Baxi Duo Tec 28HE - water light staying on

[Laticsforlife]

The issue;

• Boiler when power is on has the green water light on constantly (not flashing).
• Hot water works fine, fires up when taps turned on, pressure fine there also
• Pump can be heard continually pumping nothing after the water tap is off (not the usual 30 seconds or so before it normally goes silent and all lights go off)
• No heating at all (presumably as the boiler is calling for water)

Facts about the system;

• Boiler pressure OK to 1.5bar approx
• No leaks anywhere in the system
• Has magnetic filter, regularly cleaned, no issues there
• Recently serviced, no issues
• No error lights or numbers
• Stat is fine, turn heating up, it sends signal to power box (lights up as normal), but boiler does not fire (again presume due to boiler calling for hot water

History;
Mains water leak on road YESTERDAY, no water for a while then very low pressure, now back to normal. This problem starts right after, coincidence, I think not.

Having searched for help all over the web, some suggest the DHW filter attached under the Hall sensor in front of the heat exchanger might need cleaning or replacing (stuck pin?) and interestingly the service manual for this boiler (page 37 if you have it available on plumbase to view) suggests cleaning this after a loss of pressure.

That I intend to be my first job but it's in a real s0d of a position behind the pump (which is in the way).

Alternatively some suggest the expansion vessel might be at fault. Now about 3 years ago I had some other kind of fault (think there might have been an error code that time) and I fixed it by re-pressurising the vessel with a electric car pump, but that too is in a s0d of a position and I don't have a right-angled valve (like the pro's do).

Also in the past the DHW temperature sensor has failed, but again I think there was an error code for this and seeing as there isn't, I presume it's still OK. Also if I unplug it, there is an error code so guess it must be OK.

How am I doing so far, is there anything else the experts can suggest before calling in a heating engineer (I see these 2 fixes as no-loss if they are unsucessful, but better to rule them out before incurring costs).

 

[Combicert]

Seems to be too much of a coincidence to me too - following the water leak issue yesterday.

Just checked manual for you and you are quite correct - looks like a pain to get to.

 

[Hot&Cold]

Laticsforlife you could remove the hall sensor from the turbine and see if the hw demand light goes out.process of elimination sort of.

The turbine can easily be removed with a suitable sized (think its 18mm) a short box spanner,or an angled socket wrench.You may even have a car socket set and something in there will fit.

The turbine contains a filter,check it for scale deposits and clean as necessary.

Try not to snap off anything £££ while your working in that restricted space.Hand,finger access is from the left side behind the the gas valve.
Make sure the electric supply is isolated and water turned off before venturing inside the boiler

the fault could also not be the hall sensor or turbine but its a start

 

[Laticsforlife]

Many thanks, I did wonder about a car-type box spanner, as I have a couple. The Hall sensor seems to have some kind of plastic connection to the top of the turbine thing, and the book suggests it just comes off.

Sorry, but by disconnecting the Hall sensor and if the light goes out (or not), what is that telling me? What does the Hall sensor actually do?

I'll be having a crack at it later once I've got some batteries for my torch, typically dead when I needed it, and no spares in the house.

 

[Laticsforlife]

Ok so disconnecting the Hall sensor made the water light go out.

When connected it is red, suggesting its sensing water die to a sticking filter pin?

The damn thing isn't even a proper hex nut, 18mm socket (with multiple sides) won't grip, am about to try a proper 18mm box spanner

 

[nickso]

I use short stillsons to get the turbine out, they are often in so tight due to the crap design having the thread below the o-ring it's usually the only way to get them out.

 

[Laticsforlife]

Yup, given up for now, realised my union give free 'emergency' boiler repair so I'm phoning tomorrow.

Got my stillsons in and almost couldn't get them out, they got stuck. Don't have a small pair.

Nb Hall sensor in, red light, water, no heat.

Hall sensor out, no water, heating kicks in fine.

Seems very likely turbine needs clean or replace.