Too much condensate flowing?

[Bp89]

I have noticed recently that when I switch on the boiler to heat hot water, the amount of condensate flowing is much more noticeable than usual, in fact, noticeable by the noise of the water running. Usually, you barely hear the condensate flowing. On the other hand, when the Central Heating is switched on the condensate cant be heard. Is there an issue with the boiler? I have a Bosch Greenstar Ri 24kw and a Heatrae Sadia unvented cylinder.

Thanks.

 

[Last Plumber]

Is it flowing when the boiler is not in use?
Is it loosing pressure on the heating side?
If not, it will probably be OK. Condensing is a sign of efficiency. If you're worried, get an engineer out to it. there is nothing you can really do yourself.

 

[Bp89]

Is it flowing when the boiler is not in use?
Is it loosing pressure on the heating side?
If not, it will probably be OK. Condensing is a sign of efficiency. If you're worried, get an engineer out to it. there is nothing you can really do yourself.

Thanks. The condensate doesn't appear to be flowing when the boiler is not in use and heating the radiators appears to be OK. However, its been pointed out to me that an external copper pipe at the front of the house is dripping water but this only happens when the boiler is heating water and not when the central heating is on.

 

[John.g]

If the boiler is fully condensing (highly unlikely) then the very max condensate flow at a boiler output of say 30kw (combi on HW) will be ~ 3.5/4.0 LPH or 58/67 ml/min, normally one might get 25ml/min or so. The condensate should have its own waste pipe but sometimes the TPRV and the expansion relief valve tundish waste is teed into this or visa versa so check these individually if possible when heating DHW.

 

[Bp89]

If the boiler is fully condensing (highly unlikely) then the very max condensate flow at a boiler output of say 30kw (combi on HW) will be ~ 3.5/4.0 LPH or 58/67 ml/min, normally one might get 25ml/min or so. The condensate should have its own waste pipe but sometimes the TPRV and the expansion relief valve tundish waste is teed into this or visa versa so check these individually if possible when heating DHW.

The condensate does have its own waste pipe and I observed the tundish with the boiler heating hot water only and there was no dripping/flowing of water.

 

[John.g]

Can you run this into a container for say exactly 30sec or 1min and then measure it?

 

[Bp89]

Can you run this into a container for say exactly 30sec or 1min and then measure it?

Do you mean from the boiler condensate or the exterior discharge pipe? I can't access the boiler condensate pipe and the exterior discharge pipe shouldn't really have any water dripping from it in normal circumstances, should it?

 

[John.g]

The condensate does have its own waste pipe and I observed the tundish with the boiler heating hot water only and there was no dripping/flowing of water.

Comdensate Pipe: Normally there will/should be no discharge with burner off and only dripping with burner in service. If the condensate discharge is excessive then maybe a crack in the combustion chamber that only appears with burner firing, if so then the boiler pressure (if not a open vented system) should start falling. If you have a pressurized system then check that the make up isn't via a auto top up system

Exterior discharge pipe: If from the boiler PRV (pressure refief valve), then this should never leak. again as in the above the boiler pressure should fall excelt with auto top up.

If a combi boiler could be a leak in the plate heat exchanger.

I

 

[Bp89]

Comdensate Pipe: Normally there will/should be no discharge with burner off and only dripping with burner in service. If the condensate discharge is excessive then maybe a crack in the combustion chamber that only appears with burner firing, if so then the boiler pressure (if not a open vented system) should start falling. If you have a pressurized system then check that the make up isn't via a auto top up system

Exterior discharge pipe: If from the boiler PRV (pressure refief valve), then this should never leak. again as in the above the boiler pressure should fall excelt with auto top up.

If a combi boiler could be a leak in the plate heat exchanger.

I

Thanks. I think it's time for a service. I don't have a Combi boiler and the exterior discharge is through a 22mm pipe which I understand is linked to the cylinder on the first floor but as I explained earlier there is no dripping of water into a tundish which rules out the cylinder. If there is a major issue with the boiler, shouldn't the condensate be running strongly when the CH is on and not just when HW is on?

 

[John.g]

There is also generally another pressure relief valve installed, it's on the cold feed to the cylinder and is called a expansion valve which is set lower than the TPRV on the cylinder, the TPRV is set to 7bar and the expansion valve is set to 6bar so will open every time the cylinder is heated if a failed E.vessel or cylinder air bubble, this would generally be tied into the same waste pipe as the TPRV.

Have you checked if the cold water feed (top up) isolating valve to the boiler is shut or if its fed via that auto top up valve, it would seem that the most obvious problem is that the expansion valve is lifting/leaking for one reason or the other and that it's waste pipe is connected to the condensate waste pipe since, as you say, the condensate only runs strongly when the HW heating is on. Next time the HW heating is on, crack open a HW tap and see if the condensate flow stops.

 

[Bp89]

There is also generally another pressure relief valve installed, it's on the cold feed to the cylinder and is called a expansion valve which is set lower than the TPRV on the cylinder, the TPRV is set to 7bar and the expansion valve is set to 6bar so will open every time the cylinder is heated if a failed E.vessel or cylinder air bubble, this would generally be tied into the same waste pipe as the TPRV.

Have you checked if the cold water feed (top up) isolating valve to the boiler is shut or if its fed via that auto top up valve, it would seem that the most obvious problem is that the expansion valve is lifting/leaking for one reason or the other and that it's waste pipe is connected to the condensate waste pipe since, as you say, the condensate only runs strongly when the HW heating is on. Next time the HW heating is on, crack open a HW tap and see if the condensate flow stops.

I'll try your HW tap suggestion tomorrow.

 

[Bp89]

There is also generally another pressure relief valve installed, it's on the cold feed to the cylinder and is called a expansion valve which is set lower than the TPRV on the cylinder, the TPRV is set to 7bar and the expansion valve is set to 6bar so will open every time the cylinder is heated if a failed E.vessel or cylinder air bubble, this would generally be tied into the same waste pipe as the TPRV.

Have you checked if the cold water feed (top up) isolating valve to the boiler is shut or if its fed via that auto top up valve, it would seem that the most obvious problem is that the expansion valve is lifting/leaking for one reason or the other and that it's waste pipe is connected to the condensate waste pipe since, as you say, the condensate only runs strongly when the HW heating is on. Next time the HW heating is on, crack open a HW tap and see if the condensate flow stops.

I tried your suggestion of opening a HW tap. Firstly, after switching on the boiler for HW the condensate was flowing immediately, it soon quietened down but the occasional sound of water could be heard. After a few minutes, I opened a HW tap. I could not hear a great difference in the flow of condensate, it was relatively quiet. What I did notice was that there was no water coming from the exterior 22mm pipe but after approximately 30 mins water started to drip from the pipe: temperature related?

 

[John.g]

The HW cylinder expansion is ~ 1.7%, so if reheating say 100L without drawing off any hot water then 1.7L will be ejected during the reheat time and then stop until the next reheat time/volume. if you crack open a HW tap to give a very small flowrate of say 1LPM before reheating commences then no water wiil be ejected (through the expansion valve) as there will be no pressure rise in the cylinder. Just check that a expansion valve is actually installed.

The exterior pipe leak looks like the boiler primary water system PRV lifting probably due to a faulty E.vessel. As stated above the boiler pressure should then fall if the filling valve(s) are shut.

 

[Bp89]

The HW cylinder expansion is ~ 1.7%, so if reheating say 100L without drawing off any hot water then 1.7L will be ejected during the reheat time and then stop until the next reheat time/volume. if you crack open a HW tap to give a very small flowrate of say 1LPM before reheating commences then no water wiil be ejected (through the expansion valve) as there will be no pressure rise in the cylinder. Just check that a expansion valve is actually installed.

The exterior pipe leak looks like the boiler primary water system PRV lifting probably due to a faulty E.vessel. As stated above the boiler pressure should then fall if the filling valve(s) are shut.

There is a red expansion vessel next to a Sadia cylinder. It's reading approximately 1 bar at the moment

 

[John.g]

Can you see what this E.vessel is connected to?.

 

[Bp89]

Can you see what this E.vessel is connected to?.

Here are images of the E vessel and pipework, upper and lower. I've also included an image to the right of the vessel which includes two relief valves.

 

[Bp89]

Can you see what this E.vessel is connected to?.

Here are images of the E vessel and pipework, upper and lower. I've also included an image to the right of the vessel which includes two relief valves.

 

[John.g]

Can you look at the two attachments and answer the 4 queries in "RED EV 2106" and 2 queries in "Relief Valves 2106"

 

[Bp89]

Can you look at the two attachments and answer the 4 queries in "RED EV 2106" and 2 queries in "Relief Valves 2106"

I'm sorry but I can see my original images but not any queries.

 

[John.g]

Select my images, left click on the image to select it then left click again to enlarge it, then press and hold the (left) mouse button to drag it around and you will see my queries in "boxes".
If you have a tablet or smart phone you must use your own knacks to open/access the images.

 

[John.g]

 

[Bp89]

In relation to the image with the two relief valves, the blue valve is 10 bar and 90-95C and the black valve is 8 bar. If you want me to actually check what pressure is operating, that is a step too far for me.

 

[John.g]

That's fine and settings are OK, now can you reply to the other image queries.

 

[Ben-gee]

It’s a megaflo with an internal bubble, this needs regenerating- there are instructions written on the side of the cylinder - follow these.

 

[Bp89]

That's fine and settings are OK, now can you reply to the other image queries.

The E vessel volume is 18L.
The pipe on the LH of the E vessel is shown in the image of the pipework at floor level. The pipe connects up to another pipe going through the floor.
The pipe to the right of the cylinder is impossible to see beyond a certain point due to the closeness of the cylinder to the wall.
The pipe close to the right of the E vessel feeds the E vessel.
I think I mentioned that the E vessel is reading 1 bar.

 

[Bp89]

It’s a megaflo with an internal bubble, this needs regenerating- there are instructions written on the side of the cylinder - follow these.

......but there is no water dripping into the tundish.

 

[John.g]

It’s a megaflo with an internal bubble, this needs regenerating- there are instructions written on the side of the cylinder - follow these.

To recap (my view). We have a unvented cylinder which doesn't eject water from either the TPRV or the expansion valve since no sign of water flowing in their common tundish yet excess condensate appears from the condensate pipe when only heating hot water, also when HW is drawn off then condensate flow ceases?.

Water also appears somewhere (can't remember where) else which might appear to be from the primary (boiler) circuit, yet the red E.vessel doesn't require topping up as both filling valves are closed and presumably the pressure isn't rising to 3bar which the relief valve on top of the E.vessel is presumably set to and also discharges into its own tundish which can be observed as well.

 

[Bp89]

To recap (my view). We have a unvented cylinder which doesn't eject water from either the TPRV or the expansion valve since no sign of water flowing in their common tundish yet excess condensate appears from the condensate pipe when only heating hot water, also when HW is drawn off then condensate flow ceases?.

Water also appears somewhere (can't remember where) else which might appear to be from the primary (boiler) circuit, yet the red E.vessel doesn't require topping up as both filling valves are closed and presumably the pressure isn't rising to 3bar which the relief valve on top of the E.vessel is presumably set to and also discharges into its own tundish which can be observed as well.

 

[Bp89]

To recap (my view). We have a unvented cylinder which doesn't eject water from either the TPRV or the expansion valve since no sign of water flowing in their common tundish yet excess condensate appears from the condensate pipe when only heating hot water, also when HW is drawn off then condensate flow ceases?.

Water also appears somewhere (can't remember where) else which might appear to be from the primary (boiler) circuit, yet the red E.vessel doesn't require topping up as both filling valves are closed and presumably the pressure isn't rising to 3bar which the relief valve on top of the E.vessel is presumably set to and also discharges into its own tundish which can be observed as well.

That's a good summary. The water from somewhere else is seen dripping from a 22mm pipe on an external wall.