Vaillant Eco Tech Plus 937 issues/problems?

[eveares]

Hello all; had an extension done in the last couple of months and had the boiler (A Vaillant Eco Tech plus 937 Storage Combination boiler) installed a few months back.


Now in the last couple month or so I have noticed that the boiler tends to fire up when a cold water device is turned/shut off (such as a tap or toilet cistern filling up) and that the boiler detects this as hot water being drawn off. (As shown by the boilers LCD)

At the same time I also notice that occasionally the water comes out extremely hot and is a lot hotter than what it is set at and normally comes out at.



Could these two problems be related; and is a normal operation or a fault/problem.


Should it be a fault; it is worth noting that the plummer who installed the boiler and also did our pluming work as part of the extension in general was not the best of people and as such we had many issues with him.

Example of issue with him: (Such as using plastic corrugated pipe instead of a soldered one like Vaillant recommended for the boilers condensate what ended up spraying and leaking water everywhere when the boiler regularly discharged it under high pressure as part as a anti-freeze mechanism that's builds water up over a period of time and discharges it at once to prevent it freezing.)


Could the plummer have cause the issues described above or is it a fault originating at the factory and not because of him/how he installed it?


Let me know your opinion whats wrong and what you think I should do. In the mean time got BG coming over on Monday as then want to run a service as we have a new boiler. Lets ope they find out whats wrong.

 

[dreadnoughtheating]

As per forum rules, no Gas Safety Critical advice will be given.

I suspect that the Corrugated pipe (non-metallic) is correct (in being non-metallic) to drain the condensate fluid that should NOT be discharged into a metal pipe, as it is acidic.

The Pressure relief pipe, however should be all metal.

As to the mystery 'firing up', I am suspecting a 'dead-leg', i.e. a section of pipe with air trapped in it, which becomes compressed when taps/valves are closed, then mimicking the flow required to spin the boiler into life, giving a short fire. However, as the 937 has a storage vessel I cannot see hat this would leave a slug of hot-water above normal temperature. Are you sure it is a 937, and not an 837 (non-storage type of combination boiler)? The 937 is about the size of a washing machine hung on the wall, about 600mm depth, the regular 837 is approx 400mm depth.

DH

And, are you sure the plummer is in fact qualified (GasSafe registered for a start), and has this person registered the appliance for BOTH warranty AND Building Regulations purposes?

 

[Tipper]

My understanding is that

1 if there is a dead leg of cold pipework which may have air in it the boiler will sense a change in system pressure when the cold tap is used and will think it is hot water demand. Was this a new boiler installed during conversion to a combi system? (I may be slightly inaccurate in my description above but that is the gist of it)

2 The 937 is usually set up to run weekly to a higher temperature to safeguard against Legionella bacterial infection in the water storage tanks. Mine does this every Wednesday at 0700 which I think is the default setting.

3 Mine has a black corrugated pipe on the storage tanks relief valve discharge. I thought this was standard Vaillant kit. Condensate pipework should be plastic not copper. I think you may have confused these pipes.

I'm sure a Vaillant expert will confirm or correct me.

Just to add I am not a Vaillant expert but do have 1 in our home (937) and 3 others (824 and 831) in our rental holiday flats and am about to buy another 937 for my latest project!

 

[eveares]

Re: dreadnoughtheating

The issue with the congregated pipe was sorted within the first week of it's operating life.

(He sorted that problem back then after Vaillant told him (when he phoned them up because of the problem) that it needed to be soldered what he did what solved that issue - That was just an example of a earlier problem with him and the boiler, not related to the current issues/problems.)

I am trusting his word on this one and that the type of congregated pipe he used before was not suitable. See the attached picture below for my boilers current pipework.

Untitled

• eveares
• 29 Jun 2013
• 1

The condensate is plastic it seems, so maybe by soldered be meant pvc cerement???

All i know for sure is first of all there was a loosely fitted black corrected pipe that looked like sink overflow pipe and that the boiler was spewing water everywhere everyone often. Am not certain it was coming from this pipe, just what he said after he fixed it back then.

And for him being gas-safe, so he and what his van said. He was employed through our main builder and not by us directly. Has he registered the appliance for building regulations purposes; I don't know.

Is he competent; so he says, but i'm not so sure with all the workmanship he's done.



Moving on and to reply generally to you all

It is a 937; I chose and got the boiler because of the two 7L HW storage tanks.


As for a new boiler; it was a new boiler as part of the extension as we had a really old Worcestershire 28CDi combi boiler that was on it's last legs.

I also set the wireless controller (VRC 470F) up my self with the heat curve and everything and as such the anti Legionella bacterial function is not enabled for the the reason it heats it up to a to high temperature for my liking.

I really want to know why randomly the water gets hotter than normal and the boiler thinks hot water is being drawn off when the cold water shuts off providing it is not air in a dead leg?

Also do the storage tanks have a minimum temperature that they can/must heat to; have my HW set at 45c atm.