Follow-Up: Experiment With Low Speed for 3-Speed Circulator

The The Living Room/Dining Room/Kitchen zone is still calling, but now it has been joined by the basement zone. Delta-T stabilization for these 2 combined zones with the pump on medium speed is mimicking the Delta-T that I just observed for the Living Room/Dining Room/Kitchen zone alone, while fluctuating across the same temp range.

Mikeeg02 wrote:When is the last time that zone called for heat? The longer it sits, the cooler it gets, the more heat it dissipates returning to radiant temperature. Hense why I believe what I took from Sting, the closer to continuous circulation the better. (Although I think he likes continuous, my take on it is the closer to continuous the better. ). Less temperature swings both in the room and at the boiler.

The various of my zones have been calling at regular intervals. Somewhere along the line I moved the transmitter and I believe that I may have in the process disrupted the connection on the return side. I just re-positioned it to where I originally had it and snugged up the connections. Delta-T dropped to 20 degrees right near the end of the time with these two zones still calling, and after my snugging up.

Therefore, please disregard my above post regarding the living room zone and then the combined living room and basement zone while on medium speed. I need to redo these Delta-T figures and report back.

Bedroom loop just fired the boiler and Delta-T has stabilized at 16 to 18 degrees this time around. Pretty much the same as for this very same loop on medium speed the first time around.

Now if the living room does likewise my sanity will be restored.

I'm presently monitoring a dual T-Stat heat call from my basement and bedrooms loops, and the Delta-T is holding at 19-20 degrees (with most of the time being spent at 19 degrees of supply to return difference). It sure makes a difference how the digital/remote barbecue thermometer transmitter is positioned. Circulator is on medium speed. Throughout this process the supply and return temperature probes themselves have remained untouched. Only the transmitter has been moved... I believe I have a good electrical connection or the return loop probe at the transmitter now.

UPDATE: Lo and behold the Living Room (/etc...) zone has just joined in on the fun, and I now have 3 zones with open zone valves. Delta-T is amazingly still holding quite steady at 20 degrees across 3 zones. Extreme spread is 19-21 degrees. It tentatively appears that the DPBV is doing a much better job of managing things with the single circulator on medium speed. Either that, or my return probes electrical connection at the transmitter was questionable even for back when the circulator was set on low speed. Or medium speed is matched better to the boiler. ???

Sanity has been restored.

PS: When I moved the transmitter and began getting the wild (29 to 34 degree of so) return temperature readings I had positioned it closer to my Taco Zone Valve Control Module. Could that have introduced some sort of interference to the transmitter?

Another bedroom and basement T-Stat call combo, and mainly holding at 18 to 20 degrees of differential. Seeing 19 as I type this. Stayed at 18 for quite a long time. Seems that the Delta-T differential increases as the boiler cranks up, but I'm always seeing this latter "end game" anomaly.

My highly preliminary take as to a trend for the circulator at medium speed is as follows:

Single zone Delta-T is ~16 degrees.
Dual zone Delta-T is ~18 degrees.
Triple zone Delta-T is ~20 degrees.
Quad zone Delta-T is ???? (not cold enough for my garage zones T-Stat to make a heat call)

More steady than having only a single circulator would seem to be "intuitively" possible. Yet another indication that intuition often makes for bad science. And a tentative indication that a single circulator with a DPBV and multiple zone valves can do just about as well as multiple circulators with P and S loops at maintaining the nearly ideal 20 degrees of Delta-T.

My original experiment with low speed has morphed into an experiment at medium speed....

Finally having a single zone call from the Living Room/Dining Room/Kitchen loop (post my fixing the transmitter issue) and like the other zones it is holding steady mainly at 16 degrees of Delta-T with the circulator on medium speed. Sanity is now fully restored.

Time to put it back on low speed?

Maybe on a cloudy, close to constant temperature day, you should try both speeds over an hour or so, see which one has more boiler run time.

Personally I like the slower, slightly longer circulator running speed.

You can also judge it in the living area to see which method feels more comfortable, if there is even any noticeable change upstairs. I actually only put 160 degree water into my baseboard heaters, but my house was designed with too much radiation. (Built in 1949) But I don't feel temperature swings in the living areas.

I've been on low speed today, and I've watched single, double, and triple zones calling, with nothing touched with respect to the probes or the transmitter ever since things leveled out and began making sense yesterday, and the Delta-T on low speed has been holding roughly as follows:

Single zone Delta-T is primarily holding at ~18 degrees.
Dual zone Delta-T is primarily holding at ~20 degrees.
Triple zone Delta-T is primarily holding at ~22 degrees.

This has convinced me to leave the circulator on low speed. I fully attribute the ability of my single circulator system to hang tightly around the ideal 20 degree Delta-T mark across various combinations of zones calling for heat to the functioning of the DPBV (differential pressure bypass valve).

So...are you warm?

I just got around to reading this.... thanks for sharing! Interesting.

Sanity restored? Well, let's not debate that <running and hiding> Sorry! I couldn't resist. But, yes, it all makes sense. It would take a long study to see if you're saving electricity.....that is.... slower speed is less dollars per hour, but if it takes more minutes to satisfy the thermostat it might even out. BUT.... I do believe a lower speed will make for more comfort as it should give you less temperature swings per day. Fun stuff!

I put a three speed Grundfos on my infloor radiant loop. It runs more or less continuously during the cold weather. I was hoping that if low or medium did the job that I could save some power, but, after playing with it for one full season, it seems I have enough frictional loss that it does require high speed. Ohhhh, well, at least I know!

Rob R. wrote:So...are you warm?

Yes!

Freddy wrote: Sanity restored? Well, let's not debate that <running and hiding> Sorry! I couldn't resist.

It's always debatable.

Freddy wrote: I put a three speed Grundfos on my infloor radiant loop. It runs more or less continuously during the cold weather. I was hoping that if low or medium did the job that I could save some power, but, after playing with it for one full season, it seems I have enough frictional loss that it does require high speed. Ohhhh, well, at least I know!

In floor radiant brings with it much higher friction (head) than conventional hot water baseboards.

I woke up to minus 2 degrees outside this morning and Delta-T's I'm seeing are now much higher than when it was in the 20's to 30's outside. At low speed on the pump I was seeing Delta-T's as high as 45-50 degrees, and even with the circulator on medium speed I'm still seeing either side of 34 degrees of Delta-T. Things sure change when it gets noticeably colder outside, that's for sure.

Part of the reason for this experiment was to determine if a single Taco Bumblebee circulator (which has its speed modulated by Delta-T) could replace my current Taco 3-Speed 00R circulator and my DPBV. The highest pump curve for the Bumblebee (its speed 4 curve) falls between my 00R's low speed and medium speed curves, but the Bumblebee's highest curve is closer to the 00R's low speed curve than to its medium. What I'm witnessing now makes me want to sit back and question if the rather pricey (and many say noisy) Bumblebee (this being what they say it sounds like) circulator will be adequate to my task. Guess that for now I'll just stay with what I have.

I just looked up the pump curves for the variable speed Grundfos Alpha circulator (speed varies via Delta-P instead of Delta-T), and its 'maximum speed' pump curve falls between my Taco 00R's medium and high speed pump curves. Hmmm??? It covers the bases ....