Posted By 86turbodsl on 03/06/2009 4:46 PM
Hi,

first time poster.  I'm trying to figure out the best way to plumb my new house's HVAC system.

there's been some changes over the time my contractor and I have designed the system.
Firstly, I'm a mechanical engineer and familiar with many HVAC concepts. 

My system has been spec'd with the following:

sources/equipment:
3 ton GSHP water to water - climatemaster
40 gallon buffer tank - electric water heater
desuperheater option
40 gallon electric water heater - DHW
small 60,000 Btu boiler used as backup and some DHW heat
Steibel eltron 106 gallon dual coil solar storage tank

loads:
air handler using water coil cools whole house and heats partial house
using a zone air valve.
downstairs and both upstairs baths are heated with radiant in floor heat.
garage and basement both have in floor heat.

three temps mixed down using manual mixing valves
the wood floor radiant is one
the tile floors are one
the garage / basement is one

The HVAC guy, who is a friend, has been struggling with the system design a bit.
He's currently got a single big pump trying to push all the radiant through the
mixing valves and loads.  I know he's trying to save me money, but I've got
concerns that it's going to do the job.  Up to now, the system is only partially functional.
Our propane bill for the winter was pretty big.  I'm concerned that we may not be
getting the best efficiency.

I've also read some recent information that the desuperheater may not be plumbed correctly.  Currently, the desuperheater dumps directly into the DHW tank. 
I've also got the eltron solar tank that I eventually want to get into play, and harvest some
solar energy for DHW and maybe assist the GSHP.  Right now, we've got capacity on the geo for about 30-35F outdoor temps, and below this, the boiler is running all the time.

I am looking for suggestions on the best way to plumb this.  I've got siggys' book on hydronics, but it doesn't really get into a system this complex.  
My main thoughts have been to use a primary loop and have each source and load just tee into the primary with closely spaced tees to prevent hydraulic interaction.  I'd probably split each water temp off and feed with a pump for each, using the zone valves to turn each zone on and off.  I want to get the solar tank plumbed in,  and use it to it's best use.  Maximum heat storage is my goal, max efficiency.  House is pretty big, so I want to make it as cheap to heat as possible. 

With all that said, any suggestions on this system?  I'd like to go two tank for the desuperheater but not sure how all this integrates.   If this isn't the right forum, someone please let me know.

Thanks!

Posted By geo fan on 03/06/2009 8:51 PM
What I was saying is have 2 first stage warming tanks in paralell
both supplied with cold water , both feeding a single primary water heater
Zone valves , it miight just be my pet peev but you end up over pumped or under depending on how many zones are calling
and it seems like I replace 100 of them every winter .
Controls will be key I would definitly add a outdoor reset to modulate and lock out the boiler above your balance temp

Posted By geo fan on 03/07/2009 2:47 PM
the pipe schematic I posted would require a variable speed pump if zone valves where to be used
yes , but unnessarary if each zone has its own circ which is sized for that zone .
radiant mixing valves are thermostatic I would put a dry well thermometer on each supply and return
also each radiant zone has its own header for the loops in that zone most of which allow pressures to be adjusted for each loop in the zone as long as they are not more then recomended by the manufacturer.
The circulators dont care what the temp is
you would want to modulate the temp with the load not the pump
ps you should mix after the zone valve/circ