Underfloor Heating Commissioning

[cf-leeds]

I could so with some advice around the control of a UFH system.

I currently have a UFH installation which is plumbed in and functional, but not commissioned. Basically, as part of a kitchen conversion project, a plumber installed the pipes and connected the plumbing, but the electrical guy never turned up to do the control connectivity. After repeated calls, I figured he was never gonna show up. No money lost, as I never paid him, but I still need to get things set up properly.

Right now, I have a UFH circuit under the kitchen/dining area. Manifold and tubes fully connected and up to pressure, with their own pump. I temporarily plugged the pump into a regular power socket and if we need UFH to circulate, I flick on the power to the pump, while the heating is on. The manual dial thermostat on the manifold determines the temperature of the UFH. Not ideal - I know. I hardly had to really use it in this way, but as winter approaches, I need to automate it.

There is a motorised zone valve on the flow to the rest of the house that is not electrically connected and is in manual-override right now (via a small lever on the Honeywell valve). Flow to rest of house is therefore always on.

So.............

I'm more than willing to do some reading and get things connected, but could initially do with some pointers. E.g. How does the control of boiler and separate UFH conceptually work ?

Recommended products - UFH controller ? Thermostat for the boiler ? Inter-connectivity ?

Will a specific UFH controller/thermostat be the controller of the zone valve ?

My Vaillant boiler has no external thermostat right now, just a timer, so I guess I'll need to obtain an external thermostat also.

It all looks a little non-trivial, though I'd like to at least get an understanding and have a shot at it, before calling an "expert".

Thanks for any advice.

[John Rumm]

[snip]

ok

Is the boiler a combi and/or is there a hot water cylinder?

To an extent, that rather depends on how you want it to work. So that is probably the first thing to establish; what your requirements are?

For example, does the UFH need to be a separate zone, or are you anticipating it will be always on at the same time as the rest of the heating? Do you need separate heating zones elsewhere (say and upstairs / downstairs split)

Or a programmable stat to replace the function of the timer as well.

What model is the boiler?

Vaillant boilers support lots of options regarding controls. You could go simple traditional on/off style stat and timer, and fixed flow temperature, or full blown weather compensated operation where the system selects the ideal flow temperature based on what the weather is doing, the current room temp, the demanded temp, and even takes into account the heat loss rate of the house. The latter is more complicated to setup, but gives very good control of house temperature, better overall efficiency, lower bills etc.

[The Natural Philosopher]

I built my own. Get a big DIN rail enclosure.

First of all because you now have two circulation pumps you will need a relay so a call for 'rest of house' heat doesnt fire up the underfloor pump.

The wiring is as follows:

Boiler and main circulation pump are fed from the relay *contacts* OR (wire in parallel) from the motorised valves that control the rest of the house OR from the hot water motorised valve.

UFH pump and relay COIL in parallel are feed from the motorised valve that controls the UFH.

The three motorised valves are fed in my case from three timers (a three zone timer) and three thermostats. One for UFH one for rest of the house and one in the hot water tank.

It is simple but you end up with a lot of wires to be connected so a big box with lots of junction bus bars for neutral and earth and a lot of connectors for the varous switched live bits is in order,

[cf-leeds]

Thanks for the responses and information.

Adding some further information:

The boiler is a Vaillant Ecotec Eclusive (Combi). There is NO hot water cylinder involved.

If I think about it, the functionality that I need is pretty straight forward. I.e., the UFH will always need to be on when the rest of house is being heated.

I do however want to be able to just operate the UFH on its own sometimes, as I work from home often and I can therefore stay in that area of the house and not have to heat the entire house. The "rest of house" zone will therefore be shut off at those times.

As far as the advanced controls go; smartphone control, IOT features etc - I'm not really interested TBH.

[The Natural Philosopher]

Then you will need a relay.

If you take my previous advice and simply ignore the hot water circuit it should all work OK. Your UFH shoulld have temeparture reduction manifold to keep input temps below 50C

[John Rumm]

OK, so you need two independent zones then - one for the UFH, and another for the rest of the house. One will be controlled by the zone valve, and the other by the separate circulation pump.

Hopefully if its been plumbed sensibly you should be able to run the boiler, with the zone valve closed, but the secondary pump running to just heat the UFH.

Nor what I was suggesting - a wholly different proposition from the Vaillant eBus controllers.

There are several ways of doing what you want. If you have a Vaillant programmer, and a Vaillant wiring centre, then you would be able to drive everything from the wiring centre - it would control the pump and the valve, and give you independent settings for the two zones (although it would need an additional stat in the UFH zone).

You could also do it with traditional controls by following something similar to the S+ Plan[1]

Two prog stats, one in an appropriate place in each zone. The house one driving the live on the zone valve, and then the orange wire from the valve driving the call for heat to the boiler. The second one driving the UFH pump plus the call for heat to the boiler in parallel.

No need to worry about the main circulation pump since with a combi the boiler will handle that. No need for a relay since the microswitch output on the valve will separate the demands from the separate zones.

[1] See page 8 - ignore the DHW related bits.

[The Natural Philosopher]

Except it wont

[cf-leeds]

Thanks for taking the time to respond. That's very useful information.

I'm going to look into the Vaillant options and get the associated manuals for review in the first instance. The S-Plan schematic seems to make sense and the colours correspond to the valve that I have thankfully.

Now I'll go and do my homework !!

[Roger Hayter]

Without a relay, when the zone valve opens it will switch on the UFH pump as well as the boiler.

[John Rumm]

Sorry, left out a bit... the switch on the zone valve is connected across the 24V output and return call for heat lines on the boiler, while the pump feed from the other stat is fed into the 230V call for heat on the boiler. from memory, firing the boiler by closing the 24V contacts does not make the 230V call for heat input live.

[Roger Hayter]

Thanks, that makes sense. I didn't know that the boilers had DC control lines available. Would simplify controls.

[John Rumm]

They normally support mains and DC controls, plus also their own eBus stuff.

You get most functionality with the eBus controls since they can communicate the actual current temp as well as the desired temp, rather than simple on/off demands. They also do a number of wiring interface modules like the VR61 (discontinued IIRC) and the VR65 that can then interface lots of traditional style pumps, zone valves, UFH blending valves etc to eBus control.

I use one on my system to control three 2 port valves, giving a DHW zone, and two CH zones. The main controller acts as a user interface and a stat for one zone, and then I have an addition simpler ebus stat in the other. The boiler reads the cylinder temp, and the outside temps directly via NTC thermistors, and the controller pulls it all together to allow split temperature operation (i.e. the boiler runs low "weather compensated" temperatures for the heating, but switches to higher temps for DHW reheats).

The controller lets you see and set all the times, temps and other config options for the whole system in one place.

[ARW]

Any chance of a photo of what you have for the UFH?

[cf-leeds]

Me ?

Do you mean the valve ? Where do I post it ?

[ARW]

Ask John Rumm for a Wiki account and post to the Wiki.

I was wondering if you could have a wireless set up on your UFH. I fitted one last week. Granted it was only 2 zones but a lot easier than the 20 zone wired up stuff I have fitted.