Alpha brain

Devan

I'm finding I'm getting desired delta T on constant pressure setting vs. Auto adapt setting. which seems to settle in around 13 watts @ 1 gpm. Constant setting is 20 watts @ 2 gpm, but 10* delta on my radiant zones.



I also have a couple of alpha's on a project with home run- HWBB loops and Auto setting works great.



I wonder if constant setting for radiant (higher head) systems a better fit than letting the pump think for itself.

Jean-David Beyer

See why I want computer readout of system controls?

I have no idea about your system (and I am not a professional anyway). I do have experience in the distant past designing feedback control systems, and from that experience I have found that the more complex the control system, the more difficult it is to analyze, and the more unexpected results you can expect to obtain.



So on my system (primary-secondary with circulators to control the zones), the part that controls my radiant heating downstairs is the boiler with outdoor reset; it controls the temperature of the water delivered to the downstairs zone. And the circulator for that zone is just a Taco 007-IFC. And there it is pretty clear I should not put in a delta-T circulator instead, because that circulator would be either useless, or worse: it would fight the outdoor reset.



In some sense, the boiler is already the "brain" of the system. Were I to put another brain in there in the form of a smart circulator, it could be thought to be a system with multiple personality disorder. It is my view that usually one should use one brain in a system and increase its brain power if necessary, but to put multiple brains in there only to make the system fail soft in the presense of hardware failures. I do not know if that kind of design would be economically feasible in a home heating system.

Devan

JD

I think you hit the nail on the head. I've also thought my systems reset control playing havoc with the alpha. Now that cooler temps are steady, I'll keep monitoring and tinkering.

CC.Rob

alpha on the brain

I am thinking along the same lines. The all-in electric rate here is $0.30/kWh, and I have a pair of 007IFCs that run pretty much constantly from November through March. Was considering a simple swap for a pair of Alphas and hoping to go from ~80 watts to about 20 watts each. Simple payback is ~3.5 seasons.



But I was considering just using the fixed medium speed so that the only brain controlling the system is the tekmar.



Any thoughts on this approach?

Jean-David Beyer

Thinking about delta-T

My system has two zones; upstairs is 28 feet of finned tube baseboard, half in each of two rooms. Downstairs is radiant heat in on-grade slab. It has outdoor reset.



Last night it was 42F outside and I had the upstairs set for 67F. The outdoor reset set the water temperature to 103F and the return water temperature was 102F. The rooms had just gotten to 67F, but the thermostat had not yet noticed that. In other words, the heat emitters were putting out enough heat to heat the rooms even with that tiny temperature drop.



I suppose if I had a delta-T circulator in there instead of my Taco 007-IFC, it would have slowed down in order to get a return temperature of say 93F, but it would be going much slower than 2 feet per second, and I do not even know if it would go that slowly. Right now, I calculate that I get 2.8 gallons per minute through there. It is a mix of 1/2" and 3/4" copper pipe. About 70' if that is 1/2"; 3.5 ft/sec, and the rest (about 60', including the baseboard) is 1.75 ft/sec, so a little on the slow side already.



Now if it were 0F outside, the boiler would put out 140F. I imagine I would get much greater delta-T under those conditions, especially if the temperature up there had dropped (at floor level) to 65F.



I am not sure I understand how important controlling the temperature drop is. Imagine I had such a high flow rate that the temperature drop was almost zero. Ignoring noise and wear problems, as well as getting a large enough circulator and the power to run it, would this really reduce the heat delivered to the load? It seems to me that it would not: the baseboard would be full of hot water at boiler output temperature. Slowing down the flow would only make the baseboard near the return to the boiler cooler and less effective. The boiler might not care for the higher return temperatures and short cycle; I am not proposing actually doing this.



Since there is so much emphasis on getting a particular temperature drop (e.g., 20F for baseboard, 10F for radiant), I must be missing something. What?