Grundfos Alphas and Radiant?

[cdecker]

As I design and install my radiant system, I'm curious everyones opinion on zone valves vs zone pumps, and your thoughts on the Grundfos Alphas?

My setup will be 100% in-floor radiant, some staple-up, some in concrete (basement, garage floors). My designs originally call for a couple of large manifolds with actuators, and one pump for everything (Taco 011) on the secondary side, but as I read more and more on this forum and others, I'm wondering if that same setup would be optimized with a Grundfos Alpha in Auto-Adapt mode. On the other hand, the price on the Alphas has come down enough that Im wondering if it would make sense just using an Alpha for each zone, and doing away with the actuators completely.

I realize the whole zone valve vs zone pump topic is an age old debate, but with the new technology of auto pumps like the Alpha, and with a system that is strictly low-temp radiant (no baseboard, radiators, etc), is there a preferred setup?

Thanks!

 

[mygarageone]

Go with pumps or pump and the alpha would be a good choice.

 

[NaturallyAspirated]

Well you would most likely experience higher electrical usage with a wall of pumps system. Alphas will be vast overkill for most single zones, going with a manifold and actuators would be cheaper as well. How many zones are you planning for? A manifold mixing station might be the way to go. What are you using for a heat source? Are you pumping the heat source into a buffer tank or some hydraulic separation before the zones?

http://www.supplyhouse.com/Caleffi-...-Mixing-Station-w-Alpha-25-55U-Pump-7-Outlets

Neal

 

[cdecker]

Looking at approximately 7-8 zones, 16 loops total. All loops will be 330', some less but no less than 10%. 6 loops are in-slab (3 garage, 3 basement), the rest are staple-up.

Jury is still out on heat source. Original design was using my existing Bosch Tankless with flat plate, however that idea was scrapped for numerous reasons. Next was Navien NCB-240, but I think I've decided against that as well. Third was Viessmann Vitodens 100, but being that none of this radiant is my primary heat source, and I would still need an indirect for my domestic, its hard to justify the cost. Lately I've been leaning towards a high efficiency tank unit like the HTP Phoenix or even the HTP Phoenix Light-Duty.

One of the several designs I've had done called for a couple of 8 port manifolds, actuators, and a single big ol Taco 0011 on the closed side of the flat plate, 008 on the other. I like that design, but from my research the Taco 011 is a pretty powerful (and energy hungry) pump. Is the Alpha powerful enough to replace a 0011?

 

[86turbodsl]

Cdecker, not sure how familiar you are with radiant heating, but if you're using the typical 1/2" pex like most everybody uses, 330' loop lengths are getting a little long. Also in slab and staple up usually need very different supply temps. in slab wants something like 110F water temp max and staple up wants more like 180F. So you'd need temperature control on the slab. If you already have this under control, my apologies in advance.

 

[dfiler2]

One other thing you need to consider is the placement of your boiler, if it is in the basement and the staple up is higher you will need zone valves for that portion to prevent ghost flow, where the heated water in the system rises and the cooler water falls, the system higher than your heating source will set up a natural circulation and cook you out. I haven't had any experience with the Grundfos Alpha but it sounds a lot like the Taco Bumble Bee circulator, if they are similar I'm sure it will save yu some money in the long run.

 

[Creatherm]

Cdecker - What are you using for your insulation for the radiant floor heat?

 

[cdecker]

Cdecker - What are you using for your insulation for the radiant floor heat?

I used 2" rigid foam board (R-10) under all of my radiant slabs (garage and basement). In the garage, the edges are also insulated with 2" foam board that tapers off 45 degrees to the outside edge.

 

[Bondo]

Also in slab and staple up usually need very different supply temps. in slab wants something like 110F water temp max and staple up wants more like 180F. So you'd need temperature control on the slab.

Ayuh,.... When I designed the system in my rental, I ran both staple up rubber tubin' on the wood floors, 'n pex in the slab,.....

Both run water at 140°,....

I built it with an oil boiler as the heat source, a primary loop through the hyd. separator, a mixin' valve comin' off the separator, 'n into 2 manifolds for distribution,...

I have a Grundfos 3 speed pump for each zone off the manifold,...

I originally used a Grundfos Alpha pump on the primary loop, but 2nd season in, it died,....
At the price difference, I swapped it out to the same Grundfos 3 speed pump as the zone pumps,....

Been several more years since, 'n everything is still runnin' Perfectly,....