type "zone valve". But I'm not sure how it's all wired up - if we have a zone valve that opens and closes the feed to the UFH, then the BDR91 can control that - the zone valve then controls the UFH pump and we take the orange wire and connect that into my wiring centre somewhere so that the boiler fires? I'm not sure where exactly that would go but hopefully the heating engineer will know.

I saw the note about TPI on the BDR91, which sounds like it could be pain as I guess that means the UFH pump will keep turning on and off even when the water is up to temperature. Does that also mean the UFH valve will keep opening and closing - maybe best not to have a zone valve then, but then how do I fire the boiler if there's no orange wire? Need to have a think about all this.

As for re-wiring everything so that the heating BDR is repurposed as a boiler relay, I need to see if the heating engineer can do that. But he was talking about converting me from y-plan to s-plan so that would mean I have a dedicated zone valve for the CH controlled by the CH BDR. I spoke to my builder about it as I said I had HR91's on all the rads (apart from my bypass rad) but he said it was to stop water circulating through the CH pipework when there's no CH demand, but still give the UFH a feed.

It does sound as though I might be best off getting the whole lot rewired - at the moment I have an old sundial wiring centre (it looks like spaghetti junction!) and when we put Evohome in we just replaced the old wired room stat with a BDR for the heating and the cylinder stat was replaced with another BDR for the DHW, then we just put the old controller on "constant" to let Evohome control everything. If this guy my builder is going to use doesn't understand Evohome maybe I need to get someone else in (he was muttering about heat miser or something).

In my install, the "zone valve" BDR91 switches the pump for the UFH. I decided against an open/close valve on the UFH feed-water as killing the pump completely stops flow anyway. The boiler fires because the boiler relay (OT or on/off) tells it to via RF so at least in my house there are no orange (or otherwise) wires for firing the boiler.

[therealfronty]

So my plumber and his sparky has completely rewired my system now and converted me from y-plan to s-plan. The orange wires from both valves are used to fire the boiler. The UFH manifold is installed and they have added a zone valve. The UFH pump and zone valve are not currently connected, the actual UFH pipework is being laid next week. I couldn't really get my head around defining the UFH as a zone valve and using another BDR91, I didn't want TPI to interrupt the UFH, so I went and bought a HCC80R off ebay and I'm going to try and use that to operate the pump and zone valve (the orange wire will be connected into the others to the fire the boiler). I won't be using the HCC80R with any actuators, so really it's all a bit overkill as it's really just being used to provide a 240V switched output (the pump output). I looked at the newer HCC100 but it seems you have to be an approved installer to configure it (you need a "Residio Pro" account to log into the app that is used to configure it), which seems madness!

Anyway, I'll report back here when I've got it all working.

[therealfronty]

As an interesting aside, we had all sorts of weird issues trying to rewire the system. There must have been a cracked track or broken wire somewhere on the old sundial PCB as the only way to get the pump to run was to push down on the right hand side of the cover. Also the boiler didn't have a switched live, was permanently on, so was using the internal flow switch to figure out when to fire, like how a combi boiler works when you open a tap. All seemed very odd.

[G4RHL]

You remind me. When I installed Evohome nearly 16 years ago I intended to use the supply to the airing cupboard where there was a junction box for the tank, valve and boiler. I turned off the trip switch marked heating in the consumer unit and thank goodness did a double check before touching anything. All was still live! A couple of years later I installed Honeywell’s alarm system. I switched off the trip switch marked as that for the previous alarm system, opened the old panel and found it still live! Carefully checking everything I found the builders had wired up the heating switch to the alarm system and vice versa, or rather wrongly marked them in the panel, but also wired the alarm system to the right switch as well. The house was built 1997. Moral, don’t rely on modern builders wiring up things correctly! The Honeywell alarm system works very well. Shame they don’t make it now.