Hydro air vs. forced air furnace

Nick S

http://www.fanhandler.com/

This is the ticket. Use with a standard psc motor.

colin_4

Hydro air vs. forced air furnace

I am quoting a job on a new custom home, very tight and well insulated. The customer wants radiant floor in base-ment and forced air on main floor, with floor warming in washrooms, under ceramic, etc. I am proposing a condensing boiler, IDW for domestic hot water, and an air handler with hot water and A/C coils. The customer's opinion is that he should install a separate forced air furnace for the duct system, since the cost difference is not that much, and he would always have a "back-up heat source". As a passionate hydronics installer this does not "feel right" to me since the heat loss is quite low, and the boiler is more than capable of handling the load. I would like some discussion on the advantages of hydro air vs. forced air furnace.
Thanks, colin

J.C.A._3

2 words.....

More options !

A furnace is a furnace , with the hot water option....the world is the owners oyster. Much more flexable with the ability to have one (or more) fewer appliances to service/repair and run fuel lines/pipes to.

A true "no- brainer". MHO Chris

bigwilly104

Less options

Unless you want to use a air handler made by one of the leading manufacturers with a heat coil downstream you cant offer variable speed blowers or two stage controll. I have yet to find a hydrionic air handler that is well made other than the unico stuff but thats a diferant ball game. If you consider the extra controll and pump you will be adding to the boiler it will probably balance the cost of the gas line and flue pipe for a furnace. The back up heat is no small thing either. if a small problem shuts down the boiler its no biggie with the forced air for back up. Without it you name is mudd unless you can be johney on the spot. All thing considered I am always on the fence with this one also. Usually I lay it out for the customer and let them decide.

colin_4

Thanks for the replys. With a modulating boiler and out-door reset, Don,t we have virtual 'continuous staging?' Also,any of the AH I have worked with have 3 speed blower. Its quite easy to step up the blower speed with a programable 2-stage T-stat and a relay. Another thing, with a boiler you are basically 'energizing water'. The only way for that energy to leave the water is into the space. If the filter is partially plugged, or air flow is restricted, The heat is still in the system. Where will the heat go if a furnace heat exchanger is in-efficient due to inadequate air flow? I have also heard that a hydro-air is not as dry, and there is less stratification. (you can tell which side I'm on). I welcome being challenged on any of these ideas.

Eric_8

You don't want to "modulate" your water temp going to the hydronic coil for sure! The air has to meet a minimum temp or the customer will "feel" cool.

Robert O'Brien

Thermopride

make a ECM air handler with hydronic coil,I have no first hand experience,but their furnaces are absolutely top notch.

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Eric_8

Which allows you to "modulate" the air speed, correct?

But you still don't want to "modulate" the air temp, correct?

Eric_8

Or wait, if you "modulate" the air speed you could also "modulate" the air temp couldn't you?

Eric_8

deleted duplicate post

colin_4

So what would be the minimum water temp that would be acceptable (for comfortable warm air) if I am running an air handler with an oversized coil and a low blower speed?

Todd_27

Airhandlers 1st hand

I installed two of these (thermopride ecm's) in my parents home three years ago. These are "fan"tastic airhandlers. We used the Aprilaire media aircleaner and UV lamps.
These are supplemental to a floor warming setup and it is very comfortable. My father didn't want to reset the water temp, so they are running with 180 deg. coils.

The ECM motor is truly the way to go. Constant airflow, constant filtering, no drafts

colin_4

Still wondering if anyone has first-hand experience with minimum supply water temps to hydro-air coil at low blower speed?

Boilerpro_5

Not true!!!......

I have several fully modulated air handlers where that is not a problem. Properly locating the supplies near the ceiling and using a high volume/low pressure system provides incredible comfort,with no stratification. Think air turnover systems. Look outside the box for something better.

Boilerpro

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tom_49

110o, no problem. keep the supplies to outside walls, ecm low as possible.I find 180o water feeding a/h to be way to high except in extreeeeme conditions.You get the feeling of hot-cold-hot-cold. like a big oversized fha system.

we have tons of these out there connected to mod/cons. 110-150o max.

good luck, tom

Rich L.

Air temp & back-up

Hi Colin, I'm on your side also, Hydro's the way 2 go! How many people would put in a back up furnace for thier regular furnace? One heating appliance is enough!

I have a water to water GSHP in my house and get comfortable discharge air at 105-110* F. with my hydro coil. I'm using a High Velocity system. I have one of the new ones with an ECM motor. It's only used in the shoulder seasons when I don't want the floors to come on and potentially over shoot. It's controlled by OD temps.

In the end it's the customers decision, but it's definately our responsibility to educate, even lead them to that decision.

Good luck, Rich L

colin_4

Thanks all, the feed-back is appreciated.