Baxi 105HE - New condensate tank fitted now losing pressure

[mike1975]

Hi everyone,

Yesterday I noticed a small pool of water under my boiler, when I checked the condensate tank was leaking. The plastic cap at the top that the flexible hose connects to had cracked off. I've fitted a new tank and it's now bone dry. However I've noticed that the tank fills up in about 5 mins and starts to drip down the white plastic pipe that drains outside.

Ever since then the pressure has been dropping rapidly. Half a bar in 30 mins. I've checked all the rads and they are all dry. The thing is is that I'm not sure if the two are related. The boiler may have been on very low pressure for a while as I haven't checked for ages. However the heating has been working fine so I wouldn't have thought so. When I changed the tank the pressure was zero so surely the heating wouldn't have worked at this low pressure.

Any help would be really gratefully accepted.

Thanks
Mike.

 

[rojaca]

I'm presuming you're on about the condensate trap. (Clear plastic box on bottom rhs of blr) Chamnging this trap would have no effect whatsoever on your system pressure.
Things to check for first.
1. Water at PRV terminal (safety pipe going outside).
2. Any other external leaks to blr.
3. Set pressure when system cold. Typically between 1- 1.5 bar
What is pressure rising to when heating on. Pressure will rise but should not reach 3 bar. (above 3 bar will cause symptom 1.
Any of the above will cause system to loose pressure.

If you do not have any of the above I will be necessary to determine whether your system is losing pressure on the blr or on the system.
To do this allow the system to cool- usually a couple of hours willl do.
Increase system pressure to approximately 2bar or so.
Make amark on pressure gauge where needle is.
Isolate system on flow and return isolation valves. Far left and far right pipes.
I usually leave overnight which will show biggest pressure drop, but as your dropping pressure so quickly a couple of hours will do.
Come back to blr. DO NOT OPEN ISOLATION VALVES YET.
Check pressure gauge. If pressure has dropped now leak is on BLR and most likely secondary ht exch.
If gauge not moved noticably, open isloation valves. If pressure drops now your leak is on htg system (under floor, screeded areas etc)
Good luck

 

[mike1975]

I'm presuming you're on about the condensate trap. (Clear plastic box on bottom rhs of blr) Chamnging this trap would have no effect whatsoever on your system pressure.
Things to check for first.
1. Water at PRV terminal (safety pipe going outside).
2. Any other external leaks to blr.
3. Set pressure when system cold. Typically between 1- 1.5 bar
What is pressure rising to when heating on. Pressure will rise but should not reach 3 bar. (above 3 bar will cause symptom 1.
Any of the above will cause system to loose pressure.

If you do not have any of the above I will be necessary to determine whether your system is losing pressure on the blr or on the system.
To do this allow the system to cool- usually a couple of hours willl do.
Increase system pressure to approximately 2bar or so.
Make amark on pressure gauge where needle is.
Isolate system on flow and return isolation valves. Far left and far right pipes.
I usually leave overnight which will show biggest pressure drop, but as your dropping pressure so quickly a couple of hours will do.
Come back to blr. DO NOT OPEN ISOLATION VALVES YET.
Check pressure gauge. If pressure has dropped now leak is on BLR and most likely secondary ht exch.
If gauge not moved noticably, open isloation valves. If pressure drops now your leak is on htg system (under floor, screeded areas etc)
Good luck

Hi thanks for your reply. I set the pressure to 1.5 and it rises to about 2 while the heating is on. I think I need to do your checks. Are the isolation valves the Heating Flow and the Heating return valves?

Thanks again.

 

[mike1975]

I did as you said and the pressure still dropped while the boiler was isolated. What should I do next? Is there any way I can check if it's secondary heat exchange. Is it something I can change myself?

Thanks

 

[ChrisR]

I set the pressure to 1.5 and it rises to about 2 while the heating is on.

It would, cos the water expands.

Turn the boiler OFF at say 9pm and don't use the HW so it's all cold when you go to bed,. Then close the Flo and Ret iso valves, and check the pressure in the morning.

 

[mike1975]

I set the pressure to 1.5 and it rises to about 2 while the heating is on.

It would, cos the water expands.

Turn the boiler OFF at say 9pm and don't use the HW so it's all cold when you go to bed,. Then close the Flo and Ret iso valves, and check the pressure in the morning.

Yeah I understand that I was just confirming what I'd been told to do in the previous post. I've isolated the boiler and the pressure still drops quickly. It was on zero when I got up this morning. The boiler still works though and the rads get hot. Is it defo the second heating exchange unit?

Cheers

 

[gas4you]

If it was the plate HE I would expect the pressure to keep rising rather than falling as the cold mains pressure will probably be greater than the system pressure.

Can you see exactly where the water is leaking to? Is the condensate pipe constantly running?

I have yet to see one of these, or any of its derivitives, that have actually ever condensed.

 

[mike1975]

If it was the plate HE I would expect the pressure to keep rising rather than falling as the cold mains pressure will probably be greater than the system pressure.

Can you see exactly where the water is leaking to? Is the condensate pipe constantly running?

I have yet to see one of these, or any of its derivitives, that have actually ever condensed.

When I changed the condenstate tank and turned the boiler back on the tank filled up after about 3 mins and started dripping down the exit pipe (white plastic) that goes outside to the drain. The water trickled down the black hose that connects to the top of the tank it filled up the side of the tank and then spilled over into the other side and out down the white plastic pipe.

Just to confirm the water was running down the inside of the pipes as it should it wasn't leaking.

I can't see any leaks anywhere inside the boiler it all looks bone dry.

 

[mike1975]

Bump

 

[gas4you]

From sitting here I would suspect the main HE is leaking.