Original message
| Robert
|  "Storage tank"
, posted Wed 29 Jan 09:58  
We have a building with 251 apartments, 178 dishwashers, 286 bathrooms and 12 washing machines. We believe this building has a hot water (domestic)shortage. The tank is 13 feet long by 4 feet in diameter and being supplied by 4 boilers with a supply temperature of 180'F. Assuming we have a storage problem, which I believe is the case, how much storage, at that particular supply temperature, do we need? The existing storage tank is a "Ferrow Metal Ltd. m#FM-15190, s# H9135-65" (other numbers include FBQ55000, QM-40UW-12C). By the way, the storage tank has a heat exchanger in it which was flushed 2 years ago.
Thank you
Robert
Robert
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Replies:
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| melaman
| "Re(1):Storage tank" , posted Thu 30 Jan 17:43
How old is the building? Most likely the domestic hot water was designed to handle the amount of capacity for that building.
If the building is older and has been working properly for a long period of time, I would say you have an equipment problem. Like Xenos says, possibly your domestic hot water circulation pump may not be working, or your storage tank may not be getting a proper flow through it due to a blocked line, or a valve that was anciently closed, not sure. I would check the temperatures going in and out of the tank / heat exchanger on the boiler side and the domestic side to help determine if you are getting good flow. Other testing would have to be done to determine the cause.
If the building is newer and has been working properly for a time, it still may be an equipment problem. If the building is very new it is possible that the designing engineers may have made a mistake in their design. If this is the case you will have a hard time getting them to admit they made a mistake but you should give them a call to help determine the cause of your problem.
You may want to call the boiler mechanic who has worked on the system before, he may shed some light on your problem at a cheaper rate than an engineer. If the mechanic can’t help then you should most likely call on the help of an engineer.
Hope this has helped
R.P.
Pareto's Law
If a group of tasks are arranged in order of their priority 80% of the value come from the top 20% of the list.
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| Xenos
Webmaster 
| "Re(1):Storage tank" , posted Thu 30 Jan 15:58
Seizing is a question that should be addressed to an Engineer. A storage tank with the dimensions you have described appears to be quite large; I would consider looking at the make up rate of the heat exchanger as this should be close to the consumption rate of the tenants. Their really shouldn’t be a time when the water leaving the tank should drop below 130. Commonly in large residential apartments storage tanks are used to eliminate water temperature fluctuation’s verses capacity. Also consider that if your recirculation lines have proper flow then all the piping in the building will become storage, if however you have risers with no recirculation, these lines will cool in the evenings and when people start to use their hot water in the morning this cool water will mix with the hot water in the storage tank thus cooling it and reducing it’s recovery.
Hopefully some of the points I have addressed may help you in you quest.
Xenos
Xenos.
The best way to escape a problem is to solve it.
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