Dedicated Pump for Single Radiant Loop in Loft

mattymeek

Hello,
I'm in the process of renovating a portion of my house that is separated by a temp wall and has had no heat source. It's a large A frame w/ 20' ceiling height. The main floor level (375 SF) is over crawl space and there is a 175 SF loft portion 10' above the main floor. I'm installing radiant heat and need help specifying a pump for the loft.

BACKGROUND ON EXISTING SYSTEM:
I've previously renovated the rest of the house which is one level ranch and will open directly onto this A frame section. I installed radiant heat in the main house with 1/2" pex tubing between plywood sleepers with aluminum fins and installed engineered wood flooring as the finished surface. I have a 110k BTU triangle tube propane combi boiler in the basement which supplies heat for the radiant. The set point is 110 degrees and it has worked great with floor temps around 85 degrees in the main house.

My friend who is not a pro but has done several of these set ups designed the system and helped me install it. Near the boiler, I have 1" copper supply and returns with pumps mounted and controlled by a Taco 4 zone switching relay. The near boiler copper supply line has 3 grundfos pumps which send water to 9 loops of tubing. Instead of having a central manifold for the individual loops, the pumps are connected to larger pex tubing (Grundfos 1.25", .75" and .75") which run out of the boiler room and have T connections to the individual loops in the basement ceiling where they go up into the floor. There is one 1.25" pex return pipe which picks up all of the loop returns where they come back down from the main floor into the basement. The 1.25" return pex line goes back to the boiler room. Each loop has a ball valve in the 1/2" pex just before it T's back into the 1.25" return line. Instead of zone valves, I have three pumps with each pump controlling a separate zone (six 1/2" loops for living kitchen area, two 5/16" loops for the bathrooms, three 1/2" loops for bedrooms & hallway). It's basically a big manifold that is distributed throughout the basement and picks up each individual loop close to where it enters and exits the main floor. The loops are all less than 300' with some of the bedroom and bathroom loops being much shorter.

PLAN FOR RADIANT IN A-FRAME SECTION:
The 175 SF loft has 1 loop of 1/2" pex which will be about 350'. I decided to have just one loop as it was going to be close to 300' and the load should be less as the heat from the rest of my house will naturally rise up there. The ground floor portion will be 2 loops and I will simply run those directly off of the main floor 1.25" supply "mainfold that is already run near to this area in the basement with a ball valve ready for a new section of 1.25" pex which I can T to the 1/2" lines. This main floor zone is run by a single grundfos pump (not the Alpha 2 smart pumps, but a 3 speed model UPS15-58FC)

I'm worried that if I also attach single the loft loop to the same "main floor" manifold, it won't get much circulation the loop is longer than the others and 10' above the main floor with higher head pressure. My friend / advisor recommended adding a dedicated pump, not in the boiler room but at the end of the main floor manifold (up between the basement ceiling joists) which will push water up to the loft. This pump would need to be powered by a nearby outlet or the taco zone controller and would be connected to the taco zone controller in the boiler room so that it turned on when the main floor zone thermostat called for heat.

The alternative plan is to plumb the loft into the main floor loop just like the lower portion of the A frame and see if it works well enough. If it didn't, I could go back and add the pump later.

QUESTION:
I wanted to hear your thoughts on this plan and need help choosing a pump and the best way to connect it to my system and power the pump.


Main Floor Zone Pump (3 speed)

Bedroom / Bathroom Pumps (2 pumps like this one)

Boiler Room

Boiler Room Pumps and Zone Controller

Basement Ceiling Near A Frame Crawl Space: End of Main Floor "Manifold" piping. See the 1/2" pex lines from the loft. This is where I will attach new radiant loops

Loft section with Sleepers Installed Ready for pex tubing and fin plates then flooring

A Frame Section under renovation

hot_rod

For 1 loop even the smallest 3 speed circ will probably be oversized 

You could tun the whole home in a single circ and zone valves as every zone is probably over sized. The Alpha 2 is an ideal zone valve circulator

A small DHW recirc would do the single loop

What type of boiler, it will short cycle with a micro load like that

mattymeek

Thanks Hot Rod.  The boiler is a triangle tube prestige excellence 110k btu. I wasn't worried about short cycling as I thought I could run the single loop pump off of the same thermostat as the main house zone.  Can you power 2 pumps off the same terminal in the taco zone controller?  If not there's an open terminal and I would jumper the thermostat wire.  

My big concern is that because of the 8 ft higher floor height of the loft that loop wouldn't get any flow.  I just don't understand fluid dynamics but I'm worried about the relatively higher head pressure.  People on here say that water will flow towards the path of least resistance.  Am I over thinking this?

Jamie Hall

The flow will be determined by the resistance in the pipes, and has nothing at all to do with the height above the other floor or the boiler. Since the loop resistances will be different, however, you would do well to have three distinct "zones" (they aren't really zones, because they all run at once) with balancing valves on each: these would be the existing radiant floor, the new radiant lower floor, and the upper loft radiant floor. With balancing valves you can easily set the flow through each zone to be "just right"

What you may need to do is increase the system static pressure since the loft floor is higher. It should be set to about 15 psi cold. The expansion tank may need to be enlarged, and certainly will need its base pressure adjusted, unless you are already running at 15 . Likewise, any autofill valve will need to be adjusted.

hot_rod

I don’t see why you need another pump if the loft loop will be on the same thermostat and zone as the lower. Just tee the new loop into the manifold for the lower zone.

mattymeek

Hey guys, I just wanted to follow up to report that I took your advice and simply tee'd the new loop for the loft into the existing manifold pipe. It worked great in that the heat floor heat in the loft is virtually the same as the rest of the house loops which are 8' lower than the loft loop. While I don't have any flow meters or temp gauges for any of the loops, the return side is coming back at the same temp and the floor temp is the same as the rest of the house. Thanks for your experience and insights.

hot_rod

nice view