How would you...........

David Sutton_6

have 81 unit appt bldg, two of them, they have Raypak model 0404 Gas boilers.396,000 btu's in 316,800 out, there outside boilers, they want to up grade to something more eff.these are for hot water only, they feed inderects, the doors were locked and we could not get in till tomorrow to check the load, they said they would be willing to build little bldgs to house a new system. how would you best handle this? Thanks for the imput , more info tomorrow and pictures..Thanks... David

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Al Letellier_18

what to do

tough to say without seeing the set up, but max efficiency should be the rule and ultimate yardstick for the job. Stage firing with condensing gas boilers, if the application fits the building, would be my first consideration. Or you could use wall mount Rinnai commercial heaters (outdoor mount is a possisbility) and eliminate the storage tanks all together.

Weezbo

3+3 =6

might look into Triangle Tube and see what might be found to fit the bill.

Brad White_51

Why I like storage tanks in this case

Fully agreeing with his first precept and taking modest exception to Mr. Letellier's second suggestion:

My first reservation about instantaneous DWH heaters is the fuel input demand. You may have to re-pipe, new meter, things of that nature. Maybe it can be handled, maybe not.

With the heater building remote, I imagine you will have, by code, some continuous recirculation to keep water draw low at the furthest unit/fixture. Thus I would think some tank for storage would be desireable.

Condensing, yes, definitely. They work best during the initial warm-up and during catch-up but peter out in efficiency (lose condensation effect) as the DHW comes to temperature. On the whole, still a good value.

If in a remote building that is another reason to go with Condensing: Direct venting and not freezing out the room with combustion air.

With indirect DHW heaters, the hot water loop can also respond as a regular boiler to hit a spot of radiation or a unit heater to keep it from freezing.

I would go with an N+1 or N+2 in this case for redundancy. If two buildings are served by two set-ups might they be manifolded and shared?

Demand calculation: Hunter's Curve only gets you so far IMHO. With that many apartments, one plumbing engineer once advised me that with so many apartments and so many showers going between 6 and 7 AM, to add the fixture units converted to GPM of each apartment standing alone, rather than the cumulative and diminishing number of fixture units as a whole. Part of me thinks that makes sense, the other part says it could lead to over-sizing. So to size it, if possible, I would clock the water meter for a week or install a check meter with hourly demand to see a real number, especially if instantaneous is how it finally plays out.

My $0.02

Brad

David Sutton_6

Thanks Brad

still waiting to get in the mechanical room, there are 65 units with 1 full bath and kit. with dishwasher, there are 16 town houses with 1 1/2 baths and kit. and dishwasher,i'll have to wait till monday now to get in....David

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