Fan bearing replacement on LG Therma V ASHP

[ProDave]

Over the last winter the fan on my LG therma V 5kW ASHP has developed a whine, the fan is not normally audible inside the house but it is with this whining fan.  It has finally reached the top of my "to do" list.

 

It is extremely easy to reach and remove the fan.  Power off.  5 screws removes the plastic front over the fan section and a single bolt removes the big fan blade.  3 nuts unbolt the fan motor and you need to take the lid off to unthread the cable and unplug it from the PCB.

 

Here is the fan motor before disassembly.

 

 

3 little self tap screws undo and the front can be gently prised off.

 

Inside is a permanent magnet rotor with 2 bearings

 

 

This is a variable speed motor and all the electronics are potted into the rear part of the housing.  So beyond bearing replacement this motor is probably not servicable.

 

The front bearing  

 

 

Measures 32mm overall diameter, 12mm shaft diameter, and 10mm thick

 

the rear bearing

 

 

Measures 22mm diameter, shaft 12mm diameter, thickness 7mm

 

Both bearings have NSK Korea stamped on them but I cannot see any other numbers.

 

It appears to be the smaller rear bearing that is noisy, so while I intend to try and buy replacements for both, I will probably only replace the rear bearing for now.

 

So help please from that size information to find a replacement bearing for each.

 

EDIT:

 

Further information:

 

I now think the smaller rear bearing has a smaller diameter hole.  I measured 12mm as the shaft diameter behind the bearing, but I now think it presses onto a reduced diameter section of shaft.  I now think that is 8mm diameter, but it is hard to measure properly without removing the bearing and that is likely to put the motor out of action until I get a replacement which I don't want to do at the moment.

 

Also, I have found a number "5201Z" on the front bearing.

 

I have started looking at bearing suppliers but of course I have no idea if these are ball bearing, roller bearing or what variant so feeling a bit out of my depth.

[ProDave]

My bearing learning curve is progressing.

 

Googling 5201Z only really gave a handful of foreign hits that even when translated did not yield much information.

 

Searching for 5201Z on ebay was a little better, it gave one USA seller offering a 5201ZZ bearing from which I gleaned it was a "Double row angular contact bearing, shielded"  And i also determined from his listing the correct way to identify a bearing is bbxddxtt  Where bb is the bore of the bearing, dd is the diameter of the bearing and tt is the thickness of the bearing.

 

So my rear bearing would be 7x22x7 and my front bearing would be 12x32x10

 

Searching for those sizes presented like that gives lots of options on ebay for not a lot of money. 

 

I have that nagging doubt if my rear bearing is in fact 7mm or 8mm bore, so I am minded to order one of each (yes I have put the motor back together now and back in the ASHP)

[JohnMo]

I wouldn't buy bearings from eBay way to many dodgy ones being sold. Would try bearing boys or simplybearings, have used in the past, would be my first port of call.

Edited July 31 by JohnMo

[ProDave]

26 minutes ago, JohnMo said:

I wouldn't buy bearings from eBay way to many dodgy ones being sold. Would try bearing boys or simplybearings, have used in the past, would be my first port of call.

This is as much an exercise to confirm beyond doubt what size I actually need.  I have ordered 7x22x7 and 8x22x7 and I won't know which it is until I take the old one off.  Bearing boys only have one of those sizes.

 

Once I have it working even with a cheap bearing, I will seek to get a quality one for an ultimate replacement.

[sharpener]

Have used simplybearings for lawn scarifier (flood damage) and oil boiler burner motor (noisy as oil leak had washed lubricant out). Excellent variety (standard, high temp, end seals etc), top brands, good advice, quick service, they get my vote.

[Dillsue]

On 31/07/2024 at 12:18, ProDave said:

Googling 5201Z only really gave a handful of foreign hits that even when translated did not yield much information.

 

Searching for 5201Z on ebay was a little better, it gave one USA seller offering a 5201ZZ bearing from which I gleaned it was a "Double row angular contact bearing, shielded"  And i also determined from his listing the correct way to identify a bearing is bbxddxtt  Where bb is the bore of the bearing, dd is the diameter of the bearing and tt is the thickness of the bearing.

Are you sure it's 5201Z? 6201Z is a common bearing and is the sizes you quote.

 

When you sort out the size you need buy quality brands like SKF, NSK, Timken etc. For the few extra £ you pay, they'll last way longer than cheap s**t off ebay

[ProDave]

My cheap bearings arrived today and I have fitted one.

 

I can now confirm the rear bearing on this motor is 8x22x7.  I did not want to pull the old bearing off to measure the shaft size in case the bearing collapsed in so doing and I would have been left with the ASHP out of action until the replacement arrived, and measuring the shaft diameter when the end of the shaft is flush with the end of the bearing was less accurate, so I had ordered a 7mm and an 8mm bearing.

 

The ASHP is now running with a quiet fan as before.

 

Now I have the old bearing off, I can confirm It is an NSK 608Z1  All the writing on this rear bearing was on the side facing the motor armature so completely invisible until the bearing was off the shaft.

 

Getting the old bearing off was not too difficult.  I tried my smallest puller set, but that could not get into the limited space.  I was mindful of the rotor being a permanent magnet and no doubt not very strong.  Levering anything against that would no doubt end in a broken rotor.  So I hunted around various tubs of odds and ends in the garage, and came up with the brass nut off a 28mm compression fitting, which passed over the bearing and rested on the steel core of the rotor not the magnet, and then a screwdriver under each side to gently ease the bearing off.

 

I will now seek a better quality 8x22x7 608Z1 to have ready for when the cheap one fails.

[ProDave]

Not much luck yet.  Simply bearings and Bearing boys don't recognise 608Z1

 

I have found this that identifies my bearing but they look to be a wholesale supplier.  https://en.tradebearings.com/608Z1_C3_E-817847.html

 

And I don't trust Alibaba to supply a "genuine Japanese NSK bearing"

[ProDave]

Bearing Boys have replied offering me this  https://www.bearingboys.co.uk/Miniature-Bearings/6082Z-SKF-Shielded-Miniature-Ball-Bearing-8mm-x-22mm-x-7mm-131446-p   They claim SKF are better than NSK

 

I guess that has to be better than my unbranded ebay one?

[Temp]

SKF, NSK, Schaeffler, Timken and NTN are the biggest bearing manufacturers. Any of them should be good but beware as I'm pretty sure there will be fakes out there of all of them. Who you buy from is probably as important.

[Temp]

https://www.abf.store/s/en/bearings/608Z1-C3-E-NSK/578491

Quote

 

The 608Z1 C3 E NSK is a miniature ball bearing. This is a very small single-row deep groove ball bearing. 

• Inner (d) MM 8
• Outer (D) MM 22
• Width (B) MM 7

 

 

So I think the one from Bearingboys will be fine.

Edited August 5 by Temp