Carrier Experts Help!

[Unclev]

I have two questions that Carrier technical support and my local dealer differ on the answers. First, does the Carrier base heat pump (25HBC5) series now have demand defrost instead of time/temp defrost. Second, assuming I would have an Infinity compatible heat pump...will an Infinity control thermostat be 100% compatible with an FV4 series fan coil just like it would with the FE4/5 series?

[isuredo]

I have two questions that Carrier technical support and my local dealer differ on the answers. First, does the Carrier base heat pump (25HBC5) series now have demand defrost instead of time/temp defrost. Second, assuming I would have an Infinity compatible heat pump...will an Infinity control thermostat be 100% compatible with an FV4 series fan coil just like it would with the FE4/5 series?

The HBC series is time/temp. It is not Infinity/communicating equipment, and the Infinity controller will only work with the FE fan coil which is Carriers ONLY communicating fan coil

[Unclev]

Thank you for the quick response. One final question. I live in Pennsylvania and my current York heat pump has demand defrost and it works great. I am going to be replacing this heat pump in the near future and I think I need a stay pump with demand defrost so that limits my choices. I have been looking at the American Standard Heritage 15 model 4A6H5030E or the Carrier 25HNB530A003, 25HPA530A003 (If still available. Carrier is phasing the 25HPA5 out). I really don't need a VS air handler but If I go with Carrier I presume to get "their" version of demand defrost to work with the Infinity T stat you are saying I will need to purchase a FE air handler or will their demand defrost work with an FV4 air handler. Just to be perfectly clear. Thanks again for all your time!

[isuredo]

carriers defrost does not rely on anything in the air handler other then it will call for back up heat to temper the cold air during a defrost. Demand defrost vs time and temp are virtually the same operation. the carrier will not go into a defrost just because the timer has rolled over. It will only look at the sensor and if the coil temprature is correct, it will initiate. so if its set for 90 minutes, all that means is every 90 minutes it will check to see if a defrost is necessary

[beenthere]

Last I knew, no carrier has an actual demand defrost(defrost board that determines by line temp and air temp).

[BaldLoonie]

Carrier's upgraded defrost is still a timer. But it bases the intervals between defrosts by how long it took to defrost the previous cycle. You'll still get lots of unnecessarily defrosts since the time/temp method has no idea if the coil is frosted, but it is still better than a fixed timer.

Demand defrost uses thermistors and logic and pretty much knows if the coil is frosted enough that it should clean itself off.

If you go 13 SEER, you'd be fine with a PSC standard motor. But no point in buying a higher SEER unit without at least a fixed speed high efficiency motor like American-Standard's GAM5 or Carrier's FX4.

For example, the 4A6H5030 with standard air handler is 13.75 SEER, where it will do 16.25 SEER with the TAM7 VS. HSPF is 1 point higher too.

[mark beiser]

Demand defrost vs time and temp are virtually the same operation. the carrier will not go into a defrost just because the timer has rolled over. It will only look at the sensor and if the coil temprature is correct, it will initiate. so if its set for 90 minutes, all that means is every 90 minutes it will check to see if a defrost is necessary

Demand and time/temp defrost systems are not "virtually the same operation".

When the outdoor temperature is below around 35-40º or so, the coil temperature sensor for a time/temp system will pretty much always closed, so the system will go into defrost every time the timer is up, even if there is no frost on the coil.
This wastes a significant amount of energy.
If you jack the timer up to 90min to reduce useless defrosts, the defrost interval is WAY to long for times when there are moist cold conditions, freezing rain, etc..

With demand defrost, you only get defrost when it is needed.
This may result in rather frequent defrosts in freezing rain, and other cold and wet conditions, but they are needed under those kinds of conditions.