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Alpha Pumps Don't Work?

I have a radiant floor system with two zones. Zone #1 is 1800 square feet of staple up joist ex, and Zone #2 is 900 square feet of slab on grade (a basement). I was using 2 Grundfos 15-58 3 speed pumps, Zone #1 set on the fastest speed, and Zone #2 set on the slowest speed. The house heated fine and I was happy enough with this system. No problems.
(Each pump is installed on a 3/4" copper circuit running to Pex, and each zone came off a 1.25" copper manifold, feeding back into a second manifold the same way. The zones are equally spaced on the outgoing side and the incoming side.)
When one of the pumps started making loud noises, I thought about putting in Zone Valves to save on electricity, but instead, I bought into the idea that multiple circuit pumps were a better idea. Since I'd had good luck with that already, replaced both Zones with Alpha pumps, thinking I'd still save electricity.
But the Alpha pumps don't seem to move the water, and therefore, do not heat the house when they're set on Auto. If I set them on Auto, my house stays chilly at best. Sure, I can heat the house with the Zone #1 is set on high speed, and the Zone #2 is set on middle speed, but the "Auto Adapt" setting on the Alpha just doesn't circulate the water. And even when the speeds are set higher, I am not getting the same performance I got with the 15-58 pumps.
The read-outs on manual aren't any higher than 3 GPM, and on auto adapt, it's like 0-1gpm. When only one zone is on, you can get the pumps up to 5 GPM at the high speed.
I know by the specs that the old 15-58 pumps moved water much faster, at up to 17 GPM. They also gobbled up electricity.
I tossed out the old loud 15-58 pump, and gave away the other one. So should I go buy some new 15-58s? I need my warm house back.
I cannot believe these Alphas don't work, and I can't seem to find the answer anywhere else. Any ideas? I wonder what the issue really is, here.
(Each pump is installed on a 3/4" copper circuit running to Pex, and each zone came off a 1.25" copper manifold, feeding back into a second manifold the same way. The zones are equally spaced on the outgoing side and the incoming side.)
When one of the pumps started making loud noises, I thought about putting in Zone Valves to save on electricity, but instead, I bought into the idea that multiple circuit pumps were a better idea. Since I'd had good luck with that already, replaced both Zones with Alpha pumps, thinking I'd still save electricity.
But the Alpha pumps don't seem to move the water, and therefore, do not heat the house when they're set on Auto. If I set them on Auto, my house stays chilly at best. Sure, I can heat the house with the Zone #1 is set on high speed, and the Zone #2 is set on middle speed, but the "Auto Adapt" setting on the Alpha just doesn't circulate the water. And even when the speeds are set higher, I am not getting the same performance I got with the 15-58 pumps.
The read-outs on manual aren't any higher than 3 GPM, and on auto adapt, it's like 0-1gpm. When only one zone is on, you can get the pumps up to 5 GPM at the high speed.
I know by the specs that the old 15-58 pumps moved water much faster, at up to 17 GPM. They also gobbled up electricity.
I tossed out the old loud 15-58 pump, and gave away the other one. So should I go buy some new 15-58s? I need my warm house back.
I cannot believe these Alphas don't work, and I can't seem to find the answer anywhere else. Any ideas? I wonder what the issue really is, here.
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Comments
ramermechanical.com
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The Auto Adapt is for a system that is zones with valves or TRVs.
Don't trust the gpm readout, set the speed to the setting that moves sufficient flow.
Curious as to why the 15-58 were a problem, they run almost silent when purged properly and running on the curve.
6 gpm is about all you want to flow thru 3/4" copper tube, I doubt you were moving 15 gpm with the 15-58?
trainer for Caleffi NA
The magic is in hydronics, and hydronics is in me
Sorry for the possibility that these are dumb questions. Thanks for entertaining me.
(And btw, the 15-58 "went" because of bad bearings or something; it wasn't a problem other than that. It sure seemed to heat the space quicker.)
I agree that auto adapt does not work well for radiant. Either the constant speed or the constant pressure setting will work better.
Keep in mind that, unless your system was carefully designed, when the concrete slab is cold, the upstairs zone will have trouble keeping up.
Another possibility is that some air was introduced when the circulators where swapped. Air trapped in some of the loops would also account for the reduced performance.
If you have the means to measure the supply and return temps on the loops, this will help diagnose.
Carl
Albert Einstein
Carl, I have a temperature differential of 15-18 degrees, which is more than the 15-58 was--it was about 10.
As for air, I thought I did a pretty good job of purging the air, but still was thinking of putting on an additional Spirovent. I've read they work great and I have a couple leftover from an old job.
I also changed the expansion tank--forgot to mention that. I charged it and it appears to be working. Perhaps that could be a factor?
To answer the other issue raised, the concrete slab has always been the EZ part to keep warm. That zone usually runs only two hours a day to keep a constant toasty temperature of around 68-69. The insulation is excellent. The joist portion is more of a pig, I have to run 4-6 hours in the morning, and 4-6 hours in the evening.
I think the bigger picture is how to modulate the flow through a zone to potentially save electricity and increase system efficiency/comfort vs a constant or improperly controlled ECM circ.
As delta P only reacts to changes in "push back" on the impeller the only proper solution is delta T that will react on the zone load or zone temperature differential. There is no impeller push back change in a zone circ application so, at least to me, a delta P control strategy makes little sense.
Please remember, this is an unbiased viewpoint as we now have both delta T and delta P.