Lately I’ve been running across what I assume is called a hydronic forced air furnace. I’ve tried looking them up on the net but there doesn’t seem to be too much info about them.
They look like a car radiator mounted in the unit, (heated with water from the water heater[FONT=Calibri]that services the hot water to the remainder of the house as well) with a fan below and fed to metal ducts and registers.[/FONT]
The system itself looks simple enough but I was wondering;
[FONT=Calibri]1) [/FONT]What I should be looking out for when inspecting them?
[FONT=Calibri]2) [/FONT]Are they efficient compared to a high efficiency gas furnace?
[FONT=Calibri]3) [/FONT]Are they costly to run?
[FONT=Calibri]4) [/FONT]How often do they need service?
[FONT=Calibri]5) [/FONT]Also I’ve found a tap inside, what is its purpose?
Yesterday I ran into one where the water was heated by a tankless water heater, any opinions on that?
Got any pictures or manufacturers info? What you’re describing is common in high rise condo buildings. 2 pipe and 4 pipe systems.
I’ll get you the pictures Linus but Ive been finding them in single family homes
This is from yestedays inspection (single family home 1500 af )the unit appeared to be about 20 years old and was supplied from a tankless water heater
Inspected one yesterday and I was under the same situation. I would appreciate any info on efficiency rating, life expectancy, etc. The air at the registers was 85 degrees.
Life expectancy would be the same or less depending on use as any Water heater. Untreated hard water will create calcium build up and decrease efficiency. The heating coil would be subject to calcium build up same as the water heater
It would be as efficient as the water heater.
Also, I think that potable water should not mix with water used for heating.
Try searching for “Fan Coil Units”.
They are simpler than a gas furnace. Usually a similar air mover, and something to control the water - a valve, or a pump that comes on with demand, etc.
Efficiency depends on the heat source, heat loss in pipes.
Service like a furnace. Check filter monthly, serviced annually.
Tap could be to drain (think winterize) or bleed air, depending on position. Tankless water heater would be good heat source.
Most important factor is the water that flows through it. Untreated, hard potable water will clog the heat exchanger. (Yes, there are some systems that use potable water - Lennox CompleteHeat system, for one example. Rivals their “Pulse” furnace for biggest POS.) Closed loop with properly treated water will have similar lifespan as a furnace.
I’m in commercial maintenance and personally like these systems. They put the heat source in a central location, provide good zone control. Watch for leaks, and they are prone to problems from lack of filter changes due the tight spacing on the coil - like an HE furnace is.
Chad
I searched fan coil units and they do not appear to be the same, fan coil units are ductless systems
One concern I had was that the water heater temperature was set to 150 degrees. Does it need to be that high for the unit to perform? Because since it used the same water heater as the rest of the home, the hot water from the sink taps was scalding temperature.
If the tap is to release air, does this have to be done on a regular basis?
Kirk,
Some info from CMHC attached.
Also, I think that potable water should not mix with water used for heating.
It doesn’t, it’s a different type of water heater.
One concern I had was that the water heater temperature was set to 150 degrees. Does it need to be that high for the unit to perform?
Q = U x A x Delta T
The greater the temperature difference the greater the heat transfer.
** Because since it used the same water heater as the rest of the home, the hot water from the sink taps was scalding temperature.**
If you are in a regional area that requires water over 120°F to properly supply the number of BTUs then you simply install a mixing valve to reduce the temperature.
**If the tap is to release air, does this have to be done on a regular basis?
**
It has to be done if it ever gets air bound.
It’s a " service valve". You use it when you need it.
**1) What I should be looking out for when inspecting them?
**Water leaks. Generally at the circulation pump.
**2) Are they efficient compared to a high efficiency gas furnace?
**No they not designed to be.
**3) Are they costly to run?
**A better question is is the increased cost less than adding a separate boiler system?
**4) How often do they need service?
**Same as any HVAC system. It’s a coil it needs to be cleaned.
**5) Also I’ve found a tap inside, what is its purpose?
**Service
**Yesterday I ran into one where the water was heated by a tankless water heater, any opinions on that?
**
As tankless water heaters are not efficient, and the hydronic to air transfer is not efficient, I guess we can surmise that the entire system is not efficient.
These applications have specific uses. They are frequently used in town homes where the heating load is not that significant because they backup to one another. Building size is not large enough to facilitate a boiler and a hot water heater in each unit. Supplemental heating or zoning situations.
Considering your climate zone in Canada versus mine in Nashville, and the fact that these systems are not always the best selection here, they will probably be even less attractive in your area (Dependent upon your use of course).
This is a typical hydro-air system We seen them in McMansions with multiple AC units.
Many run anti-freeze in the boiler units. Each zone valve corresponds to a high-density coil mounted in the air handler.
They are as efficient as the boiler rating, and can provide near instant heat to a room. Similar to a conventional furnace, rooms tend to cool off quickly. I disagree with Charley however, in the life expentanncy of these coils, which I believe is around 20 years.
These systems, in conjunction with a boiler mate, are becoming pretty populat in areas where natural gas is not available. They run on fuel oil beautifully.
Inspect boiler as you would any conventional system. nspect air handlers as you would any conventinal air handler.
If air handler is installed in unconditioned and cold spaces, ask if the unit is running anti-freeze.
I have seen a lot of these combinatin units in canada .
http://www.docstoc.com/docs/128925371/Combination-Heating-System-2
http://www.municipalaffairs.alberta.ca/documents/ss/STANDATA/gas/2012-P-G-08-02-REV3.pdf
The original question concerned a water heater not a boiler. My staement was simply about the inside of the coil building calcium at the same rate as the water heater nothing less. If the inside of the coil tubes becomes calcium coated the efficieny goes to hell in a hand basket. There was no mention of antifreeze. The thought was water heaters with dual purposes
But we don’t know that for this particular situation…
Closed loops shouldn’t have air in them. After the system is filled, the dissolved air separates and is released by manual or automatic air bleed valves. The need to repeatedly bleed air means fresh water is being added because of a leak.
Required temperature of the water depends on BTU’s required. Controls for this application include a reset to raise the temperature as the outdoor air temperature decreases.
Gylcol is a necessary evil in some cases. It’s expensive and can’t carry as much heat as water, and requires more energy to pump.
Thanks to everyone for their help…much appreciated!