pump control question

varadhammo

Hi all,

I'm in the process of figuring out the controls for my system. I have a tekmar 356 for injection mixing, grundfos alpha for the system pump. the zones are all radiant floor, with a combination of manifold actuators (2-wire no end switch) and zone valves. I have been planning on using a taco zvc zone valve control, but I realized that with the alpha autoadapt mode, it should just stay powered all the time and not be switched on and off by the ZVC. This leads me to think I could eliminate the ZVC altogether. But when there is a call for heat, I do need to trigger the 356 and the boiler primary pump. So is there a way I can somehow add a relay that will power the 356 injection controller and boiler pump based when the Alpha runs? I can't think of anything besides some kind of current sensing relay, but the power draw of the Alpha is so low that it probably wouldn't work properly. So any way to "detect" when the Alpha runs? Or does it make more sense to just use the ZVC and trigger the 356 & boiler pump from X-X? Thanks!

SWEI

Wire the boiler terminals (#5 & 6) on the 356 to the boiler's TT terminals and let the internal pump relay on the boiler take care of the circ.

hot_rod

My friend Nathan up in Alaska uses the Phenix model 9993 current sensing relay with ECM delta P circs. It senses from .1- 7 amp, around 25 bucks.

varadhammo

hot rod said:

My friend Nathan up in Alaska uses the Phenix model 9993 current sensing relay with ECM delta P circs. It senses from .1- 7 amp, around 25 bucks.

Hr, that looks perfect. Is he using it for something similar to what I described?

What I'm thinking is: current sensing relay on Alpha N.O. contacts close -> 356 mixing demand terminals & RIB dry contact relay to power primary circ at the GARN.

SWEI

Interesting idea. So the ECM circ becomes the demand indicator?

varadhammo

Yes, exactly.

SWEI

Why not just let the internal Garn controls manage the primary circ?

hot_rod

yes he has used that Phenix adjustable current sensing relay to fire tekmar controls with Wilo and Grundfos ECMs.

varadhammo

I'm planning on having the GARN primary circ wired to a RIB dry contact relay whose contacts will be closed by the GARN air intake damper end switch as well as the demands from the two buildings, so it will run whenever there's a heat demand and also whenever the GARN is charging (to provide a bit of extra tank mixing).

SWEI said:

Why not just let the internal Garn controls manage the primary circ?

I'm not sure I understand what you mean... the Garn is just a storage tank sitting there, its controller just manages the batch burn, it doesn't respond to a call for heat in any way.

hot_rod

I think the RIB folks offer them too, if you have access to that product line.
http://www.functionaldevices.com/building-automation/currentsensors.php

SWEI

I thought Garn had at least some basic onboard controls (like a pump relay.) I'd probably suggest an aquastat to start the pump once the boiler actually heats up.

FDI has current sensors with power relays included -- see the lower third or so of the link above.

varadhammo

It looks the RIB ones don't go down as low, only to .25A. What is the Alpha's lowest draw when it turns on? The Grundfos literature says low fixed speed ~ 5-8W which wouldn't even be 0.1A @ 120Vac... but maybe the pump wouldn't ever really run that low?

SWEI

Even more options here.

The Wattage displays on ECM circs are not particularly truthful