What is the range of temp for air entering a supply duct or temp leaving registers? Alternatively what is the temp rise?

This assumes a properly sized unit with properly designed CFM.

 

In some other post someone indicated air leaving registers might be a little cold for comfort. It could be that the person referred to particular velocity that would make it feel cold. Nevertheless, I would like to know what the realistic values are.

 

Thx in advance…

You are looking at 23-25 degrees delta for first stage and 25-28 degrees delta for second stage operation, depending on the blower speed. Return air is about 70, so supply air is around 95 degrees. You loose a few degrees depending where your register is, average is about 88-90 on the register. You can check some live data. http://welserver.com/WEL0288/

I'm good with Doc's deltas.

Proper register placement and diffuser slat orientation should deal with "wind chill" from warm air. It is a valid concern. Newer systems with ECM blowers allow for some customization of CFM settings as well as starting slowly to minimize noise and cold blow.

"Proper" depends on tradeoffs you or the manufacturer make. If you really want warmer register air, you can get it with some cost in efficiency.

By the time your oil burner is ready for retirement (or maybe sooner), air source heat pumps using CO2 (aka R744) as the working fluid may finally become available in the US which will take some wind out of geothermal sails.  With output temps of above of 50C/122F you can get comfortable temps out of an air-handler coil, heat your hot water with it directly.  Current technology CO2 heat pumps peak out well above 150F considerably hotter than with flurocarbon refrigerants.  (The Sanyo units only spec out 65C/149F ratings, but industrial-sized units in Germany run fine with ~175F outputs.) At comfortable space-heating  or domestic hot water output temps they can deliver a COP>3 with outdoor temps down to ~20-25F, and are still in ~2 COP territory down to -10F (yep, that's below zero.)  Your peak loads are probably about 12-15kw, and occur at temps where the COP is starting to flag a bit so you'd need some sort of backup.  The 9kw Sanyo units sold in Europe are probably fine for you down to about 0-5F, but may be good to even lower if you can reduce your peak heat loss with more insulation, or can apply insulated shutters/shades when it's actually cold out, etc.  But there are other vendors, other sizes- it's not rocket-science to scale up to US-type heat loads when they decide to market them here.

Geothermal CO2 heat pumps are surely coming as well.  As a retrofit in hot-air furnace situations the high output temps of CO2 heat pumps would be a far preferable solution than the current technology available in the US. (Did you ever feel like a second-tier country in technology terms? Energy policy in the rest of the world has put them ahead of USA on some of this stuff.)  Currently the air-source units work well enough for the milder European climates that the additional cost of going geo isn't cost effective- air source CO2 pumps  are more expensive than old-school heat pumps, but still a fraction of a geo installation cost, and in many climate zones it's at least as efficient as geo using old-skool heat pumps.

We'll see how long it takes.  It took at least a half-decade for the Daiken Altherma hydronic air-source heat pumps to arrive at these shores (and there are as-yet but a handful of US installations).  Maybe by 2015  R744/CO2 heat pumps will start to trickle in?  Stay tuned, but don't be holding your breath now...

I'm not sure that increased output temperature is worth the COP reduction that CO2 has over R410A at typical geothermal temperatures. I agree that it will improve air source heat pump COPs in cold climates.

Daiken's front running residential ASHP (in the US) equipment uses 410 that they manufacture themselves. Perhaps since they make their own R410a it pays better than CO2 equipment. Perhaps we are confusing residential and commercial equipment.
Or maybe like so many other kinds of equipment (including geo), it is not a one size fits all solution.
J

Your air temp rise should be between 20-30'f. I would disagree with the idea that warmer air equals greater comfort. It is just the opposite. Hotter air equals hot and cold spots. Geo should produce very even temps around the room. It does require proper design,but when done right you should not even know when it is on or off.

For comparison only:

I have a Daikin air-to-air heat pump and use the crawl space as the supply plenum and the attic for the return. I have plenty floor registers around the perimeter of the house, and almost as many return grills in the ceiling. The air handler is in the crawl space. It runs constantly at low speed, and on high when the heat pump is running. The air velocity from each register is quite low. You have to be close to and above the register to feel the air movement. During the heating season this past winter the house temp was a fairly constant 74F with no set backs. The supply temp would therefore be close to that, maybe 73F. The crawl space temp seldom went above 85F, usually was 78 to 83F. There are no drafts in the house, warm or cold. Room temp was pretty constant from floor to ceiling. A ceiling fan on low speed will create a cool draft indicating the air at the ceiling is not warmer than at sitting level.

In short, air from the registers less than 10F, and as little as 3F, above room temp can keep the living space quite comfortable.