Replacing complete CH & DHW system advice.

[Notch7]

I thought I’d update this rather than start a similar thread.

I’ve reached an agreement with BG re the controls for system. They have agreed to not fit the Hive controls and will fit Vaillant controls that I supply and commission the system.

It’ll be open vent Ecotec Plus 418 with the Gledhills SSL 210ltr unvented cylinder. Although the 418 was based on the simple 230v controls as they add 3kw for hot water on top of their calculations. Whereas the 415 can produce 18kw for a DHW demand.
Any thoughts on dropping down to a 415, or just range rating the 418?

Now the main questions, perhaps @ScottishGasMan can help?

I think I need this package for Control; VRC720f SensoComfort. This is a package that has a remote wireless (rf) wall mounted controller/room stat, rf outside temperature sensor and an rf communication receiver unit for connecting to the boiler. Vaillant part No; 0010036820.

For wiring centre I think I need the wiring centre VR66/2. Vaillant part no; 002013585

The trade off for all of this is I own the controls hardware and hence no warranty on them via BG.

Im not sure about the Vaillant boilers but after discussions with my plumber we decided on an Ideal vogue max boiler 18kw and a hot water priority set up. 12 year warranty and prices includes Ideal magnetic filter

the set up is a 2 pipe system

the Ideal Vogue has 2 switched live connections on the boiler, one for hot water and one for heating.

when the hot water cylinder stat calls for heat it turns the NO diverter valve on heating on and the NC hot water diverter valve to open and at the same time sends a connection to the boiler which ramps up flow temp to 80 deg

when the hot water cylinder does not call for heat, the valves are set so water flows around radiators and the boiler lowers its flow temperature, which its sets according the weather compensation telling it the outside temperature (today the external temp is 11deg and flow temp is around 54deg with return temp of 40deg)


We also went for a McDonalds ultra fast heat recovery cylinder 120litres

Currently the system is set up with drayton conventional room stat and programmer, but i think Im going to upgrade to Tado system as I think my set up will cause too much cycling -which the Tado should damp out

Im going to experiment with keeping all TRVs set high and letting the low temp flow temp reach a stable house temperature and see how that goes -zoning can cause too much cycling and increase higher flow temps



If it was me, I wouldnt choose BG, I would go to a local heating engineer who understands hot water priority.


Im not sure about Vaillant, do they have 2 switched lives built into them and do you need a 4 pipe system?

 

[ScottishGasMan]

can I assume the vaillant controls only use the 3 wires(LNE) and the other 2 are not used?
From a controls perspective it’s open loop and no positive feedback on the position of the valve is used, strange imhe? Anyone know why they chose to ignore these standard contacts?

There not standard. Well, they are to the UK, The UK does everything weird compared to the rest of europe. The Vaillant system doesn't need them as it's telling the valves what to do, traditional UK system the valves tell the boiler what to do.

 

[HarryW]

Im not sure about the Vaillant boilers but after discussions with my plumber we decided on an Ideal vogue max boiler 18kw and a hot water priority set up. 12 year warranty and prices includes Ideal magnetic filter

the set up is a 2 pipe system

the Ideal Vogue has 2 switched live connections on the boiler, one for hot water and one for heating.

when the hot water cylinder stat calls for heat it turns the NO diverter valve on heating on and the NC hot water diverter valve to open and at the same time sends a connection to the boiler which ramps up flow temp to 80 deg

when the hot water cylinder does not call for heat, the valves are set so water flows around radiators and the boiler lowers its flow temperature, which its sets according the weather compensation telling it the outside temperature (today the external temp is 11deg and flow temp is around 54deg with return temp of 40deg)


We also went for a McDonalds ultra fast heat recovery cylinder 120litres

Currently the system is set up with drayton conventional room stat and programmer, but i think Im going to upgrade to Tado system as I think my set up will cause too much cycling -which the Tado should damp out

Im going to experiment with keeping all TRVs set high and letting the low temp flow temp reach a stable house temperature and see how that goes -zoning can cause too much cycling and increase higher flow temps



If it was me, I wouldnt choose BG, I would go to a local heating engineer who understands hot water priority.


Im not sure about Vaillant, do they have 2 switched lives built into them and do you need a 4 pipe system?

The Vaillant is also 2 pipe system, but only has one 230v control input for ‘heat’, hence it doesn’t know if it’s a demand for CH or DHW when using 3rd party stuff like Hive. Hence going for Vaillant controls for a Vaillant boiler which are eBus low voltage controls.

The 418 open vent (and 618 System) produce up to 18kw in CH mode and 25kw in DHW mode when using vaillant controls.
The controls also allows for full weather and load compensation too. Default control is set a PDHW too.

 

[HarryW]

@ScottishGasMan falling at first hurdle… the base station green led is not flashing to allow pairing… help..

 

[HarryW]

@ScottishGasMan falling at first hurdle… the base station green led is not flashing to allow pairing… help..

No sweat on this now, found break in eBus wire between boiler and rf base station, all now resolved and all up and running, let the learning begin!

 

[HarryW]

Rather than start another thread (or should I?).

The external ABV is passing all the time regardless of its setting or the pump speed. It even does it for DHW demands where the circuit is less complex than the CH.
In DHW mode I’m seeing 20-25c D40/41 delta as it warms the unvented tank, no fault codes, just a scalding ABV output. In CH (back in March/April) I was seeing 12-15c deltas.
The ABV (Honeywell straight 22mm) is between the pump output and the zone valves (S plan) and then connected to the return line to the boiler. I’ve called BG back and they’ve replaced it but with no change to the symptoms. The guys gone to ask system designers for pointers as he’s never seen similar in 16years!
Any thoughts as to why this could happen.

I will add the system seems well but I can’t but think the ABV apparently permanently passing is not going to help efficiency.