wet under floor heating/boiler

[yekal_tytwr]

Hi All,

We are building a house with wet underfloor heating which goes back to 2 control units, which have all the wiring completed, only leaving

2 wires from each unit going back to the boiler (volt free). the boiler has now been installed (Worcester Greenstar 12/18) which I could not find any volt free connections, I spoke with Worcester bosch technical today and all they could tell me was that the boiler doesn`t have the appropriate connections, but could not tell me how I could resolve this problem. Anyone shed any light???.

[YAPH]

Is that an oil boiler? I don't recognise the model name as a gas one.

Not sure what your UFH control units require. You say they want volt-free connections but not whether the connection is a signal from the boiler to the UFH controller or the other way. If the former maybe the UFH controller has its own mains power for its pump and just needs a contact closure to tell it to run the pump. In that case I'd be thinking along the lines of fitting a pipe thermostat to the boiler's flow pipe to tell the UFH when there's heat coming from the boiler.

Alternatively if the volt-free connection is a signal /from/ the UFH controller /to/ the boiler from a set of contacts in the controller, then I'd think along the lines of connecting across the boiler's LS and LR terminals.

I think you really need to scan and post the UFH instructions somewhere for us all to see (or point us to the mfr's docs online).

[Yekal]

Yes this is an oil condensing boiler

thanks for your reply , I can`t work out if it is possible to post the wiring diagrams on here, would you mind if I email them to you?.

[Cash]

Scan - or photograph the picture[s] using a digital camera and upload them to

give a 'Tag' (or name) and then post the IMG Code for Forums & Message Boards link to the group. Example below (it works if you want to view the image):

[IMG] Note: leave out the [IMG] either side and post link thus:

- note the coloured and underlined text that indicates a valid link.

Hope this helps

Cash

[Yekal]

Thanks for all that, I will give it a go fingers crossed!!

this one is the boiler wiring diagram

and this should be heating diagram

this link has not gone blue as yours hopefully it will appear blue when I post, well here we go!

[YAPH]

OK the "boiler relay / volt-free" connection is a pair of contacts which close when the controller wants the boiler to run. It's "volt-free" because neither of the contacts is tied to anything of a set voltage, such as mains live. If you wire that pair of contacts to LR and LS (leaving NS not connected to anything) then the boiler will fire up when the controller wants it to. Assuming the boiler has a pump built-in then that wil run too, without you having to connect anything to the boiler's "pump relay / voltfree" contacts.

[Yekal]

The boiler does have its own built in pump, and as per one of your previous posts the heating controls do have their own mains pump. If i understand this, I just need to connect the L & N from both the upstairs and downstairs heating controls to LR & LS of X2 on the boiler, (does it matter which wire goes to which connection?). Do you think I will be OK using the integral programmer? (which was purchased seperate and now fitted), or will I need to get an external one? as last time I spoke with Worcester they seem to think the integral one won`t work with underfloor heating.

Cheers Yekal.

[ARWadsworth]

John you are correct and the relay (marked in ball boint pen on the scan) that says L and N Boiler Relay volt free is of course bollocks. It is not a L and N but just a volt free switch. Something lost in translation pehaps?

Sticking these two terminals across the WBs Ls and Lr terminals will do the job.

And to the OP. it does not matter which way round they are insterted.

Adam

[YAPH]

I think you need to use a timer external to the boiler to control the heating. From what I saw of your UFH controllers it looks as if they either have or need to have their own time controls. If you just want the whole house heating on or off at the same times then you can use one timer. If you want zones controlled separately e.g. downstairs warm during day, warmer in evening, practically off at night; upstairs background during day, warm evening, cool night, warm morning; then I'd use separate programmable thermostats for the zones.

Is the boiler a combi? If so you don't need a time control for hot water (unless the boiler has some sort of pre-heat or storage function which can be switched on & off). If it has, or if it's a conventional non-combi, then you'll need a time control for that. BTW a "programmer" is conventionally a device with independent timer controls for heating and HW in one box.

[The Natural Philosopher]

After calcuating the time constant for my floors, which are screed and wet UFH with not a huge margin over whats needed in temps like this, I decide to simply run the thing 24x7 on its own thermostatic circuit.

The overshoot is much less. - about half a degree instead of a degree, and the heating isn't running as hard as it used to.. To be brutally honest, timing wet screeded UFH is almost a waste of time in the winter.

Probably far better to simply hard wire it to a thermostat and a switch.

[Yekal]

UFH with not a huge margin over whats needed in temps like this, I

Thanks everyone, got everything ready to go, but can`t get delivery of oil till next week, then I will know if it all works!.

[The Natural Philosopher]

with not a huge margin over whats needed in temps like this, I

You can tell if the boiler has been running here, by the 4 cats draped over the pipe runs in the corridor..never did install heating on the landing above..not needed.