Ghl doser 3 back siphoning

[suikerspin]

Hey r2r,

Ive received a new ghl doser 3 this friday. Ive been spending all weekend now trying to get it not to back siphon.

Its only head 1 & 2 that back siphon. Ive checked the cables theres no holes in it. Only thing i noticed is that the tubes attached to the dosing head on both are longer then the ones on 3 & 4.

Ive adeed some pictures, anyone seeing any issues or can help me before i open a support ticket with ghl.

 

[BeanAnimal]

For it to back siphon the tubing has to be open, which means that it is not being fully occluded by the rollers. I have had a lot of problems with Doser 3 heads stalling and with low speed consistency. I gave up testing due to time and didn’t check for siphoning or full occlusion.

@Lasse thoughts?

 

[suikerspin]

Yeah its doing 0.2ml dosing every time so its running at a low speed is that whats causing it? Would diluting the solution so i can dose more at once help?

 

[BeanAnimal]

Yeah its doing 0.2ml dosing every time so its running at a low speed is that whats causing it? Would diluting the solution so i can dose more at once help?

The issue isn’t the dosing amount. In theory and practice the rollers should pinch the tubing shut and prevent siphoning.

How fast is the siphon?

 

[suikerspin]

The issue isn’t the dosing amount. In theory and practice the rollers should pinch the tubing shut and prevent siphoning.

How fast is the siphon?

it varies sometimes its empty within the hour example: last night i primed it before bed, woke up it was still primed, hour later it completly drained

 

[Lasse]

If all tolerances is OK - I can´t find any explanation why the two of the pump heads back siphons. As I see it - at least 2 of the rollers always press the tube against the wall, hence hinder back siphoning. I have run GHL dosers from version 1 to the whole 2 series for many years without this problem - both at home and other places.

I have an upgraded 2.0 into 3.0 but have very little experiences how it perform in sharp use.

IMO - it could be a good idea for you to run in smal doses (0.1 or 0.2 ml/min) at speed setting 0 and try to catch and make a photo of how the wheels position look like when back siphoning occurs.

You could also test to force a little bit more of the tube to be inside the pump house for head 1 and 2. I think you can do that thru moving the smal clip on the pressure side a mm or so closer to the pump tubes ending . Why I suggest this is because you notice that the tubes in head 1 and 2 seems to be a little longer. The could be longer but it could also look like they are longer but that it is because there are lesser of the tube inside the pump house compared with head 3 and 4. However I do not think this is the problem but it may be worth to test.

Sincerely Lasse