AC motor airco

[Kjelt]

So just finished mounting everything back again and it is running nicely 
So thanks to every contributor so far for making this happen, much obliged to you all   

Now two questions left:

1) I was looking for replacement bearings:
http://www.klium.nl/zoeken?orderby=position&orderway=desc&search_query=kogellager+608&submit_search=Zoeken&p=2
and it resulted in a staggering amount of 608 bearings, can anyone point me to a translation table that explains the differences between all these types, they vary from €3 to €40 a piece 
Sean you mentioned the RS2 types but which of the 9 possible ones should I choose for my application?

SKF 608-2RSH
SKF 608
SKF 608/C3
SKF 608-2RSH/C3
SKF 608-2RSH/C3GJN
SKF 608-2RSH/GJN
SKF 608-2RSL
SKF 608-2Z
SKF 608-2Z/C3
SKF 608-2Z/C3GJN
SKF 608-2Z/C3LHT23
SKF 608-2Z/C3LHT30
SKF 608-2Z/GJN
SKF 608-2Z/LHT23
SKF 608-2Z/WT
SKF 608-Z
SKF 608-ZTN9/LT
SKF 608-ZRZ/VK251
SKF 608-2RSH/C3LHT23
SKF 608-RSH
SKF 608-2ZTN9/LT
SKF 608-2Z/C4
SKF 608-2Z/C3WT
SKF 608-2RSH/W64
SKF 608-2RSL/C3
SKF 608-2RSL/C3LHT23
SKF 608-2RSLTN9/HC5C3WTF1


Stainless Steel:
SKF 608-2RS1
SKF 608-2Z
SKF W 608

2) How can I reduce the rpm on this one phase motor so it makes less noise at night? I tried the variac to 170VAC but it makes no difference so that one is out. It it possible at all with this motor?

Thanks all for all the help so far, it is very much appreciated 

[cs.dk]

1) I was looking for replacement bearings:
http://www.klium.nl/zoeken?orderby=position&orderway=desc&search_query=kogellager+608&submit_search=Zoeken&p=2
and it resulted in a staggering amount of 608 bearings, can anyone point me to a translation table that explains the differences between all these types, they vary from €3 to €40 a piece 
Sean you mentioned the RS2 types but which of the 9 possible ones should I choose for my application?

SKF 608-2RSH
SKF 608
SKF 608/C3
SKF 608-2RSH/C3
SKF 608-2RSH/C3GJN
SKF 608-2RSH/GJN
SKF 608-2RSL
SKF 608-2Z
SKF 608-2Z/C3
SKF 608-2Z/C3GJN
SKF 608-2Z/C3LHT23
SKF 608-2Z/C3LHT30
SKF 608-2Z/GJN
SKF 608-2Z/LHT23
SKF 608-2Z/WT
SKF 608-Z
SKF 608-ZTN9/LT
SKF 608-ZRZ/VK251
SKF 608-2RSH/C3LHT23
SKF 608-RSH
SKF 608-2ZTN9/LT
SKF 608-2Z/C4
SKF 608-2Z/C3WT
SKF 608-2RSH/W64
SKF 608-2RSL/C3
SKF 608-2RSL/C3LHT23
SKF 608-2RSLTN9/HC5C3WTF1


Stainless Steel:
SKF 608-2RS1
SKF 608-2Z
SKF W 608

2) How can I reduce the rpm on this one phase motor so it makes less noise at night? I tried the variac to 170VAC but it makes no difference so that one is out. It it possible at all with this motor?

Thanks all for all the help so far, it is very much appreciated 

You can see the standard bearing designations here: (This is the prefix-table, remember the suffix-table also) http://www.skf.com/au/products/bearings-units-housings/ball-bearings/principles/bearing-basics/basic-bearing-designation-system/prefixes-and-suffixes/prefixes/index.html

Ie. a C3 type bearing has more clearance than a normal bearing.

I think a 1-phase in - 1-phase out VFD is the best way to reduce the rpm's. They are rare though.

[Kjelt]

You can see the standard bearing designations here

Thanks that makes things more clear, still not sure what to choose besides the RS2 that Sean advised but I will call the company and ask their recommendation replacement.

I think a 1-phase in - 1-phase out VFD is the best way to reduce the rpm's. They are rare though.

I just googled a bit on that term and I read that you also have to have a special motor that has better insulated windings to withstand the induction peaks. Hmmmm I do not think this cheap motor will have that.
So another option would be to go to 24VDC? Those I can just PWM or does that also require a special circuit. It does not have to be stepless or something like that I just need two settings, one normal full power and one a bit more silent during the night.
I am not sure how I would calculate a replacement motor, can I just take the same power so, 240VAC 0,46A is aprox. 110W so if I get a 24VDC 100W motor with the same axe diameter would this work or do I need to calculate more parameters like rpm and torque or something like that?

[Seekonk]

Motor can be slowed down SLIGHTLY by increasing motor slip with reduced voltage.  My furnace has used a buck transformer for ten years to reduce speed, maximum reduction in voltage is about 20%.  Downside is motor heating increases as airflow decreases. 

[BradC]

I think a 1-phase in - 1-phase out VFD is the best way to reduce the rpm's. They are rare though.

Use a 1-phase in - 3-phase out VFD (they are everywhere and cheap) and just connect the motor between two of the phases.

[Seekonk]

Many 3 phase inverters will work on a single phase. Many 3 phase inverters will fault driving only two phases.

[cs.dk]

I think a 1-phase in - 1-phase out VFD is the best way to reduce the rpm's. They are rare though.

Use a 1-phase in - 3-phase out VFD (they are everywhere and cheap) and just connect the motor between two of the phases.

Cool
I have that setup on some cealing-fans, but i wasn't sure it was safe, so I said nothing bout it.
I just checked the voltage and frequence, and hooked the thing up. FWIW Omron/Yaskawa V1000 can run in this configuration, without problems.

[BradC]

Many 3 phase inverters will work on a single phase. Many 3 phase inverters will fault driving only two phases.

I've never found one that can't have the phase balance fault disabled.

[SeanB]

With this application you just use the cheapest bearing with either 2RS ( rubber seals) or 2Z ( steel dust seals) and you will be fine. As to slowing it down it is a matter of getting a motor with more poles, so basically you are stuck with the speeds it comes with, unless you just use a SCR and cut every second cycle out so it runs slow. It will make noise at 25Hz though. You do get some motor speed controls that use pulse skipping to reduce the frequency of the motor.

[Kjelt]

Even with the re-greased bearings this unit makes too much noise so I now definitely want to replace the whole motor and fan with a more silent version.

I found this one from Papst (see datasheet below) it is ofcourse a different mounting so I have to measure if it fits.
The thing that I have absolutely no idea about is the chart on the last page.
The original unit has a 23cm fan with a 490m³/hour air flow.

The Papst fan can even on 1000rpm do this but this depends on the P_fs the increase in pressure. But I have no idea how to measure that.
So what do you guys think just try it and see how it works out?
Other suggestions with the same mounting as the original but more silent?

[BradC]

Even with the re-greased bearings this unit makes too much noise so I now definitely want to replace the whole motor and fan with a more silent version.

Yes, but you've already ruined the bearings leading up to the re-grease, so they'll be functioning but probably quite noisy. I'd spend the couple of bucks and get *new* bearings before tossing the whole fan unless it was this noisy when you first put it in and you just put up with it.
Once a bearing becomes noisy, you will *never* get it back to like-new noise levels with a re-lube. Noise is caused by damage and it's irreparable.

Replacing a fan on paper without having all the pressure and airflow measurements becomes an expensive case of trial and error. Don't let me stop you however.

[Kjelt]

The original unit has a 23cm fan with a 490m³/hour air flow.

Can anyone answer these two questions please:

- if you have three fans of 150m³/hour air flow mounted next to eachother will this result in about 450m³/hour air flow ?

- if one fan produces 31dB of noise how much dB will three fans produce?

Thanks, i am looking at using three 12V industrial fans:
http://www.noctua.at/main.php?show=productview&products_id=83&lng=de&set=1

[cs.dk]

40,5 dB if I calculated correctly. + maybe some unknown added turbolence because of the design change.

I still don't get it. Bearings costs next to nothing, renew them, and it will run for 10 more years. You still have the opportunity to slow it down a little.

[Kjelt]

I still don't get it. Bearings costs next to nothing, renew them, and it will run for 10 more years. You still have the opportunity to slow it down a little.

Thanks for the calculation, it will be much better than the 230 fan.
The reason is that even with brand new bearings (which I don't have the correct tools for to change them) this motor still makes too much noise, we moved the bedroom next to the wineroom where this thing is working and I must say now I turn it off every night I sleep much better than I ever have 
Turning it off every night is not an option in the summer, and the suggested products needed to slow it down costs much more than three brand new silent 12V fans that produce the same airflow and are easy replacable and maintanable by me. 

[BradC]

Those muffin fans have wildly varying airflow figures depending on pressure on either side. The only person who can answer your questions is you, and the only way you can do it is to just do it. So why don't you do what you plan to do and then come back and tell us if it worked?

My guess? Too much static pressure at the fan exit will choke the airflow and you'll ice the evaporator completely stopping all airflow.
Muffin fans are mostly configured in puller applications precisely because they don't deal will static pressure well at all. We've tried to tell you, so prove us wrong.

[Kjelt]

Those muffin fans have wildly varying airflow figures depending on pressure on either side. The only person who can answer your questions is you, and the only way you can do it is to just do it. So why don't you do what you plan to do and then come back and tell us if it worked?

Because I hoped there were some people on this forum that know this stuff and did this before and can tell me right from wrong in this situation.
The only advise I got is to replace the bearings or the same noisy motor which is understandable and good solid advice but I am now looking for an noise improvement so I need another motor or fan. If there is someone who can show me a 230VAC or 12VDC or 24VDC equivalent power and axis motor that makes less noise I would be very happy, I am not able to find it.

My guess? Too much static pressure at the fan exit will choke the airflow and you'll ice the evaporator completely stopping all airflow.
Muffin fans are mostly configured in puller applications precisely because they don't deal will static pressure well at all.

Thanks for the advise this is good stuff  So if I understand you correctly it would be better to place these fans on the outside of the coolingevaporator so that they suck the air through it instead of blowing it through it, is that what you mean with pulling application?

We've tried to tell you, so prove us wrong.

When did you try to tell me? This is the first time I consider the low voltage fans since the first Papst 230VAC fan is too large for the hole and there is no room inside and I am not willing to spent more then a day metalworking a hole and innerworks to make it fit and then find out it doesn't work. If my experimentation fails I will have to be able to reverse it all.
If nothing works than I have no alternative than to revert to a new original motor or new bearings and a shop that can replace them.

[Kjelt]

Update:
In the meant time I ordered replacement bearings and I bought the three Noctua IP67 fans and they have a lot of airflow.  In order for them to suck the air through the evaporator unit and not sideways I had to make a construction to make it airtight against the box on the outside. Up till now not a big success.

So today I replaced the bearings of the motor which was quite a challenge since the pulleytool would not fit under the bearing 
The low bearing was a no go, the upper bearing I sanded off the pulleytool hooks more flat so they would just fit.
After that it was a piece of cake to remove the first bearing.
The second took me a while with some self made pulleytools which failed but in the end I used two large screwdrivers and wricked it up. It came off eventually.

I mounted the low bearing by using a drillpress which worked great and I made a small alu pipe, mount it in the drillpress and pressed to the upper bearing which also worked quite nicely.
Mounted the motor back and.................... a lot less noise 
Maybe not low enough to sleep again (since we are used complete silence by now) but still a very good improvement.

Thanks all for the recommendations and support esp SeanB many thanks, it is much appreciated