Ferroli Hawk hot water issues.

[Armsta01]

Hello all,

I have a Hawk II that was in the property when we bought it. over the years usually when the weather gets colder, but not always, the hot water starts playing up. The boiler will fire up on hot water demand run for between 10-30 sec the water will get warm but then the boiler will shut down and the water will run cold. After a few more seconds the boiler will fire up again and the water will get warm but again after 10-30 sec it will shut down.
The CH seems to be fine radiators get to the required temp and give out plenty of heat.
I have managed to fix the problem before by replacing the thermistor/flow sensor (sorry not sure which it is) on the HW feed, this works for about 6-8 months and the problem will re-occur.
I have tried the same this time but it hasn't fixed the problem which has got me thinking that it might not be down to this sensor. Also why would so many sensors go faulty? I've currently replaced 3.
Any ideas would be greatly recieved thanks.

 

[Tibbot]

Also why would so many sensors go faulty? I've currently replaced 3.

They're not faulty. It's you choosing to replace them for a problem they don't cause.

 

[dcawkwell]

Given age of boiler I would be inclined to think block up plate heat exchanger and perhaps a passing diverter valve. I would start by mains flushing the central heating system. Can't remember the configuration of this
boiler. It may not have a plate heat exchanger.

Nothing wrong with the sensors.

 

[picasso]

No plate on this boiler, I was thinking more aps faulty perhaps.

 

[dcawkwell]

No plate on this boiler, I was thinking more aps faulty perhaps.

Yes it was ringing a bell. See ferroli was way ahead of intergas.


Can't think air pressure switch would be the cause as it would be the same on central heating.

I would check boiler is correctly modulating. Sounds like it isn't.

 

[Armsta01]

No plate on this boiler, I was thinking more aps faulty perhaps.

I wasn't expecting such quick replies, thanks. Forgive the ignorance but is a faulty air pressure switch something I could have a look at myself or is it going to be a call to a service engineer?

 

[Armsta01]

I would check boiler is correctly modulating. Sounds like it isn't.[/quote]

Thanks for the reply, I'm presuming I would need an engineer to check the modulation?

 

[Armsta01]

No plate on this boiler, I was thinking more aps faulty perhaps.

Yes it was ringing a bell. See ferroli was way ahead of intergas.


Can't think air pressure switch would be the cause as it would be the same on central heating.

I would check boiler is correctly modulating. Sounds like it isn't.

I'll try that again, sorry, just getting to grips with this forum thingy!
Presumably I would need an engineer to check the modulation?

 

[picasso]

I think an engineer would be your best choice, please post back the fix.

 

[dcawkwell]

Yes. He should be able to put a pressure guage on it and monitor the
gas mb pressure the boiler is applying to the burner. If it is running
flat out the water will rapidly heat up and then the boiler cuts off.

 

[Armsta01]

Ok so I'm not sure if the plot has thickened. As a last ditch attempt I thought I would have one last go at swapping the DHW temperature sensor. Pointless exercise, possibly, but here's what has happened.

1. Switched the water off at the stop cock
2. Loosened the sensor and allowed the system to drain
3. Replaced the sensor with a spare, which has been in the boiler before with the same symptoms as previously posted.
4. Turned the water back on and ran the cold water.
5. Turned cold off and ran hot water, a bit of spluttering for the system to refill and the boiler fires up.
6. The boiler then ran with no problems giving lots of very hot water until I turned the water off.
7. Switching the hot water back on, the boiler reverted back to the original problem, only now the water is getting hotter before shutting down.
8. Last night before any of this, the HW ran long enough to run a bath.

I've posted a picture of the sensor I've taken out compared with another spare! (I've got a few!) View media item 72140
Are we still looking at a modulation problem, as well as this sensor? should I just be replacing this sensor every 6 months?

Thanks again.

 

[dcawkwell]

Ok so I'm not sure if the plot has thickened. As a last ditch attempt I thought I would have one last go at swapping the DHW temperature sensor. Pointless exercise, possibly, but here's what has happened.

1. Switched the water off at the stop cock
2. Loosened the sensor and allowed the system to drain
3. Replaced the sensor with a spare, which has been in the boiler before with the same symptoms as previously posted.
4. Turned the water back on and ran the cold water.
5. Turned cold off and ran hot water, a bit of spluttering for the system to refill and the boiler fires up.
6. The boiler then ran with no problems giving lots of very hot water until I turned the water off.
7. Switching the hot water back on, the boiler reverted back to the original problem, only now the water is getting hotter before shutting down.
8. Last night before any of this, the HW ran long enough to run a bath.

I've posted a picture of the sensor I've taken out compared with another spare! (I've got a few!) View media item 72140
Are we still looking at a modulation problem, as well as this sensor? should I just be replacing this sensor every 6 months?

Thanks again.

Faulty wire or contacts.

 

[Armsta01]

Hot Water!!
Thanks to everyone for their suggestions. I now have a happy wife!
It was indeed a poor connection between the DHW sensor and the connector. I have prised open the prongs a little on the sensor to make the connection tighter and now have a fully functioning boiler.