[Greenbuilding] [BULK] Radiant heat boiler

[Dr. C.F. Vasile]

Why are you guys on the "GREEN" Building List; three (3) tankless water 
heaters are "excessive" because 80-90% of their outputs (shower power & 
energy) are wasted down-the-drain; when 50%-60% of it could be recycled 
(www.gfxtechnology.com)!

----- Original Message ----- 
From: "Lawrence Lile" <LLile at projsolco.com>
To: "David Seth Melchert" <dmelchert at earthlink.net>; "Greenbuilder list" 
<greenbuilding at listserv.repp.org>
Sent: Tuesday, February 06, 2007 7:33 PM
Subject: Re: [Greenbuilding] [BULK] Radiant heat boiler


> Well, a shower head is about 3 GPM, you can figure your peak flow from
> there.  For the most part, people don't use the shower and the sink at
> the same time in one bathroom, and the shower generally can't be used at
> the same time as the tub.  You can also figure peak flows from the
> number of occupants - are there enough people in the house to take 3
> showers at a time?  People may also use the washer and dishwasher at the
> same time as a bath.  In my current house, they won't do this more than
> once, since we have a wimpy tankless that can't keep up with more than
> one load at a go.  Brrr.
>
> In my new house, a Tagaki jr, model is keeping up with two showers at
> once.
>
>
> If these bathrooms are not grouped, or if the kitchen is not nearby,
> you'll want two sources of hot water.  A typical tankless heater has
> several seconds of delay (My tagaki waits 6 seconds before firing) plus
> the long run, can mean minutes of wait to get hot water.  The buffer
> tank sounds like a good idea actually - I was considering putting
> something like that in a kitchen that has the long run problem.  Add
> extra insulation to whatever the manufacturer thought was enough,
> because the buffer tank defeats some of the savings associated with the
> tankless.
>
> I can't imagine 3 tankless heaters, seems pretty excessive.  Do the math
> and see what you come up with.
>
>
>
> Lawrence Lile, P.E., LEED AP
>
> -----Original Message-----
> From: greenbuilding-bounces at listserv.repp.org
> [mailto:greenbuilding-bounces at listserv.repp.org] On Behalf Of David Seth
> Melchert
> Sent: Tuesday, February 06, 2007 6:04 PM
> To: Greenbuilder list
> Subject: [BULK] [Greenbuilding] Radiant heat boiler
> Importance: Low
>
> We have started a large residential remodel in Orinda, CA. The 2,800 sf
> house will be heated with radiant floor heat. We were planning to use a
> Baxi Luna 330 instant heater for combined radiant and domestic hot
> water. I really love the Baxi Luna for its compact design and simplicity
>
> of installation, not to mention its general high efficiency.
>
> However we are concerned about its capacity to serve the demands of a 3
> bath house. The homeowner consulted with a supplier who suggested that 5
>
> gpm, delta 70 degrees is the minimum required, more than the 144,000
> BTU's the Baxi Luna provides. Baxi has a new Modula supplemental tank
> that holds 21 gallons and serves as a kind of buffer for temporary high
> demands. My homeowner is concerned this will not cut it. They are edging
>
> towards having separate heat sources, such as a Noritz or an efficient
> large tank for DHW.
>
> Here are my questions: how many gpm should we figure for hot water needs
>
> at any one time, and how often might a family of four run into
> insufficient hot water using the Baxi? Would you agree that providing
> separate heat sources for radiant and DHW would be the best path?
>
> Thanks
>
> Seth Melchert
> Oakland CA
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