Worcester Bosch Oil Heatslave 26/32 Overpressure

[geoffkimpton]

My 26-32 Boiler is overpressuring on the heating circuit.
About 3-4 hours use & the pressure gauge hits the limit, if left if will leak from underneath the boiler.
At present i am draining water from the nearest radiator to relieve pressure.
The servicing instructions have a fault finding chart but not including this problem.
Anyone encountered this problem before?

 

[Burnerman]

Most likely, the filling loop is open a fraction....its best to actually disconnect it if possible.
John

 

[geoffkimpton]

Thanks John but the filling loop has 2 isolation taps, both closed.
Also the pressure only increases when the heating is on. Have tried leaving it off for a couple of days & no pressure increase.

Most likely, the filling loop is open a fraction....its best to actually disconnect it if possible.
John

 

[Burnerman]

Ok, if you are sure that the filling loop is not letting water through, the next thing is to check the expansion vessel for air pressure. (The pressure in your boiler will always increase when the CH is on....this extra pressure should be catered for via the expansion vessel).
The system needs to be depressurised for this, so bleed water out of a convenient rad valve until the gauge reads zero. Then, check the pressure in the EV using a car tyre pressure gauge. (If water spurts out of the valve then the EV is scrap).
Repressurise the EV to 10 psi using a foot pump, then repressurise your system up to 1 bar using the filling loop.
If this still fails, then we may suspect a leak between the HW and CH heat exchangers, I'm afraid.
John

 

[geoffkimpton]

When i bleed water out of nearest rad the pressure gauge shows .5 bar even when water stops running. maybe the gauge is inaccurate.
Pumped EV to 10 psi, showing 1 bar on gauge.
As i already had 1 bar showing I did not open filler. Pressure rose by .2 bar in 5 mins.
I fear you may be correct about the leak between heat exchangers as im thinking where is the CH getting its water from when i,ve been draining 2-3 liters of water a day for several weeks without ever opening the filler!

Ok, if you are sure that the filling loop is not letting water through, the next thing is to check the expansion vessel for air pressure. (The pressure in your boiler will always increase when the CH is on....this extra pressure should be catered for via the expansion vessel).
The system needs to be depressurised for this, so bleed water out of a convenient rad valve until the gauge reads zero. Then, check the pressure in the EV using a car tyre pressure gauge. (If water spurts out of the valve then the EV is scrap).
Repressurise the EV to 10 psi using a foot pump, then repressurise your system up to 1 bar using the filling loop.
If this still fails, then we may suspect a leak between the HW and CH heat exchangers, I'm afraid.
John

 

[slapper]

Turn the cold feed off to the Heatslave tank,youll get no hot water.

Thats gonna stop water entering the domestic side, run the central heating and see if the pressure goes up,also recheck as John says,the EV for a perforated diaphragm ie water out of the schrader valve.

 

[slapper]

Also disconnect the filling loop,dont assume because theyre in the closed position that water isnt passing by

 

[theplumberkev]

hi, regarding your increasing pressure. It can be only two things:

if the pressure increases when the boiler is both on and off, ; your heat exchanger is allowing mains pressure domestic water to pass into your heating circuit. Repair by replacing the heat exchanger, simple job 4 nuts to slacken, flow switch to remove and just a partial drain down, should take you around 1 hour.

If the pressure raises only when boiler is on, expansion vessel is faulty, don't mess about simply replace it, again simple job, 30 mins at most.

regards kev.