humming transfer switch

enblethen wrote:
It could be dirt on contacts. Could try to use some canned air to blow out the switch. Disconnect power first to be on safe side!
What is make and model of your transfer switch? If I remember there was some recalls on some!
recall

The recall was for improper torque on the 120 mount screws. It was a OEM install issue, not a fault with the Transfer switches. It was a fire hazard. Doug

7craneway wrote:
any advice on transfer switch humming all the time some times very loud..do they make a quite one???

What brand and model do you have? How old is it?

Does it make noise when plugged in or on generator power or both?

Have you opened the transfer switch to look for heat damage or loose connections?

Yes a new transfer switch should be near silent.

Iron laminations. Coated with silicon layer (not silicone). They can resonate. For years GM alternators with 7-pair rotor poles were famous for this. The hummmmmm can actually loosen lamination rivets over a long period of time. Large tramsformers used for transmission lines can sometimes be heard for a hundred feet amd they are submerged in oil. Nevertheless any increase in noise is cause for a rapidly scheduled inspection IMHO :)

It could be dirt on contacts. Could try to use some canned air to blow out the switch. Disconnect power first to be on safe side!
What is make and model of your transfer switch? If I remember there was some recalls on some!
recall

It might be possible to lubricate the switch or clean it with a contact spray. Only do this with power REMOVED from the system.

BTW, graphite in a pencil will conduct electricity (until it burns).

so I opened the switch(removed cover) there are 2 switches inside..the one hooked up to the shore power hums very loud when plugged in..wanted to make sure the plunger was fully engaged took a pencil and pushed in on it ...ah... it wasn't ...just a slight hum know...I checked voltage was ok..line side and load side.. 115v..so what do ya think..replace switch...???

7craneway wrote:
any advice on transfer switch humming all the time some times very loud..do they make a quite one???

JOKE: Teach it the lyrics....

Serious: First: Make sure it is the transfer switch and not something else like a converter mounted nearby.

Now: There are basically two types of transfer switches,, I have not "Confirmed" but I suspect that one type is "3 way transfer" NOTE that this is suspicion only. (I will have to research this later tody) but that does not matter.

The 3-Way would be Inverter (no other power source present) Generator (if present) or shore power IF present.

Mine is a 2 way (Shore/Generator) the inverter has its own transfer switch which is also 2 way.

Two way switches like mine, when SHORE POWER is being used, there is NO energy to the solenoids.. They do not HUM, they just sit there, Cool as the room around them.

If the generator is runnign power is sent to the solenoids.... They may HUMM or not (if they do I don't hear it) but that is the only time they have power.

3: way
If shore power is present one bank of solenoids pulls in,, Generator the other.. They may hum.

Why do they hum?
The solenoid has a metal Core, this core, around which the wire is wound, is made up of many thin layers of iron, you lay in a layer, coat with varnish, lay in another varnish, and another varnish, till you have the core built up to the size you desire.. over the years the varnish dries, hardens and flakes away, now the leaves can vibrate against each other.

The solution.. Well there are 3
1: (Easiest) replace the switch
2: (less costly) Replace the solenoids
3: (Requires an electronic technician/engineer, IE: ME)_ convert the feed to the solenoids to DC, that way they won't hum, Some disadvantages to this but it can be done, one advantage too. Requires modification of the switch, voids all warranties.

KD4UPL great info.

Find out what they high rollers use like Kountry Koach (sp?) Quicksilver has a 3P/DT Mercury switch with rectifier. But the gen and the inverter have been extracted.

thanks for all the imformation..its got me thinking...any suggestions on changing out to a new switch..??make or model i got a 50amp power coard

Some transfer switches use AC to hold the coils. This can cause a hum because the AC power is always flowing in the coil at 60 Hz. Some better transfer switches use DC coils. This reduces hum since the coil power is DC. It does add some cost and complexity because now the switch incorporates a rectifier circuit to make the DC.
The quietest should be a switch with contacts that are mechanically held. This wouldn't involve any power flowing thru the coils except when the switch changes position. This type is commonly used in large generator transfer switches for buildings.