Home>Discussions>INSULATION & HVAC>radiators vs. air handler with hydracoil
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radiators vs. air handler with hydracoil

I am heating a 1 floor, ca. 1800 square feet commercial space (we own), currently running hot water through 6 radiators, located in the Northeast (cold winters). I love the way the radiators heat up and remain warm throughout the entire work day, but as we are remodeling, it would also be nice not to have them there. We recently installed a new AC air handlerwith a hot water coil which has not yet been piped to our furnace.
If we went with this system for heat, we would leave at least one (maybe 2) radiator at the far rear of the space as it the ductwork only properly reaches the front 2/3 of the space. My HVAC / Plumber tells me that while the radiators do indeed stay hot for many hours, they take a lot of energy to heat the iron and the many gallons in the system, so that while the hydracoil may need to fire much more often, we will probably find that it is more energy efficient in the long run.
Anyone have experience with this?
Much appreciated.

Re: radiators vs. air handler with hydracoil

I wonder if the HVAC guy has done the proper HEAT LOSS CALCULATION to determine if the hydra-coil is large enough in heat output to heat the entire 1800 sq.ft.---another issue would be the extension of the ducting to properly heat the back 3rd of the space.

The starting point in these issues is to get calculations done on the amount of heat loss per hour that the building experiences on a cold day (considering location, insulation, square footage, # of windows, height of ceiling, etc)---this is known as a Manual J calculation run thru a computer & your HVAC guy has to be able to do this--you can Google "heat loss calculation" to get some free rudimentary on-line heat loss calcs---some "professional" calcs will charge $50-$100 for the service.

Very roughly, the 1800 sq.ft. is multiplied by 40 (btu/hr per sq.foot) to get a rough estimate of how much heat you need per hour; thus, 1800 X 40 = 72,000 btu/hour needed to heat the space (if there is little or no insulation in the walls & roof, a high ceiling, or loads of windows, multiply by 50 or 60 to get a rough estimate).

Next, consult the name plate on the AC/heater to see if it lists the heat output of the hydra-coil---
otherwise,check the internet for the mfgr of the AC/heating coil system & use the model number on the unit to determine the heat output of the hydra-coil---the output of the hydracoil should closely match the heat loss calculated, 72,000 btu/hr, or whatever it is,

Whether it will be more economical to hook up one or two radiators to the hydra-coil, or leave them off is hard to say--most radiators are sized & designed to operate at 180 degrees water temperature, check to see of the hydra-coil can produce water at that temp. or better.

There is a formula to calculate the output of a rad: assign 170 btu/hr for each sq.ft. of radiator, then multiply by the # of rad sections: Thus, a 24 section rad that is 1/2' wide & 1.5' high = .5 X 1.5 = .75 sq.ft. X 24 = 18 sq.ft. X 170 = 3060 btu/hr heat output of this rad.

Re: radiators vs. air handler with hydracoil

Thanks Nashua,

assuming the hydracoil is indeed properly sized, and disregarding the back of the property, do you have any experience about whether the hydracoil system is equal to or more efficient than radiators in general? My debate is whether or not to get rid of radiators as a purely aesthetical decision, keeping in mind that I do not wish to become less efficient in heating the premises.
In short, if two exact properties are compared, one with radiators, one with hydracoil heat, which one is more efficient as far as fuel consumption.
Radiators take a long burn time to heat up, but then remain very hot for hours (mostly for the rest of the working hours)while the hydracoil will heat up quite easily but need more frequent heatings.



Re: radiators vs. air handler with hydracoil

Not directly familiar with the hdracoil equipment you mention---if you want to post the make & model numbers of the equipment you have I'll try to see if I can find anything in my manuals.

If I read your posts right, you have a new AC unit with a heating coil (model # & mfgr) you might want to hook up, and are currently running 6 radiators (dimensions of each & # of sections to each rad) off a hot water boiler (model #, mfgr & age of boiler ?).

Re: radiators vs. air handler with hydracoil

thanks Nashua,

(was out of town, took some time to reply).

# Sections L x W x H height of sections only (not feet)
1 25 61 x 9.5 x17
1 16 39 x 8.5 x 36
2 9 21 x 8.5 x 36
1 12 29 x 9 x 36
1 17 42 x 9.5 x 36

Air Handler with Coil about 2 years old
Faincoil unit 27JF
Model # 48HBXB-HW
10.7 Amp 3/4 HP

Low Pressure Boiler (Hot Water)about 3 years old

Re: radiators vs. air handler with hydracoil


Was unable to find any data on the heating efficiency of the 48HBXB-HW---the manuals rate the heating coil at 105,000 btu/hr, which would seem adequate for the size building you have if you decided to extend the ducting to the entire space involved.

I would tend to agree with your sense that the Burnham PV83 boiler and radiator combo would provide more comfortable heat----many people have a difficult time getting used to forced hot air after they've experienced the comfort of rads.

Cast iron rads heat in a different way that many people love---combining a radiant and convective type of "fat" heat that you don't get with forced hot air.

You would also have more control over the Burnham boiler in comparison to the air handler in that you could "down-rate" the nozzle in the Burnham oil burner closer to the 72k btu/hr that you seem to need---this would save quite a bit on fuel without compromising heating comfort.

The Burnham boiler's output is rated at 123k/btu/hr at 83% efficiency, but it can be down-rated closer to the 72k btu/hr by simply changing the nozzle to a smaller size--a $2 item.

If you can change your TOH "personal profile" so that you can receive personal messages, I can provide you with other online tech heating forums--- they may have direct experience with the issues you raised on this forum.

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