[OpenTRV-dev] OpenTRV install problem

Damon Hart-Davis EMAIL ADDRESS HIDDEN
Mon Jan 27 20:25:15 GMT 2014


Hi,

Thank you.

I would have to start to disassemble the boiler to see which pins were being used internally, and was reluctant to do that as it make people nervous even if not actually illegal.

I was hoping to stay out of the boiler itself and so I just connected in at the Drayton SCR box.

The arrangement in 4.18, or one like it, is what I have designed for and seems to work elsewhere.  It is *possible* that I just have a dud SSR, or it is possible that the Drayton box is having its nose put out of joint by the parallel connection in some way.

Rgds

Damon


On 27 Jan 2014, at 20:15, Adrian Godwin <EMAIL ADDRESS HIDDEN> wrote:

> The instructions I have are not the same as the link you found  : it's http://www.vaillant.co.uk/mediaarchive/2013/10/ecoTEC-installation-servicing-2009.pdf
> 
> See Fig. 4.18 on page 28 for the reasons why I think it's ok to add an SSR load, which appears to conflict with the diagrams in  http://www.vaillant.co.uk/mediaarchive/2013/09/ecoTEC-plus-installation-service-manual.pdf
> 
> 
> On Mon, Jan 27, 2014 at 7:51 PM, Adrian Godwin <EMAIL ADDRESS HIDDEN> wrote:
> Are you using pins 3,4,5 to connect to the boiler ? 
> It does seem to have a normal mains supply as it's possible to use the thermostat hysteresis heater. You could try putting a small load in the same position (ie pins 4,5) - perhaps a 5W light bulb or anything that meets the minimum load for the SSR.
> 
> I have the same boiler, but it's connected to a Vaillant controller (I think via eBus). 
>  
> 
> 
> On Mon, Jan 27, 2014 at 7:34 PM, Damon Hart-Davis <EMAIL ADDRESS HIDDEN> wrote:
> Hi,
> 
> An odd one: I wonder if any of you can offer any optinions or solutions (and it’s something that OpenTRV is likely to deal with in other boiler installs).
> 
> On an installation today, now with 5 OpenTRV-controlled rads and a separate unit only doing boiler control:
> 
> Boiler: Valliant ecoTEC plus 837
>    http://www.vaillant.co.uk/mediaarchive/2013/09/ecoTEC-plus-installation-service-manual.pdf
> Controler boiler end: Drayton Digistat SCR (part of Digistat RF system)
>    http://www.draytoncontrols.co.uk/WorkArea/DownloadAsset.aspx?id=28360
> 
> There is a problem in that though the SSR indicator LED operates appropriately, eg in response to call for heat (so the hub is working), the boiler never seems to go off as if the zero-switching SSR (crydom D2W203F-11) does not ‘release’.
> 
> There are some off voltages seen across the ‘call for heat’ contacts (with the SSR and normal controller removed, boiler on):
> 
> DMM VDC: 0V
> DMM VAC: ~200V (cf mains ~235V)
> 30kOhm/V analogue MM: ~220V
> 
> So it seems to be AC and near but not quite mains.  (Not the 24V alternative that can be used with the boiler.)
> 
> I wonder if thie boiler is being ‘clever’ and either the circuit is high impedance (too high for the SSR to power itself correctly) or some such.
> 
> Any ideas?
> 
> If for some reason I cannot use a normal ZC SSR there, I may have to use a real old-fashioned relay (I can’t find an SSR that provides the volt-free 24VDC—240AV volt-free switching that the Drayton SCR unit manages), driven somehow from the logic 3.3V output from the OpenTRV unit.  Is there a neat unit that I can use to do that, small and low power and that I can stick on the wall in place of the SSR box?
> 
> Rgds
> 
> Damon
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