Baxi Eco 80 Hot Water Problem.

[vsynth]

Hi, just got back after a week away and there's a problem with our boiler.

If you turn on the hot water the boiler ignites and the water gets hot.

After 20-30 secs the boiler switches off, the water gets cold, sometimes the boiler re-ignites sometimes it does not.

Turning the tap off and back on again makes the boiler re-ignite.

There does not appear to be a problem on the central heating side, just the hot water.

Any ideas what might be at fault?

 

[Agile]

I dont expect that you have read much on this forum about this very common fault before posting that..

Usually a blocked plate HE but sometimes a failing diverter valve or even a failing pump.

Tony

 

[vsynth]

Thanks, I did a search on the web but there's quite alot of conflicting information out there.

Also I forgot to add, when we got back from holiday the pressure guage on the boiler was reading zero, I have repressurised it back up to just over 0.5 bar.

 

[clf-gas]

Increase pressure to 1 or 1.2bar.

 

[vsynth]

Pressure increased to 1.2bar now.

I have noticed that sometimes the boiler fan comes on and the gas switches on but when it ignites the led only comes on for a fraction of a second and then the gas switches off and the fan stops...not sure if this is another problem.

Would it be worth me adding some sludge remover / descaler to the system? and if so is this a good device to use http://www.diy.com/diy/jsp/bq/nav/n...refview=search&ts=1235231028029&isSearch=true or would you recommend something else?

 

[Agile]

Some people use those injectors and find them useful. I dont have one though.

I realise that most DIYers seem to think that all heating chemicals are the same. My advice is to stick to the top two, Sentinel and Fernox, or to keep Keith happy, Camco as well.

The first thing you should do is to drain out your system a couple of times until the water is clear. Then add X800 or your preferred choice of sludge remover from the above.

Then drain and refill adding inhibitor, X100 is my choice!

Water from EXVs is often black even if the rest of the system is clean.

Tony

 

[vsynth]

Thanks Tony, I'll give your advice a go and let you know if things improve.

How do you add chemicals to a pressurised system without the use of an injector?...or is that a trade secret? oh I guess you use a powerflush

Ideally I would like to add the chemicals via the top up loop but I don't think that injector comes with fittings for that.

 

[Agile]

I usually do it within the boiler ( AAV etc ) or by isolating a rad and draining three litres and then adding through a 1/2" top tapping which carries the bleed screw. ( if fitted ).

I find my 50 ml syringes very helpful!

Tony

 

[vsynth]

I filled the system with X800 for a couple of days and have now drained/refilled the system a few times and refilled and added X100.

The water coming out was dark with a few ( very few ) tiny black particles in it but nothing major.

Problem is still there, I going to test the APS switch next then call in a plumber as I'm not going to start taking off gas fittings

I can't see any electrical problem with any of the switches, the temp sensor goes from 11KOhm cold to 3KOhm hot so that looks OK.

My guess is it's either the PCB or the gas valve itself...the gas is either on or off it doesn't modulate like it should.

I'll let you know what the outcome is.

 

[Agile]

My guess remains the same as I originally told you!

If you are calling someone, my recommendation is that you call a boiler engineer instead of a plumber!

Tony

 

[namsag]

Does the green demand light for water stay on when its turning off,

You may just have a weak diaphragm that just cant keep the pin out and activate the microswtch

 

[vsynth]

The pin is staying out and making the switch, it doesn't have a green demand for water led...I'll make sure I get an engineer

 

[namsag]

I would first suspect dodgy microswitch then . if it was the plate blicked it would stll cycle on and off as it cooled.
But yours is not comng back on

 

[vsynth]

I've checked all the easy things now, all the switches are OK and the temp sensor is OK.

Just at the point where the water gets hot and the gas flames should start modulating it turns the flames off completely.

Turning the tap off and on again starts the sequence all over again.

Same happens on central heating too now so whatever is wrong is common to both, rads get hot, boiler switches off, turn switch to off and back to central heating, boiler fires up again.

 

[Agile]

How do you know that the DHW demand switch is OK ?

Do you get a flame lockout light?

If its not modulating then the gas valve setup may be wrong.

Tony