Nexus 300 probs

[netsukekoi]

So how low is 'too low' for a bottom drain lid - I have similar symptoms which I resolve by choking the pump output but that is just a waste of power and unnecessary wear on the pump.

Jules - can you remember how much 'gap' I had on the drain to my Nexus (and do you know if I changed it since you last saw it? )

Martin

[Davej]

Hi Martin

For the surface area of the gap to equal that of the bottom drain pipe the calc would be

(RxR)/D = H

Where R is drain pipe internal radius and D is the internal diameter of the bottom drain bowl .H is the height of the cover!!

This would be the absolute minimum. BUT I found it easiest to fettle after setting at 20mm by looking at the head loss in the Nexus and adjusting the drain height.

Certainly nothing like 2” a gap.

Could be other causes of a head loss though , if you know your pipe details, bend radius etc it is possible to easily calculate theoretical flow rates and head losses.

Regards

Dave

[Jules]

Martin as I recall there is a gap under you rlid 2 fingers width approx 40mm. A rough and ready calculation but one I have never had any problems with before. I have seen situations in the past where a normal plastic lid has flexed and completley covered the inlet due to the draw on the bottom drain creating zero water entering the pool and a new stem needing to be fitted. An airated lid you shouldn't get htis flex.

I am just wondering if the extra K1 has dispersed that little bit extra water creating the loss in head as the systems struggles to get more water from the inner to the outer chamber. Try it with no media in and see how you get on. If it works fine I would say take out 50ltrs of K1.

Jules

[norfythenorf]

I have a similar problem with my 200 in that the K1 doesn't bubble on one side even though the air pump output is above the minimum spec required. I have spoken to a dealer for advice and his opinion is that EA may have made too many holes in the air pipe so that all the air escapes from the holes nearest the input. I have yet to try his suggestion of getting some stainless screws and blocking off a couple of the holes which do bubble as the water is cold and I'm a wimp ha ha ha.

[B.Scott]

Now I am thinking, how about that mossy stuff that grow inside the pipe sometime or likewise there could be something stuck/wrapped around the support for the BD like a carrier bag / bin liner / blanket weed.

[Michaelb]

Today i have taken out 50 litres approx of K1 made absolutely no difference ,it still doesn't turn over all the way around. Secondly I put on an old Aquamax 10000 in place of the Optimax 15000 the water level in the Nexus barely dropped an inch from the pond level

Mike.

[Andy H]

If you mean the pump was too powerful and you want to use it then perhaps you could fit a dimmer switch to tone it down a bit, or is this a bad idea??? Someone will know....

I was thinking of doing this on an air pump over winter.....?

[norfythenorf]

Michael, taking media out isn't going to make any difference if the air tube isn't bubbling all the way round which is what I think is happening, my 200 is the same. Try reaching down to the tube if you can and feel round for the holes and I bet you are going to find that there's no air coming out where the K1 isn't moving. If so the easiest fix (I'm told, haven't tried it myself yet but I will) is to use stainless screws to block off some of the holes on the side where it does bubble. Try a couple first and see what happens.

[Michaelb]

how do you connect your air tube to the boot ?

[norfythenorf]

how do you connect your air tube to the boot ?

I don't really know what you mean by that Mike. My 200 has an air tube that I just connect to my air pump using a plastic connector. The boots on mine are for connecting 2" and 4" water pipe to the filter.

[koimod]

Very Strange,

I too had a problem on my 200 where the media gathered in one area, after checking the Nexus was level, I spoke to Harvey at E/A , he asked if i was in a hard or soft water area. Where I am the water is hard, however other items can block the air holes. He suggested drilling the holes out to 2 mm each , no extra as when discussed there is a die at e/a so all have the same amount of holes. By making larger holes released the air better and now my media turns brilliantly all around my Nexus and also where I had the 2 dead spots.

I cannot understand why a dealer would suggest blocking holes ? Just try the way E/A told me to do it.

You do not need to get cold fingers / hands as well as just put the centre pipe in and use the small ball valve to drain the outer bio area of the nexus. It should only then take a couple of minutes to do the holes.
My drill didn't fit so I used a 2mm drill bit clamped onto my mole grips, worked a treat!

[Michaelb]

norfythenorf, How do you connect the nexus air ring to the rubber boot on the air pump ,mine appears to be a different diameter.I wondered because i have it clamped to the rubber hose if i am losing air pressure ?

[norfythenorf]

Koimod, dealer had experienced a similar problem himself and it worked for him, seemed a simple fix to me thats all. Mine doesn't have any blockage, I did find that raising the air tube slightly in the affected area did enable it to start bubbling so maybe it's not quite level. Never checked that as it's stood on palletts on what I thought was a level concrete garage floor, so something for me to check. As far as I'm concerned it isn't a mega issue as there's enough movement going on to cope with my system but I will get the spirit level out at the weekend out of curiosity at least. I'm reluctant to drill bigger holes as the air simply isn't reaching the existing holes so I don't want to let it out even quicker where it already bubbles. Incidentally, my water is hard too, what difference does that make to whether an air tube bubbles or not? From day 1 it's never bubbled in the area furthest from the air inlet so it's not a limescale issue if that's what they think could cause a blockage.

Mike, I have connected my Hailea air pump via a length of flexi air hose which then attaches to the Nexus with a plastic connector - no rubber boots in sight I'm afraid. Different models I guess.

[netsukekoi]

Norfy, I find I have to prick out the holes on the air ring in my Nexus 200 every 3-4 months as they block up with algae. Once done it bubbles like a good'un for 3 months or so and then I get a dead spot again as it blocks up.

Jules, Just emptied the K1 out of the Eazy and opened all the valves - the pump still pulls water out of the Nexus faster than it is going in, so the level drops significantly in the outer ring. So either the holes between the inner and outer have got blocked (with K1) over the past few years or my pump is too powerful. As it is an Aquzmax 16000 I presume the latter - so I'll stick a bubble bead on the other side - that ought to soak up some of the extra oomph.

Martin

[Jules]

Martin a quick and easy way to check the moulding between the inner and outer chambers is to place the centre pipe in the Eazy and allow to fill. Emty all the water and K1 from the outer chamber and then take the pipe out of the centre pipe. The water should transfer into the outer chamber evenly all the way around the moulding. If this is the case great. If not there may be a section of the moulding that has no holes. In this case you need to take photographic evidence and call EA.

Jules