Vailant Extotec Pro 28 - pressure loss

[Scott6488]

I used to lose pressure on my rubbish Ocean Alpha 240P because of tiny leak inside the combi. Because the leaking water was so hot it used to evaporate pretty quickly. That said, the loss in pressure was no where near as fast as yours. I only discovered it when I took the cover off.
/QUOTE]

Haven't noticed any leaks within the boiler, but I have read how this may happen with a faulty heat exchanger and that you may not be aware because there are no easily visible signs

 

[Scott6488]

A difficult one, because pressure is very dependant upon temperature - your system would have still had some heat left in it when you topped the pressure up, but I would say from that you do not have a leak.

Now leave the plastic bag in place, run the system normally and see if any water is ejected into the bag.

Bag has been left in place. Nothing coming out of it so far. Will leave it for a day or so and see what happens

 

[Harry Bloomfield]

Bag has been left in place. Nothing coming out of it so far. Will leave it for a day or so and see what happens

Hopefully, you don't have a leak in the boiler.

 

[Scott6488]

Hopefully, you don't have a leak in the boiler.

The boiler is around 7 years old and we don't think it is suitable for the size of property. When we've been looking just in case we need to replace it, and most searches are suggesting a 30 or 35kw boiler.

 

[Scott6488]

Latest update, boiler worked OK during the day. During the night pressure dropped from 1.2 to 0.1bar

 

[Harry Bloomfield]

Latest update, boiler worked OK during the day. During the night pressure dropped from 1.2 to 0.1bar

All pointing towards a boiler issue! No water in the plastic bag on the PRV?

 

[Scott6488]

All pointing towards a boiler issue! No water in the plastic bag on the PRV?

No, but nothing at all

 

[Scott6488]

Grasping at straws now before having to spend lots of money. Could it be the pressure sensor that is at fault?
Returned home today 0.3bar being displayed. The smallest amount of water put into the boiler and its now happily running at 1.5bar

 

[Harry Bloomfield]

Grasping at straws now before having to spend lots of money. Could it be the pressure sensor that is at fault?
Returned home today 0.3bar being displayed. The smallest amount of water put into the boiler and its now happily running at 1.5bar

I would not expect so, you are regularly putting water in and the water cannot just disappear, it must be leaking out somewhere. You have more or less proven it's nothing leaking external to the boiler.

 

[terryplumb]

When you isolated the boilers flow and return ,and left overnight in that state,upon opening the valves did pressure immediately drop ?

 

[Scott6488]

When you isolated the boilers flow and return ,and left overnight in that state,upon opening the valves did pressure immediately drop ?

No and there was no sudden movement of water which made me think that the pressure in the pipework remained, meaning no leaks on that side

 

[terryplumb]

Probably a perforated heat exchanger. Where does the condensate pipework run to ,can you find a point where you can disconnect it ?

 

[Deleted member 267285]

The smallest amount of water put into the boiler and its now happily running at 1.5bar

Sounds like an expansion related issue. If it was the sensor, I’d expect the analogue gauge to remain at pressure.

 

[Harry Bloomfield]

Probably a perforated heat exchanger. Where does the condensate pipework run to ,can you find a point where you can disconnect it ?

You mean as the temperature of the boiler increases, a leak develops in the boiler?

The op should be looking for signs of rust discoulered water, coming out of the condenstate drain, to confirm a boiler leakage.

 

[Scott6488]

Probably a perforated heat exchanger. Where does the condensate pipework run to ,can you find a point where you can disconnect it ?

Sorry not sure what you mean by the condensate pipework. I have a bag over the outlet from the prv and there's nothing coming out of there