Flushing Raw Water side of AC

[Andy Bav]

Hi All,

We have quite a slow flow through the raw water side of the AC system. The inlet is furred up as she is due to be hauled out in 4 weeks time for her annual painting etc etc as the strainer had around 3 inches of mussels in it. The furthest unit away from the pump shows an HPF code every now and again…

If that doesn’t improve the flow, the constriction may be further upstream. Seems I have two options, one use a mousing cable to “rod” from unit end to outlet (through the exhaust water outlet into the sea), or alternatively rig up a “closed loop” circuit using a large bucket, a bilge pump and some connecting hoses. The question is what solution to circulate. In Spain they sell “aquaferte” which is basically hydrochloride acid, so am considering usig a diluted soltion of that…

Be interested if others have done something similar, and how you approached it. (Fairline Targa 52 2006)

NB we had 2 of the 3 units regassed a couple of months ago..

 

[superheat6k]

Restricting the water flow will force up the discharge pressures (HP), and will put more load on the compressor/s, and if, you have them, could cause a safety valve to lift, which would immediately reduce the amount of gas in your systems. Indeed we reckon that any safety valve that has lifted will need replacement because they do not re seal on their seats as tight and so can continue to lose gas afterwards.

Can you install a temporary supply through an alternative inlet, or even disconnect the pump and run its suction somewhere else.

 

[starfire]

Hi All,

We have quite a slow flow through the raw water side of the AC system. The inlet is furred up as she is due to be hauled out in 4 weeks time for her annual painting etc etc as the strainer had around 3 inches of mussels in it. The furthest unit away from the pump shows an HPF code every now and again…

If that doesn’t improve the flow, the constriction may be further upstream. Seems I have two options, one use a mousing cable to “rod” from unit end to outlet (through the exhaust water outlet into the sea), or alternatively rig up a “closed loop” circuit using a large bucket, a bilge pump and some connecting hoses. The question is what solution to circulate. In Spain they sell “aquaferte” which is basically hydrochloride acid, so am considering usig a diluted soltion of that…

Be interested if others have done something similar, and how you approached it. (Fairline Targa 52 2006)

NB we had 2 of the 3 units regassed a couple of months ago..

Closed loop is the way to do it, circulate in the opposite direction to normal flow.

Agua fuerte may be a bit too fierce, better if you can get some descaler from a plumbers merchant which is inhibited so as not to attack the metal.
Eg fernox or similar.

 

[Andy Bav]

Indeed we reckon that any safety valve that has lifted will need replacement because they do not re seal on their seats as tight and so can continue to lose gas afterwards.

That may account for that unit being out of gas - thanks.

Agua fuerte may be a bit too fierce, better if you can get some descaler from a plumbers merchant which is inhibited so as not to attack the metal.
Eg fernox or similar.

Thanks - that’s a good shout. We are driving out at the end of June, so already filling the boot !.

 

[Andy Bav]

Thought you may be interested in an update on our aircon which turned into a bigger job than I thought, but also resulted in updating 3, 16 year old units to brand new ones.

Started by "rodding" the thicker raw water inputs using a mousung cable... The pipes (around 8 feet in total) were packed full of mussels about the size of the end joint of your little finger, so felt that a closed loop of rydlyme or something simalar would be fruitless, and with the trickle of water coming from the outlet, may stay in the system for too long and potentially damaging to it.

So the rodding carried on upstream of the 3 way inlet manifold - pipes were similarly blocked. It seems as though the 3 way manifold is a restrictor in itself, so that's another job.

Flow seemed OK, but then man maths kicked in, and for the price of 2,500 litres of diesel, ordered and installed a new 1,250 GPH pump (which was half the size, but more flow, than the original pump) and 2 x 12,000 BTU units and 1 x 16,000 unit from Dormaire.com who did us a very competitive deal and next day delivery - all covered with 2 year warranty. Units are comparativly whisper quiet. I'm not sure how that equation would have worked out if fuel was cheaper!

Very impressed, so far with new units, as diagnostics warn of low flow, compared to old units which just seemed to rattle away with an HPF message.

The 16,000 circuit needed more rodding / flushing with a hose, as display was flashing low flow, so this was done, flow was better and all is good... For now.

Will add a T connector so that when we leave her, we will fill the circuit with fresh water so as to delay, if not halt, growth which is notoriously aggressive in SCM.

 

[Hurricane]

Do you close your seacocks when you leave, Andy.
I think that will stop the growth inside the pipes.
In the last 3 years or so, the growth in the A/C raw water has been very black.
I make a point of cleaning the raw water filter regularly.
And for cleaning the filter basket, I DO use Aquafuerte.
After a quick wash, I use a yougart pot and stand the basket in neat Aguafuerte.
That removes all the black stuff from the basket.

I also find that my seacocks are easier to operate if left closed for most of the time.
When we lift and scrub, there is always growth on the angled grille skin fitting thingies.
This year, I made a point of antifouling the grilles but that probably didn't last very long.
I had to fit a new raw water pump about 18 months ago.
Couldn't swallow the extortionate price of the Dometic one so spent some time sizing one at a sixth of the price.
The new pump works fine so I bought a spare.

Without hijacking your thread, I would like to openly ask @superheat6k a question.
Our systems use R-417a refrigerant.
It is becoming increasingly difficult to get it.
Our local A/C people say they cant - I suspect it is rather that they "won't"
I have a unit that needs topping up - the other 4 are OK
Any ideas where I can get some at a good price - perhaps 1kg containers would make the price easier to swallow.
Or is there a good "drop in replacement" for R-417a (I know R-417a is supposed to be a drop in replacement for R22)
I know it would need vaccing out.

 

[Andy Bav]

We left them open Mike - lesson learned I guess... But looking at the size of some of the shells, I reckon it was the first good service it's ever had, so happy now with a clean circuit, and new units.

You are right about the black cr4p in the pipes though, reckon that was an accumulation over the last few months...

Would seriously take a look at Dormaire, if you are looking for any replacements - units or pumps. Based in Alicante and next day delivery... kept Ricci on his toes.!