AM radio and TV fuzzy??

[workingman]

i have never come across this before but here goes. the house we are dealing with is an old two wire house with a brand new TRANE furnace. When the furnace kicks on and the fan starts running the Am radio in the customers bedroom gets really whinny, also the tv in the living room gets really snowy. when the units power is cut off thosr items are fine. i am not sure what causes this but it may be harmonics of sorts. would bonding the ductwork to the panel be of help?? The breakers are push button type. she is wanting a panel upgrade but i am not sure if that would help as i am not sure the house is grounded properly. Any help would be great

 

[kevinware]

Workingman,

I believe you touched on where to start looking for a problem, the grounding system. Sounds like the motors in this equipment is introducing electrical noise on the system. Does this house have three prong receptacles? Sounds like it does not. You can rule out harmonics. You don't have that type of problem on a single phase service. Look at the new equipment and see where the equipment grounding wire (green) is connected. You may find it is not connected at all or the white wire is being used to ground the unit case thus the motor case and this might be where the noise (High frequency) is coming from. You may also find you do not have an equipment grounding path at all. But I am an apprentice also so lets see what others have to say.........

Kevin

 

[james wuebker]

workingman, for the time being, put the furnance on the other phase coming in the house. If it's on( a )phase now put ot on the( b) phase. I bet this will help until the new upgrade for the is completed.
Jim

 

[petersonra]

Re: AM radio and TV fuzzy??

i have never come across this before but here goes. the house we are dealing with is an old two wire house with a brand new TRANE furnace. When the furnace kicks on and the fan starts running the Am radio in the customers bedroom gets really whinny, also the tv in the living room gets really snowy. when the units power is cut off thosr items are fine. i am not sure what causes this but it may be harmonics of sorts. would bonding the ductwork to the panel be of help?? The breakers are push button type. she is wanting a panel upgrade but i am not sure if that would help as i am not sure the house is grounded properly. Any help would be great

I suspect the furnace has some kind of variable speed drive running the blower. These things can create a LOT of noise if installed incorrectly.

A couple of comments.

1. Make sure the neutral is actually grounded.

2. Try moving the furnace motor to the other leg as suggested by another poster.

3. I doubt that any amount of bonding of anything will reduce the noise getting to the TV and radio.

4. It is possible that the wiring for the furnace and the wiring for the tv/radio share a conduit. if that is how the noise is getting to the TV/radio, the only answer will be to run power direct to the furnace from the main panel.

 

[wmgeorge]

Trane Unit

Trane Unit

The new furnances MUST be grounded (bonded) to a equipment ground. Water pipe and/or ground rod, and the neutal grounded at the service, which I doubt the old 2 wire system has.
It might also have the VFD type motor as one poster suggested.

The flame sensor on these new units looks for a capacitance ground though the flame.

 

[ramsy]

Re: AM radio and TV fuzzy??

4. It is possible that the wiring for the furnace and the wiring for the tv/radio share a conduit. if that is how the noise is getting to the TV/radio, the only answer will be to run power direct to the furnace from the main panel.

As suggested by Kevinware, is it remotly possibile that noise traveling along the neutral could get to the TV/radio through bootleged/false grounded receptacles? This could energize the case/housings providing a shock hazard, in addition to any emf antennae interference.

Look at the new equipment and see where the equipment grounding wire (green) is connected. You may find it is not connected at all or the white wire is being used to ground the unit case thus the motor case and this might be where the noise (High frequency) is coming from.

 

[physis]

It seems odd to me that nobody has considered the "fact" that EMI dosen't need a conductor.

This could very well be airborne noise.

Edit: The furnace is a transmitter.

Edit again: I souldn't say "could very well be" I should say "is".

 

[benaround]

Sam,

Bill Clinton had trouble with that word also!

 

[physis]

Cute Frank :lol:, Good to see ya.

There are relatively useless and stupid FCC regulations that might be getting breached by this furnace. I'd talk with the contractor or manufacturer.

Edit: No existing error code.

 

[iwire]

There are relatively useless and stupid FCC regulations that might be getting breached

Be careful they are watching. :shock: :wink: :lol:

 

[petersonra]

new furnace noise

new furnace noise

one possible solution to your problem would be to install a 115-115V isolation transformer right at the furnace.

you would need to run a ground wire to your GES for the secondary of the transformer, but it removes the rest of the homes electrical system from the equation.

 

[ramsy]

Re: new furnace noise

Re: new furnace noise

Does GES = "Ground Engineering System", and is that equivelant to a nutral bus bar at the panel, or grounded phase for Delta's?

 

[don_resqcapt19]

Bob,

you would need to run a ground wire to your GES for the secondary of the transformer, but it removes the rest of the homes electrical system from the equation.

How? The GEC for the SDS will be connected to the home grounding system and to its grounded conductor.
Don

 

[eric stromberg]

Is the TV fed from a cable system? Is the cable connected to a grounding block that is then connected to the Electrical Grounding System? If so, buy two Baluns (Balancing-Unbalancing) transformers and connect them back to back. The first will be the kind that has a female coax connecter on one side and a twin lead pigtail on the other. The second will one that has two screws for the twinlead connection on one end and a push in type male coax on the other. Screw the twinlead of the first balun to the screw terminals of the second balun. This will decouple the shield of the cable from the chassis of the tv set. Both will still be grounded, the cable through the block and the tv through the AC cord. This will stop the circulating currents that create picture noise when there is potential on the ground system.

Eric Stromberg, P.E.

 

[steve66]

I don't think you should have to install anything special. Hook up the think according the the manufacturers instructions, and verify the owner has your basic grounded electrical service.

If the furnace still causes noise on the TV and radio, its time to call the manufactuer to check it. It might have a capactior or filter that's bad.