Problem with new boiler setup

[bradshaw]

Hi,

I have recently had a new boiler installed but I think that it may not have been set up correctly.

The problem is with the hot water system. When the taps are turned on the boiler fires up correctly and the water becomes hot. However in the bathroom is a combined tap/shower on the bath, when this is turned from water coming out of the taps to the shower the boiler turns off and the water goes cold. I can only get a hot shower when the central heating is turned on.

I've read the manual and it says when setting up the boiler you should use the tap which is furthest away from the boiler - which is the bath. Could the problem be a loss of pressure when using the shower as compared to the taps? If I adjust the water pressure will this cure the problem?

The boiler is a sime format 80 C I think.

Sorry - I don't know very much about boilers. There is no hot water tank, the water is heated whenever the taps are turned on. The boiler is set on the summer setting to give hot water only. The shower is attached to the top of the taps by a pipe. If the boiler can sense the water pressure to know when to start heating would the shower being above the taps mean that the pressure is lower? therefore stopping the boiler from recognising that the water needs to be heated.

Thanks

 

[oilman]

See THIS

 

[croydoncorgi]

Sounds like the flow of water through the shower head is not enough to trigger the boiler's water switch. With a new boiler, that's unusual.

If you are turning the water on, adjusting the temperature using hot AND cold taps, THEN switching on the shower, you need to change the procedure. First, adjust the hot water temperature on the boiler DOWN a bit (some people tend to leave the water temperature on max and then wonder why the water's too hot!), then turn on JUST the hot water tap and switch on the shower. If it's too hot, turn down the hot just a little then add some cold - idea is to keep a reasonable flow of water through the boiler, enought to keep it running.

If the shower head is old, it may be scaled up: take it off the hose and use kettle descaler on it (check makers instructions first - there may be another procedure for cleaning the head).

If that does no good, try a new shower head with bigger / more holes in it - the idea is to get MORE water through the boiler so that it switches on.

 

[weargas]

If the cw flow rate is a lot higher that the dhw flow rate, will it in effect push back the dhw stopping the dhw flowswitch from operating?

 

[croydoncorgi]

Other way round, usually.
Opening a cold tap often drops the pressure on the cold supply to the boiler, so there's not enough flow to keep it burning. That's why I suggested reducing the boiler HW thermostat setting as a first step.

 

[bradshaw]

Thanks for the advice.

By holding the shower head as low as possible in the bath and supporting the pipe to the shower head so that the water only ever has to flow downwards gives enough flow rate for the boiler to fire up. This is with hot tap on only. I've tried the hot and cold on at the same time whilst the shower head is attached to the wall but this doesn't help. The flow rate on all taps in the flat is poor at the best of times ( i live on the top floor of a 200 year old building) which may explain why this is happening even with a new boiler.

Tonight I shall descale the shower head / pipe and clean up whatever else I can. I'll let you know if I have any luck with this.

 

[bradshaw]

OK I've descaled the shower head and stuck pins in the holes to make sure they are unblocked etc. I also tried every single combination of thermostat / hot and clod taps. Unfortuanately this hasn't cured the problem.

I attached the pipe that ususally has the shower head attached to it to the wall and turned on the water. Apart from getting the floor wet and upsetting the missus the boiler did fire up. It is definately the shower head which is slowing the water flow, I'm gonna buy a new shower head tommorrow and hopefully this should fix it.

Cheers.