Fitness club dhw retrofit, Pro advice needed

NYplumber

Good evening readers,



The current heat source, a 680kbtu 100gal AO Smith water heater and three 120gal storage tanks are due for replacement. One of the storage tanks are isolated due to a leak. The system isnt very energy efficient, and the equipement have age.

The system is piped with the storage tanks feeding the buildingand the three tanks circulating through the water heater with equally spaced t's.



As far as sizing the required load and storage, I will contact the manufacture of whatever brand we choose.







The question:

Normaly we would use a mod-con with an indirect (Superstor, Turbomax, Lochinvar, etc), however the mechanical room is far below grade away & away from exterior walls.



What are the options?

Cast iron boiler with indirects? (Multiple boilers staged.) New dhw heater with storage tanks?



Advice please.

Thanks in advance.

Charlie from wmass

If you are producing domestic hot water

a cast iron may be just as efficient as a condensing boiler due to high return temperatures to the boiler. Pick your favorite boiler and indirect and make sure it is sized to the load. two smaller boilers may be better than one big as you can stage them and if one is down the other can supply a partial load.

CMadatMe

Away

Further then 200' for venting distance?  The heaters are venting into something. Can the existing venting means be used as a chase? May I ask what is the actual domestic demand vs just trying to give advice based on what is there.

Mark Eatherton

I'd FIND a way to get plastic venting in...

A good mod con boiler, like a Knight by Lochinvar coupled with a reverse indirect domestic hot water heater would reduce their fuel bills by a minimum of 30%, maybe more depending on how other "parts" of the system are configured and controlled. If there is absotively, posilutely NO WAY to use plastic, then I'd throw a near condensing boiler (85-6% er) in and put a termomix anti condensing valve on it and let IT rip.



People get confused. They look at the AFUE numbers, which aren't even applicable in DHW systems, and think that the difference between an 85% er and a 95% er is only 10 points, but they discount the short cycling influence on the bill, which will be virtually gone with a good and proper design. They would see a minimum of 30% reduction in fuel consumption just for the change in combustion technology. That, coupled with the 99% efficient heat transfer ability of the reverse indirect keeps the package in the condensing mode even when its doing DHW, and the closed loop side doesn't see any of the harmful effects of continuous fresh make up water.



Now you're cooking with gas...



I'd recommend that before you yank the old system out, that you do a study with data loggers and determine exactly how much energy they actually use, versus over estimated manufacturers numbers. HOBO makes a nice line of data loggers. Quite honestly, there are a BUNCH of people out there offering data loggers for fairly cheap. If nothing else, set a gas meter on the existing water heater and take readings numerous times per day.



If nothing else is being dumped into the existing B vent, you could do the pipe within a pipe trick that Lochinvar now allows on certain models...



ME

NYplumber

Data logger

We are trying to figure out actual demand. Onset makes many devices, can someone please point me in the direction of one for my application?



The direct vent applications are not applicable for this job. Dual boilers with storage tanks will most likely be the most cost effective choice with adding some redundancy.