heat loss/heat gain calculation

Constantin

Up to now, most homeowners have been content with a single 50 gallon water heater... those things have an input rating of 50kBTU, and achieve <em>maybe</eM> 30-40kBTU net into the water??? Currently, I guess people need more and more hot water... but this trend is likely to reverse a bit as the energy prices start to bite.

To me, the biggest net benefit of ultra-turndown gas valves like the ones found in the Trinity 400 is that practioners like you will be able to reduce the mass of heating systems even further... the high maximum input ratings on such boilers allow you to use ever smaller buffer tanks as long as they have large HX surfaces... thus allowing the reduction of standby losses, space savings, etc.

greg_28

heat loss adjustment for indirect DHW

When calculating heat loss for specing a boiler, do the wallies add an adjustment(like 50K btu/hr) to accomodate an indirect water heater? I plan on using a Taco multi-circ control with a priority setting for the Indirect.

Thx

Alan(CaliforniaRadiant)Forbes

Not usually

unless there is a large hot water demand and a low heating demand.

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Unknown

size boiler for heating, size indirect to meet load with boiler sized for the heating load. Use DHW priority controls. Poof!

Bob Sweet

greggy

Whats your heat loss calc? What's your domestic hot water load going to be?

hr

Size to the larger load

These days, with well insulated structures, it is not uncommon to find the DHW load as big or bigger than the heating load.

ICF and SIP constructed homes, or buildings insulated with spray foams, can see BTU/ ft requirements in the 10BTU/ ft arena.

A 2000 square foot home could heat just fine with 20K. That's a bit low to drive an indirect with good results, imo. Heck the instantanous water heaters start around 150K and go up.

Even some of the tiny 50K condensing boilers kick up to 80K for indirect DHW recovery. It's hard, if not impossible, to give a customer too much hot water, too fast Harder yet, and more expensive, to go back and upgrade a under performing DHW problem.

This is another area that modulating boilers play so well to. A bit of an oversize, to speed DHW, doesn't hurt as much when the boiler has a 5 to 1 turndown rate.

hot rod

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greg_28

I get it with respect to sizing for the greater load. House will need net 80K oil hot water boiler. Does anyone have a sizing chart for DHW demand? Rule of thumb? "normal family" 2 adults, 2 kids, 2 bathrooms, dishwasher, - no hottub. Thx again

STEVEN MARKS

Crown website has a sizing chart for the megastors.

Ron Schroeder_3

rule of thumb

for five people and a good DHW storage tank 200L and a 100KBTU boiler is a good combination. If you want to have a soaking bathtub with or without jets, choose a 300L tank.
Before everyone jumps on the do a real heatloss band wagon, this has worked for the past 14 years in a 3700 sq ft two story wood fram contstruction with -11C design temp. You may extrapolate to your specifics.