Ravenheat CSI 85 Combi Boiler - Pressure Keeps Dropping

[walkthewalk]

I have a Ravenheat CSI 85 Combi Boiler. The pressure gauge keeps dropping down to between 0 and 0.25 bar.

I have read these posts that talk of the Pressure Relief Valve:
//www.diynot.com/forums/viewtopic.php?t=83966
//www.diynot.com/forums/viewtopic.php?t=37170&start=0&postdays=0&postorder=asc&highlight=

I’ve left a tin under the Pressure Relief Pipe to see if water is escaping here, but nothing.

I’ve taken the front off the boiler and I can’t see any leakage inside.

If I look at the bottom rear left of the boiler (with the front off), the clear condensing box is quite full of water. Not sure if this is where all the water is going? I can’t really tell as the pipe connecting this is plumbed into the kitchen sink waste.

I flushed the CHS two weeks ago and added inhibitor. Bleed the radiators several times. Could the dropping pressure somehow be related to this?

Any ideas greatly appreciated.

 

[twgas]

did you top up the pressure after each time you bled the rads?

 

[walkthewalk]

did you top up the pressure after each time you bled the rads?

Yes I did. I had my son at the filling loop, pressurising back to 1 bar after I bleed each rad.

 

[bengasman]

How long to fall from 1 bar to 0?

 

[walkthewalk]

How long to fall from 1 bar to 0?

A couple of hours roughly.

 

[walkthewalk]

Slight addition to the story..... regarding the small transparent condensing tank to the rear left bottom of the boiler I noticed was full of water.

I noticed a small puddle of water under the boiler and investigated.

The tank is plumbed into the kitchen sink waste U-bend. I disconnected it and found it blocked with U-bend scuzz. Once I cleared it out with a screw driver, the tank emptied. It has obviously overflowed and caused the puddle.

Could that somehow be causing my problem?

I’ve refilled to 1 bar, bleed all rads (which seemed had very little air) so will see what the pressure’s like in the morning. After about 30 mins no change.

BTW, that condensing tank has about 1cm of black sediment at the bottom. I don’t know if that’s normal? Boilers 4 years old.

 

[bengasman]

Bleed all rads before you go to sleep.
TURN BOILER OFF AT THE SPUR, and make sure nobody turns it on.
Pump system up to 2 bar
Close isolation valves for flow and return off.
Check the pressure in the morning, if it is still 2 bar, you have a leak in the system.

 

[walkthewalk]

Bleed all rads before you go to sleep.
TURN BOILER OFF AT THE SPUR, and make sure nobody turns it on.
Pump system up to 2 bar
Close isolation valves for flow and return off.
Check the pressure in the morning, if it is still 2 bar, you have a leak in the system.

Ok I've done that.

Does that mean:
Pressure drop tonight=leak in the boiler
No pressure drop tonight, but drop after I open isolation valves=leak in the pipework or rads?

Thanks for the troubleshooting tips.

 

[kevplumb]

Does that mean:
Pressure drop tonight=leak in the boiler
No pressure drop tonight, but drop after I open isolation valves=leak in the pipework or rads?

yup

 

[walkthewalk]

Checked the pressure in the isolated boiler this morning. It had dropped from 1.9bar to 1.2bar.

Guess that means the leak is in the boiler. I had a good look for water leaks, but could spot nothing.

That got me thinking….. I turned the boiler on for a bit last night with the condensing pipe still disconnected from the sink U-bend. There did seem to be a noticeable trickle of water coming out.

I have a theory (which admittedly the seed was planted in my mind by a Central Heating Engineer who’s looked at the boiler before): Could the leak be in the condensing heat exchange, with the water leaking into the condensing drain tank? Is there anyway of verifying that? Is it replaceable? The CH Engineer reckons that Ravenheat ones are aluminium and corrode and perforate easily.

Any other ideas/advice gratefully received.

PS. Is it ok to run a combi in just DHW mode whilst the CHS is isolated?

 

[twgas]

Although your findings may indicate a leak in the condensing h/ex, it doesn't sound as though you followed through the tests as instructed, therefore I would sugest you do as bengasman said and report back again tomorrow.

 

[SortedPlumbing]

Condensing Hex is prone to leak on these!

An easy way to test is to turn boiler off, isolate it from system, disconnect condesate connection( a job for a Gas installer - as it is connected to Products of Combustion!)

If when condensate connection is disconnected and your getting a steady flow of water from it - this would indicate that the Hex has a pinhole leak inside it! (Not cheap part)

Good Luck

 

[walkthewalk]

Although your findings may indicate a leak in the condensing h/ex, it doesn't sound as though you followed through the tests as instructed, therefore I would sugest you do as bengasman said and report back again tomorrow.

Was it the fact that I didn't go right up to 2bars or did I misunderstand something else? It didn't really seem to want to go higher than 1.9 and there was a lot of creaking.

Just to be crystal clear, this is what I did:
1. Bleed all rads
2. Turn off electricity supply to boiler
3. Pump system up to 1.9bar
4. Close flow and return isolation valves
5. Check the pressure before turning the isolation valves back which read 1.2bar, about 10 hours after step 4.
6. Turned the isolation valves back on, about 45 mins after step 5 and noticed the pressure read 0.25 bar.

What bit(s) did I screw up?!

 

[walkthewalk]

Condensing Hex is prone to leak on these!

An easy way to test is to turn boiler off, isolate it from system, disconnect condesate connection( a job for a Gas installer - as it is connected to Products of Combustion!)

If when condensate connection is disconnected and your getting a steady flow of water from it - this would indicate that the Hex has a pinhole leak inside it! (Not cheap part)

Good Luck

Ouch... the parts £145 on ebay
http://cgi.ebay.co.uk/Ravenheat-CSI...arden_Hearing_Cooling_Air?hash=item334f7b0e24

Any idea how long removal, test, refit would take?

 

[SortedPlumbing]

It isnt the hardest part to change but bulky to remove and takes a wee bit shaking around! :
Flue Bend needs to be removed and the fan, drain boiler down, water and condensate connections, Defo a job for Gas Safe Engineer