Calculating atmospheric vs modulating for cost savings

Weezbo

what type of emitters do you have? is it a radiant system?

some hydronic heating systems use hot water base board some coils with in a forced air arrangement some through large chunks of iron others through panels of various descriptions within floors, walls, ceiling or beams...

the boiler itself is able to net you some real savings ....however the system side can be controlled to do the same.. i tend to think that in order to make the best stab at it you consider some of the other variables as well.

As Andrew said, the Triangle Tube might be a pretty good value...

Arthur Binder

Calculating atmospheric vs modulating for cost savings

Is there software available or (if not then how do I) calculate the yearly saving from changing to an 80% atmospheric boiler to a 87% 5:1 turndown boiler. I live in central Illinois so there are several degree days. Any help would be most appreciated. Thanks

ALH_4

Mod

That's a difficult prediction. Is outdoor reset also part of the plan?

Seems to me that if you are going to the trouble of installing a modulating boiler, maybe it would be worth installing one that will condense as well? The Triangle Tube Prestige is a good design with a good price.

Brad White

On-Off vs. Modulating

Even without "condensing" efficiencies (you stated 87% and condensing is roughly 92% plus), the modulating boiler gets the nod.

Consider that you do not drive by flooring the accelerator then coasting to a stop. You do not simmer a stew by turning on a 15,000 BTU range burner and hope for the best. No, you gradually add and withdraw fuel to match the need.

Add condensing to that, you have the best of all things. As Weezbo pointed out, the emitters you have (radiators, finned tube baseboard, radiant floor, radiant panels, air coils), each have their own preferences for water temperature supplied to them. Cast iron radiators (if oversized) and radiant floors are prime candidates for the lowest temperatures. Fin-tube baseboard can also work, especially if generously sized but also if conventionally sized, provided an aggressive outdoor reset schedule is used.

That goes to Andrew's point- outdoor reset coupled with modulation will give you the greatest benefits. Add condensing and you have it all. Does that sound feasible?

Arthur Binder

Baseboard with two indirect fired water heaters (180 degree output).

Kal Row

for startes...

just look at the btu input verses the btu output, on a cast iron natural draft boiler as compared to a mod-con boiler – the cast iron natural draft is typically 20% different and the mod-con 10% different, so before we even start the mod con is 10% more efficient – and this is worst case – ie the mod-con going into a 180f load – you cant put your hand on the flue outlet of a reg boiler – but it’s no problem with a mod-con, and it gets better as the return temps go down – and of course matching the fire to the load is a real big deal

as for the heat emitters – stay away from air based – ie fin coils – heating air to heat people is a bad idea – use in floor heat, OR, a bunch of flat faced cast iron radiators at 110f do just fine

you home-run pipe them with pex off a regular radiant manifold , and can put a thermostatic valve on each radiator ,

you can you can uses a wilo stratos pump to give automatic head and flow into them into the system – ie, the stratos pump will maintain the correct head as radiators open and close, yet slow down the flow if the return water temp shows ,that you are not really using the btu’s

as for sizing the radiator just make them twice as big as usuall, ie – they are usually rated for about 340btu per section for high temp water – so assume 160btu per section and run with that – put insulation and aluminized bubble wrap behind it, paint it to blend into the room, and “presto”, radiant heat on the cheap!!!

mosses of eny is doing tons of these in condos all over now and people love it - and it don’t look bad either - see pics – and to me the biggest advantage is, that while it has enough mass so that your boiler can go off and do domestic hot water for 2 hours without worrying about heat, at the same time, it’s not so high mass, that you need the weather channel driving your outdoor-reset 12 hours in advance – if a radiant house is comfortable 5am on a cold but sunny winter day, by 11am your are opening the windows, even if the boiler is long off, this is probably why, radiators are more popular in Europe than in-floor