Megaflow installation

[BuildingNovice]

Have recently had a new vaillant system boiler/vaillant unistor cylinder fitted.

If shower pressure falls and shower temperature falls/rises when hot or cold basin taps are opened respectively, is that sufficient to conclude there is insufficient pressure or flow rate for a 'megaflow' system?

If so, is the only solution to increase size of pipe entering house?

NB I will be asking installer for the readings he got for pressure/flow before the installation.

 

[Agile]

It certainly looks that way.

I expect you had a nupty installer who did not measure anything. Open pipe flow rate is NOT enough. Its dynamic flow rate.

I hope you have not paid him fully yet?

To install an unvented you have to have a qualification. Does yours have that? Its illegal for him to install it without the qualification. Same with the gas boiler and gas registration.

Tony

 

[ChrisR]

If shower pressure falls and shower temperature falls/rises when hot or cold basin taps are opened respectively, is that sufficient to conclude there is insufficient pressure or flow rate for a 'megaflow' system?

Absolutely not. It could be to do with internal distribution pipework. Seen it lots.

If so, is the only solution to increase size of pipe entering house?

Well, there could be all sorts of things wrong.
If you screw a £10 pressure gauge into the cylinder's inlet valve, all is revealed. I don't know why they don't include them.

All too often the problem IS a pillock installer using an inadequate supply, but not always.

 

[BuildingNovice]

Not fully paid and will give him a chance to explain.

In shower at 7.30am this morning, flow/temperature OK and then turned shower off and back on again, and no cold water! Just managed to finish off shower with scalding hot water.

Tested shower 1/2 hour later and back to normal.

Any clues as to what may be happening?

 

[mysteryman]

This could be a fault in the shower - is it compatible with an unvented cylinder, or does it require servicing? They can stick.

Furthermore, has your installer taken the cold water feed for the shower from the balanced pressure cold offtake in the unvented safety kit upstream of the cylinder? This is a common error, and it comes up every few days in this forum.

 

[BuildingNovice]

I doubt shower is at fault as have used it for many years prior to this new unvented installation.

Thanks for the pointer regarding cold water feed

 

[mysteryman]

That could be the problem- if it was on a gravity supply it may not be compatible with a pressurised system. The new work may have introduced a bit of debris. I would check the shower itself and where the cold is coming from.

 

[BuildingNovice]

Thanks Mysteryman, will do!

 

[Agile]

I doubt shower is at fault as have used it for many years prior to this new unvented installation.

Thanks for the pointer regarding cold water feed

As said, if the shower was being used on a gravity system then its operating parameters were completely different from the new unvented system.

Any competent and qualified installer should be able to work out whats wrong. But most of the problems we hear about on forums result from a substandard installation.

As Chris suggests, a pressure gauge would identify the incoming pressure when different combinations of hot water useage are taken.

In most cases for simplicity a pressure gauge fitted anywhere would probably be adequate to identify a serious deficiency with the supply. Its usuallt easier to fit them on test to an outdoor tap or a kitchen tap. If it were internal supply pipework before the cylinder then it would have to be measured at the cylinder.

There are a whole range of installation faults which can have been made like crossover flows because no non return valves have been fitted to mixer taps/showers just to add to the possibilities. Often pipework has been tiled over to add to the difficult of identifying a problem.

Tony

 

[BuildingNovice]

Thanks to all of you professionals for taking the time to reply.

Is there a guide for laypeople which explains the basic workings of an unvented system, with explanations of terms such as return valves etc? Just enough for me to be able to have a sensible and productive conversation with the installer.