Controling Grundfos Alpha on boiler with DHW coil

Brent H.

Greetings,



I'm looking for a cost-effective solution to control a Grundfos Alpha pump I just installed that drives 3 zones controlled by zone valves. My boiler currently has 3 circulators controlled by switching relays (SR501s) connected to a triple aquastat since there is a tankless coil w/priority. I'm trying to avoid spending another $50 - $60 for a SR501 since I'm hoping to replace the boiler next year and am planning on using the Alpha to drive the whole house. Since the Alpha can be left powered on, my thought was to use a RIB relay that would connect ZC and ZR when the end switches close on the zone valves. I would also use ZC to power the Alpha so the circulator would be shutoff if the temperature got too low. The remainder of the time the circulator would be powered on and the zone valves would prevent flow. Does anyone see any flaws in this?



Thanks.

Brent

Tim McElwain

Be careful depending

on the piping you could be dead heading the pump. That is not a good idea.

Brent H.

Explanation Please

Hi Tim,



Can you explain your concern? The folks at Grundfos told me that the Alpha can be left powered on and it will just go into a low current mode when all of the zones are closed. Alternatively, I supposed I can power through the same relay that connects ZR & ZC on a heat call.



-Brent

Steamhead

Are you using

3-wire ZVs such as Taco's 570 series?

Brent H.

Zone Valves

Correct.... they are Taco 571s

Steamhead

OK

using a relay like the RIB would be your best choice. Even though the Alpha can crank back to almost nothing when the ZVs are closed, it's still not completely off.



Wire the relay coil between the terminal-#3 leads from each ZV and the "common" side of the transformer (the one that does NOT connect to the #2 terminals on the ZVs. The relay's contacts can then shut down the pump whenever the coil is not powered.



I like to use a "fan center relay" for this, since it has a 40VA transformer and a relay mounted on a standard 4x4 junction box cover. Makes a neater installation, and can run three 570-series ZVs.

Brent H.

Just to confirm...

My setup actually consists of the 3 zone valves being located at the other end of the house from the boiler/circulator. What I plan on doing is mounting a 40VA transformer next to the ZVs to drive them and also feed 24V back to the boiler from the end switches. This 24V will drive the RIB relay. When the relay closes, ZC will provide power through to ZR and the Alpha circulator.... does this seem correct? I think this gives me wiring equivalent to how my SR501s are hooked up.



Thanks for the help.

ChasMan

Are you..

Planning on running the pump on the automatic setting? Have you confirmed with Grundfoss that the pump will not forget what it learned when you shut the power off? It would seem to me that adaptive on the fly learning would be lost much like the time of day when you power off a thermostat. It remembers the program but not the time of day.

Brent H.

According to Grundfos....

Grundfos claims that it is not an issue. It can be left powered all the time or switched on and off with a relay.

ChasMan

Thanks

I am going to try one of these. I have been debating on it for a while.. Too many other things to do first but this pump might solve my water hammer issue.

NRT_Rob

that doesn't make any sense to me

If you're going to spend the money on a low energy pump, I don't see the wisdom of powering it up 24/7 if you aren't running it.



I'd run it like a regular system pump, and if nothing is calling, it turns off.

Brent H.

Longterm

Longterm, that is what I'm planning on doing. Once I get the boiler replaced in the spring I'll set it up to shutoff when heat isn't being called for. But for now, I want to avoid buying another relay that I probably won't need once I replace the boiler.

ChasMan

Well...

The pump Installation & Operating instructions certainly leave one with the impression that it doesn't need to be switched. It almost leaves one with the impression that it shouldn't be switched. Just the cordset it is supplied with left me scratching my head.  

Brent H.

Next Year

When I talked with Grundfos, it sounded like they will have a hardware version available in 2010.