[RML] Air Pump Selection Report

Subject: [RML] Air Pump Selection Report
finsen at optusnet.com.au
Date: Fri Nov 19 2004 - 05:53:07 CST

Hi All,

After all the help from the RMLers, I thought I would post a report on the background and selection process of the new Air Pump.

As a summary, I selected a Medo LA-80B linear air compressor that is better know as the Seawater SL44H in the US.

The report is in Word 97/2000 format (included below by PJU).

Enjoy.

Thanks
Graeme Finsen

Voyage of Discovery

The Search for Pump III

Introduction:

As posted recently to the Rainbowfish Mailing List (RML) and as discussed among various members of the Australian and New Guinea Fishes Association (ANGFA), I have been in search of a centralised air pump for use in my fishroom. Following is the story of the trials and tribulations.

Pump I:

After reviewing Adrian Dawson's fishroom sometime in 2000, I was in awe of his central air pump that delivered consistent air to his many tanks. At the time I had a setup similar to most fish keepers, that is many and varied brands of small diaphragm style air pumps that would deliver 2 to 5 litres per minute of air (suitable for between 3 and 6 outlets). Some of these pumps where my father's and where over 20 years old (along with the rubber diaphragms). Sourcing replacement parts for the variety of german, Italian, Japanese and chinese pumps (especially the flapper valves) was a near impossibility. Of course the endless tuning of such a system to ensure constant airflow was annoying not to mention that some filters flowrates where next to zero given the amount of air passing through the system. As such Adrian's system seemed a godsend. However the price of the pump Adrian utilised baulked me. As luck would have it, a unit called the Resun LP-60 was sourced and was very economically priced at the time. However a move to a new house in 2001 saw the pump packed away for several months to allow for the removal. Moving tanks and fish (and associated equipment) is not a pleasurable experience. However the move was complete and it allowed the installation of an air ringmain (an air loop) with individual droppers into each tanks to power the airlift filters sometime in mid 2002. The installation of the Resun pump was seamless and was delivering air successfully for the next 8 to 9 months. After this time a distinct loss of pressure was noticed coupled with a "rubber" odour in the bleed airlines. Upon examining the Resun via the trusty "put your whole hand on it to check its temperature" method, it was found to be running hot. Very hot. So hot that the "put your whole hand on it to check it's temperature" method resulted in blisters to the palm and a couple of fingers (ie/ in excess of 70 to 80 degrees Celsius). The Resun was immediately shut down and dismantled to examine what had happened. Basically the rubber diaphragms had deformed and pulled the magnetic oscillator into physical contact with one of the electromagnets. This resulted in the dramatic levels of heat in the pump. Fortunately spare diaphragms and flappers were sourced and installed. But to no avail. For some reason the oscillator still rubbed on the electromagnets. Unfortunately due to my move, the pump was well out of its warranty. Writing the unit off as an unfortunate incident a new unit was sourced in 2003 which is another story:

Pump II:

The new pump was a later generation of Resun LP-60 and was approximately half the price of Pump I. It was immediately pressed into service and gave sterling service during 2003 and 2004 up until another move to my current address. During August and September (14 months after purchase) the pump appeared to be running a little hotter than normal, again via the "put your whole hand on it to check its temperature" method (which would imply temperature between 50 and 60 degrees Celsius). So in late September it was dismantled to see what was wrong (if anything). What was found was that the oscillator had just started to come into contact with one of the electromagnets. Contact was limited though and it was assumed that replacing the diaphragms would result in the oscillator being returned to a more normal "central" position.

Which it didn't. For some reason the oscillator would not come away from the electromagnet. Which led to the question: Why did the diaphragm deform to allow the oscillator to drift, thus causing the heat to deform the diaphragm more??

This led to the current situation, the Search for...

Pump III:

After spending about $300 on Pump I and about $170 for Pump II, it was decided that Resun LP-60's where not capable of performing in the Brisbane environment (although now I live in Ipswich, on the outskirts of Brisbane). Examining the internet, it was found that Resun LP-60's now retail for $125 AUD (inc GST & Delivery) so a case could be made for purchasing one unit every 12 months. However this was not seriously examined for fear that one of these units could spontaneously cause a house fire (my current fishroom is located under my bedroom). After a discussion with the supplier of Pump I and Pump II, they indicated that they had dropped the complete Resun range due to poor performance. Another reason not to select them.

So I canvassed the experts, the members of ANGFA and the RML. Three options where initialled examined, a high volume air blower, a high volume diaphragm style air pump, and the relatively new technology linear air compressor. There where three main criteria

1. Price (always important)

2. Reliability (given the fun I have had with Pump I and II)

3. Noise (as my fishroom is under my bedroom).

A table was drawn up to compare the eventual selected pumps.

Fortunately colleagues within ANGFA had sourced a Sweetwater Air Blower and I was able to discount this type of air source due to noise. Air delivery, power requirements and reliability were all excellent. The price of such units was certainly acceptable but the noise generated would make it untenable in my current fishroom (although the future room could see a blower...).

So scratch the air blower. Other members of ANGFA had sourced Hagen "The Pump" and have had them in continuous operation for several decades and as such it was highly recommended. However Hagen no longer manufacture these units nor do many stores in Australia carry them. And those that do carry them have only old stock some 8 to 10 years old. Also something not favouring "The Pump" was its price, which was quoted at between $800 and $1000 for a "Pump 80". As it turns out though, "The Pump" where actually manufactured by Techno Takatsuki and Hagen (amongst many others) badged these units as their own. After discussion with the supplier in Australia for Techno Takatsuki technical details and pricing for the HiBlow 80 were sourced.

However after the events of Pump I and II, I was not convinced that diaphragm style air pumps where technologically a way forward. After typing in "aquarium air pumps compressors" into Google and the result pointed me towards the Medo linear air compressors. A telephone call to the Australian distributors (whose head office is conveniently located in southern Brisbane) gave me technical details and prices. As it turns out, the Sweetwater SL range of linear compressors are actually Medo LA series pumps badged by Sweetwater, according to both Medo US and the local agents (refer to: http://jehmco.com/PRODUCTS_/HARDWARE_/Central_Air_Pumps/central_air_pumps.html and http://www.aquaticeco.com/index.cfm/fuseaction/product.detail/iid/6579/cid/1769 versus http://www.medousa.com/Linear_Piston_Blowers.asp and http://www.nitto.co.uk/pumps/la_series/la80a/index.html).

So these where the two units selected for comparison, in effect the "best of breeds". Below are the technical details with a weighted price to a percentage relative to the HiBlow (which was arbitrarily weighted at 100%). Rather than give out prices and sources here, feel free to email me directly and I can give you the sources, contacts and pricing for the two units. Both units have thermal cutouts, the HiBlow at 130 degC, the Medo at 120 degC. The HiBlow has an additional "long stroke" cutout should the oscillator exceed its travel.

 

HiBlow HP 80

MEDO LA-80B

 

Rated Voltage

240

240

Vac

Hz

50

50

 

Normal Pressure

0.01471*

0.015

MPa

Volume

80

80

lpm

Noise

36

45 **

dBA (1m)

Power

71

75

W

Connection

 

18

ID of connection

Weight

7

5.3

kg

 

 

 

 

Cost

93.63%

98.1%

AUD (inc GST)

Delivery

6.37%

0.65%

AUD (inc GST)

 

 

 

 

TOTAL

100%

98.75%

 

 

 

 

 

Notes

* 0.15 kgforce/cm2 = 0.01471 MPa

 

 

** email from Australian agent

Conclusion:

Based on the above table, both pumps where technically equivalents of one another. Both were capable of delivering the required pressure and airflow. Both units had exactly the same warranty (12 months) but the Medo representative was willing to offer additional extensions if he could examine the particular installation.

The Medo was slightly more expensive but the HiBlow's delivery costs were significantly higher due to the HiBlow supplier being located in Sydney. The HiBlow was quieter and slightly more economical to operate. However the Medo was cheaper in repair parts and the cost amortised over 3 years (including initial purchase price and running costs) saw the Medo cheaper by 2% over the HiBlow. But the HiBlows published noise levels were significantly lower than the Medo. So the Australian Medo agent invited me to examine the unit a unit in operation and to hear how quiet one was, which as it transpired was much less than the published 45 dBA (at 1m). Mind you, 45 dBA (1m) is, theoretically, as quiet as normal suburban area at night.

So coupled with the analysis above, online discussions of the Medo/Sweetwater unit (mainly in Koi sites in the UK), and the general opinion regarding linear air pumps, the Medo LA-80B was selected.

Having local representation was an advantage as the agent hand delivered the unit and installed it (both for free). Based on the installation and his examination, he gave the unit a 2-year warranty, which was a 12-month extension on the normal offer (again for free).

Postscript:

It remains early days yet before I can comment about the real advantages of the Medo or other styles of linear air compressors over any other model or type. No doubt if problems crop up, people will hear of Pump IV.

After its first full day of operation, I found that the air delivered by the pump is very warm, almost hot to touch. However, after some discussion with the supplier, this is normal operation.

Acknowledgements:

Special thanks to Aimee Brooks, Adrian Dawson, Jennifer Palmer, and Dave Wilson.


: Tue Jan 04 2005 - 17:37:20 CST