constant running circulators for comfort/boiler efficiency diagram

gblanchard · December 3

I have looked all over the web and have been unable to find any diagrams or plans how to set up circulators to run constantly with any system let alone a regular old cast iron boiler. Does anyone have anything for me to look at?

fentonc · December 3

I've effectively modified my CI boiler to run constantly as part of a thermal purging scheme I implemented, but it gets kind of messy if you have multiple zones. Do you have a zoned system with zone valves? Describe your setup more.

pecmsg · December 3

power hot all the time.

gblanchard · December 3

https://forum.heatinghelp.com/discussion/comment/1824362#Comment_1824362

I actually would like to do this on multiple set ups that I have, but I'll pick one for now... Way oversized oil burning Utica boiler hot water heat. 3 zones with sep circs and zone circuit board. 2 upstairs zones single loop copper fin tube baseboard. Downstairs single loop CI radiators. Circs are on the return side down low as the water returns into the boiler. Hydrolevel 3250 plus with low temp off, thermal purge on, high temp 180 and economy set at 3. Have not installed the odr yet. I'm more concerned with setting up the constant circ for the downstairs unit with ci rads, because it's really hard to keep the temp somewhat comfortable. Its's either too hot or too cold. I was thinking about moving the thermostat into the hallway where there is no radiators too. I'm also concerned with condensation.

fentonc · December 3

You might be better served with getting a thermostat that supports remote sensors that can be averaged or something if you're just trying to improve comfort.

With multiple zones, you really can't do continuous circulation for all zones if you can't control the water temp independently in each zone. If the upper floor zones run less than the lower floor (through a higher ratio of radiation to heat loss), you could try to rig it so that the lower floor runs continuously, but the aquastat only gets enabled when that zone (or the other zones) are calling for heat, but that will tend to overheat the lower zone when the upper zones are calling for heat a lot.

Jamie Hall · December 3

Several considerations here. There are both piping and pumping aspects to be considered and control aspects, and it all depends somewhat on what kind of radiation (e.g. heavy radiators vs. finned baseboards).

The ideal setup will use primary/secondary piping, with a separate boiler pump and, very likely, several secondary zone pumps. That way you can control the boiler circulation — and its temperature — to avoid condensation and at the same time provide just the right amount of heat for your other zones.

Now I would set up the various zones so that the zone pumps were pulling away (could be on either the supplies or the returns) from tempering mixing valves, drawing the hot side from the primary loop and the cold side from the return from the radiation. The downstairs cast iron loop would certainly benefit from outdoor reset on its tempering valve, but actually not as critically as the upstairs copper fin baseboard, since that type of radiation has very low thermal inertia and really benefits from constant circulation. It's temperature, though, would be different from the CI, so you'd need another ODR to control those tempering valves.

Do look into some of Caleffi's Idronics publications — or contact @hot_rod directly — for more thoughts.

gblanchard · December 3

I forgot to add that all 3 zones have separate set back thermostats. Hi temp max is 71 and sets back to 68 after 3 hours.

constant running circulators for comfort/boiler efficiency diagram

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