Portal econet_noises

Compressor

Remember during your inverter training, you were told that inverters make different sounds than standard single or even two stage units make? The primary source of sound comes from the compressor. A standard scroll compressor spins at approximately 3450 RPM. The inverter compressors, depending on model can range anywhere from 1200 RPM up to 7000 RPM in overdrive. The ramping rate also can make different sounds as well. Had this been explained to the customer in the beginning, this may not be a problem now.

All the inverters start from 0 rpm and go to 1200 RPM in about 2 seconds, then it takes about 5 seconds to ramp from 1200 to 1500 RPM where it holds for an additional 10 seconds. Occasionally, especially if the unit has been off for a while, the scrolls may make odd noises upon start up. (chatter, or clicking). If it occurs for the first few seconds, this is considered normal. This is NOT a defective unit or compressor.  If it lasts for more than 15 seconds, a conversation with your Distributor Service Coordinator may be in order.  VSODU Firmware changes now increase the speed at 15 seconds after start up to help extended noise issues. 

Units manufactured in late 2017 or later use a long slide reversing valve, which takes less pressure to shift.   If you have a unit built before this, and have extended chatter, you may consider a change in the reversing valve.  Just make sure you use the part number spelled out in the parts site, not the part number on the valve itself. 

When an inverter goes into overdrive, it will wind up to higher RPM's resulting in higher frequencies many of us are not used to hearing. In your training, you may also recall the RPM clamp feature in the thermostat settings. If overdrive noise is objectionable, use the clamp to limit the compressor overdrive speeds to a point where it is acceptable. This is a design feature allowing you to adapt it to your customer. You will be exchanging some overdrive capacity, but this is a give and take.

Dual Fuel

For sure one thing we see an increase in is dual fuel systems. Many customers who already have gas typically didn’t have a heat pump and all of the sudden now in winter, they hear all these noises outside they simply aren’t used to. We all know heat pumps and condensers are not supposed to be installed below the bedroom window, but there it is. Remember, in the dark of night, noises are amplified by cooler air and the lack of other ambient sounds we hear during the day. When you purchase a new car, the sales person should show you how all the features work, where to find the trunk release, or how to operate the navigation system. You can’t just walk away from an installation without offering the same to the customer.

Defrost

When a reversing valve shifts, you may hear the sound of high pressure refrigerant going to low. This will most certainly impact the tones coming from the compressor. In recent years, you may have noticed on single stage equipment the compressor shut off at the time the reversing valve shifts. For the inverters, because of ramping, we don’t want to do that. In a natural defrost event, the compressor will slow down or speed up to a model dependent designated speed called the defrost shift speed. It will remain at that speed for 30 seconds before shifting the reversing valve. This speed has been selected to ensure enough mass flow is there to shift the valve, as well as reduce compressor noise. Coming out of defrost the same thing happens before the compressor is commanded to a predetermined oil return speed. Once again, first time heat pump owners will certainly notice this. It would have been great to explain that up front, rather than being on the defensive later.