Hydronic Piping Practices for Zone Heating

while there are infinite "rules" on hydronic piping,my normal practice is to have the supply and return piping for each zone on the perspective supply/return piping of the boiler. with the addition of a bypass line to let some supply water back thru to the return, this of course prevents condensation inside the boiler at lower recovery temps(below 140), and prevents boiler shock. Needed on cat iron boilers. I use this method especially for radiant in floor heating, and when storage is used. However for coal boilers I've noticed mostly steel being used for the boilers, and no storage. I'm moving my system to the south end of the basement and rerouting the entire zoned heating system. thinking on one small loop with the return lines 4 or 5 pipe diameters downstream of each supply on all zones. Any takes on this method? My system will be ran at 170/190 degrees. water will still be mixed to the return, and the system should maintain a pretty constant temp.

nuthcuntrynut wrote: thinking on one small loop with the return lines 4 or 5 pipe diameters downstream of each supply on all zones

I am having a hard time picturing what you described. Are you talking about primary/secondary piping?

Regardless of how you handle the zone piping, I like to install an "equalizer" between the supply and return on the boiler. When nothing is calling for heat and the boiler sits idle it will keep the boiler at a more uniform temperature. This might not be a big deal on a small boiler like the LL110, but on the bigger units it helps prevent stratification within the boiler.

Am I the only one here who is running zone valves instead of zone circulators?

lsayre wrote:Am I the only one here who is running zone valves instead of zone circulators?

Nope. I have two boilers, three circulators, and six zone valves.

There are many rules for hydronic heating piping, some good, some not so good. The rules were created for installers (plumbers) when there were also the designer of the heating system, sizing, equipment choice, installation, etc. Today all of these choices are much easier with the aid of computer design/selection software. Since each installation is unique, a optimum design for your installation can only occur if you do the design and select the design trade offs important to you. The single most comprehensive hydronic heating design software is offered by http://www.hydronicpros.com/ There are many others, many that are much better in their specific area. But, the free or trial versions offered at Hydronic Pros, are sufficient to design the typical residential hydronic heating system.

I too, I'm not sure of the question you are asking. While all boilers have many similarities, coal boilers are unique because they can and do make substantial heat when there is no demand. The expanding heated water has to go some where. If you don't have a dump zone you have to oversize your expansion tank. If it overheats and pops the safety valve, depending on the location of your circulator pump/check valve, it may not recover automatically when it cools and the automatic fill valve refills the system. Why? Because the pump impeller may not have any water in it, because a closed check valve prevented water flow to it. For this reason I put the circulator pump on my coal boiler on the return side.

My system is a primary/secondary oil and coal boiler system. Zoning is done with circulator pumps. I bought into the belief that pumps are more reliable than zone valves. Not sure that's the case today.

Rob R. wrote:

nuthcuntrynut wrote: thinking on one small loop with the return lines 4 or 5 pipe diameters downstream of each supply on all zones

I am having a hard time picturing what you described. Are you talking about primary/secondary piping?

Regardless of how you handle the zone piping, I like to install an "equalizer" between the supply and return on the boiler. When nothing is calling for heat and the boiler sits idle it will keep the boiler at a more uniform temperature. This might not be a big deal on a small boiler like the LL110, but on the bigger units it helps prevent stratification within the boiler.

The system I am describing is basically a primary secondary loop, however the return line for each zone instead of all teeing into the dedicated return line are teed in about 6" downstream of that zones supply tee. Water generally does mix, but like one of my zones that would literally dump 50-60 degree water upon first turning on, its return is mixed with that of the supply water before it gets back to the boiler. It doesn't make a whole lot of differenence as compared to the traditional supply line all zones are teed off of that and return zone piping being tied downstream of all the supply zones, except it does help stop migration through a check in the circulator, and all water is generally mixed so that the boiler doesn't receive a slug of exceptionally cold return water. That and it saves some extra copper and installing a bypass valve. I may have to try to get some pix and examples from my classroom. Just trying to get ahold of how fast coal can recover in a small hydronic system like the LL110. For example my system now is a depressurized outdoor wood boiler, with a primary secondary loop system. The primary pump ran 24/7. Soon after install we noticed "ghosting" of the hot water , second floor was wicked . Water would migrate right thru the flowchecks. One option was to set the return lines on the secondary system downstream of their perspective supplies to curb this, another was to pull the zone circulators and simply install zone valves, or install zone valves on the return lines either way I had never messed with a hydronic system that was at atmospheric pressure, it was quite an eye opener. With a new system going in just hoping to get some ideas even newer innovative ways. Besides that I am looking at a 100 gallon pressurized storage as an option as well. As well it always gives something new to teach, and research projects for my students.

If you want a primary/secondary setup that offers the same temperature water to all the zones, tempers the return water before it hits the boiler, and allows some gravity circulation through the primary loop when things are sitting idle...check out this sketch. You can ignore the comments since this was for a different install.

efficient loop, and good deal for a boiler that idles
thank you