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8:12 pm
November 7, 2009
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Stephen M
| | Perth, Western Australia | |
| Member | posts 6 |
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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!!
I look forward to hearing from you. Thanks. Stephen M.
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11:29 am
November 8, 2009
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Steve Pooler
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Post edited 8:41 pm – November 8, 2009 by Steve Pooler
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~
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1:53 pm
November 8, 2009
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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~
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11:09 am
November 9, 2009
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Stephen M
| | Perth, Western Australia | |
| Member | posts 6 |
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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.
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12:11 pm
November 9, 2009
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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 http://www.meridianyachtowners.com/ and try to help out there from time to time…I have read that the 411 salon A/C units are overhead ?…Or is that the 459 ? (I think I also read the 459 is a 411 with cockpit)…If so, I have some threads here & over there discussing water flow & pumps on Meridians http://marine-ac.com/forum/mai…..rger-pump/ 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 
Steve~
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6:22 pm
November 9, 2009
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Stephen M
| | Perth, Western Australia | |
| Member | posts 6 |
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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.
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7:12 pm
November 13, 2009
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Steve Pooler
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Hi Stephen~
Lookin forward to your Saturday tests…Let us know the outcome ?
Steve~
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7:19 am
November 15, 2009
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Stephen M
| | Perth, Western Australia | |
| Member | posts 6 |
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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.
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1:16 pm
November 15, 2009
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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~
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9:53 am
November 17, 2009
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Stephen M
| | Perth, Western Australia | |
| Member | posts 6 |
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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.
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