Grundfos Alpha compared to

Steve Minnich

Taco's VR1816 in your opinion? I haven't had any problems with the Alpha and haven't tried the VR1816. Yet. I know there's sight differences in their curves but other than that, why would you choose one over the other?

njtommy

The Taco VR1816 just has a few more options when dialing in cir speeds in my opinion. I've only installed 1 so far. I guess it really depends on what application you want to use it for.

hot_rod

Looks like the Alpha 2 is out with a few more features. I've heard the Alpha 3 is available in Europe

No doubt the Alpha has a longer track record if that matters, built in Fresno, California.

Just make a list of all the wants and needs, see which comes closest to the ideal pump for your applications. For a fixed speed ECM with lots of speed adjustability, the B&G Vario s nice.

Harvey Ramer

I kind of like the vario. Strap the temp sensors on the system and dial in the pump to perfection. Great for some systems, not for others.

I don't have much to offer on the VR1816 other than I have rarely been disappointed with a Taco pump. As far as that goes, I like the alpha as well. In my experience, the autoadapt is best suited for trv's. That function is a bit underwhelming in the majority of American systems.

Try them all and pick your flavor.

Harvey Ramer

I read the white paper on the autoadapt, so yes, I know what it does and what it is intended to do. It is rather complicated, but works well with low mass rads and trv's.

The pump comes from the factory with a preset constant pressure setting. Imagine the preset as being a straight line with time durations of pump speed taking place both above and below the line depending on the position of the trv's. Wider open equates to lower pressure drop and increased pump speed to maintain pressure. As the valves find thermal equalibrium with the conditioned space, defined patterns will appear. If the control sees the majority of the time is spent with the pump speed higher than the imposed line on the curve, it will shift the line and pressure setting upward. If the majority of the time the pump speed is below the imposed line, it will shift the pressure point downwards. It will continually adjust the pressure point to maintain a point that has an equal duration of time/speed both above and below the line.

That is why it is a brother to TRV's and little else. In a system like this, it will find the lowest possible pump speed to maintain comfort.

That is also what Taco's proportional pressure is intended to do. I don't know the algorithms of their pump though.

Jason_13

I was actually told by Grundfos tech that the #gallons that is illuminated is just calculated and may be off by 30%+ dependent on the system.

Chester

After some obsessive observation I found that my Alpha on Auto ultimately adapted downward such that it was pumping below the speed of my 3-speed internal boiler circ pump, which is already on it's lowest setting. In other words the Alpha wasn't pulling away all the heat the boiler was sending out so I was recirculating some of the boiler output back through the P/S header and therefore unnecessarily raising the temp of the return water the boiler was seeing. I played around with it and found that the lowest setting of the 'constant pressure' feature did the trick.

Irrespective of whether the Alpha's 'gallons/min' display is correct I'd assume that the wattage it shows is accurate since that's something it should actually be able to measure.

hot_rod

The Alpha 2 shows an Improved flowmeter reading.
It's not so easy to read flow accurately, and inexpensively, Especially with the variety of fluids used in hydronics, from what I have learned.

I believe anytime a manufactures develops one of these smart pumps there is a learning curve, both for the manufacturer and the installers. There are a lot of opinions out there what should be offered and programed, and how much access to give the installer into the control.

I think all the manufacturers try to do as much R&D in the labs, but until the product is out in actual installations you will not get actual hard data.

Hats example of matching two control functions, boiler and pump, shows how much there is to learn.

I found the delta P function is fairly workable, it seems easier to react to pressure changes in a zoned system. With temperature control you have the sensor lag in addition to the contol reaction.

SWEI

Harvey Ramer said:

That is also what Taco's proportional pressure is intended to do. I don't know the algorithms of their pump though.

From what I have read, the VR1816 Proportional/Variable Pressure Mode looks like what Wilo refers to as ΔP-V.

I find that constant pressure mode works quite well for the low resistance reverse-return piping layouts we design.

SWEI

Constant pressure mode on the VR1816 is given as five feet on the low setting. That seems about right based on the units we've installed so far.

hot_rod

Hatterasguy said:

hot rod said:

Hats example of matching two control functions, boiler and pump, shows how much there is to learn.

I was mulling over the possibility of using the Alpha for the UFT to avoid the incessant cycling of speed on the VT. The Alpha would remain at constant speed independent of RWT. There would not be a massive speed increase at startup due to the cold RWT.

The Alpha would increase speed when additional zones open to provide more flow.

Then I took a look at the speed curves on the VT and found that speed 2 can work for the entire range desired by the boiler. Even a fixed speed pump flows more water when another zone opens. The head drops by 30%, typically. This is all that is required.

It is seriously overpumped on a call from a single zone and the DT would be about 5 at design. However, the same situation would apply with the Alpha as the low end, at 6 feet, is almost identical to the VT's speed 2 on a single zone with this system.

Neither option is desirable for efficiency but I might be stuck with one of them.

Does the UFT have a pump output PWM or 0-10?

SWEI

Hatterasguy said:

SWEI said:

Constant pressure mode on the VR1816 is given as five feet on the low setting. That seems about right based on the units we've installed so far.

What flow rate are you achieving at that pressure?

Different flows in different systems.

On a recent gravity conversion we are getting something approaching 12 GPM when all of the (proportional) zone valves are 100% open. This is a direct-pumped a Triangle Tube PTS175.

The first one we installed on a RFH system we designed that is fed by a Thermolec and has roughly 5 feet of head at design conditions. Another was retrofitted (along with another Thermolec) to an existing baseboard system with similar calculated head losses at design flow.

Next week we are going to direct-pump a CDN040 with panel rads and TRVs using another VR1816F.

We don't yet have a good means for measuring flow in existing systems, but we do have a Capsuhelic setup to measure head up to 35 feet with reasonable accuracy.

SWEI

I'd love to see something something like a VTR1109 (with ΔT, ΔP, and 0-10V inputs.)

We also need stainless or FRP volute options. The existing ΔT and setpoint modes should work fabulously for DHW recirc.

Harvey Ramer

Hatterasguy said:

Harvey Ramer said:

I read the white paper on the autoadapt, so yes, I know what it does and what it is intended to do. It is rather complicated, but works well with low mass rads and trv's.



The pump comes from the factory with a preset constant pressure setting. Imagine the preset as being a straight line with time durations of pump speed taking place both above and below the line depending on the position of the trv's. Wider open equates to lower pressure drop and increased pump speed to maintain pressure. As the valves find thermal equalibrium with the conditioned space, defined patterns will appear. If the control sees the majority of the time is spent with the pump speed higher than the imposed line on the curve, it will shift the line and pressure setting upward. If the majority of the time the pump speed is below the imposed line, it will shift the pressure point downwards. It will continually adjust the pressure point to maintain a point that has an equal duration of time/speed both above and below the line.



That is why it is a brother to TRV's and little else. In a system like this, it will find the lowest possible pump speed to maintain comfort.



That is also what Taco's proportional pressure is intended to do. I don't know the algorithms of their pump though.

Thanks.

What I get from the above is that the pump will seek to find the "average" pressure as its setpoint. The average pressure would be defined as the point where approximately 1/2 the TRV's are open and 1/2 are closed (simplified example).

Once it finds this point, it will maintain this pressure, presumably forever.

I do not see this as the lowest possible pump speed to maintain comfort, however. There is nothing driving this pump to a lower pressure as the setpoint.

Close but not quite.
Until the pressure point changes, it is a constant with the pump speeds varying. When it changes It seeks a pressure point that is calculated to have equal pump speed run times both above and below the imposed line.
Since the TRV's modulate based on actual load conditions, the pump will continuously recalculate and adjust the pressure point based on system performance and seasonal shifts.

It will maintain continuous circulation. As the TRVs modulate their positions based on load the pump recalculates to maintain the minimum speed that is required to heat the space.

In this type of system, you will find the system D-t's that have been ever eluding you, provided the emitters are of the correct nature and the supply water is correctly calculated. A TRV is far more effective at modulating flow based on load conditions than a D-T pump.

Gordy

Why not run constant circ, and eliminate the 3 minute approach of the vt?

Harvey Ramer

You're definitely missing the main function.
The pump does not change it's pressure point based on pressure. It changes based an time/speed derivative. The system flow will change with imposed load, due to the TRVs. That's what TRVs do. They modulate the flow based on room temperature. The greater the load, the wider they open and vice versa. The pump sees the change in flow due to the change in pump speed. A direct indicator of imposed heating load.

If the pump spends the greater amount of time at a higher speed proportional to the constant pressure point, It will shift the pressure point upwards. This means the building has a higher load and the TRVs are modulated wider open. The exact opposite happens when the building is at a lower load.

The TRV controls the system delta. They will have their way regardless. It opens very slowly based on the temp gradient of the room. So the flow in the rad starts at a trickle and never exceeds what is needed to heat the space.

Think about it for a while.

4Johnpipe

@hot rod what is a PWM? UFT has. 0-10 volt terminal

Harvey Ramer

Sorry for hijacking the thread Stephen.

Steve Minnich

No worries...I'm soaking it all up.

Harvey Ramer

Without a system flow control based on demand, Auto adapt/ proportional pressure, is like a 3 year old in a busy airport terminal with no one to look after it. What will it do, who knows? The results have historically been less than satisfying.

Harvey Ramer

I don't know where it starts. The white paper doesn't specify. I would guess somewhere in the middle.

I don't see it as a point of great consequence.

Gordy

If there is no flow controlling devices in the hydronic system then why use a delta p pump to begin with? If everything is wide open which will probably be (seldom) then it just acts like any other circ. Delta p and delta t Circs have similar characteristics they speed up, and slow down to maintain a certain parameter all though a delta p is a constantly changing one depending on the system it is lashed to.