I have both a Taco HEC-2 and a Grundfos Alpha 15-55F in my multi-zone multi-boiler (way to complicated) system. I'm a retired electrical engineer/real time software programmer, which is part of the problem.
It's a primary/secondary system with the boilers on an injection loop controlled by a Tekmar 356 outdoor reset control. The 356 pulses a (non-smart) 15-42F to control the water temperature in the primary loop based on outside temperature, and there's 6 zones fed by various age 15 series pumps (3 fixed speed, one variable), one with a zone valve. Until a few months ago the injection loop had a propain boiler in series with a 3 way zone valve that switched a Jensen indoor boiler into the loop if it's water temp was high enough. The Jensen (and zone valve) was recently replaced with a w-w heat exchanger connected to an outdoor wood boiler. With dual pumps in the LP boiler and the primary circ there's around 10 pumps in the heating system; don't ask why... Except for the Tekmar and whatever's in the gas boiler, all the controls are relays or mechanical aquastats.
The outdoor boiler loop is OWB->water heater sidearm->HE->50K garage heater on basement shop ceiling->OWB. The heat load varies considerably based on what's on. This loop has the Bumblebee, set for a 30 degree temp differential, and always on per the OWB manufacturer's recommendation. It spends most of it's time around 11W, bumping up to it's max 41W when it's -20F and the basement heater's running. There's an Azel dual temperature remote reading thermometer sitting in a box, waiting to be installed if the arctic blasts ever leave, so no temp loss monitoring yet. The couple times I put the thermocouple thermometer on it was pretty close to 30 degrees. The sensors are getting a closer look at their positioning when it warms up a bit, since I suspect the return temp is too close to the boiler and reading warmer than it really is. The piping is pex-al-pex and seems to have some insulating value so the sensors are currently on iron Ts with a quick insulating job. Did I mention you should never start installing one of these in the fall before a record cold winter?
The Alpha replaced a non-smart newer variable speed circ that developed an unnoticed air bubble and died, and is feeding a well insulated basement office with a 4" heated slab (where I'm sitting now). It's set for auto-adapt and from it's display runs at 14W.
Bumblebee:
The temperature differential mode works well with it's varying load. Since the flow resistance is constant, unaffected by heat load, delta T looked like the best choice with all other factors equal.
It lives up to it's namesake, with a high pitched whine that increases with speed. It's on the OWB, no one can hear it scream (except when filling the beast, when it's kinda reassuring), but inside it could be noticeable.
The sensor hookups are on a push-in terminal block. It was easy to connect, but far too easy to bump and knock loose. When off the pump quits with an error code. I'd consider this a major design defect; it should have gone into full power fallback mode, trading extra power cost for replacing frozen pipes (yes, I have backup, but if this were a single pump no-backup system you'd be paddle-less up the brown creek). As soon as it warms up it's getting hot glued into place. Stupid, stupid, programmer decision.
With our 25 cents/kwh power cost it pays the difference in price over a stock 80W circ in 12 months, and it's complete cost (I got it locally at higher than the online price) in 24, assuming an average 20W power consumption.
With only a month of operation I can't predict it's reliability. Online reviews show it's got some early failure problems.
Programming is tougher than it should be, using long and short presses on a couple buttons. I've got a section from the manual stuck behind some pipes next to it, and despite considerable experience programming similar devices have to refer to it if I change anything. Definitely fails the user interface design test.
It starts up at full speed for two minutes, then switches into the programmed mode, so it can reach sorta steady state and measure an honest temperature drop.
It has a constant speed mode that doesn't require the sensors, but still saves a lot of power usage over the old AC pumps.
During startup while trying to work out the air bubbles it airlocked and said it was running at full flow with no actual water movement. Didn't test that one for more than a few minutes...
Alpha:
It's driving a constant flow resistance zone, but since it's only one large room with a very large heat sink that doesn't matter. I could have set it for the lowest constant power mode, but decided to let it do it's thing. It picked close to it's lowest power.
It's very quiet, not noticeable over low sound level of the other pump(s).
The fried pump was set at it's lowest speed, 60W per the datasheet. It doesn't run a lot once the floor is warm, so while it'll be cheaper assuming it lasts the 20 or more years like the older Grundfos pumps, it's quite a slow payoff even at our outrageous electric costs. YMMV...
While purging out the air it also ate a bubble and quit pumping, but it noticed and reported 0 GPM. Also just a short term test.
Both:
They both have LED displays showing the current power use and what supposed to be the current GPH, plus a few fixed mode LEDs for the Alpha. The BB displays the current mode in seven segmented letters. The GPM numbers are probably suspect - I'd guess the BB calculates it from rpm, and the Alpha from load and rpm. I wouldn't use either for flow balancing, but they're interesting.
Overall, both pumps are doing their job. I'm considering replacing my 200W primary loop pump with a bigger Taco delta-t pump if the bumblebee holds out, as it's the fastest payoff of the remaining pumps - although I'm concerned that it may be as noisy, or noisier, then the screaming yellow zonker. I may drop in at least one Alpha on the higher on-time zones over the summer, using the removed pump as a spare to keep the OWB going. In most situations I'd pick the Alpha over the Bumblebee, given the extra cost, noise, and failure prone sensor wiring connection with a freeze your pipes failure mode. The BB can be used as a higher cost higher noise substitute for the Alpha, but without any reliability data it would be difficult to wonder why. In a situation where you can take advantage of it's differential temperature mode, and where noise doesn't matter, it's a reasonable choice.
Kirk
