Thermostatic Mixer Shower - instalation help

[Lyn123]

Hi

I have just installed a thermostatic mixer shower (bar type). The cold feed is mains fed (as is all cold water in the house as we have no tank in the loft) and the hot water feeds directly from the hot water tank (heated via imersion heater) , which as far as I can make out is high pressured as the cold water from the mains goes into it via a 15mm pipe and out of it in 22 mm and straight to the bath and bathroom sink.

I have taken a feed for the cold straight from the feed up to the tank and the hot from the 22 mm supply pipe to the bath.

Now when we turn the shower on it comes out cold up to 25c and if you turn it hotter it stops working altogether. The pressure when it is cold is great.

I was under the impression the pressure on hot and cold would be the same as they are both mains fed and the pressure at the taps in the bathroom looks similar.

I am starting to think I may have an air lock on the hot pipe as the feed pipe to the shower is not even getting warm?

Any ideas?!?

 

[seco services]

something tells me you haven't got an airlock or mains pressure hot water but a combination cylinder.

 

[Lyn123]

Yes I think I might have it has two elements to it. What does this mean and how can I fix the problem....

 

[seco services]

does it look like this.

https://supreme1.sslpowered.com/cgi...in/home/Shop/Cylinders/Telford.txt&item=00025

 

[Lyn123]

Yes kind of. It is green and has two sections to it. The top is smaller than the bottom but the feed for the hot water to the bath (from which I have tee'ed off for the shower comes from the bottom. The cold water comes off before it goes any where near the tank. There doesn't apopear to be any pipes going into the top, unless they are round the back and I can't see them.

Have I plumbed it up wrongly? It looked so simple I was sure I could do it myself.

Lyn

 

[seco services]

their should a cold pipe gos into the top about 1" down that is the mains cold fill to the ball valve. if you remove the lid you'll see the ball valve.

then about 15" down should be the 22mm pipe that is your bath, basin hot feed. if you turn on your basin hot the pipe should get hot.

and at the very bottom should only be a draincock.

 

[sooey]

Have I plumbed it up wrongly? It looked so simple I was sure I could do it myself.

Sorry for laughing but,

 

[Lyn123]

Yes that all sounds right.

So to clarify my hot water cylinder encompasses a cold water tank which fills and supplies the hot water tank when hot water is drained down.

Now I have taken the hot water to my shower from this cylinder and the cold water from the mains so I presume it is not working as I have unequal pressure as the hot is gravity fed and the cold is main fed.

is this correct and where should I be taking the feeds from?

 

[seco services]

yes your right.
but combination cylinder are not practical for supplying showers.

1 you will get hopeless flow/pressure.
2 if you add a pump your cold supply tank is not really large enough
regs require 50 gals or more.
you will only get about 4 mins then you willbe roasted cause your cold will run out first.

 

[Lyn123]

Oh dear the only reason we fitted this shower was becasue we have fitted an electric one downstairs and have been advised that we can't have two in the house due to wiring regs.

The instructions for the shower gives a diagram for hot gravity, cold mains system and we are plumbed up according to that so why won't it work?!

 

[seco services]

tell me the shower make and model.
but i have never met a bar mixer that will operate on unequal pressures.

 

[Lyn123]

It's a swirl as seen on screwfix

http://www.screwfix.com/prods/80880...ic/Swirl-Thermostatic-Mixer-Shower-Slide-Rail

 

[seco services]

can't find anything on instructions from swirl.
you sure you have read it correct as mixed pressures on a bar mixer is not common.