Saunier Duval Boiler problem

[badbaz]

Hi, I'm after for some advice on a pressure issue with my boiler.

It's a Saunier Duval Themaclassic F18E SB. When the heating switches on via timer the boiler won't fire because the pressure gauge is flashing showing only 1bar of pressure, the red light is also flashing. If I open the water supply valve the pressure rises and immediately the boiler fires up and will run all day.

Overnight, maybe over a couple of days the same problem occurs as the pressure drops too low. There is no sign of leaks, the radiators are all full and when bled only water comes out. It seems no matter how much I pressurise the system it drops back again and no heating!!

Thanks for looking.

 

[gas_man_gaz]

most likely ya vessel is flat or ya have a blockage in the hose to the vessel, does the pressure rise to 3 wen the heating is on? do ya have water leaking from the pipe outside?

 

[badbaz]

most likely ya vessel is flat or ya have a blockage in the hose to the vessel, does the pressure rise to 3 wen the heating is on? do ya have water leaking from the pipe outside?

is the vessel the big blue cylinder mounted above the hot water tank?

what do you mean flat?

the pressure does go up to 3 or thereabouts but not always, more so shortly after start up from cold

can't say for sure if water leaks outside or not

 

[gas_man_gaz]

its on the back of the boiler and is norm red, has a schrader valve same as ya car tyre. i mean flat as in no air in it should be charged to 1bar wen sys empty

 

[badbaz]

its on the back of the boiler and is norm red, has a schrader valve same as ya car tyre. i mean flat as in no air in it should be charged to 1bar wen sys empty

if I remove the big grey panel with the viewing window in it for the burner is it easy to get to? can i check the pressure with a tyre gauge? does this mean it just needs repressurised? is it something I can do, I have ability to get air into it if that's what I need, or is it going to need a specialist?

thanks for the advice

 

[gas_man_gaz]

dont take the cover off, jus look over at the back of the boiler

 

[badbaz]

dont take the cover off, jus look over at the back of the boiler

not possible for mine due to mounting position!

shall I remove the cover?

 

[gas_man_gaz]

nope, no point its on the back of the boiler

 

[badbaz]

I can see the bit you mean, well the bottom of it, connected via a flexible braided hose? If I get over the top somehow, how would I pressurize it?

 

[gas_man_gaz]

with a foot-pump, let the water out using the drain off at the bottom and leave it open whilst ya do it. your model is really common for the braided hose getting blocked tho

 

[badbaz]

Thanks for the help - today I took off the braided hose and checked to see if blocked - not sure if it may have been just barely blocked - refitted and pumped up the expansion vessel which did have pressure to begin with but not sure how much!

Time will tell if it's a success!

Cheers