Trying to find a replacement relay #2

Thread Starter

mattyuk2000

Joined Sep 28, 2020
13
Hmmm. that's interesting - i've just noticed that on one of the datasheets i shared it shows 80vdc max switching voltage and on the other it shows 30v max switching voltage. i wonder if one is a typo....

80.jpg
 

Thread Starter

mattyuk2000

Joined Sep 28, 2020
13
What motor is it controlling? Never seen a relay involved in the belt motor, most likely is the track raise/lower motor.
Determine the motor and see what the rating on the plate is.
Max.
Hi Max it's controlling the ac input line into a rectifier. then the rectifier feeds the motor. it's the main treadmill motor, rated 220vdc 10a c142d34oz3a. This treadmill doesn't have a raise/lower motor, although it had a sister model that did that might have shared the same power board? I'm getting no ac input to the rectifier and there's not much before it to have failed and the relay is acting a bit strangely when tested.
 

SamR

Joined Mar 19, 2019
2,760
how can it be both 20A at 30VDC and 16A at 30VDC at the same time
Due to the physical nature of Direct Current and Alternating Current the same physical contact must be rated differently. I'll just leave it at that without going into theory but has a lot to do with arc suppression when opening the contact under load. Since the relay can be used to switch either DC or AC they give the ratings for each. What does not change is the coil DC rating V. I didn't go into the coil current rating but it typically is around 2A for that type of relay which is pretty standard and more than enough under normal usage. Typically only uses a couple hundred mA or so. Max knows a good bit about treadmills and their motors so he can help you there.
 

MaxHeadRoom

Joined Jul 18, 2013
21,601
In my opinion, switching a load such as a TM DC belt motor is pushing it for a relay such as this. The ones I am familiar with do not use a relay in the belt motor circuit.
I suspect in that application that normally the relay contacts would be switched dry, IOW open and close when no load is present.
When looking for a quicker replacement, as all ready suggested, look through some of the relay suppliers catalogues for one with the same footprint and order from Mouser, Digikey etc.or your usual UK suppliers.
You need a 230VAC switching rating for the contacts, at least 10a rating.
Max..
 

Thread Starter

mattyuk2000

Joined Sep 28, 2020
13
Due to the physical nature of Direct Current and Alternating Current the same physical contact must be rated differently. I'll just leave it at that without going into theory but has a lot to do with arc suppression when opening the contact under load. Since the relay can be used to switch either DC or AC they give the ratings for each. What does not change is the coil DC rating V. I didn't go into the coil current rating but it typically is around 2A for that type of relay which is pretty standard and more than enough under normal usage. Typically only uses a couple hundred mA or so. Max knows a good bit about treadmills and their motors so he can help you there.
Brilliant. Thanks Max. I will look into the theory. Thanks for the help and advice!
 

Thread Starter

mattyuk2000

Joined Sep 28, 2020
13
In my opinion, switching a load such as a TM DC belt motor is pushing it for a relay such as this. The ones I am familiar with do not use a relay in the belt motor circuit.
I suspect in that application that normally the relay contacts would be switched dry, IOW open and close when no load is present.
When looking for a quicker replacement, as all ready suggested, look through some of the relay suppliers catalogues for one with the same footprint and order from Mouser, Digikey etc.or your usual UK suppliers.
You need a 230VAC switching rating for the contacts, at least 10a rating.
Max..
Thanks Max. The treadmill is a million years old (Tunturi J3F) so I expect they do things differently now. I'm afraid I don't understand your dry switching comment - I think it's a normally open relay. When the treadmill kicks in after a countdown, the relay can be heard switching. Except it was behaving very suspiciously. I replaced the relay today and the treadmill works! Thanks for your help with this. Can I ask one more favour? I replaced it with RM85-5021-25-1012 SPST-NO https://www.tme.eu/en/details/rm85-5021-25-1012/miniature-electromagnetic-relays/relpol/ I think this is actually a 16A rated relay and that I possibly need 20A? Is that correct? If so I'll order the original or your recommended replacement from China and just be patient.
 

MaxHeadRoom

Joined Jul 18, 2013
21,601
There has to be some kind of RPM control of the motor, when you hear it switching, is the motor actually moving?
What are the motor plate details? If any?
If in fact motor current or board current does not actually switch with the contacts, i.e. power is on the board when the relay turns on/off.
Then that version should be OK.
If in the UK, then the plug has a 13a fuse anyway, right?
Max.
 

djsfantasi

Joined Apr 11, 2010
6,947
A relay is made up of two different components. The coil and the contacts.

First, you need a relay whose coil voltage and current matches the circuit controlling the relay.

Secondly, the contacts must be rated for what it is switching. The ratings are different for AC and DC, as you have been told. The allowed current switched in a DC circuit will always be lower than the allowed current when switching AC. These ratings can be found on the specifications of the relay.

If you’re switching 230VAC at 20A, the switched load AC current and voltage rating must be less than the relays switching rating. Current is the most critical value.

So if you’re switching 230VAC at 20A, the relay contacts should be no less than 230VAC and more than 20A... 25A or 30A are suggested ratings.
 

MaxHeadRoom

Joined Jul 18, 2013
21,601
But also keep in mind, if this is a T.M. with a motor that states 20 on the label, in this application you may not come close to a 20amp load.
I would also guess this relay is not switching under load.
As I mentioned, you would have a 13a fuse limit anyway.
Max.
 

Thread Starter

mattyuk2000

Joined Sep 28, 2020
13
Thanks Max/djsfantasi good points both. Yes it has a 13A fuse on the main plug - good point. Attached is the plate on the motor. It does say 10A max which is interesting. Re. RPM control, I think this is done using pulse width modulation by an IGBT which is on the board, but I could be wrong.

I also include a photo of the board too for interest. As mentioned the treadmill is up and running with the relay I mentioned. As long as it wont explode when in use, then I'm happy!

motor.jpgpbc.jpg
 
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