Baxi 105e DHW

[rmh]

Hi

Was just wondering if any guys on here might be able to offer a suggestion or two on what might be wrong with my combi, as the last two plumbers couldn't. Over the last few months the temperature of the hot water is a lot lower when running the hot water tap at full flow. If I slow the rate by closing the tap half way all is fine and nice and hot. Also if the central heating is on then no problem at whatever flow rate the water is red hot. Had plumbers in and confirmed gas pressure is fine burner rate is fine etc, but there must be a fault somewhere. Would anyone have any ides?

Many Thanks

 

[mickyg]

plate heat exchanger most likely, also possibly diverter valve.
very easy to check, I would have assumed they would have checked these???

 

[rmh]

Thanks for the reply, yes I would have assumed they would check all possibilities but the last one kept saying that it was because we have had a cold spell and the mains in is colder than normal. This maybe so but I have never had this problem before in cold weather. Suppose I had better get someone else in.

Thanks

 

[holty]

from cold if you turn the hot tap on does the heating flow and return pipes get hot.

 

[gas4you]

Have either of the engineers done the simple basic burner pressure and working pressure tests?

 

[rmh]

Hello Holty and gas4you

Thanks for your replies. i have just tried the hot water before the heating kicks in and yes the heating flow pipe did get hot after a few seconds of the hot water tap running!
The plumber did check the burner pressure and adjusted it as required, both of them also checked the meter and for any signs of gas leakage which also checked out fine. I get the feeling that you have a good idea what might be wrong Holty?

Thanks

 

[holty]

sounds like the divertor. im pretty sure its a diagphragm one. if so try changing the dia first as this is least expensive. it could work enough to actuate the micro switch but still let by on central heating.a good way of telling. is isolating the flow and returns on the boiler then run the hot water. but make sure you turn the isolators back on.

 

[rmh]

Hi Holty

Thank you for that, I will try turning off the flow and return as you suggest in the morning before the heating comes on and then run the hot water and see. If it is the diverter valve/diaphragm could or would this have any impact of the efficiency of the central heating performance?

Thanks

 

[gas4you]

The diaphragm gone would stop the boiler firing for HW, or at least make it sluggish.

As you have the ch flow getting hot when HW is demanded, you need a new DV.

 

[holty]

or new diaphragm as i said. at least try this first. i wouldnt warrent changing a divertor before at least changing the dia first. ones about 5-10 pounds while the others about 8 times as much

 

[sooey]

If the diverter is sticking it will soon knacker a new diaphragm though, then you get called back and look an idiot, I'm with Dave, change the lot.

 

[banditbarron]

It will be either the diverter valve or the rear of the pressure diff stuck slightly in the heating position i work on these every day and its a common problem.

Is this an instant or non-instant?

 

[Slugbabydotcom]

It will be either the diverter valve or the rear of the pressure diff stuck slightly in the heating position i work on these every day and its a common problem.

Is this an instant or non-instant?

Welcome to the forum. Perhaps you would like to join the combustion chamber?

 

[rmh]

Hi Guys

The boiler is the 105e which is the instant.
I tried as Holty suggested and indeed the hot water was much much hotter and stayed that way with the tap open full bore.
So I guess it's a case of either changing the diaphragm first and see or go for a replacement diverter valve. Is there anything that can be adjusted on the pressure diff or is there a way to check if this is "slightly stuck in the heating position"?
Many Thanks to all

 

[holty]

if its the instant it will have a stepper motor.and changing the divertor is a pig of a job on the instant.