Worcester Bosch Greenstar 28i Junior - cold showers

Hi all,

I have a Greenstar Junior 28i combi boiler in my house. We moved in in May, and after putting in a thermostatic shower mixer upstairs, found that the hot water temp/pressure was poor but just about usable. We put this down to having a small boiler (the house is 4-bed, which seems a wee bit too large for a boiler this size). We recently endured about two months without the shower, due to a leaky connection on the valve virtually destroying the tiling job, leading to a protracted repair job (protracted because we were skint, and couldn't afford the quick repair). Now that the leak has been fixed and the wall retiled, I've been unable to get a decent shower out of it. When the hot water is coming through, it's tepid at best, and it doesn't take long for the hot to switch off altogether. If I open up the valve to full pressure, it will only give cold.

So, long story short, shower was below average, out of action for a while, it's now not usable at all. The water pressure hasn't changed much, but it's considerably colder.

My layman's diagnosis is: mains pressure is too high. I don't have any figures, but the cold pressure is significantly higher than the hot. The shower experience is noticeably colder now than it was three months ago because the cold water is a lot colder, thereby reducing the overall temp. Is this a daft conclusion?

Can anyone shed light on the likelihood of alternative causes? Could it be the diverter valve (I have run the hot water continuously at the kitchen tap, and seen the burner switch off after thirty or forty seconds, though this might be normal for all I know)? Is the boiler just too small? Could the valve be buggered?

If the mains pressure is too high, will a pressure-reducing valve improve the shower experience, or could it kill it off completely?

And before anyone asks: yes, the temperature control on the valve is all the way over to the hot side, and is not being stopped by the over-ride switch.

Many thanks in advance for your help, and apologies for any vagueness.

I have this feeling that you are thinking too much.

If the boiler delivers 9 li/min at the hot tap then the problem is likely to be within the shower unit.

As a first check can you turn off the cold water into the boiler and see if any water comes out of the hot tap?

Tony

Thanks for the reply Tony - you're dead right, I over-think everything. When I've over-thought something enough, I then over-Google it.

A couple of simpleton questions: to turn off the cold feed to the boiler, will the mains stopcock do the job? What are you expecting to happen?

I'll test it tonight.

Boiler is not too small. It will comfortably heat a house twice the size.
It is also not the water pressure, it can not be too high
It certainly is not the diverter
The “I” series and junior models are very often poorly installed and even worse for maintenance.
If the hot water was okay before you changed the shower, and poor after that, it would lead to a simple deduction.
Apart from the above, if you do not know the last time the system was serviced, it is probably too long ago.