UFH newbie

[therealfronty]

Hi all,

Been happily running Evohome for a number of years now, and we're looking to add UFH for our new extension as there will be very little wall space for radiators.

Basically the back wall is being knocked out, a huge steel is going across the back of the house and it's all going to be opened up from the existing kitchen/diner out into the extension. The kitchen is then going to be moved so it runs one side of the house from the back out into the extension, there will be a breakfast bar and dining area out there, then coming back into the house where the old kitchen is, that will get ripped out and replaced with a snug.

So I'm starting to think about how the UFH will be zoned but I have no idea how long the pipework can be off each port on the manifold. Is it possible just to use one port and have one huge long run of pipework, or are there some guidelines? I assume ports <> zones, so we'd have one new zone on the Evotouch but that can control multiple ports? Or maybe we could have two zones, one for the existing area (which will become a snug) and another for the extension (new kitchen and dining area)? So I can use two external temperature sensorts and Evohome and turn on either or both zones depending on demand.

I don't really understand how the ports on the manifold are controlled, do you use an HR92 on each port or something like a MT4 actuator - the MT4 appears to be wired so does that get wired into the HCC80? If it uses HR91/HR92s then that's more batteries to faff about with. I see there's a new controller out now, the HCC100, but not sure I need that, seems I can get an HCC80 off ebay for 100 quid or so.

And if I have two heating zones, but have to use multiple ports for each zone (due to pipe lengths) how does that all work, do you bind multiple actuators/ports to each zone, so maybe ports 1-3 are for the extension and port 4 & 5 are for the snug.

I really don't have a clue, is there an idiots guide somewhere? Thanks.

[bruce_miranda]

Are you really going to have zones in the UFH system i.e. Rooms that you can close off from one another?

If not then dont bother with zones.

Also a large space will still have multiple short runs of pipe. Otherwise you will run out of heat before the end.

If you are not going to zone a manifold, then the UFH controller is completely unnecessary.

[therealfronty]

Thanks, like a I said I am a complete newbie. So I could just have it all as one zone, but I guess will need to use multiple ports on the manifold so I don't run out of heat. How do I know how long each pipe run can be, are there some guidelines somewhere? Also without the UFH controller how do I control each port, the flow temps and the UFH pump? I was assuming the UFH controller did all this?

[philchillbill]

I have a large open-plan downstairs with UFH that's all just one zone as far as Evohome is concerned. A BDR-91 controls the pump on/off overall. The individual loops in the floor are just balanced with allen-keys as a one-off after install and never touched again.

[therealfronty]

I have a large open-plan downstairs with UFH that's all just one zone as far as Evohome is concerned. A BDR-91 controls the pump on/off overall. The individual loops in the floor are just balanced with allen-keys as a one-off after install and never touched again.

Ah that's interesting, what zone type would I select if I just wanted to control a BDR91?

[bruce_miranda]

In the UK, if you have a normal radiator system, most plumbers will add a motorised zone valve and a separate loop directly from the boiler into the manifold. If the entire UFH zone is a single zone with no doors that can actually be closed between spaces then there is no point at all using an Evohome UFH controller.
You simply pair a BDR91 as the Acutator and a wall sensor as the temperature sensor. The zone type will be a Zone Valve. Let the BDR91 control the motorised zone valve, the orange wire (microswitch) of the motorised valve will power the manifold pump. This will ensure the pump starts only after the valve has opened and shuts off before the valve has closed.
All the ports on the manifold are manual and balanced at install. You dont need actuators on each port. The entire manifold is controlled as one unit.
It's a real pity that the HM80 is no longer available because that is ideal for using in this instance. But the HM80 is a legacy product and no longer supported too.

However the BDR91 + wall stat is the cheapest option. Just remember that the BDR91 has TPI built in. This will mean that the UFH will start and.stop. Nothing you can do about it, unless you plan to override the system using my method using Home Assistant and an HGI80 (or clone).

P.S. If at all possible,try and dissuade the plumber from using a normal zone valve for the UFH loop from the boiler. While they work fine, they are not designed to stay open for long periods of times. They are.deaigned for HW and CH, whereas UFH can often be on for days, weeks and months at a time. You dont start.and.stop UFH like you do CH.
There are special UFH actuators that are designed for this. However more plumbers will just stick a zone valve in because they know it will work atleast until their call back obligation has passed.

[philchillbill]

It’s set as type Zone Valve and the Evotouch performs sensor duties

[therealfronty]

In the UK, if you have a normal radiator system, most plumbers will add a motorised zone valve and a separate loop directly from the boiler into the manifold. If the entire UFH zone is a single zone with no doors that can actually be closed between spaces then there is no point at all using an Evohome UFH controller.
You simply pair a BDR91 as the Acutator and a wall sensor as the temperature sensor. The zone type will be a Zone Valve. Let the BDR91 control the motorised zone valve, the orange wire (microswitch) of the motorised valve will power the manifold pump. This will ensure the pump starts only after the valve has opened and shuts off before the valve has closed.
All the ports on the manifold are manual and balanced at install. You dont need actuators on each port. The entire manifold is controlled as one unit.
It's a real pity that the HM80 is no longer available because that is ideal for using in this instance. But the HM80 is a legacy product and no longer supported too.

However the BDR91 + wall stat is the cheapest option. Just remember that the BDR91 has TPI built in. This will mean that the UFH will start and.stop. Nothing you can do about it, unless you plan to override the system using my method using Home Assistant and an HGI80 (or clone).

P.S. If at all possible,try and dissuade the plumber from using a normal zone valve for the UFH loop from the boiler. While they work fine, they are not designed to stay open for long periods of times. They are.deaigned for HW and CH, whereas UFH can often be on for days, weeks and months at a time. You dont start.and.stop UFH like you do CH.
There are special UFH actuators that are designed for this. However more plumbers will just stick a zone valve in because they know it will work atleast until their call back obligation has passed.

Ok thanks, I'm starting to get a bit more of an understanding. So if I shouldn't use a standard CH 2 port motorised valve, what should I use?

Also I'm sure I read somewhere that the water in UFH loop should be heated to a cooler temperature than the main CH (I'm sure I read 30-35 degrees somewhere), so I assume that the manifold ports are balanced using allen keys like Phil mentioned so only the required amount of heated water is let through to maintain a lower UFH flow temperature, and the zone valve controls whether any heated water flows into the UFH loops at all (so you can basically turn it off). As I already have 2 x BDRs (one for CH and one for DHW) I guess the TPI schedule on the UFH could cause the boiler to fire and push water around the CH circuit even if it's not required, but all the rads should be closed anyway apart from the bypass rad in the bathroom.

[philchillbill]

I don’t even have a zone valve. Turning the UFH pump on/off is easier. The BDR I use for that is set to be of zone valve type but it’s not a valve at all. At least in NL all UFH manifolds have a manual mixer valve to set the temp of the water for the floor. It just decides the mix between the incoming hot water from the boiler and the return water coming back out of the floor.

[therealfronty]

I don’t even have a zone valve. Turning the UFH pump on/off is easier. The BDR I use for that is set to be of zone valve type but it’s not a valve at all. At least in NL all UFH manifolds have a manual mixer valve to set the temp of the water for the floor. It just decides the mix between the incoming hot water from the boiler and the return water coming back out of the floor.

When the main pump is on for CH or DHW demand, don't you get hot water being pushed into the UFH when it's not required?

[philchillbill]

No. There’s a bypass bar in the manifold that just short circuits the floor circuit when the UFH pump is off.

[bruce_miranda]

If your plumber is happy to install the UFH loop without another zone valve that would be the best option. Then as Phil says, use a BDR91 to run the UFH pump as required. When there is no demand for the UFH and it's pump is off, there is no flow into the manifold mixer and the entire manifold is bypassed. It all works quite well.
As for the lower flow into the manifold, that is controlled by the manual TRV on the manifold and you can see the flow temperature into the manifold via the thermometer on the manifold.

[bruce_miranda]

If you currently have 2 x BDR91s controlling the CH and DHW zone valves, it means that they are firing the boiler via their Orange wires. Depending on how your UFH loop is plumbed you may need to consider how a UFH only demand will fire the boiler.
If all your radiators have HR92s on them, you dont really need a CH zone valve..I would simply latch the CH zone valve permanently open or better still removed. Repurpose the CH BDR91 as a Boiler Appliance Control. So that way Evohome is in direct control of the boiler and you gain some of the added functionality like Load Scaling etc. More importantly though, UFH, DHW and the radiators can all demand the boiler via Evohome as opposed to the zone valves controlling the boiler. Even rhe HW Orange wire to the boiler can be disconnected.

[therealfronty]

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).

[G4RHL]

Have you thought of going electric? OK, electricity in the UK is not cheap, but in time it will get better, although how long depends a lot on politicians. However, with lots of high quality insulation electric heating could be viable. I seriously looked at it 5 years ago when my boiler was replaced. But it was the running cost put me off. However, I costed out a complete installation for a 4 bedroomed detached house at £5k. This included removing the existing system and radiators. An electric heating installation can be a DIY job needing an electric drill, a screwdriver, some wall plugs and a spirit level. Oh, you do need the skill of being able to push a three-pin plug into a wall socket. You may have to go on a course for that! Seriously though, other than the cost of electricity it was viable, very efficient, needs no maintenance. Out of curiosity I costed the radiators again recently and no change in price. I suspect increasing demand for such has kept the prices competitive. Today I certainly would think again in that direction if having to replace a boiler.