Plumbing Question - Shower not hot

[brianmoooore]

Reason i am confused is that there is talk of the shower take off from the cylinder being lower than the top take off and there is talk of the pump running when either tap or shower are running.

There's a Suffolk flange fitted, so the shower hot water comes from about three inches lower down the cylinder than the rest of the hot water. This shouldn't make any difference to comparative water temperatures until the hot water is nearly all used up.
It would be very unusual to feed downstairs taps from the same pump that feeds the shower, but not impossible.

 

[plugsandsparks]

OK so maybe impeller has fell off, could try turning pump off and running shower to see if it is exactly the same?

 

[mainline]

I wonder how the OP is getting on.
It's always nice to have an update on the outcome.

 

[Mark Wright]

I wonder how the OP is getting on.
It's always nice to have an update on the outcome.

I hate that when they just disappear
Sorry, as you know I turned the thermostat up on the tank and yes it is warmer but it's not right and I do feel this has led me in the right direction because I did feel it wasn't right from when the boiler was changed.


I would like to get a thermometer suitable to measure the temp if anyone could recommend one?

Another thing if I quickly turn the temp right down and right up it is hot for like a second.

Also this has made me what to learn S and Y plan etc I've been putting it off - I'll probably start another thread at some point.

But I'll say it again this is a great forum with some really helpful people.
Mark.

 

[Mike Johnson]

I think the problem may be the shower mixing valve is designed for mains pressure and the OP has only tank gravity pressure, or the pump may be caput and will not operate correctly with the pressure now available with the new boiler, which again may be designed for mains pressure and only has gravity pressure, both need checking, whatever is causing the problem seems to be a disparity between the boiler, shower pump and tank pressure differentials.

The lack of gravity pressure equipment is a continuing problem for older house's and installations.

 

[brianmoooore]

I think the problem may be the shower mixing valve is designed for mains pressure and the OP has only tank gravity pressure, or the pump may be caput and will not operate correctly with the pressure now available with the new boiler, which again may be designed for mains pressure and only has gravity pressure, both need checking, whatever is causing the problem seems to be a disparity between the boiler, shower pump and tank pressure differentials.

The lack of gravity pressure equipment is a continuing problem for older house's and installations.

The shower valve in question is designed for a minimum pressure of 0.4 bar.
It is fed from a purpose designed shower pump which should be capable of providing a pressure of 1.5 bar - 3.0 bar, depending on the exact model, so it should work properly.
The design and layout of all the plumbing we can see in the pics is OK, although a little odd in places.
There's something that has failed, is not set up properly, or is partially blocked.
I'm still unclear if the shower worked properly when the water was heated by electricity, or was just 'better'.

 

[Mike Johnson]

Ten pages of going around in circles eventually we will disappear up the shower head, seems to stem from the replacement of the shower mixer and boiler at the same time?

 

[LukeD]

This is so simple..... get the temp of the hot water tested as close before the mixer as possible . If its as hot as expected .Buy a new mixer ..... !

 

[Mark Wright]

This is so simple..... get the temp of the hot water tested as close before the mixer as possible . If its as hot as expected .Buy a new mixer ..... !

It's a brand new shower.

 

[Mark Wright]

Anyway like I said I feel I've been put on the right track - for some reason the water entering the pump isn't very hot, unless I use the Immersion. I think I'll measure the temp(i.need a thermometer) and just go to the company that fitted and say look this is the temp here's what I found, fix it.

 

[Mike Johnson]

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[mainline]

Anyway like I said I feel I've been put on the right track - for some reason the water entering the pump isn't very hot, unless I use the Immersion. I think I'll measure the temp(i.need a thermometer) and just go to the company that fitted and say look this is the temp here's what I found, fix it.

Have you tried turning your tank stat and boiler temp up ?
The tap hot water temperature is going to be the same as the immersion tank

 

[Mike Johnson]

I have in the past cured a very strange temperature difference by turning on all the taps in the bathroom, seems that if I have been working on the plumbing I sometimes get an air lock and this cures it, have you tried running the shower without the thermostat in place for a while and then carefully testing the water temperature?

 

[Mike Johnson]

Have you tried turning your tank stat and boiler temp up ?
The tap hot water temperature is going to be the same as the immersion tank

He has hot water at the taps, it's just not hot at the shower pump.

That gives me a thought (lonely I know) is there a temperature compensator fitted on the flow to the shower, one that mix's hot and cold water? something like this: Water Valve Control Pipe Replace Supplies Tap Temperature Thermostatic | eBay - https://www.ebay.co.uk/itm/285144708639?

 

[mainline]

The only thermostatic mixer is going to be in the shower mixer bar
He could just fit a mixer that’s not temperature controlled

 

[DPG]

Just have a bath. You must stink a bit by now

 

[mainline]

Just have a bath. You must stink a bit by now

He will be ok it’s not his.

Anyway cold showers are good for you and cheaper to run.

 

[Mike Johnson]

The only thermostatic mixer is going to be in the shower mixer bar
He could just fit a mixer that’s not temperature controlled

Not now days with the mains pressure hot water system being fitted in most new builds, the thermostatic temperature mixer is almost mandatory.

 

[mainline]

Not now days with the mains pressure hot water system being fitted in most new builds, the thermostatic temperature mixer is almost mandatory.

He hasn’t got mains pressure on the hot side it’s header tank fed (vented) hence the need for a shower pump.

 

[brianmoooore]

I sometimes get an air lock and this cures it,

The only place there could be an airlock is before the pump. The pressure after it would overcome any thing like that.
Is the length of pipe that includes the gate valve running downwards slightly as it goes away from the cylinder, or at least horizontal?
A surrey flange has a small hole internally between the top of the shower dip tube and the rest of the hot water/vent outlet. A blockage of this hole is likely to cause airlock problems.

Not now days with the mains pressure hot water system being fitted in most new builds, the thermostatic temperature mixer is almost mandatory.

TMV is mandatory on the supply to a bath. Water from a bath tap must not exceed 48 degrees, which must waste loads of water, since you can't just top up the temperature of your bath with a bit of 65 degree water. You now have to partly empty the bath and top up with loads of 48 degree water.

 

[Mark Wright]

Have you tried turning your tank stat and boiler temp up ?
The tap hot water temperature is going to be the same as the immersion tank

This is one of the strange things - The Tap is hot no matter what. The water entering the pump(for the shower only) is seems hot when the immersion has been on.

 

[brianmoooore]

What is the flow temp. at the boiler (if it's calibrated)?

 

[Mark Wright]

What is the flow temp. at the boiler (if it's calibrated)?

Hehe how do I check ?

 

[Mike Johnson]

Hehe how do I check ?

See post 101

I don't think that will help if you have sufficiently hot water at the taps with just the boiler on, its the temperature into the pump that is the problem, the water is either restricted into the pump or temperature is being bled off prior to getting too the pump.

 

[mainline]

Have we determined what sort of boiler he has ?

Is the ball cock in the immersion header tank defiantly getting a drop when using a hot tap ?
Does the boiler start when using the hot taps ?

I see he's got an indirect immersion tank.

We need to know what boiler this is, does it also run central heating ?


The op said it started happening with the boiler change and that the taps are always hot. Combi ?
The tap hot feed could be direct off the boiler and the shower left on the immersion.
The indirect heating of the tank could be down to low hence when electric immersion is used it's fine.

 

[timhoward]

I've just read all 12 pages, the biggest clue to date seems to be that the immersion heater is capable of producing hot shower water and the boiler is not. The pump sounds as though it is functioning.
Yet the water from the tap is a decent temperature when the immersion is not used.

As this is a very strange set of circumstances it's making me wonder if the tap hot water is actually coming from the cylinder.
Could it have it's own under-sink heater?!
Or could something very special have happened, such as the boiler being changed to a combi, the tap being supplied by hot water on demand from the boiler, the cylinder coil ended up connected to the heating flow/return, and the shower being the only thing fed from the cylinder. I realise that is exceptionally unlikely, but so far something like that is the only thing that seems to fit all the reported test results.

If the OP can run the basin tap (as suggested before I think) and confirm the header tank for the cylinder starts to fill up?
Have we had a picture of the boiler yet?

 

[mainline]

I've just read all 12 pages

Obviously not all #115

 

[mainline]

It could be just a matter of turning the boiler temperature for heating up, which is why the indirect coil temperature is low ?

By turning the stat on the tank he should hear a click and the boiler fire up ?

 

[mainline]

It looks like this is NOT a combi boiler op stated it's a GREENSTAR FS 30CDi & FS 42CDi Regular


Ensuring that the heating temperature on the boiler is at max is the next step.

 

[brianmoooore]

Ensuring that the heating temperature on the boiler is at max is the next step.

We've just had a winter of Government sponsored TV ads telling us all to turn out boiler temps down.