How much impact will this have ?

[flotmangooner]

Hi,

I have a fume tube from one of my drains which is about 2 foot tallker that the side of my house. With the low sun at the moment, the last 2 or 3 hours of the day casts a shadow of the tube onto one of my panels. The shadow is not that large and i think it only goes onto one panel. Will this have much affect on the generation performance or is it so small it's not worth worrying about ?.
I was thinking about cutting a bit off the tube so the shadow will not hit the panels .

 

[malcolmsanford]

In all probability it will have a marked affect on your systems performance, But really it is dependent on many things, if it is a single inverter installation, then yes it would be more affected much more than Micro inverter types.

It would certainly affect the individual panel and by that panel being affected it could affect the whole installation, depending on installation design and component installation. ie micro inverter. I'm sure though that the company that installed your system would have taken all these conditions into account and I would feel sure if they are reputable, you could ask them about this.

To help yourself you could start to monitor the output at various times and see what the difference is fully unshaded and then shaded

 

[flotmangooner]

Hi
It is a 4kw system with a single SMA 4000-TL inverter.
The company who installed it did highlight it when they planned the system. I think i will chop off the top of the tube this weekend.
My performance can be seen on the pvoutput.org website - name of the system is "puds power".
Since 16th November i have acheived an average generation figure of 2.71kwh - our system faces WSW so will benefit much more in the summer months as opposed to now when the sun is very low.

 

[dansk]

Can you post a picture, any shadow isnt good TBH, we chop then were we can/if its going to cause a shadow.

 

[sharpener]

Before you chop the vent pipe think about whether it is near any windows or ventilation openings, you don't want to swap a small loss in output for an unpleasant smell. The height of such vent pipes is AFAIR specified by the Building Regs for this reason.

With the low sun at the moment, the last 2 or 3 hours of the day casts a shadow of the tube onto one of my panels. The shadow is not that large and i think it only goes onto one panel.

Provided the panel in question has the bypass diodes that are usually incorporated, the shadow will only affect that one panel and you will lose very little output particularly if it is not in the middle of the day.

I have a shadow from a similar pipe affecting one panel in one half of my array but on the sunniest day yet seen the difference in output between the two halves was only 6.5 Wh in nearly 5kWh.

 

[jerriais]

Before you chop the vent pipe think about whether it is near any windows or ventilation openings, you don't want to swap a small loss in output for an unpleasant smell. The height of such vent pipes is AFAIR specified by the Building Regs for this reason.

Correct. The top of the vent pipe (aka soil pipe) must be at least 900mm from any opening. Many solar companies do tell customers that it's fine to chop off and leave it venting under the panels. Apart from then often being within 900mm of a window this also leads to a potential corrosion issue with the panel that sits over the vent pipe. Best would be to take off the pipe inside the attic space and fit an air admittance valve so pressure is still equalised but no air escapes, but always good to check this with your Building Control Officer but you should be OK as long as a house on your sewer line still has a vent or soil pipe in case of positive pressure in the sewer (if the whole neighbourhood had air admittance valves fitted then there would be nowhere for air to vent from the sewer when necessary)

 

[wstevew]

I have east west split and same issue on the east early morning. There is no significant difference to the generation curve between sides.

 

[flotmangooner]

I will post a photo of the pipe in question.

Not even sure what purpose it serves as it is connected to the drain that the bath/sink water goes down. It is not connected to the sewer pipe.

 

[moggy1968]

if it is only shading for a short period of the day and only this time of year then overall it's not a major drama. If it can be easilly fixed then do it but I wouldn't expend any great time/effort on it.

 

[sharpener]

Best would be to take off the pipe inside the attic space and fit an air admittance valve so pressure is still equalised but no air escapes

As it sounds as though the pipe in question goes up the side of the house, and you can easily get at it, you could cut it just below the roof line and put the AAV on the end. If it does go through the loft cut it just above the roof if you can, this will save you having to re-do the tiling and even if the valve fails you will not get any smells inside the loft.

You may also find there is a short vent stack just inside your property boundary, this arrangement used to be quite common. Smells were supposed to be prevented by a mica flap behind the grille, though they are usually broken by now.

Funnily enough I was on to Anglian Water this very morning asking them to remove this vent arrangement, as will be in the way of our new garage (and I have a new AAV elsewhere on the system).

 

[jerriais]

Hi,

The purpose is to manage the pressure in your drainage system. If you imagine emptying your bath without a vent pipe in the system, then as the water travels down the drain into the sewer it will create a negative pressure behind it. At the moment that pressure is made up by air being drawn in from the vent pipe. If you sealed this pipe then as an alternative the system would suck in air through the plug holes of your bath/sink etc which would suck out the water in the U bend which wouldn't be great as then you would have nothing preventing the air from the drainage system coming up through the plug holes.

 

[jerriais]

I'd be careful of putting AAVs outside, my understanding of the regulations is that they are only permitted for use inside as they are quite susceptible to freezing.

 

[solarsavings]

You can get external air admittance valves. FloPlast