Unintended consequences of retrofitting — Part 3

Nov. 2, 2012
This is the last in a series of articles on the hidden consequences of water and energy retrofit considerations in mid-rise multifamily buildings.

This is the last in a series of articles on the hidden consequences of water and energy retrofit considerations in mid-rise multifamily buildings.

In last month’s article, we discovered that a replacement booster pump was generating pressures in excess of the shower valve cartridges capacity, compounding cross connection issues associated with blown diaphragms on the pressure balancing spools of the shower/tub valves.

Back to what else changed.Based on what we saw in the field, all lavatory faucets were retrofitted with low-flow aerators. All shower heads were replaced with low-flow shower heads. The toilets had been replaced with a “pressurized flush” style of toilet. The previous system had no low-flow aerators or low-flow shower heads, and conventional float style toilet fill valves, so on a draw of water the system saw significant flow rates.

These significant flows could have been masking the failed cross connected shower/bath tub cartridges that were discovered. It is my belief that these failed cartridges had been there all along, but were not noticed until water and energy conservation items were installed, and the new higher pressure drop reverse indirect came online.

The original domestic hot water heat generation was done via immersed coils in the tops of the boilers with a circulator that moved water between the coils and the storage tank. On draw in that system, the potable water realized very little pressure drop other than the inherent pressure drop associated with the operation of the anti-scald tempering valve serving the system, and the minimal pressure drop associated with the oversized piping distribution system. Remember that the plumbing system for this building was engineered during a period of time (circa 1960) that water conserving, low-flow fixtures were non-existent.

In the course of my investigations, I discovered that the circulation return mains were piped in a parallel direct return fashion. There were balance cocks installed at the individual branches, but they had failed over the years due to the packing glands leaking. The return was out of balance, and the furthest branches were suffering from poor flow conditions. I proposed installing remote non-electric thermostatic control valves on all of the 13 individual branches. In this way, once hot water got to the top of the risers, the valves would partially close, causing more flow to go to those branches that were still cool. Not really anything new, just applying the same principles we’ve been employing in the hydronics world to the domestic potable water world. I would then replace the 1-1/2 horse power circulation return pump with one of the newer ultra efficient DCECM motored variable speed, constant pressure pumps. The resultant reduction in energy consumption would pay for the pump replacement in less than two years. It would take longer to recover the costs of the non-electric thermostatic radiator control valves, but there would also be thermal energy reductions during the summer cooling months, as well as avoiding hydraulic erosion corrosion occurring in the currently constant run circulation return system.

The lesson learned on this project for other contractors is that we as contractors have to look at these plumbing/heating systems as a whole, and not just component parts. If there is any hint of “existing issues” the contractors should be very aware of them, and should have a caveat in their proposal that if anything raises its ugly head, that those issues will be dealt with separately from the retrofit consideration. I would suggest that any contractors involved in performing this type of retrofit develop an existing building survey whereby these questions are asked and answered so that these potential issues can be taken into consideration in advance of the retrofit project.

To their credit, the installing contractor went above and beyond in their efforts to satisfy the seasoned citizens and administration on this project. In fact, I suspect that their meager profit margins were totally consumed in attempting to correct an existing situation that was being masked by the significant waste occurring within the system. In reality, it wasn’t their “fault,” but due to the fact that they were the last ones who worked on the project, it was their problem. Once things were returned to normal, there were a lot of very happy senior citizens roaming the halls of this subsidized housing project. And they smelled real good.

Tune in next month as we take a hard look at the new Radiant Professionals Alliance, a division of the International Association of Plumbing and Mechanical Officials. Until then, happy Presidential Election hydronicing! Remember our troops who have given the ultimate sacrifice by getting out to VOTE! It is the least we can do.

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