[OpenTRV-dev] OpenTRV install problem

Mon Jan 27 20:15:51 GMT 2014

The instructions I have are not the same as the link you found  : it's

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

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
>> _______________________________________________
>> OpenTRV-dev mailing list
>> http://lists.opentrv.org.uk/listinfo/opentrv-dev
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