No hot water to shower mixer

[Cotty]

Funny situation, I have the below shower mixer (not bought from Bathstore, only picture I could find) that was installed a couple of months ago. It did not have enough control over the tempreture, the mixer knob only moves about an inch and does not really do anything. When it was first installed the water was too hot and I had to change the water tempreture on the boiler just so I could stand under it.

Got the guy who installed it to adjust it so I can add some cold. He said he fixed it, but when I used it the folowing day I could only get cold to luke warm water from it. Realising he could not fix it I called another plumber and it has stumped him. I only have one combie boiler and the basin tap runs hot and its the same source.

He thought the 3.5 bar cold pressure was overpowering the hot so as an experiment isolated the cold water feed to the mixer. We got a few seconds of hot then it goes back to Luke warm. What we can not understand is if it only has hot water going into the mixer why are we not getting hot water out?




Made by Roper Rhodes http://www.roperrhodes.co.uk/

Yours

Stumped

[dirkgently]

Is the boiler modulating properly? It may be firing on full and then shutting the burner down on the hi limit stat

[Cotty]

I do not know what "hi limit stat" means. The basin tap runs hot so why does the shower not, they are on the same supply.

Putting hot water into a mixer valve with the cold water turned off should produce hot water

[dirkgently]

Cotty said:

I do not know what "hi limit stat" means. The basin tap runs hot so why does the shower not, they are on the same supply.

Putting hot water into a mixer valve with the cold water turned off should produce hot water

A modern combi boiler modulates the gas supply to meet the demands of the water flow. The shower may have a relatively low flow rate so the boiler fires up on full power but instead of modulating down to low it just shuts the burner down.

[Ferg]

dirkgently said:

Cotty said:

I do not know what "hi limit stat" means. The basin tap runs hot so why does the shower not, they are on the same supply.

Putting hot water into a mixer valve with the cold water turned off should produce hot water

A modern combi boiler modulates the gas supply to meet the demands of the water flow. The shower may have a relatively low flow rate so the boiler fires up on full power but instead of modulating down to low it just shuts the burner down.

Good call. Also the valve may have flow restrictors which need installing/adjusting to ensure the boiler feeds correctly.

[Cotty]

dirkgently said:

Cotty said:

I do not know what "hi limit stat" means. The basin tap runs hot so why does the shower not, they are on the same supply.

Putting hot water into a mixer valve with the cold water turned off should produce hot water

A modern combi boiler modulates the gas supply to meet the demands of the water flow. The shower may have a relatively low flow rate so the boiler fires up on full power but instead of modulating down to low it just shuts the burner down.

So if it shuts the burner down why is the water luke warm rather than cold and why does the basin tap still run hot?

[Ferg]

Have you run both at the same time?

[Ferg]

Just as a thought...
the hot and cold are the right way 'round aren't they?? That would cause just these symptoms. It is possible to remedy this quite easily on that model.

Edited by Ferg on Sunday 19th April 17:25

[Cotty]

Ferg said:

Just as a thought...
the hot and cold are the right way 'round aren't they?? That would cause just these symptoms.

The trouble-shooting guide states if after instilation the shower only runs hot or cold and will not mix then the hot and cold supplies are plumbed the wrong way. The cartridge would then need to be rotated by 180 degrees. This has been done but does not resolve the problem.

[Ferg]

I'd initially acertain the correct orientation of that cartridge for the pipework you have, ensuring that there isn't any other fk up such as feeding in on one of the outlets (yes, I've seen it done). Then, so long as you are confident hot and cold are present and flowing ok (take the cartridge out and momentarily turn the isolators on), it should be possible to adjust the thermostat to achieve a decent mix. Make sure you run the basin tap at this point to make sure the boiler has full gas to the burner.

Best I can do without coming to see it!!

[Cotty]

Ferg you sound like you know what you are talking about and would love you to take a look. The new plumber is going to talk to the previous plumber and the manufactuer tomorow to find out where to go from here.

It is so frustrating, I have spent a lot of money on a new bathroom and I can not have a hot shower. I mean how difficult is it to mix hot water with cold water to create the correct temperature

[530stew]

i have the very same mixer arrangement as yourself. We occasionally have the same problem. In the past i have taken the front plate off and behind are two non return valves, one for the hot, one for the cold.

Isolate the water
drain water from pipes by leaving tap fully open
using a socket set remove non return valve. These valves are made of brass and on both occasions mine has been stuck in the closed position. Once the valve is removed you can free it off with a bit of 'persuasion'.

replace valve, close taps and put water back on, enjoy a hot shower.

Worth remembering of the hot non return valve is stcuk closed, there will be a load of warter behind the valve which will leak out once the valve is removed. Get ready with a towel to saok all this up or it will all run behind your wall.

you might have a different issue of course, but this is an easy thing to check. I plumbed my own bathroom in so was aware that these may need access for maintenance, consequnelty when i tiled i made sure there was room to get a socket in remove the non return valves.

HTH

Stew

[OzzyR1]

You haven't got a hot water feed from a tank and a cold water feed from the mains have you? If so, this can make it very difficult to regulate temperature in a mixer.

They both need to be from the same type of source - ie mains or tank.

[Cotty]

Cheers 530stew

OzzyR1 said:

You haven't got a hot water feed from a tank and a cold water feed from the mains have you? If so, this can make it very difficult to regulate temperature in a mixer.

They both need to be from the same type of source - ie mains or tank.

The plumber thinks that because the mains pressure is 3.5bar then it is overpowering the hot from the combie. He is thinking about puting regulators to control the flow. He is talking to the manufacuter today and they may have some answers.

[dirkgently]

Cotty said:

The plumber thinks that because the mains pressure is 3.5bar then it is overpowering the hot from the combie.

Get a new plumber!

[Ferg]

dirkgently said:

Cotty said:

The plumber thinks that because the mains pressure is 3.5bar then it is overpowering the hot from the combie.

Get a new plumber!

If the mains cold is 3.5Bar then the hot will be 3.5Bar (less a trivial little bit)

Methinks he's talking about the flow, because you won't restrict pressure with a flow restrictor.

[Cotty]

530stew said:

i have the very same mixer arrangement as yourself. We occasionally have the same problem. In the past i have taken the front plate off and behind are two non return valves, one for the hot, one for the cold.

Isolate the water
drain water from pipes by leaving tap fully open
using a socket set remove non return valve. These valves are made of brass and on both occasions mine has been stuck in the closed position. Once the valve is removed you can free it off with a bit of 'persuasion'.

replace valve, close taps and put water back on, enjoy a hot shower.

Thats exactly what the manufacturer told the pumber, top advice. New cartridge (no 3) coming wednesday hopefully will get sorted this week and I can stop filling my bath with a hose and I can actually have a hot shower