A coil sizing conundrum! (PAH)

hot_rod

A mental chalenge. Here's the drill Phil............................

Condensing boilers have peak efficiencies when in condensing mode.

Wanting to install hydro-air coupled to a condensing boiler, it's necessary to size the coil by plugging in lower water temps so that the hydronic water remains in the condensing realm. Let's say 140 degree F supply with a 20 degree delta-T for arguments sake. Now let's seek 120,000 Btu's net output. So far so good, right?

Ahhhhhh, but now we see the coils Btu ratings fall below those sized to match the rated CFM's of the air handler at 140 degrees F & that particular air handler was matched to the 3.5 ton cooling coil CFM rating of 1,400. No charts & no conversion factors to derate the coils rated at much higher CFM's. I think I gave an engineer a headache today! GPM flow rates? Whatever she'll take Scotty - warp 5? Doesn't matter cause we're using primary/secondary piping/pumping - his headache just became a migrane! "What's that?"

Oh what a tangled web we weave when Btu numbers crunching deceives! So far everyone in the stream of distribution says why in the world do you want to size to 140 degrees F??? Because I'm a Wet Head(G). Or as Gallagher would say... Because I'm an Amuurican! Or as Dan says - Because I can!

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ken_6

cfm hydro heat

1-look at lennox complete heat air modules

2-oversize the coil

3-slow down the fan

4-try fanhandler(no website yet)(modulates fan based on disharge air temp (hoffman has a unit that does the same)

going to do the same