Vokera Linea 730 - dropping pressure

[jaw]

Hi

I was called to the boiler as it was dropping pressure over a 24 hour period. I have checked most of the pipework, radiators and valves without finding any leaks. I have not been able to check them all as the builders who have added extensions over the years have blocked / built walls under the floor boards which as prevented me gaining access to certain areas. I have also checked the soundness of the expansion vessel and its pre-charge pressure, this is OK. When I tested the PRV I found that it was passing, so I have replaced it. Job done I thought until the customer called me today to say that the pressure had still dropped. During our conversion he mentioned that when the heating was on the gauge was at a steady 2 bar for a while before rising to 3 bar. He then switched it off for a while before switching it back on again. The pressure on the gauge had dropped to 0.5 bar.

Due to not being able to gain access to all the pipework under the floors I can only think of isolating the boiler from the flow and return pipes before testing the pipework with a test pump. If a drop is seen then the customer will seriously need to think about ripping up floorboards to locate the offending pipe.

Are the any other faults that could be causing the problem - my head is starting to hurt now !!!:6:

 

[woodsy]

I would suggest that from your post that the problem is boiler related and not system related.

 

[jaw]

Thanks Woodsy, any ideas on the possible boiler problem?

 

[woodsy]

I would be getting customer to check prv discharge point again when boiler running at 3bar as i would suspect that this will be where you are losing pressure.

 

[jaw]

But the PRV (which I replaced yesterday) will discharge pressure when it reaches 3 bar, it doesn't explain the total drop over 24 hours. Hope I understood your post correctly.

 

[rm1]

jaw check the flexible pipe that goes from the pump to the expansion vessel there will be a blockage causing the boiler to over pressurise resulting in the water discharging from the prv

 

[jaw]

RM1, why would this then cause the boiler pressure to drop down to the point where it locks out? I will check it though

 

[rm1]

jaw think about it if there is a blockage where can the water expand too, it blows off from the prv then when the water cools the volume decreases resulting in a loss in water pressure

 

[jaw]

Got ya, when the water cools could it drop the pressure by that much that the boiler locks out? Have you had this problem before? Could there be any other blockages elsewhere that could be causing the problem?

 

[rm1]

remember you are actually losing water from the prv aswell i have had this several times on many boiler types if you think there may be a water leak under the floor why dont you isolate the flow and return at the boiler and leave it over night return in the morning and check that the water pressure level is the same when you left it if it is not then the boiler is losing pressure and needs investigated if the pressure is still the same open up the flow and return valves if the water falls on the boiler this will confirm that you have a leak on the pipe-work

 

[jaw]

Yes, that makes sense

 

[jaw]

Just thinking RM1, if i decide instead to use a test pump on the pipework to check for leaks how many bar would you suggest it be tested at and what sort of time length would I expect to see a drop?

Thanks

 

[rm1]

if you carry out the tests i have given you you will not need to carry out a pressure test good luck let me know how you got on

 

[Nas]

jaw think about it if there is a blockage where can the water expand too, it blows off from the prv then when the water cools the volume decreases resulting in a loss in water pressure

The very narrow pipe going to the EV could be blocked hence causing the PRV to discharge.

 

[jaw]

Nas, you're an absolute star. Stripped the flexible pipe to the expansion vessel this morning - it was bunged up to buggery! Cleaned and refit it, all back to normal. The customer has had this problem for the last 2 - 3 years, They've been topping up the system daily! Four different plumbers have looked at it over the years without success. Makes you feel good when you solve it, customer well chuffed. Thanks again.

 

[maks_rt_011]

Your expansion vessel is flat , pump it up to 1.3 then check how it running , your pressure should stop rising so much and PRV won't loose any water.

 

[Nas]

Nas, you're an absolute star. Stripped the flexible pipe to the expansion vessel this morning - it was bunged up to buggery! Cleaned and refit it, all back to normal. The customer has had this problem for the last 2 - 3 years, They've been topping up the system daily! Four different plumbers have looked at it over the years without success. Makes you feel good when you solve it, customer well chuffed. Thanks again.

Very common problem on vokeras with the flexi pipe.