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HFP problem but water flow fine!
November 29, 2009
11:32 am
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Steve Pooler
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November 12, 2008
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Stephen M said:

Whilst re-installing the water pump I took the opportunity to install a gate valve in the hose to the lower aircon units, incase I ever need to restrict water to these units whilst increasing the flow of water to the upper units. I'm thinking that on a very hot day (over 40 degrees C)when only using the salon/upper aircon units, to maximise water flow to these two units I can now partially restrict water flow via the gate valve to the two aircon units not being used and consequently force more water to the two units being used. What is you view on this Steve?

This weekend was warm and sunny and we were pleased to have the aircon units finely working. The moral of the story is as always, check the basic things first, like "is it switched on?", "is the inlet blocked!" Thank you for your support again. I learned a lot from you and from the whole incident!

Kind regards, Stephen M.


Hi Stephen…Really glad you found the issue !!!

I always check the thru hull first…Why didn't I ask you if you had ?…I guess since you said you just purchased the boat ?

Anyway…Yes…Always check the Simple things (thru hull) first…The way I do it is with the strainer top off when I check/clean the strainer…Then open the valve & let water run out the top…You will get used to how much should normally be exiting…If it seems less than normal, then you know what to do….Sometimes it can be cleared from inside by removing that hose between the strainer & thru hull completely (did you check it as well for growth inside ?) & poking out the thru hull with a long screwdriver if the water is a bit chilly, or dark to dive overboard.

As I have said before…I'm not fond of restricting flow in any way To, or From, those pumps…It causes cavitation & wear of the housing & impeller…

That installation really needs two pumps, thru hulls, & strainers…It would solve a lot of maintenance & flow problems…It  would improve the "while away" situation by only running water thru 2 units instead of 4 for humidity removal (thus reducing growth in the other 2)...Plus provide a redundant system so that the whole boat is not hot (with all A/C down) when the engine room is too hot to work in (during or just after a cruise)

No one wants to mess around down there after a long day of enjoyment…They usually want to cool off, get a drink, a meal & some rest…Then attack the problem in the morning (or later) after everything has cooled down a bit…  

Thanks for the report and resolution…

Steve~

November 29, 2009
8:53 am
Stephen M
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Steve,
Well finally I resolved the HPF issue. After removing and testing the pump to find it was working fine, and didn't have to replace the impeller, I dived over the side to check the water inlet in the hull. All metal below the water line, except for the props were covered in a thick (1 to 2 inch thick) barnacle encrustment, the inlet to the aircon pump was effectively blocked! This explained why the impeller also had barnacles on it.

I had the boat out of the water only 3 months ago for a hull inspection prior to purchasing the craft, and was amazed to find that after 10 months since the previous owner had anti-fouled it, the hull was spotless except for a little bit of growth around the trim tabs and metal inlet covers/strainers. All metal parts were cleaned by a high pressure hose, which would have removed the anti-foul. Since buying the boat I have moored it in the Swan River (tidal) but very merky over the last three months from winter rains. I think the excess nutrients in the river from the run off of rain water with fertiliser etc. has caused a rapid build up of hard growth on the metal parts in less than 12 weeks! Once the encrustment on the inlet cover/filter/strainer (not sure what it's called) was removed, not only did I get water pouring out the the two outlets in the bow (servicing the lower two aircon units in the State Rooms)but for the first time water also flowed out of an outlet mid-ships, which is the water from the upper 2 aircon units with the HFP issue. So now all 4 aircon units work fine.

Whilst re-installing the water pump I took the opportunity to install a gate valve in the hose to the lower aircon units, incase I ever need to restrict water to these units whilst increasing the flow of water to the upper units. I'm thinking that on a very hot day (over 40 degrees C)when only using the salon/upper aircon units, to maximise water flow to these two units I can now partially restrict water flow via the gate valve to the two aircon units not being used and consequently force more water to the two units being used. What is you view on this Steve?

This weekend was warm and sunny and we were pleased to have the aircon units finely working. The moral of the story is as always, check the basic things first, like "is it switched on?", "is the inlet blocked!" Thank you for your support again. I learned a lot from you and from the whole incident!

Kind regards, Stephen M.

November 17, 2009
10:50 am
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Steve Pooler
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Stephen M said:

Steve,

Thanks for your further good advice. The hoses are too difficult to remove from the boat so how should I go about giving them an acid wash in situ?

I cleaned the strainer when I bought the boat 2 months ago, but didn't see any barnacles.

I'll be removing the pump this week to get the impeller replaced and have the motor tested. I agree that the hoses will have to be acid washed, some how!

Kind regards, Stephen M.


Not a problem Stephen~

We have many posts on pump & hose maintenance right here on the forum...Check out this link & read thru... ** you don't have permission to see this link ** 

It may be something that you would hire done...It's not safe, or easy to do & every boat is different, so it might be hard for me to explain the exact procedure here...You will need a pump & bucket for the acid...

After reading the posts in the link and if you have specific questions please come back & ask...

Steve~

November 17, 2009
9:53 am
Stephen M
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Guests

Steve,

Thanks for your further good advice. The hoses are too difficult to remove from the boat so how should I go about giving them an acid wash in situ?

I cleaned the strainer when I bought the boat 2 months ago, but didn't see any barnacles.

I'll be removing the pump this week to get the impeller replaced and have the motor tested. I agree that the hoses will have to be acid washed, some how!

Kind regards, Stephen M.

November 15, 2009
1:16 pm
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Steve Pooler
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Stephen~

If the impeller was covered with barnacles (actually never seen that here) then it's a good bet to expect them to be elsewhere too...

It's really hard for barnacles to attach to anything that is spinning that fast so the system may have sat idle for quite a time.

What's strange is that you found no barnacles in the strainer...Maybe someone disassembled & cleaned the strainer just before your purchase ?

The high pressure water flush will do nothing to remove any growth that is attached...In fact it may cause the loose stuff to move to a restricted section and pile up there making the restriction a blockage.

The best thing to do now is acid flush to dissolve any growth before it collects somewhere (causing a complete blockage) that you can't get acid to...acid needs to push out the water before it can get to the restriction...If it can't push out the water first, It can't get to the restriction/blockage.

Steve~

November 15, 2009
7:19 am
Stephen M
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Steve,
Water is definitely not reaching the upper aircon units. The bronze impeller was covered in barnacles which I cleaned off, but water still doesn't get to the upper units. Will be replacing the impeller this week. I'll also try and flush out the hoses with mains pressure water hose.
Will let you know if this fixes the problem. I think it will thanks to your good advice.
Kind regards, Stephen M.

November 13, 2009
7:12 pm
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Steve Pooler
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Hi Stephen~

Lookin forward to your Saturday tests...Let us know the outcome ?

Steve~

November 9, 2009
6:22 pm
Stephen M
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Guests

Steve,
Yes, the aircon units on the 411 are overhead, in front of the helmsman station on the bridge.
I'll check for hose blockage by blowing as you suggested, and will check the pump impeller although water flow over the side seems strong as it shoots out from the hull about 1.25 feet (350-450mm).
I understand what you explained about the pump having to overcome "the head" in trying to get sufficient flow to the top aircon units.
I'll get onto this on Saturday, if not before.
Thanks. Stephen M.

November 9, 2009
12:11 pm
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Steve Pooler
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Ok Cool...And that water temp should not be a problem at all...It's Much better than here in the summer months...

I have not yet been aboard a Meridian but am a member over at the Meridian Owners forum ** you don't have permission to see this link **; I really believe they are all going to have a problem with water flow & pumps if all are installed as described (my thread/post explains why)

Your pump at 5 years is certainly old enough to have the cavitation/erosion problem I detail...That may be your problem...The bronze impeller is worn down from cavitation and now the pump's flow is reduced drastically...It's never very good to over size a pump. 

If you can blow or breath (after the water is pushed out) thru each hose to & from the salon units...It's likely not a restriction & I would be removing the pump head to inspect the impeller...They can seriously wear down to almost nothing and still pump some water...

If your salon units are overhead...That's quite a bit of natural restriction (known as "head") to overcome and what water the pump can pump is going thru the lower units due to less head...Water is going to take the path of least resistance, then any extra pump capacity over the plumbings ability to handle easily will be "Forced" to the upper units...Reduce that pumps capacity with wear and it won't happen reliably, which would explain why you getting underway (scoop on bottom of boat) helped force the water over the hump and started flow again. 

Let us know  Cool

Steve~

November 9, 2009
11:09 am
Stephen M
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Steve,

Great to hear from you so promptly. Thank you for your reply.
The boat has 2 thru-hull water overboard outlets servicing all 4 aircon units.
Perth water temperature is 20 to 23 degrees C winter & summer. In the north of our State, in the tropics, the water is 30 degrees C, but we don't cruise that far north.
The boat was imported into Australia with the 240 volt electrics factory fitted when built.
I will carry out the various tests you suggest over this next week and let you know what I find. Given that both salon systems have the HPF issue it strongly suggests that it is a restricted water flow issue.
Thanks again. Kind regards, Stephen M.

November 8, 2009
1:53 pm
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Steve Pooler
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One or two other questions ...What are the seawater temps in Perth...Now and during the hot months ???

The 37.0 degrees C you mention is actually 98.6 F. Which is already quite hot... What are the hot months air temps ???

At those type operational temps...Best Water flow is Paramount...Can't stress that enough unless the seawater is cooler than here in summer (32 C---90 F)

You mention the boat is 5 years old...Is the A/C setup for your power (50 cycle) or did you purchase over here & ship over ?

Steve~

November 8, 2009
11:29 am
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Steve Pooler
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Hi Stephen…Thanks for joining & posting….

First…Forget the raising the low fan speed, That would only help HFP faults in the heat mode.

We need to establish if you actually ARE getting water flow thru the salon units…All or most of the water could be going to the others.

Does the boat have a overboard thru hull for each unit, or is it One or Two overboards for all four units ?

The easiest way to verify flow to a unit is to gain access to that unit and feel that condenser coil (the part the water runs through) with your hand while the compressor is running…Compare how it feels to another unit that does not show a HFP fault.

The unit not getting sufficient flow will be much hotter to the touch than the one that is getting flow…HFP is an indication of High Head Pressure…Normal is between 200 to 260 psi depending on seawater inlet temp….Higher the pressure…Higher the temperature…Pressure & Temp coincide…A hot condenser means it's not removing enough heat.

The High pressure switch is set to shut the unit off at 425 psi to protect it (and you) from damage….Reduced water flow will cause this pressure to rise above normal…Lower the flow….Higher the pressure will run, and the harder the system will work (including increasing amp draw with the higher pressure)

It could be time for a complete system flush if it has never been done, or it could be time to just flush the units themselves.

Another possibility is that the pump relay is not starting the pump when the salon units call for it…Therefore they get no water unless one of the stateroom systems are calling for the pump.

To test this…Start each system by itself (no other unit running)…Then quickly (Before it can shut down on HFP) verify pump operation for each by looking overboard each time you start one system.

Let me know what you find…We can attack the problem once we narrow down the possibilities…

Steve~    

November 7, 2009
8:12 pm
Stephen M
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Hi Steve,

Two months ago I bought a 5 year old Meridian 411 with 4 Marine Air Systems.During September when it was cool in the evenings the heating worked well. Last week on a hot 37 degree C day (95 degress F) when both saloon systems were on, HFP flashed up on both control panels. I checked the water flow out of the hull to find no water was flowing so closed down both systems. After checking the stainer (perfectly clean) and driving the boat for 30 minutes, when I switched both air systems back on the water flow was strong, but after a few minutes HFP displayed on both control displays again. I have switch both systems on and off a number of times, together and independently, but still get HFP warning.
There must have been a temporary water intake blockage at the hull that caused the initial HFP warning. Now that water flow appears to be normal (the air conditioning systems in both the master and guest cabins are working perfectly)what do you think needs to be done to get rid of the HFP warning on both saloon sysstems? The manual says to increase the low fan speed setting from it's default value of 50, to its highest value of 55, which I haven't done as yet. But what else should I look at/do?
It's much cooler in Perth today, but with summer almost here and plenty of really hot days coming up good air con is a must!!Cool
I look forward to hearing from you. Thanks. Stephen M.