Thermostatic shower - temperature?

[matthew.larkin]

Hi

We've had a thermostatic shower fitted - one of those where you turn one dial to set the heat (notionally marked in deg C) and the other to set the water flow strength.

But to get an acceptable temperature, the heat setting has to be set as low as possible, otherwise it would scald. Is there likely to be something that can be adjusted in the shower mixer so that the heat markings are more closely approximate to the actual temperature being output? For the record, I like a really hot shower, so its not just me not able to handle the heat!

Hot water is supplied from a combi.

Thanks!

Matt

[Andy Burns]

Certainly the Mira Excel allows you to offset the temperature range, by removing the knob, turning the spindle and replacing the knob.

Suggest you identify the shower and seek out an online manual.

[Jim Alexander]

Probably not, but if so will be mentioned in the instructions which the installer left with you.

It might be more useful if you tell us where the cold is fed from.

You need to tell us the make and model of the shower mixer and who selected it.

Jim A

[matthew.larkin]

We selected it (based on price), fitted by the plumber that worked on other bits in the house when we had an extension done. Didn't really test the temperature for ages as the tiling took a while to do.

I think its a tre mercati bar-type mixer. I'll try removing the end tonight as well as searching for a manual online (certainly wasn't left by the plumber unfortunately).

Thanks for the quick responses.

Matt

[Doctor Drivel]

Turn down the Combi DHW temperature.

[Jim Alexander]

There is not an obvious thermostatic bar-type mixer on the Tre Mercati website so I am puzzled. In my experience generic bar-type thermostatic mixers work well with a wide range of supply pressures and also with unbalanced supply pressures but not all thermosatic mixers work well with unbalanced supplies. Specifically is the cold feed from the rising main or from a header tank?

May seem obvious but have you checked that the mixer hot port is supplied with hot? Difficult without the installation instructions of course.

Jim A

[matthew.larkin]

Yes, I spotted that on the Tre site too....

I reckon hot must be supplied with hot as turning the dial down (in deg C terms) does bring down the heat to a sensible temperature.

It did surprise me that it wasn't putting out closer to 38 degrees at first as I'd imagined that there would indeed be some thermostatic thingummyjig inside it which controlled the temperature; otherwise why put the deg C on the dial in the first place?

Thinking about it, though, when it was installed I remember the guy having some problems with excessive cold water supply such that he had to fit some sort of valve on the cold water mains to reduce the pressure. For some reason we've got two cold water mains in the house too.

Matt

[matthew.larkin]

Don't seem to be able to do that; certainly there isn't an obvious dial on the Potterton Combi 100 that can be used to do this.

Turning down the cold water supply pressure might be the more appropriate option though.

Matt

[David Hansen]

On Tue, 25 Mar 2008 06:43:46 -0700 (PDT) someone who may be [e-mail] wrote this:-

Even a thermostatic shower should be fed by supplies at nominally the same pressure. One way of doing this is to take the cold from the feed to the hot.

[Tim Downie]

Is there a problem with the cold supply to the shower mixer? Any restriction in the pipework at a shut off valve or just too circuituous a route leading to poor cold flow?

Must admit I'm surprised there's no DHW temperature control on it.

Tim

[Tim Downie]

Sounds like you need to get your plumber to sort it out as I think this is the likely cause of the problem.

I'm guessing that the cold supply pressure (or more importantly FLOW) is now a bit borderline for the mixer to create the mix of hot & cold that you want.

I'm willing to be that rather than fit a pressure reducing valve, there will be a simple stop-c*ck somewhere in the cold supply that supplies the shower and it will be screwed down strangling the supply of cold to the shower mixer.

Tim

[John Stumbles]

Not really: hots's on the left, cold on the right (looking at the front of the shower, so vice versa looking at the pipework side)

[John Rumm]

I take it you have checked that it is plumbed the right way round? (I.e. the hot and cold feeds have not been swapped)

[Ed Sirett]

[e-mail]...

It might just need calibrating (i.e resetting the position of the temp knob to cover the range you want). The intructions when you've found them will help. Or careful and thoughtful investigation of how the knobs are fitted.

[matthew.larkin]

Had a look at the pressure valve last night for the cold water feed that feeds the shower, and that is showing as restricted to a pressure of 3 bar. I'll try increasing that slowly tonight to see if I can get to a more optimal shower temperature range.

Matt

[Jim Alexander]

If you like but 3 bar is a perfectly reasonable pressure setting for a PRV on a cold feed. Anyway it's the pressure/flow at the shower cold port not the PRV which may be the issue. Have you verified it's on the rising main and not a header tank? Have you verified the shower is connected the right way round?

Either you have a faulty mixer or a faulty installation. Both callback issues.

Jim A

[matthew.larkin]

There's no header tank in the house. Other than saying that the temperature does decrease as the dial is turned as I'd expect, I can't check if the hot goes to the cold and vice versa, but I'd say that was extremely unlikely given the first part of this sentence.

You're probably right about the callback, just thought I'd see if there was an easy diy fix instead.

Thanks

Matt

[David Hansen]

On Wed, 26 Mar 2008 03:46:58 -0700 (PDT) someone who may be [e-mail] wrote this:-

There should be. As it is a bar type shower one side/end should be hot when it is running and one end cold. The nuts where it fastens to the pipes are a good place to test on many such showers, or the ends of the bar if it is a more fancy type.

It is a fair certainty that the left hand side should be the hot one and the right hand side the cold.

[matthew.larkin]

right logical effect on the water temperature, I'm reasonably certain that it is plumbed the right way round!

Matt

[Jim Alexander]

Beg to differ. Done a quick test on my bar mixer. Isolated the hot side at the service valve. At full temp no cold flows. That's logical. At minimum temperature a good flow of cold, also logical. But you have to consider how a combi delivers hot water. Depending on how your combi is set up but typically at low flow rate the delivered temperature is higher than at higher flow rate which is what your are reporting. One symptom, two possible explanations.

We are trying to help but in the face of the problem you ought to at least test our theories. You did ask.

Jim A