Thermostatic Shower Valve Uneven Flowrate

mpc · 21 Nov 2006

Hi,

I moved into a new house, only to find the shower had a cheap nasty thermostatic plastic valve - which had settled on 2 settings - cold or red hot.

The house has a new Woucester Boiler (combi condenser). I replaced the plastic shower valve with a Sirrus 1503 thermostatic valve.

Now I find that the water from the shower gets hotter, depending on how far you turn the dial which is right. However, after about 2 mins the flowrate beings to alter, pulsing, then becoming weaker and then increases and is cold for a while. This is worse the hotter it is set.

The cold feed does have a govenor, which I turned in an attempt to see if the previous plastic valve could be fixed.

I thought that the rate might be dropping off because the cold pressure is too low - but I'm a bit stuck

Any suggestions, would be most gratefully recieved -

Thanks Matt.

Sider · 21 Nov 2006

mpc wrote

Any suggestions, would be most gratefully recieved -

Yeah , fit a good unvented cylinder.
Thermostatic valves dont seem to work to well on combination boilers but someone may know one which will work OK.

mpc · 21 Nov 2006

Thanks for the reply.

Would I be better off just fitting a standard mixer valve?

Thanks

Sider · 21 Nov 2006

mpc wrote

Would I be better off just fitting a standard mixer valve?

Sorry ,Dont know.

Have just read stuff on forums about them thermostatic mixers not performing to well when coupled to a combination boiler.
Ive only fitted them to UV cylinders and have never had any problems.

Sider · 21 Nov 2006

A standard manual mixer with an internal pressure balancing machanism fitted may well perform better than a thermostatic mixer on a combi system.
The main requirement is that the hot supply should remain relatively constant.
I think the combination boiler should acheive this . The modern ones should modulate back when the flow through them lowers so they should still provide a constant temperature at a lower modulation .

bster · 21 Nov 2006

My thermostatic Bristan 'Aquaeous' bar mixer (£140) works perfectly with my Baxi 105e combi

scaby · 21 Nov 2006

a commom problem with these, is the hot and cold supplies connected the wrong way round

mpc · 26 Nov 2006

Okay, an apology here.

Everything is now working very well, flow rate is good, much better than an electric shower. Temperature regulation is also good.

I made a very basic mistake. I forgot to open the extra wheel valve on the shower cold supply. The 1-2 mins that the shower was working was just the standing water in the hot feed !! This problem was driving me mad for 3 days

After opening the wheel valve and opening the govenor the problem vanished.

Just for your info, my boiler is a Worcester Bosch 28i Jnr and the Valve is a Sirrus Thermostatic 1503.

Thanks for everyone who took the time to suggest solutions

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Thermostatic Shower Valve Uneven Flowrate

scaby

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