Help with Vaillant Controls Needed

[RoyMacDonald]

I've had a Vaillant ecoTec 637 fitted and I specified the commercial Valliant weather compensation upon Vaillant's advice. My house has a normal S plan system but has two Range Tribune HW cylinders so the domestic version couldn't be used. (according to Vaillant)

However when the electrician tried to connect up he realised the cylinder sensor and overheat sensors were in the same pocket so couldn't use the pocket. Vaillant's solution was to zip tie the Vaillant sensor to the outside of the immersion heater. I refused to allow this because I could not see how the sensor would be able to get any meaningful data from the inside of the cylinder.

They have returned the Vaillant controls and fitted a basic Honeywell controller to get the system up and running but I still want weather compensation fitted as due to the nature of the building the basic standard controls they have used are proving very unsatisfactory.

I want to insist they fit the Domestic Vaillant weather compensation with a relay so that the VCR 470f will receive one signal from the pair of Tribunes. there is no need for completely separate control of each cylinder. As long as there is a demand signal when one of the HW valves open.

Can any one suggest a suitable relay so that I can point them in the right direction? Or give any other advice?

Thanks.

PS There will be a set of Honeywell controls going for free when this gets sorted. CM927 etc.

 

[ALEC1]

you need to wire the hot water up through a three port mid position valve so it can do one or both of the cylinders at the same time.

This may put an unacceptable delay on the heating though as the system runs on hot water priority and assumes one cylinder with rapid recovery is the set up.

 

[RoyMacDonald]

you need to wire the hot water up through a three port mid position valve so it can do one or both of the cylinders at the same time.

This may put an unacceptable delay on the heating though as the system runs on hot water priority and assumes one cylinder with rapid recovery is the set up.

The H/W system cannot be re-plumbed. We have to use the existing pair of H/W zone valves. (at opposite ends of the house)

Thanks for the suggestion though.

 

[ALEC1]

do the cylinder primaries go back to the boiler room uninterrupted?

 

[RoyMacDonald]

do the cylinder primaries go back to the boiler room uninterrupted?

I believe so but they are not visible or accessible due to the nature of the building.

 

[ALEC1]

I suspect that the tee will be near the closest cylinder. The separation must exist or the rads would get hot in summer when the heating is off..

 

[RoyMacDonald]

I suspect that the tee will be near the closest cylinder. The separation must exist or the rads would get hot in summer when the heating is off..

I think the tee is in the boiler cupboard as far as I can see. It says cylinder 1 and cylinder 2 on two pipes teed off from the main flow pipe out of the boiler.

Just to add, the installation was existing but with a non condensing boiler.

 

[ALEC1]

thats where the three port valve goes then, with the flows stopped down by the two two ports.

the control sequence becomes cylinder stat>over heat stat>2 port valve>3 port valve> vr 65 240v call for heat..

 

[RoyMacDonald]

thats where the three port valve goes then, with the flows stopped down by the two two ports.

the control sequence becomes cylinder stat>over heat stat>2 port valve>3 port valve> vr 65 240v call for heat..

Where are the two 2 port valves wired to? Is it the Vaillant wiring centre that comes as part of the domestic weather system or to the 3 port valve?

Any plumbing changes in the boiler cupboard are perfectly acceptable. So thanks for that.

 

[ALEC1]

the greys get a permament 240vs, and the orange drives the three port valve.. then the 240v from the three port picks up on one of the two terminals that takes the 240v from the cylinder stat... one is a permament live the other is a switched live which tells the vr 65 that there is a call for hot water...

 

[RoyMacDonald]

the greys get a permament 240vs, and the orange drives the three port valve.. then the 240v from the three port picks up on one of the two terminals that takes the 240v from the cylinder stat... one is a permament live the other is a switched live which tells the vr 65 that there is a call for hot water...

And I take it that the existing 2 port heating zone valve is replaced by the 3 port?

It seems such a simple solution I can't understand why Vaillant made is so complicated for me. They also said the same to the heating engineer. So thanks very much for the suggestion.

 

[ALEC1]

you keep the existing two ports, as they always close when the cylinders are satisfied.


In fairness to vaillant the two cylinders is the elephant in the room, as I previously said with hot water priority which compensation controls require! only one cylinder is used to ensure that the heat up is rapid.

with two cylinders there is the risk that two consecutive draw offs could keep the boiler in hot water mode for too long...

 

[RoyMacDonald]

you keep the existing two ports, as they always close when the cylinders are satisfied.


In fairness to vaillant the two cylinders is the elephant in the room, as I previously said with hot water priority which compensation controls require! only one cylinder is used to ensure that the heat up is rapid.

with two cylinders there is the risk that two consecutive draw offs could keep the boiler in hot water mode for too long...

The hot water use here means that the cylinders are hardly ever in use at the same time and water consumption here is really low. Hot water demand never causes the boiler to run for more than about 10 minuets at a time as we all get up at different times and every body showers.

One cylinder only does one shower and the kitchen tap. The other does two showers and hand basins. It's had to understand why two cylinders were fitted in the first place to tell the truth.

 

[RoyMacDonald]

Also Vaillant were happy for both cylinders to be on the system if the commercial weather compensation version were used.

I wasn't happy about zip tying the Vaillant probe to the immersion casing though, as there would have been no proper control of the temperature of the water in the cylinders with the heating probe on the outside of the tank insulated from the water inside as they suggested doing.

They did originally think that we could remove the existing Range Tribune probe and replace it with theirs when the system was being ordered. The electrician refused to remove it though as it contained the safety cut-off probe as well. I believe that safety cut-off probe is a building regs. requirement as well.

 

[ALEC1]

well thats why I said through the over heat stat...the vr65 accepts either 1 sensor OR 240v switching the latter gives greater options but you loose functionality of the VR470

if hot water usage is so low on the second cylinder why not just heat it electrically with the immersion heater?

you will also need a by pass with my suggestion as the vaillant has pump overrun for hot water