wet under floor heating/boiler

[Yekal]

Hi all,

several weeks ago I asked for wiring advice, see original post:

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???.

The replies seemed to be unanimous:

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.

I now have oil, and have boiler up and running hot water working fine, but the heating is not ciculating after looking into it, the pumps on each of the underfloor heating cicuits are not starting, I have swapped the wires over on the LR and LS and still won`t run, I have checked all the wiring on the heating control units and can`t find any fault there. Anyone any clues.

Thanks.

[Rob G]

Ummm .. have you tried putting a voltmeter on the pump terminals to see if you are getting any volts ?

I'm sorry if this sounds critical but as that is so basic from an electrician's point of view, I'm concerned that you are tackling anything to do with wiring at all. You are not telling us what testing you have done other than 'it doesn't work' and this does make me suspect you don't really know enough about electrical wiring to be wiring up these pumps.

I don't think you should be taking advise on something as dangerous as wiring from the internet if you lacking the base knowledge about wiring.

Get a professional, or someone with competent knowledge, in is my advise.

Rob

[SantaUK]

If I'm following you right, I would be tempted to put in a relay that takes its feed from the pumps, and use the contacts to fire the controllers for the underfloor heating. But as Rob G suggests, a expert called in could save time, expense and disaster.

[YAPH]

...

I'm inclined to agree with Rob and co: if you're swapping over wires without any apparent understanding of how the system ought to, or could be made to work, there's a real danger you could blow up your expensive boiler PCB by connecting something wrongly. I'd find someone who really understands these sorts of systems to sort it out for you: may be cheaper and safer in the long run.

[Yekal]

Thanks all,

Myself and the Oftec heating engineer spent a couple of hours attempting to get the heating side of the boiler running, there is nothing at the heating contol end although the control units are live, it appears there is no call from the boiler to start the pumps. it ended up with the heating engineer saying he can wire boilers up but he is not a qualified spark and to get an electician, and eventualy left, I have spoken with a local electrician who has been up this morning and had a look he said he didn`t know why it wouldn`t work as it is not his job to be wiring boilers. I asked him who I should be turning to next and he said heating engineer, and we know what he said!!!.

Anyone know who would be able to advise?

p.s. I have spoken with the underfloor heating supplier and they seem to think it is wired correctly.

[The Natural Philosopher]

How many auxiliary pumps and zone valves do you have? and where do they drive their voltages from?

[The Natural Philosopher]

And nor should there be.

The call should be from the timer then zone thermostats, then the zone valves to open th watter circuits, and the switches ion the zone valves should start the auxiliary pumps , and then you need a relay (to avoid th hot water starting the pumps) connected to those to also call for the boiler.

it

Me, if you are in east anglia. At least to the point of drawing up a suitable circuit diagram.

I am sure they do, but believe me, neither my plumbers nor electricians had the faintest idea how to wire mine up. I got most of it from a heating engineer employed by a builders mercnat, and desinged and built my own control box.

[Yekal]

I have copied the schematics for the underfloor heating and the boiler, at present the pump relay volt free is wired to the boiler via the room stat connections LS & LR, which I have been told is correct, unless you know otherwise!.

heating electrics: [IMG]

electrics: [IMG] this is enough info for someone to help!, I have 2 manifolds, one upstairs and one downstairs, both have their own pump and thermostatic valve, with 5 actuators on each.

[The Natural Philosopher]

I dont think the zones are wired correctly.

Ok...it took me more than a few minutes to work out WTF they had done. Talk about complicated!

I suspect you should have the BOILER relay on LS, LR actually. I presume that is to 'fire the boiler', But see below, that should work..but..

OK. when you say thermostatic valve, do you mean a temperature reducing valve..?

Are there actual thermostats on these zones?

And where do the pumps connect to?

Look I am beginning to see WTF is going on.

I assume that your only connection to the boiler is the mains itself and those LS, LR and NS terminals right? All the other stuff is internal to the boiler, and its got a timer control somewhere for CH and for DHW?

And that when you expect the CH to work, the boiler comes alive, but the auxiliary pumps do not, yes? If that is the case the boiler is working fine, and there is no need to poke around in that area any more. It's all UFH now..

IF that is the case its pretty clear that the auxiliary pumps are not correctly wired.

How the units should be connected is this, I think.

You want to us the BOILER contacts on the UFH to go to the boiler. I suspect thy do exactly the same job as the PUMP ones, but its nice to be logical.

Then somehow the pumps themselves should be switched by the PUMP contacts. I am tempted her to say that you should connect LS on the boiler to both BOILER RELAY L and to PUMP RELAY L. BOILER RELAY N goes to LR in the boiler.

And PUMP RELAY N goes to on side of the pumps, with the other side being brought back and somehow connected to neutral.

I am 99% certain the problem is in how the zones themselves are wired.

And sing that there is one problem, its likely the installer was a complete tosser.

Can you tell me as much as you know about what wires are running between them and the UFH control center, and what thy connect to at each end.

Do you have each thermal actuator connected to a separate Zone output on the UFH control center? Or are they in parallel?

Do you have thermostats in every room? Do you have *any* for the UFH?

How are the pumps connected to the UFH control center?

I've had a look at the thermalfloor site, and I have to say it very lacking in detail..and the kits they sell dont seem really to match up to what that controller seems to want to do. Its not quite plug and play.

If you can photo the manifold stuff and post a link to it, that might be very helpful.

Or juts get the UFH installers back to finish the job properly.

[Yekal]

Cheers

The boiler has a built in timer for CH/DHW and a mains supply of its own and two wires connected to LS and LR which go to boiler relay volt free in UFH wiring centre, that is the only wiring to and from the boiler. You are correct when the boiler comes alive for the heating the auxilary pumps don`t run.

Now the wiring centres for the UFH each zone is wired seperatly e.g. each zone has to it thermal actuator and room stat, also inside the UFH centre there is main power in, the heating pump is wired to pump relay volt free, and boiler relay volt free go to the boiler LS and LR.

I have copied a picture of manifold assembly from the installation book, the only difference with that and mine is we have more zones. [IMG]

this has answered all the questions!.

[The Natural Philosopher]

Right.I think what you have there is essentially 'volt free' pumps ;-)

If you connect you need to connect the live side of the boiler wires to the live side of the pump relay contacts.i.e bridge two connectors so that teh live from the boiler feeds both sets of contacts... and the live sid of the pumps to the other pump relay contact. and then the return neutral from the pumps should go to system neutral somewhere..

Yes.. I hop I hav too.

[The Natural Philosopher]

Gosh, I didn't type check that did I?

Perhaps I can be more clear.

There appears to be no way to get power to the pumps in your current setup. Volt free pumps connected to volt free contacts will not operate!!

However there is no point in running the pumps when the boiler CH timer is not set for CH. So you need to use the *switched* live FROM the boiler timer - that comes in on 'BOILER switch L' on the UFH panel, and wire that across to PUMP RELAY L, as well.

Then wire the pump lives to the other side of that - boiler relay N - and run the pump neutrals to a mains neutral..preferably the same one the boiler is on

That way when the boiler timer is on, both pumps will run until the room stats are both satisfied, at which time the pumps will stop. As long as the pumps run, the boiler will be set to fire as well, and will modulate according to its output temperature.

[geoff]

If you had, it would have been a first ...

[Yekal]

Thank very much Sir, I have just had chance to wire the heating today and it works! that was all it needed.

Once again thanks for the advice.

[The Natural Philosopher]

Hey that is rally GREAT news.