Firebird Combi - No hot water

[GizFab]

Evening Folks.

Struggling to get Hot Water in my boiler. I replaced the circulation pump last week which fixed the heating, But since fixing the central heating i've developed an issue with the hot water side of things.

> Turn Tap On
> 10 seconds Cold Water (Normal)
> 20-30 Seconds of scolding hot water
> Water goes Cold
> Boiler fires up, Shuts off after 2-3 seconds
> (Hot water Tap still flowing)
> 10-20 Seconds later, we get Scolding Hot water at the Tap again
> Water goes Cold
> Boiler fires up, Shuts off after 2-3 seconds
> (Hot water Tap still flowing)
> 10-20 Seconds later, we get Scolding Hot water at the Tap again

Rinse and repeat. It seems the boiler is being fired up to provide hot water, but as soon as the boiler fires up, its shut down. I'm pretty sure my system has two pumps. Is the hot water received at the taps as a result of the boiler turning the pump on?

The Central Heating side of the system works.

 

[muggles]

Firebird have made a lot of different combis, which model do you have?

 

[GizFab]

Enviromax 90 if i remember correctly. Identical to this model externally.

https://www.boilerguide.co.uk/data/imagecache/content_images/wpimages-boilerguide.co.uk/2016/11/15160350/Firebird-ENVIROMAX-COMBI-Oil-Boiler-12-20kW-243x300.jpg

Someone suggested it is the water flow sensor, but i cannot seem to locate this sensor. Tracing the wiring from the board doesnt find any other sensor i havn't already found

 

[oilhead]

The flow sensor is a small capillary on the cold inlet to the DHW heat Exchanger.

 

[Hairymelon]

if it has 2 pumps , if the hw heat bank is hot then the fault is either dhw flow switch not calling or plate hex is blocked with system carp

 

[GizFab]

After spending 3 hours trying to find a plumber to come and have a look and failing, understandably every ones busy this close to Crimbo. (Not a chance till near year).

I did stumble across one gent who couldn't apologise enough for not being able to come have a look, but after describing the Diag over the phone he diagnosed the issue to be the Plate Exchanger at the front of the boiler. Unable to get one until early next week.

I resorted to giving the current plate exchanger some light taps with a hammer and i appear to have hot water again (Enough for a shower at least)