controlling Grundfos Alpha

Kestrel

Hi gang, almost done with project (heat next week just in time to miss the occasional Seattle blizzard - ugh)

A straightforward question - the system is a mix of TRV-controlled radiators and 6 loops of joist space tubing (with Joist Trak) - all to be run at the same temp, controlled by outdoor reset and a system temp sensor.  A single Grundfos Alpha to supply all (plus a boiler circulator and a circ for the indirect) - the floor to be supplied when a t-stat controlled zone valve opens pipe to floor loop manifold.



The question - can I run the power line from the Alpha to the system pump hook-up on the boiler (that also hooks up the boiler circ and the indirect circ)?  Or should it hook up to line voltage with just its own on-off switch?



My concern is that it needs to respond to valves opening and closing, and that this water movement will result in the water temp dropping, which is what will activate the boiler firing and boiler circulator.



The attached picture is of the alpha and the two manifolds, the upper for the floor loops, and the lower for the radiators.  The Caleffi Z55 is at upper left, between the pump and the floor manifold.

kcopp

I would just.....

plug it in. I think the response time will be fine. Unless you have huge temp drops outside... I din't think that happens in The Pac NW all that often... now if it were the Dakotas that may be a diff story. kpc

Rob Blair

Grundfos Alpha on the system circuit

I usually put that onto the system pump circuit, otherwise it is constantly looking to see if a valve is open.

Rob

Kestrel

It should always be looking, I thought

I usually put that onto the system pump circuit, otherwise it is constantly looking to see if a valve is open.



I thought that's what I wanted - to have it looking all the time.  That's the whole point of the TRV's, right?

I thought that either a radiator/TRV would open, or the thermostat would open the floor manifold, and the Alpha would start to pump.  Then, as the water temp began to fall, the system temp sensor would pick up on the water temp drop and fire the boiler and turn on the boiler pump.



If the Alpha only has power when the boiler knows to fire, then the opening of the TRVs or the zone valve would be meaningless, as the Alpha would be 'off'.  right?



I guess my question is - wiring the Alpha to the boiler will tie it to when the boiler goes on and off - which with my control scheme, is not what I want, I think.

Limamikemike

Alpha pump

The WHN boiler has a WWSD option for constant circ on the system pump. The pump will be powered regardless of what the boiler is doing.

Kestrel

sounds good

That's sounds like just what I need.  So I wire to the system position on the line voltage bus?

BTW, what does WWSD stand for?

Limamikemike

WWSD

Warm weather shut down. You can change the mode of operation through the smart control menu.