OT: RFI from Modern Furnaces

[Don Nelson]

Hi all,

There was a discussion some time ago about RFI emanating from front loading washers.

This note is about the possibility of RFI emanating from microprocessor controlled house furnaces. We had to have our house furnace replaced last week because of a failure. Yes we winter camped for a over a day as a result. We now have a 95 percent efficient microprocessor controlled furnace installed. I did not think about possible RFI that it might emit at the time of choosing that furnace.

The good news is that I have not found any RFI on the HF bands as yet while the furnace is active or not active. My question to the group is: was I lucky? The furnace control has a very nontrivial computer control and could cause plenty of noise. It would be nice to think that the designers of furnace control systems are sensitive to RFI radiation issues.

The furnace is a Lennox model G71MPP.

Don, N0YE

[Jack Smith-6]

We have a Carrier high efficiency propane furnace nearly 20 years old
with an inverter powered blower motor. It radiates RFI in the 100-300
KHz range, but fortunately nothing higher.

Jack K8ZOA


On 3/4/2010 11:47 AM, Don Nelson wrote:

> Hi all,
>
> There was a discussion some time ago about RFI emanating from front loading
> washers.
>
> This note is about the possibility of RFI emanating from microprocessor
> controlled house furnaces. We had to have our house furnace replaced last
> week because of a failure. Yes we winter camped for a over a day as a
> result. We now have a 95 percent efficient microprocessor controlled furnace
> installed. I did not think about possible RFI that it might emit at the time
> of choosing that furnace.
>
> The good news is that I have not found any RFI on the HF bands as yet while
> the furnace is active or not active. My question to the group is: was I
> lucky? The furnace control has a very nontrivial computer control and could
> cause plenty of noise. It would be nice to think that the designers of
> furnace control systems are sensitive to RFI radiation issues.
>
> The furnace is a Lennox model G71MPP.
>
> Don, N0YE
>    

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[Jim Brown-10]

On Thu, 4 Mar 2010 08:47:43 -0800 (PST), Don Nelson wrote:

>My question to the group is: was I
>lucky? The furnace control has a very nontrivial computer control and could
>cause plenty of noise. It would be nice to think that the designers of
>furnace control systems are sensitive to RFI radiation issues.

The most likely source of RFI on the HF bands would be a variable speed motor
controller. These are essentially switching power supplies driving square
vave generators that are pulse width modulated to control motor speed. If you
had that problem you would kiow it. Big time.  :)

73,

Jim K9YC


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