Hot water demand but big delay in flame kicking in.

[electrified]

Hello

I have a Vaillant turboMAX Plus 828E and here are my issues:

-When i call for hot water there will be a short burst of hot water then goes cold ( i assume what’s in the pipe).

-Boiler flame does not kick in on demand, i’ve timed it before and it took about 1m 50s on average flow, and a bit less on a faster flow.

-Heating seems to work fine and kick in on demand via thermostat.

- May get an influx of lukewarm water then goes cold again, noticed this more in mixer shower than just running the hot tap alone.

-Looked at the output on the turbine sensor plug (RED-BLACK= 4.8V) (BLACK-GREEN= 4.8V), when i turn the hot water on the Green sort of jumps all over the place with its voltage, however flame does not kick in still.

Really strange one.

First thought is the impeller/turbine, could it be this?

Many thanks.

 

[CountryFan]

Yes it could be the be impeller/turbine. Does the micro switch make ok?

 

[electrified]

Yes it could be the be impeller/turbine. Does the micro switch make ok?

where is this located?

 

[electrified]

Yes it could be the be impeller/turbine. Does the micro switch make ok?

i will change the impeller and go from there hopefully it sorts the issue.

 

[CountryFan]

where is this located?

I might have been thinking of a different Vaillant model. Go with the impeller and don’t forget your 26.9 checks afterwards

 

[electrified]

I might have been thinking of a different Vaillant model. Go with the impeller and don’t forget your 26.9 checks afterwards

No worries.

Do you think it’s the whole aqua sensor given my voltage readings, or it’s just the plastic turbine impeller at the back?

 

[CountryFan]

Do you think it’s the whole aqua sensor given my voltage readings, or it’s just the plastic turbine impeller at the back?

I don’t know, I’ve only ever replaced the whole thing.

 

[electrified]

I don’t know, I’ve only ever replaced the whole thing.

I’ve replaced the plastic turbine and have tried the water, it still has a delay in heating the hot water and it goes lukewarm and cold still, worth mentioning that one of the propellor wings looks broken ( don’t know where the piece is), and also it is quite brittle, I had high hope that was my issue but it’s not unfortunately, any ideas??

 

[Johntheo5]

The MI's I'm looking at is a PLus 8282E but presume the 828E is the same
This model (2E) has HW pre heat.

Have you this switched on or inhibited?.
If switched on then this might account for the initial burst of HW but wouldn't think there should be much/any delay after this
If you inhibit it, run off say 5L of "HW" with the boiler switched off then switch on the boiler again and just open any HW tap just enough to get the boiler to fire up and see what happens, see does it get hot at the boiler outlet very rapidly first.

turboMAX plus combination boilers incorporate a
warmstart facility that keeps the domestic hot water
heat exchanger hot, providing an instantaneous delivery
of domestic hot water.

 

[electrified]

This one is just an 828E, does this incorporate it?

 

[Johntheo5]

I don't thik so, try just opening the hot tap just enough to get the boiler to fire up then see do you get continuous hot water just at the boile.

turboMAX plus provides both central heating and
domestic hot water, with the domestic hot water
supplied directly from the boiler. The boiler will operate
automatically to provide domestic hot water whenever a
hot water tap is opened, and automatically adjusts to
meet the demand for both central heating and domestic
hot water in the most economical way.
thermoCOMPACT provides central heating

 

[electrified]

Yes to get continuous hot water and for it to kick in take over a minute, replaced turbine impellor still same issue, is it possible it’s the hall sensor? and not the whole unit, i’ve taken the hall sensor out of its slot and spun the old impellor really fast next to the hall sensor and nothing happens, wonder if that my issue.

voltages i seem to get is 4.8v on red to black, and black to green(signal) is 4.8v with no flow, that doesn’t seem right?

 

[electrified]

okay i’ve worked something out, taking the hall sensor that sits next to the impellor out but leaving it electrically connected still. The boiler still fires up after say a minute anyway, telling me that the boiler will fire up on its own accord regardless of the signal from the sensor. So this may mean that the hall sensor is faulty and not sending the correct signal??

 

[Johntheo5]

Can't assist you there I'm afraid but it does seem to be associated with the flow required to start the boiler since you said it kicks in faster with a high(er) flow.

What is this "don’t forget your 26.9 checks afterwards" from @CountryFan post #5?

 

[electrified]

Can't assist you there I'm afraid but it does seem to be associated with the flow required to start the boiler since you said it kicks in faster with a high(er) flow.

What is this "don’t forget your 26.9 checks afterwards" from @CountryFan post #5?

yes yes higher flow faster it comes on which makes me think it’s coming on quicker because the heat exchanger is getting colder quick, making the boiler fire up but not on the hall sensors accord, maybe but i’m not sure.