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Need help with an improperly balanced DHW system
I have a multi family with 10 risers (5 kitchens and 5 baths) and the hot water stubbornly doesn't want to reach the furthest riser (bath).
Supply is provided by by 1" coming out of a Holby mixing valve at the steam boiler with a new adequately sized domestic hot water coil. We placed a recirculating pump with aquastat on the 3/4 return line just before the boiler. Though this has modestly improved hot water to some fixtures in the building, it hasn't made much of a dent in the problematic riser (both the hot water supply and return) remain luke warm on that riser. We've even tried to set the aquastat on the pump so high that it continually runs, but not much effect either.
The only time it gets hot on those fixtures is when water has be running for like 10-15+ min, and even then it's not consistent.
On one particular occasion we lost hot water for an hour on one whole side of the building (opposite the boiler) and I happened to notice that the unit directly above the boiler was taking a long shower and had sufficient hot water. It could have been an coincidence, but shortly after the shower was finished, hot water came back to the whole building. This has not been noticed to have happened since.
All of this leads me to believe that the water is not properly balanced across all risers (maybe at some point it was, but no longer).
I was going to place another recirculating pump at the bottom of the return of the problematic riser (horizontally right before it meets the common 3/4 return to the boiler where the previously installed pump sits some 30-40 feet away.
Any thoughts if this would help?
Should I instead look into trying to restrict/better balance all of the risers across the building?