Unvented h/w system - poor shower pressure

[stanmore]

I have just has a new boiler and a Gledhill 250ltr unvented cylinder installed by a heating engineer, who turned out to be a complete nightmare but that is a whole different story.
As part of his work he installed a new 25mm MDPE water pipe from the mains and 22mm running to the cylinder. However the flow rate on the second floor shower is poor in comparison to the old unvented system with a 20 psi salamander pump. The boiler and cylinder are within the cellar area of our Victorian house and the shower is probably a good 10m above but in quite a straight vertical run. Is there any way that we can increase the flow rate at the shower as i have been told that we can't fit a pump to an unvented system ? Yet the original installer has said that he can refit the old pump, however it turns out that he hasn't installed an unvented cylinder before, i wish he had told me that before !
Can you also tell me what a secondary return is as the cylinder is fitted with one of these.
thanks

 

[Fluffster]

Your plumber has to be certified and hold an upto date G3 card to install an unvented hot water storage cylinder. They can be dangerous if not installed by someone who has not been trained and certified competent.

As a matter of course I would urgently advise you to get this inspected by a certified plumber with a G3 card.

A secondary return is used when a hot water run is long and so feeds back on itself to provide hot water quicker as the cold water sat in the long run is fed back to the cylinder.

A certified installer would have tested your flow and pressure rates before and after installation to ensure they are within the mi parameters.

Pete

ps this cylinder installation has to be notified to your local building control too

 

[mysteryman]

It is unlikely to be the cause of the problem, but check that he has taken the cold supply for the shower from the balanced pressure cold outlet in the unvented safety kit [which supplies the cyl with water]. Missing this is a common mistake, even for those with G3 cards, who should know better.

 

[Agile]

Its not essential to connect the shower cold to the point after the PRV but it is good practice and makes for smoother shower operation.

In this case it seems that the mains pressure is just insufficient to get the water up to the second floor with sufficient pressure.

Thsi is a typical example of an enthusiastic owner wanting something he thinks is good and an installer whose skills are lacking and who cannot turn it down because he is short of work.

About the only simple fix that I can suggest is a Grunfoss home booster set costing about £900 plus installations ( free of course by your nupty because its his lack of good advice which has put you in that position ).

Tony

 

[1CANHELP]

*****************

 

[OLLIE20]

yeah but 1 can help who would listen to you, youre not even tile association registered ive got get on that course big time

 

[bengasman]

Whenever I read the name Gledhill, I wonder. Your comment about the quality of the installer seems to confirm my general opinion in that respect.
I wouldn't be surprised if he had made his own life a bit easier, and only replaces most of the smaller old pipe, or used the wrong stop valves on them. Is it possible for you to check this?

 

[stanmore]

The cylinder is branded Viessman but appears to be a Gledhill cylinder. I have been provided with a Benchmark booklet for the cylinder which whilst part of the job was undertaken and signed off by his brother, who i presume is G3.

All the work undertaken by the company i employed has demonstrated corner cutting and poor advice, however two other companies i approached in relation to the work all suggested unvented systems to replace a WB 30CDI (4 years old) and a gravity fed system with a 20psi shower pump. All the companies were Gas Safe and nobody suggested that pressure would be lower on the shower, even with a new mains. I didn't stipulate the type of system installed ie unvented over combi and nobody mentioned the need for a pressure booster. I now have a catalogue of errors to address and i need to find a heating engineer who is impartial, knows his field and can sort out the mess i have been left in.

Can anybody recommend somebody suitable in South Manchester ? the boiler is a Viessman 200w 35kw.

 

[bengasman]

A 35 kW heat only boiler?
You either have a massive house, or they stuck the wrong boiler in. At least it's a good brand.

 

[bengasman]

Why did you replace a 4 year old boiler?

 

[stanmore]

I only recently moved into the house with the WB boiler having been installed by the previous owner. This had been incorrectly installed and never serviced, the system was not fully working as the c/h was not staying on. Which was possibly a diverter valve however 10 radiators needed replacing as these were 20 + years old - single panel. I Hoped i wouldn't have to replace the boiler as i had two WB combi's in previous properties but the 3 companies i had round all said that they couldn't re use it !!

All 3 installers also suggested 35 or 37KW boilers, the house is a Victorian 4 storey property with 6 bedrooms 2 reception rooms, a conservatory and a full foot print of cellars. It's not massive but probably 250m2 internal area exc cellar.

The pressure water pressure at the PRV by the cylinder is reported to be, on the benchmark, 2.5 bar however since the cylinder was installed the water main has been replaced - should this make any difference to the flow rate for the shower ?

 

[edtheplumber]

The shower should be about the same or better then the original pumped system.

Flow rate with new mains should be better unless:
It is a small bore shower designed for a higher pressure but low flow rate.
or
Pipework to shower is too restrictive (eg. 15mm for 2 floors and a bunch of bends.)

But at the very least, shower should not drop when someone uses the kitchen tap, dishwasher or flush the loo.




Are you sure the pressure was different at the cylinder? Is it installed in the loft?

Flow rate or volume is usually the problem with unvented cylinders. If you had the mains replaced and it was worse - you are likely to have a line strainer partially blocked.

Most plumbers don't find them because most plumbers do not install them, (or know they are installing them.) They can be part of the balanced cold valve assembly.

There are often filters /screens on shower hot and cold feeds.

good luck.