Need Help With Vaillant Boiler/Immersion Wiring

[nlbhoy]

Hey Guys,

I'am an Electrician (just qualified) but I have limited experience with heating systems.

My folks have a hotel which has just had a vaillant ecoTEC plus boiler installed, with programmer, along with dual 600/800 ltr cylinders. Both cylinders have dual thermostats with no motorised valves.

Long story short, the Electrician who was supposed to do the wiring tomorrow can't make it due to
family circumstances, as the hotel opens to the public on Friday I'm going to have to do this myself
as we need this operational as it's heating 10 rooms.

So I need some help/guidance with the wiring?

I'm aware I need to take a 1mm supply over to boiler and that boiler needs to be protected by 3amp fuse
and that I need a 2.5mm supply to each cylinder, where I'm getting stuck is what connections to use in the boiler going to programmer? I need a 4 core to programmer but what connections do I use?

Also where do I take the cylinder thermostats? do I take a cable from boiler to all 4 thermostats and link them?

Any help would be much appreciated.

Thanks in advance

 

[Octopus]

Enjoy Jura, make sure you have time for a wee dram

 

[Leesparkykent]

I would of thought you would need the VR65 wiring centre which would then connect to the boiler via ebus.

 

[davesparks]

If the cylinders have dual stats then that implies that they are unvented cylinders, in which case each cylinder must have its own 2 port motorised valve operated by its the dual stat. The two stats in a dual stat are the normal thermostat and a safety overheat stat.
If the two port valves aren't fitted then they overheat stats must be connected so that they shut off the source of heat (boiler).

You don't necessarily need a 2.5mm supply, what you will need is a 16A supply if you want to use the immersion heaters. This could be 1.5mm, 2.5mm, 4mm, 6mm depending on your calculations, which being newly qualified you should already be fully aware of.

 

[nlbhoy]

If the cylinders have dual stats then that implies that they are unvented cylinders, in which case each cylinder must have its own 2 port motorised valve operated by its the dual stat. The two stats in a dual stat are the normal thermostat and a safety overheat stat.
If the two port valves aren't fitted then they overheat stats must be connected so that they shut off the source of heat (boiler).

You don't necessarily need a 2.5mm supply, what you will need is a 16A supply if you want to use the immersion heaters. This could be 1.5mm, 2.5mm, 4mm, 6mm depending on your calculations, which being newly qualified you should already be fully aware of.

Thanks Dave,

Yes, I'm aware for the calculations.

Any help on who to connect these stats? or any wiring diagrams of this type of system?

Thanks

 

[davesparks]

Thanks Dave,

Yes, I'm aware for the calculations.

Any help on who to connect these stats? or any wiring diagrams of this type of system?

Thanks

You'll have to adapt the standard S plan wiring diagram I assume. There is no standard wiring diagram for this setup.
This is where understanding the control system rather than just blindly following a wiring diagram is important.

You'll need to connect the DHW on from the programmer to both dual stats, then each of those stats will operate the valve motor for their respective valves.
The micro switch in each valve will fire the boiler as per normal.
The heating is the same with the CH channel of the programmer connected in series with the room stat which operates the valve motor, the micro switch fires the boiler.

 

[PEG]

Hi dude,presumably,the plumber,or "heating engineer"...(they like that better:devilish will have designed your system,and the electrician was to wire as per design.

Are you certain there are no motorised valves?

 

[nlbhoy]

So I had a chat to the plumber on site today, the boiler is only controlling hot water, it's not (at this time) controlling the
heating. My folks will have heating changed over to gas in near future.

There weren't any valves and boiler was to be controlled by cylinder stats, so I wired stats in series. I then went from last stat
to programmer to switch water. Then from first stat to RT connection (240V) in boiler. I'm happy to say all worked first
time... big relief.

Thanks for the help

 

[davesparks]

So I had a chat to the plumber on site today, the boiler is only controlling hot water, it's not (at this time) controlling the
heating. My folks will have heating changed over to gas in near future.

There weren't any valves and boiler was to be controlled by cylinder stats, so I wired stats in series. I then went from last stat
to programmer to switch water. Then from first stat to RT connection (240V) in boiler. I'm happy to say all worked first
time... big relief.

Thanks for the help

Well that's a ridiculous way to control the heating of two cylinders. And if they are unvented cylinders it may actually be very dangerous (they can explode in a big way if they overheat), contrary to the regulations in effect and may even be contrary to statutory requirements.

You have created a situation where if the safety overheat stat operates then heat will continue to be delivered during the pump overrun. You would probably need to connect the safety stats so that they cut off power to the whole system.

With the stats in series then whichever cylinder gets hot first (they will not both heat up at exactly the same rate) will shut off the heat to both cylinders, this will lead to one of the cylinders not achieving the correct temperature and so dangerous bacteria can grow in the stored water, particularly the legionella bacteria which is a major concern and the subject of regulations.

Put simply you may very well have placed people's lives and property in danger.

 

[Leesparkykent]

Would be an easy job if the plumber had fitted a two port valve for each cylinder.

 

[EvilDrPorkChop]

Pressurised cylinders require a two-port valve by regs as it's one of the many safety features to prevent them from overheating. Even a three port valve isn't good enough (I've seen many fitted with a 3 port too!) The cylinder stat for each cylinder should control the motorised valve for that cylinder, which in turn will control the demand for heat from the boiler. If your plumber has not fitted motorised valves i'd be getting him back ASAP to rectify this. Just relying on your boiler to shut off the heat isn't good enough.