Vaillant ecoTec Plus & Megaflo

[M.Joshi]

We've had a new CH and hot water system fitted which consists of a Vaillant ecoTec Plus 630 boiler and Megaflo tank.

The system is installed with an external wired (Sunvic) room thermostat and Horstmann programmer. However, the jumper across pins 3 & 4 in the boiler has been left connected in the boiler?

Looking through the installers manual, it states that the jumper should be removed and an external room thermostat connected across them. The manual however, does not mention anything about using the boiler in conjunction with a hot water storage tank?

If a room thermostat were connected to pins 3 & 4, how would the boiler know to switch on if only hot water was required to heat the tank and not central heating?

 

[stevetheplumber]

normally with a ecotec and megaflow the auxilary switches in the motorised valves are connected in paralel across terminals three and four with controls ie clock and stats switching the supplys to the motorised valves
also check that the resetable stat on the cylinder is wired to cut power to the boiler im pretty sure vailllant will have a diagram for this

 

[Rydell]

I would suggest that you get a 'Part P' qualified central heating installer to check the wiring within the boiler to the external controls. The correct wiring to the Ecotec is that the terminal 3 supplies the live to the programmer and terminal 4 is the switch live back from the completed controls. So the link between the terminals 3 / 4 should be connected to the exteral controls not left in.
Section from install book:

4.15.2 External electrical controls​

The boiler terminals 3, 4 and 5 are for connecting external
electrical controls such as a time switch and/or room
thermostat. Terminals 3 and 4 are linked together when
the boiler is supplied. If external controls are used, this
link must be removed, and the controls connected
across terminals 3 and 4. Terminal 5 is an additional
neutral connection for external neutrals such as from​

the anticipator of a room thermostat.

 

[migoplumber]

rydell. spot on
shaun

 

[M.Joshi]

Looking at the installation instructions for ecoTec Plus boilers, it does not indicate how to wire the boiler terminal strip for use with a hot water cylinder. It only indicates how to wire it for central heating i.e. room stat and programmer.

I noticed that one of the accessories available is a VR 65 (control centre for UK cylinder installation - eBus). Looking at the installation instructions for the VR 65, there is no indication of how to wire it up with an external programmer or room stat?

I understand what stevetheplumber is saying about connecting both the auxilliary switches on the valves to pins 3 & 4 but, why doesn't the boiler installation instructions give details of use with a cylinder and 2x2-port system?

If you do have to use a VR 65 (which I think isn't necessary but may simplify wiring), why don't they indicate how to wire an external programmer and room stat in the instructions?

 

[Rydell]

Your question has been answered above! The boiler needs to send out the live to the external controls (room stat and cylinder stat) via the method controls (2 / 3 port valves) then from either one of the extenal controls the switch wire back to the boiler! This allows the boiler to shut down completely if the safety controls within the boiler need to kick in!

 

[Deleted member 2053]

Speculating, I would suggest that the problem here may be that the external controls have been wired into main power side of the boiler so that when demand ceases the whole boiler turns off. Does the display on the boiler remain active when the demand ends? Alternatively if you have individual two port valves for the CH and HW perhaps they are being allowed to close and he boiler simply left to it's own devices i.e. hitting the stat level and circulating through the in-built auto by-pass. BTW it is not strictly necessary to take the switched feed from pin 3. You can feed the live back from the programmer/controls/valves as long the entire electrics are under the control of the main switch which should be adjacent to the boiler. Essentially there must be no way for pin 4 to remain or become live when the boiler isolator is off. Sadly Part P qualification seems to be no guarantee that a plumber is actually comfortable with electrics or indeed really understands them.

 

[M.Joshi]

Spot on grahamep - We had British Gas come and carry out an annual inspection on the boiler. It turns out that the Central Heating controls were supplying the live feed to the boiler. So when the demand has been satisfied, the boiler would shut-off completely.

They explained that the wiring was incorrect which I agree and also that since the boiler shuts off, it doesn't give enough time for the pump to dissipate excess heat away from the heat exchanger.

....and yes, before anyone says it I know what most professionals think of British Gas engineers - I tend to agree. They are usually young apprentices/carry out shoddy work! During the service, the young chap kept having to call Vaillant for advice as he didn't know what was causing the CO/CO2 flue ratio reading to be low (~7.4%). As a result, they have deemed the boiler at risk and placed a yellow label on it!

I wasn't satisfied with British Gas carrying out the corrective electrical work required so, I seeked the advice of a large reputable plumbing company. The reason for my original question was because, we are being told that a VR 65 is required to use the boiler with a hot water cylinder and as there are only two flex feeds from the boiler to the wiring centre, we would need to have a wireless room stat installed too?

One flex would be required to supply power to the boiler and the other to run the eBus conection to the VR 65 next to the hot water cylinder, replacing the existing wiring centre.

I am thinking that the extra cost of replacing the wiring centre with a VR 65 and replacing the wired room stat with a wireless one unnecessary?

I also agree with your comment about Part P grahamep - it's odd that somebody not having touched electrics before can sit a simple assessment/exam with a little prior reading and then be allowed to work on electrics. Yet with a degree in Electronic and Electrical Engineering and knowledge of electrical wiring, I would not be deemed competent to touch the wiring as I do not hold a Part P qualification!

 

[Deleted member 2053]

....and yes, before anyone says it I know what most professionals think of British Gas engineers - I tend to agree. They are usually young apprentices/carry out shoddy work! During the service, the young chap kept having to call Vaillant for advice as he didn't know what was causing the CO/CO2 flue ratio reading to be low (~7.4%). As a result, they have deemed the boiler at risk and placed a yellow label on it!

....The reason for my original question was because, we are being told that a VR 65 is required to use the boiler with a hot water cylinder and as there are only two flex feeds from the boiler to the wiring centre, we would need to have a wireless room stat installed too?

One flex would be required to supply power to the boiler and the other to run the eBus conection to the VR 65 next to the hot water cylinder, replacing the existing wiring centre.......

....I also agree with your comment about Part P grahamep - it's odd that somebody not having touched electrics before can sit a simple assessment/exam with a little prior reading and then be allowed to work on electrics. Yet with a degree in Electronic and Electrical Engineering and knowledge of electrical wiring, I would not be deemed competent to touch the wiring as I do not hold a Part P qualification!

Whilst we all make a practice of loving to hate BG engineers I have to confess that I have met some very good ones. I think the big problem is that they do not make up the majority and hence the overriding impression is incompetence.

I have installed system boilers quite happily running HW and CH and never used a VR65. Is there something more complex about your system: multiple zones? Part underfloor? Where are you located in the UK?

Did your BG engineer try and adjust the CO2 level? The adjustment is on the gas valve and usually has a bit of white tape stuck over it.

There seems to be a lot of misinformation about Part P - well it is the what-passes-for-a-brain child of Two-Jags Prescott so what would you expect? CORGI haven't helped either. I have been told by the relevant examiner in a very reputable training establishment that a better (and cheaper) route is to simply take your 17th edition. Then as long as you can demonstrate competence in the testing protocol you can self-notify. When I have time to do a bit more research I will post something about this with chapter and verse bibliography.

 

[Rydell]

I also agree with your comment about Part P grahamep - it's odd that somebody not having touched electrics before can sit a simple assessment/exam with a little prior reading and then be allowed to work on electrics. Yet with a degree in Electronic and Electrical Engineering and knowledge of electrical wiring, I would not be deemed competent to touch the wiring as I do not hold a Part P qualification!

I can't agree with this comment. The standard of the 'Part P' training and testing is excellent! This engineer that installed your very expensive equipment incorrectly must have had no idea what he was doing therefore putting your money at risk as well as your safety! Anyway if we as heating engineers show we have a under standing of the electrical installation, by taking Part P, then the boiler would be wired correctly. Otherwise he should not have touched it. This is the minimum standard that gas engineers should be to install gas heating system controls. The customer should feel that the money they have paid is for someone who is competent and has installed the equipment correctly. Your statement regarding you having a degree in Electronic and Electrical Engineering and knowledge of electrical wiring, would not be deemed competent to touch the wiring is showing me the reason why you contacted the forum for advice you could not work it out for yourself. Hence why you need a Part P heating engineer to sort it out for you.

 

[M.Joshi]

grahamep - The British Gas chap adjusted a screw on the side next to the fan which controls the gas-air mixture. We have an S-Plan system with underfloor heating. We are in NW-London.

Rydell - I am familiar with an S-Plan system configuration and wiring as I have worked on our previous installation with Sunvic valves and Randall programmer prior to Part P. My query relates to the Vaillant installation manual not providing details of how to configure the boiler for use with a hot water cylinder and the ambiguity in the VR 65 installation instructions with regards to using a room stat and programmer.

I wanted to establish whether a VR 65 is required to use a hot water cylinder with the ecoTec 630. It is not that I am not confident/competent with the wiring but rather the options/modules that are required. This information is given in other manufacturers' documentation but seems to be lacking in the Vaillant ones.

 

[flat pack]

call you plumber back
?or may be there no plum ¿



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[M.Joshi]

I have tried to contact the Corgi registered plumber who certified the installation and the company he worked for. Can't get in touch with the plumber and the company say that he no longer works for them - surprise, surprise!

I have also checked with the Gas Safe Register and they cannot locate him from the old Corgi number? The company doesn't appear on their records either although, they could be under a different name?

 

[stevetheplumber]

ive wired lots of these systems with no need for any fancy stuff one five core flex into the boiler fom a ten way junction box everything is then wired from the jb
the grey wires on mv's are both fed from terminal 3 and both orange wires to terminal 4
the rest is standard s plan swithing the feed to each valve from respective clock feed via each stat regardless of wireless or not
i personally wire the feed to everything via the resetabble stat on the cylinder this way a fault shuts the whole thing down

 

[M.Joshi]

Thanks stevetheplumber for your reply.

It's interesting that you wire the whole system through the resettable cylinder stat. Does this mean you remove the direct link between the stat and resettable fuse? Otherwise, wouldn't the whole system shut-off once the water temperature had been satisfied regardless of a room stat?

 

[stevetheplumber]

resetable stat thats on the cylinder should cut power if cyl goes overheat the last wiring diagram i saw showed it cutting supply to mv however if the valve failed in open postion and it could recive heat from boiler so i use it to cut supply to boiler