Greatful for any advise re problem with Worcester Heatslave

[bluesue34]

I have a screeching noise coming from my Worcester Heatslave 15/19 oil boiler mainly when the hot tap is turned on first thing in the morning. I've also noticed that the pressure drops to zero (on the boiler gauge) when this happens.

Any advise appreciated.

TIA

 

[Burnerman]

I think it could be a good idea to first check the air pressure inside the expansion vessel.....this needs to be filled with air to around 10 psi when the boiler water pressure is at zero.
If the schrader valve emits water when pressed, the E.V is goosed.
So, set the E.V pressure (use a car foot pump) and then pressurise the boiler to 1 bar on the pressure gauge.
After that, lets assess the situation again as there could be a problem with the heat exchangers - I've had noisy circulating pumps on these, and also clattering flow switches but first things first.
John

 

[bluesue34]

I think it could be a good idea to first check the air pressure inside the expansion vessel.....this needs to be filled with air to around 10 psi when the boiler water pressure is at zero.
If the schrader valve emits water when pressed, the E.V is goosed.
So, set the E.V pressure (use a car foot pump) and then pressurise the boiler to 1 bar on the pressure gauge.
After that, lets assess the situation again as there could be a problem with the heat exchangers - I've had noisy circulating pumps on these, and also clattering flow switches but first things first.
John

Burnerman thanks for the above advice, you was spot on. The EV was full of water. I changed the EV a couple of weeks ago and all was running fine no bangs or screechs but I turned the heating off for a week as we were running low on oil. I had a delivery today and have started to use the heating again and the banging has come back. Once again it happens when the hot water is run. Any ideas please?

 

[Burnerman]

I could be adrift of the mark here, but the Heatslave water pump is used to circulate domestic hot water around the heat exchanger and the water jacket, so its off with the top of the boiler to reveal 3 bleed screws (radiator square type) on the visible pipework.
Crack these open, and see if air comes out. Theres also an auto bleed valve in there - (a circular brass thing with a car tyre dust cap on top) so see if anything comes out from there at the same time.
John

 

[bluesue34]

I could be adrift of the mark here, but the Heatslave water pump is used to circulate domestic hot water around the heat exchanger and the water jacket, so its off with the top of the boiler to reveal 3 bleed screws (radiator square type) on the visible pipework.
Crack these open, and see if air comes out. Theres also an auto bleed valve in there - (a circular brass thing with a car tyre dust cap on top) so see if anything comes out from there at the same time.
John

I've took the top off and located 2 (maybe 3) of the bleed screws. 2 of them are on the pipe work but one isn't. I can't seem to locate the auto bleed valve. The only thing I can see with a dust cap is the one on the top of the EV.

I've uploaded a photo so you have an idea of what I am looking at.

And thanks for your help, it's much appreciated.

 

[bluesue34]

I could be adrift of the mark here, but the Heatslave water pump is used to circulate domestic hot water around the heat exchanger and the water jacket, so its off with the top of the boiler to reveal 3 bleed screws (radiator square type) on the visible pipework.
Crack these open, and see if air comes out. Theres also an auto bleed valve in there - (a circular brass thing with a car tyre dust cap on top) so see if anything comes out from there at the same time.
John

I've took the top off and located 2 (maybe 3) of the bleed screws. 2 of them are on the pipe work but one isn't. I can't seem to locate the auto bleed valve. The only thing I can see with a dust cap is the one on the top of the EV.

I've uploaded a photo so you have an idea of what I am looking at.

And thanks for your help, it's much appreciated.

I'm not sure where the photos gone, I did upload it?

Edit: Can you view it here
//www.diynot.com/network/bluesue34/albums/ ?

 

[Burnerman]

Thats absolutely correct so far - 2 bleeds on the pipes and one on the top of the water jacket.
The AAV should be just forward of the flow switch (black thing on the incoming cold water main, wires coming out) just out of the photo shot and screwed into the boiler top.
As far as I know, they've all got one.....!
John

 

[holty]

you sure its not the dhw pipe work banging. e.g not clipped. is it a constant banging noise or when you just turn the taps off?

 

[bluesue34]

you sure its not the dhw pipe work banging. e.g not clipped. is it a constant banging noise or when you just turn the taps off?

It's just one clunk / bang a couple of seconds after the hot water tap is turned on.

I've done that John, air did release from one of the back bleed nuts. I'm gonna take another look now for the AAV. The bang has got quieter.


TY.

 

[oilhead]

The clunk is probably the diverter valve closing. Happens often on heatslaves. If it is annoying, then replace it.