No hw - heatline vizio 24...pcb?

[GasMan1983]

Hi,

Been out to see a lady with a heatline vizio 24.

Symptoms:
CH is fine, no HW.

When i put the appliance into "summer mode/hw only" and run a tap, the pump runs but the fan doesn't.

When in "winter mode/ch+hw" the CH operation IS interupted by the dhw demand. However again only the pump runs, it doesn't go any further down the ignition sequence.

I initially thought i had a flow sensor/housing issue as i had no indication from LED's(possibility there isn't supposed to be) but have now come to the conclusion as the CH is interupted then the chb recognises a demand for hot water. So therefore confiming flow sensor/housing is operating correctly.

I believe the PCB has an intermittant fault causing it to falter as it begins the ignition process for dhw demand.

Can anyone chime in with they're thoughts or past experience?

thanks in advance.

 

[Billy Bob Bob]

i dont think its anything to do with the pcb,check the diverter valve/motor

 

[GasMan1983]

Surely the pump wouldn't run though unless the motor has moved into dhw position?

 

[GasMan1983]

Ok so fixed the hw problem. Ita was the dhw sensor.
Reason the pump was running only was because chb thought it had to get rid of the heat.

 

[Simon Kelly]

Can I just ask gas man a question.

I have a Vizo 24 and contary to all other posters it has been fine for 5 years, unfortunately this morning the hot water wont come on(switched to winter mode and heating is fine). I have had a friend round to have a look and we came to the conclusion that it may be the DHW sensor too.

Just to clarify - how does the sensor control the valve motor, as I thought the sensor was a simple thermostat - just so I can understand the problem a little more.

Si

 

[RoryD]

I just spent 3 days with parts etc... measuring flow switch voltages at the board - 5vdc out and a variable voltage dc back, if thats ok then the flowswitch is good. Please check the dhw out and the mains in are correct way round (which was my prob). Ask if it's EVER worked!! I'm reliably informed usually it's the interface board

 

[Billy Bob Bob]

Can I just ask gas man a question.

I have a Vizo 24 and contary to all other posters it has been fine for 5 years, unfortunately this morning the hot water wont come on(switched to winter mode and heating is fine). I have had a friend round to have a look and we came to the conclusion that it may be the DHW sensor too.

Just to clarify - how does the sensor control the valve motor, as I thought the sensor was a simple thermostat - just so I can understand the problem a little more.

Si

by dhw sensor i believe you are referring to the dhw thermistor in which case you need to measure the sensors resistance should be 11.5 k cold it has no bearing on the valve motor it tells the gasvalve via the pcb to modulate up/down or off

 

[Billy Bob Bob]

I just spent 3 days with parts etc... measuring flow switch voltages at the board - 5vdc out and a variable voltage dc back, if thats ok then the flowswitch is good. Please check the dhw out and the mains in are correct way round (which was my prob). Ask if it's EVER worked!! I'm reliably informed usually it's the interface board

and from experience with tatline technical i can reliably inform you its unlikely to be the interface pcb,what fault symptoms are there?

 

[Simon Kelly]

by dhw sensor i believe you are referring to the dhw thermistor in which case you need to measure the sensors resistance should be 11.5 k cold it has no bearing on the valve motor it tells the gasvalve via the pcb to modulate up/down or off

Right then that sorted I was looking at the thermistor.

What controls the valve motor to tell the boiler that I want hot water only. The pin in the valve motor seems to work fine when isolated.

Obviously there must some kind of flow switch that is sticking or worn out(the manual doesnt make it aboundantly clear were it is), or the PCB has gone in which case I will reluctantly have to get a new boiler something I could do without at the moment.

Once again thanks for the previous reply

 

[Simon Kelly]

I've now found were the flow sensor is after looking at the updated manual on the Heatline website.


I am going to have a look tonight and will inform with progress.

Any tips

 

[Simon Kelly]

Right Ive had the DHW sensor out and replaced to no effect.

Any other suggestions?

How can I check the sensor electrical connection?