Baxi 105e domestic hot water problem

[attland]

Hi

I had my 4year old combi serviced in November. Just afterwards we had problems getting hot water and our plumber diagnosed a diaphram fault and fitted a replacement. Since then we can get really hot water but the teperature falls steadily to being just warm. We get enough for a sink full of pots but a shower and a bath becomes tricky involving much switching on and off. Our plumber is as puzzled by this as we are. Anyone out there able to offer some advice? We would be most grateful.

Attland

 

[powell30]

What happens when you call for hw? Does the boiler cycle on and off? what lights show on the front of the boiler? does the temp lights reach 60?

 

[attland]

Thank you Powell30 for your reply.

Ran the water for a hot bath this morning. The hot water light came on and after the usual wait hot water arrived. Then it stated to cool off but remained warm, not hot enough for a bath though. I switched the tap off then on again and the initial burst of hot followed by cooling water was repeated. During the time the tap was on the power, hot water mode and burner lights remained on. The temperature neon lights reached 80 degees. Oddly after about the 5th attempt the water stayed hot and I was able to take a bath. The water was nowhere near as hot as it used to be, in the past it has always been necessary to add some cold.

Later my wife took a shower and with the control set at max heat she said her shower was comfortable. Previously at that setting it would have been scalding hot.
So our mystery remains.

Attland

 

[powell30]

possible scaled/blocked heat ex or your dhw temp stat faulty. You probably need a boiler expert on this one

 

[GodKnows]

Ur primary side on the DHW plate HEX is clogged up with dirty water fella. Was system flushed and inhibitor put in on install? Inhibitor needs to be re-applied every five years

 

[ACIDTECHNO]

Hi

I had my 4year old combi serviced in November. Just afterwards we had problems getting hot water and our plumber diagnosed a diaphram fault and fitted a replacement. Since then we can get really hot water but the teperature falls steadily to being just warm. We get enough for a sink full of pots but a shower and a bath becomes tricky involving much switching on and off. Our plumber is as puzzled by this as we are. Anyone out there able to offer some advice? We would be most grateful.

Attland

I have the same boiler, and same problem. If I keep the bath tap only slightly open, it stays hot, but any decent flowrate and it goes cold. Same with shower, but can't really get it to trickle out.
Thread here: http://www.diynot.com/forums/viewtopic.php?t=209097

 

[Agile]

Ur primary side on the DHW plate HEX is clogged up with dirty water fella. Was system flushed and inhibitor put in on install? Inhibitor needs to be re-applied every five years

But he said wife had a good shower!

Best to get a boiler engineer rather than a plumber who can actually diagnose the fault.

Needs a thermal survey inside boiler and a measurement of gas settings and sensors.

Tony

 

[GodKnows]

Hi all,

OK, I hope that remark is directed as the clients plumber agile. I can suggest that probably the max + min burner settings need to be adjusted, and the DHW NTC would also need to be tested for correct operation. This should of been done at the service not long ago

Plumber's, unless he is GasSafeRegistered shouldn't really be doing fault diagnostic work on your boiler fella...

 

[tdesnos]

Do you have old bath taps on your bath at all? This is a common problem when a new boiler is fitted to an old system, as the new bath taps allow the water to flow out of the taps at a greater rate than the boiler can provide. Which is why that guy above suggested only opening the taps slightly - most people just do this and seem to live with it! Modern taps have a sparkler inside them which reduces this flow rate and allows the boiler to keep up.

The burner pressures may need adjusting. But i doubt it.

Has this only been a problem since the boiler had the diaphragm replaced in the flow switch?

 

[ACIDTECHNO]

In my case (sorry if I'm hijacking the thread) there is a big pipe leading to the bath, which the engineer said would normally be 15mm, this is leading to a high flowrate, which the boiler can't keep up with <he said> . However, we used to be able to have tap on full and fill bath quickly with hot water. Also, the shower worked fine until recently, now it can't get hot enough.
Opening the bath tap slightly I could live with (even though something is wrong, as it used to work fully open) but we need to shower to work. I'm aware that the water enters the system a lot colder in winter, but last winter it was fine.

 

[transam]

To the O.P , I would tend to ignore any derogatary remarks made on here about plumbers !!

 

[tdesnos]

Transam: I might be at risk of being a bit sensitive here, but i feel as though you mean operating pressure by O.P? Referring to my burner pressure comment? It wasn't derogatory, my first trade is as a gas engineer. I'm aware of the importance of this, it's just in my experience with the kind of symptoms described this isn't the fault. Perhaps, since that comment fleetingly passed you of, cheaply, as all knowing; you might care to enlighten us with an equally lucid diagnosis?

 

[ACIDTECHNO]

Transam: I might be at risk of being a bit sensitive here, but i feel as though you mean operating pressure by O.P?

OP = Original Poster.

 

[tdesnos]

Transam: I might be at risk of being a bit sensitive here, but i feel as though you mean operating pressure by O.P?

OP = Original Poster.

Gotchya.

 

[ollski]

I got really stumped by one of these the other month with a similar fault, it would fire up on full gas pressure and just fall away until it ran cool with gas pressure at 4.5mb max. Ended up as being the pcb.