Vaillant turbo max plus 824 E dhw problems

[rayplumber]

Coustomer called me out today as dhw was running hot cold hot cold boiler was showing no faults so replaced the plate heat exchanger but problem still is there tried changing ntc sensors around still happening any thoughts would be greatly appreciated. Boiler does not seem to be modulating does any one know the ohms that should be at the nct and volts at the gas valve cheers :dizzy2:

 

[RGII79]

check flow turbine

 

[RGII79]

Aqua sensor

 

[rayplumber]

aqua sensor is that the ntc on the plate heat exchanger return

 

[rayplumber]

the flow turbine how do i check this mate

 

[RGII79]

Get the manual for the boiler and youl see where it is and clean the impellar in the aqua sensor
its the dhw flow switch to the right hand side of the plate hexchanger

 

[rayplumber]

will try this tomorrow mate thanks very much this boiler has my head done in is there a way of seeing if it is faulty cheers

 

[Millsy 82]

If the HW sign comes on the display and stays on it wont be the aqua sensor. If the boiler isnt modulating and fires up then goes off then it will prob be a circulation problem. Are you GSR?

 

[RGII79]

If the HW sign comes on the display and stays on it wont be the aqua sensor. If the boiler isnt modulating and fires up then goes off then it will prob be a circulation problem. Are you GSR?

what controls the modulation on dhw millsy

 

[rayplumber]

yes gsr tried swapping the nct sensors do you know the voltage that is meant to be at the modulating end of gas valve is it 24v dc i was thinking check if the right voltage is at gas valve then if the voltage is there it must be gas valve thought it was a nice easy dhw heat exchanger the nature of the beast lol any help would be greatly appreciated

 

[rayplumber]

i thought the nct sensors control the modulating side of gas valve is it the aqua sensor on these?

 

[Millsy 82]

what controls the modulation on dhw millsy

Unless I'm thinking of the wrong part the aqua sensor is the DHW flow switch so to speak modulation is controlled by the DHW temp sensor.

 

[Millsy 82]

It is best to speak to vaillant whilst in front of it to find out the resistance accross sensors. Does the water get scalding hot?
Do you know which gas valve is in it?

 

[rayplumber]

thats what i thought does the aqua sonsor just switch the boiler over to dhw mode it seems this boiler heats the water fine and while watching the display the temp keeps going up to 62 then boiler goes out but no faulds on boiler display my brain automatically thought plate heat exchanger but changed and problem still exists was trying to test the resistance on the nct sensors i beleive thay should be 3400 when at 20 degrees c is this right

 

[RGII79]

if you open your hot water outlet tap to full flow to achieve a set temp then turn it down to a dribble what tells the boiler the amount of water passing through

 

[rayplumber]

mmm you might be right but on other boilers the thermistor or nct tells the gas valve the temp of flow return and then the gas valve responds to this and modulates the gas to keep to temp. its funny how it shuts gas off at 62 though every time then stays off until temp display goes to 45 then relights proper head banger lol

 

[Millsy 82]

The flow of water makes no difference the aqua sensor only tells the boiler that water is flowing through it.

Not sure what the resistances are off the top of my head I always double check with manufacturers whilst on site (Easier said than done with vaillant tech though as they do tend to take a while to answer)

 

[RGII79]

The flow of water makes no difference the aqua sensor only tells the boiler that water is flowing through it.

Not sure what the resistances are off the top of my head I always double check with manufacturers whilst on site (Easier said than done with vaillant tech though as they do tend to take a while to answer)

so the speed the impellar moves doesnt effect the amount of heat needed to heat the required flowrate

 

[Millsy 82]

so the speed the impellar moves doesnt effect the amount of heat needed to heat the required flowrate

No it just acts as a flow switch.

 

[rayplumber]

rg1179 have you ever changed a aqua sensor if so how did you diagnose it then i will go and try with this cheers

 

[RGII79]

No it just acts as a flow switch.

if its just a flow switch how does it modulate

the aqua sensor/ halls sensor is an accurate way of maintaining constant hot water temp.reads the flow rate to give precise modulation

 

[RGII79]

seen a few inpellars cracked or badlly worn sending incorrect reading to pcb

 

[rayplumber]

so any one done anything with aqua sensors before and does the dhw sensor and the flow sensor ie sensor on the flow side of main heat exchanger create the voltage for the modulating side of gas valve and if so does any one know the voltage that should be produced at the gas valve

 

[rayplumber]

i will check the aqua sensor then if not replace nct sensors then if that doesnt work i think i will give up and give them a new boiler for free lol

 

[RGII79]

you will get readings from ntc hot water outlet and ntc plate heat exchanger too yes youll need to get values from vaillant