Hot water pressure issue

[ajt2018]

I have a Worcester heatslave 15/19 oil fired boiler. The expansion tank was recently replaced however I am still having issues where the hot water pressure is not consistent.

Examples being you run the kitchen tap and it seems to take a while for the hot water to come out but then when it does come out it runs hot and is fine.
In addition we have an oldish triton shower which has a thermostatic mixer the water from the shower will run hot for a while then runs cold and goes in this repeated pattern. I am confident that there is no issue with any fault on the shower, when the shower is running you can feel the hot water pipe elbow joint next to the shower unit and can feel the pipe going from hot to cold in sync with the hot and cold water coming out the shower head when it should just be consistently hot.

All the radiators were bled after the expansion vessel was fitted and the bled valves on the boiler have also been bled. The motor is fine therefore after doing lots of research on the net so far I am still trying to find out what could be causing this.

Any suggestions would be appreciated. Thanks

 

[Burger]

Hi, none of the taps in the house are mixer taps.

Shower plumbed in correctly? As in the correct orientation?

 

[ajt2018]

Does it stay the correct temperature if you run a hot tap slightly elsewhere to increase the demand? If so, I'd be looking at a flow switch fault

Hi, I finally managed to get a boiler engineer\plumber to come out today and he has had a quick look and believes it is an issue with the flow switch. When the hot tap is run in the bathroom at the same time as the shower then the shower does appear to stay the correct temperature. I have ordered a new flow switch. I have read some things on some plumbing forums where some people have been able to fit the new flow switch themselves. To replace the flow switch is it a case of turning the boiler off then isolating the mains inlet valve and removing the existing flow switch and attached sensor then putting the new one in situ then reopening the flow for the mains inlet? Thanks

 

[Chuck]

I have read some things on some plumbing forums where some people have been able to fit the new flow switch themselves. To replace the flow switch is it a case of turning the boiler off then isolating the mains inlet valve and removing the existing flow switch and attached sensor then putting the new one in situ then reopening the flow for the mains inlet? Thanks

No. It's a job that needs to be done by a plumber or heating engineer who is on the Gas Safe Register. A legitimate GSR may well refuse to fit a flow sensor that you have bought yourself because they need to be sure it is the correct and genuine spare part.

 

[ajt2018]

No. It's a job that needs to be done by a plumber or heating engineer who is on the Gas Safe Register. A legitimate GSR may well refuse to fit a flow sensor that you have bought yourself because they need to be sure it is the correct and genuine spare part.

Thanks for the reply. The boiler is an oil fired boiler so I don’t think being gas safe registered applies. I have replaced other parts on the boiler last year without issue. Any other replies would be appreciated from anyone who has knowledge of this particular type of boiler. In case the thread doesn’t say it’s a Worcester Heatslave 15/19 RSO.

 

[Chuck]

Thanks for the reply. The boiler is an oil fired boiler

My bad - I missed that. You are correct Gas Safe is not applicable and the regulations are not as strict. I would still, however, recommend that you employ a OFTEC registered technician to do the work.

 

[SimonG]

Why didn't the plumber/heating engineer fix the issue?

 

[ajt2018]

Why didn't the plumber/heating engineer fix the issue?

Because he didn’t have the part. It took quite a while to go any plumber/boiler engineer to
Come out as they either don’t bother getting back to you or so they will come and they don’t. Hence why I would rather replace the part myself.

 

[John.g]

Hi, I finally managed to get a boiler engineer\plumber to come out today and he has had a quick look and believes it is an issue with the flow switch. When the hot tap is run in the bathroom at the same time as the shower then the shower does appear to stay the correct temperature. I have ordered a new flow switch. I have read some things on some plumbing forums where some people have been able to fit the new flow switch themselves. To replace the flow switch is it a case of turning the boiler off then isolating the mains inlet valve and removing the existing flow switch and attached sensor then putting the new one in situ then reopening the flow for the mains inlet? Thanks

I believe your boiler is a storage combi and has a heatslave tank that holds 45 litres of hot water, when there is a demand for hot water, the flow switch starts up the circ pump to circulate the hot water from this storage tank through a heat exchanger which heats the water passing through it. A thermostat in the storage tank controls the temperature by firing the boiler on/off.
I know the flow switch is the suspected fault but if you open a hot tap only and if the water temperature is and stays normally hot then that would tend to rule out the switch, when the water starts flowing first then if the stored water is at its correct set point then one would think that the boiler should not start up until the tank temperature falls to its cut in point. It might be worth checking out the tank thermostat as well when changing that flow switch.

 

[ajt2018]

I believe your boiler is a storage combi and has a heatslave tank that holds 45 litres of hot water, when there is a demand for hot water, the flow switch starts up the circ pump to circulate the hot water from this storage tank through a heat exchanger which heats the water passing through it. A thermostat in the storage tank controls the temperature by firing the boiler on/off.
I know the flow switch is the suspected fault but if you open a hot tap only and if the water temperature is and stays normally hot then that would tend to rule out the switch, when the water starts flowing first then if the stored water is at its correct set point then one would think that the boiler should not start up until the tank temperature falls to its cut in point. It might be worth checking out the tank thermostat as well when changing that flow switch.

Hi, thanks for your reply as I mentioned I had a plumber/boiler engineer come around yesterday he has already diagnosed the fault as the flow switch. Due to the time it has taken to get a plumber I’m trying to ascertain if the flow switch is something I can replace myself and if it’s just a case of isolating the cold water inlet supply either on the boiler or at the mains in order to remove the old part and install the new one. Thanks
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My bad - I missed that. You are correct Gas Safe is not applicable and the regulations are not as strict. I would still, however, recommend that you employ a OFTEC registered technician to do the work.

If anyone else can answer my original point that would be appreciated.

 

[Tea-Break]

Test the flow switch first with a multi meter, if your plumber has done this, why not get him to replace it?
Easy repair, less than an hours labour.
However, I would (as John.g suggested) test slave tank stat. first.
All straight forward stuff really.