outdoor reset, boiler temps

Brad White_22

yes, outdoor reset will benefit you so long as the house remains comfortable (the goal!) and the boiler return water temperature remains above the point of condensation (usually 130 degrees in the boiler).

Doing it automatically will be an obvious convenience for you.

Now, about that circulator pumping INTO the boiler.... always pump away from the expansion tank. Your tank seems to be connected to the boiler air purge connection but is not clear. But if so, the circulator is pumping into the expansion tank. A no-no and another subject entirely... :)

L. Dahl

outdoor reset, boiler temps

I'm curious if an outdoor reset would benefit with cost savings with the heating system. I live in Minnesota, and we have had an exceptionally warm January. The house is heated with a 3 zone hot water baseboard system, with 2 zones set on 60 24/7 and the third zone is on an automatic setback at 70 in the morning and evening, and 65 during the night and day. Usually I run the boiler temperature down manually during moderate 30 degree days like we have been having now. Before I began doing this last fall, it was always set at 190 degrees. I've noticed the heat has been much more even, as the pump runs more continually, and boiler runs less. When the wind picks up, and temperature drops to 20 below, I usually have to run the water temperature way up again. Am I doing any damage, or saving in money by manually setting the aquastat this way? How low can I go with the water temperatures? Would an outdoor reset pay for itself? I've attached a picture of the boiler...it's an old Hydro therm job.

Plumb Bob

Yes, heating with 190F is called "bang bang" heating...short bursts of very high temperature, quite unpleasant but mysteriously the standard method of hot water heating in the US.

Outdoor reset won't save you any significant money if it's only for the small range between 190F and say 150F (supply temperatures), but it will increase comfort as you have already discovered. If the supply water goes below ~140F (return below ~130F) you could do damage to your heat exchanger.

You can get full-temperature-range outdoor reset by using a bypass, but this requires some plumbing done by an expert. Also, baseboard output drops very sharply with temperature, so it's not as if you really need the full water temp range from 190F all the way down to room temperature. Come to think of it, 150-190F is fine and you can install that yourself if you are handy,

mark schofield

would the reset schedule affect/lower only the hi limit below the aquastat setting depending on outdoor air temperature, while the low limit is left the same (150 deg for boiler safety?). There is a thread further down that discusses the Beckett Heat Manager. One might be able to accomplish this with a simple programable controller for building energy management systems. could you please post your solution. thanks, Mark S

L. Dahl

Thanks!!!

I recently discovered this site, and especially like the pics of the old installations. I'm a teacher, but do have my boiler's license, so I do get to babysit the huge old steam job at school on occasion... Anyways, I leave the repairs and troubleshooting to you professionals. Thanks for your advice about the 3 zone hot water system that keeps me warm on the nights and weekends. Regarding the comment about the circulator pumping right into the boiler...yes it does, and the pressure tank and pressure relief are piped out of the boiler immediately following that, so yes, the pump does essentially pump right into the tank. Maybe that is why I get some weird gurgling, bubbling on occasion. The boiler has a manual fill, and I add a little squirt each fall to keep it at 15psi, and it pretty much holds that pressure all season. The pump and zone valves were replaced a couple of seasons ago, the originals were 40 years old remnants from the original oil boiler install. I would have thought that the installer would have caught some of the piping issues, but anyways, should I have that piping issue corrected? It has been piped that way for at least 25 years or so.

I've noticed 150* is pretty much the magic number with this baseboard heat, much lower and they produce very little heat. When it was previously at 190*, each zone would call for heat for just a few minutes. Now, at 150*, usually a couple of zones are always calling for heat, and there isn't the pinging and banging when a new zone opens up. If I'd decide to go with the outdoor reset, do any of you have a reccomendation that you'd make regarding a good brand to go with? I'd probably leave the install to a professional...You guys that work with this stuff are amazing, I kind of envy your jobs...seems like it could be fun to watch one of those old 75 year old steam systems in action. But for me, a little knowledge is probably a dangerous thing, so I don't plan on monkeying around with this boiler too much. For now, I think I'll just leave it at 150* and when the wind picks up and we get a cold snap, I'll up it 20 to 40 degrees. Thanks for your advice.

Brad White_22

Pumping away....

The comment I made regarding pump location and direction is the ideal. Some systems work fine with that arrangement but others suffer air binding, gurgling and so-on. Smaller systems with generously sized piping (low head losses for the pump) do better than others.

"If it isn't broke, don't fix it" is the word here. But if you replace the boiler and/or near-boiler piping in the future, seize the opportunity to "do it right".

Enjoy!

Brad