what speed setting for 3 speed air handler

tom_49

As lo as you can go, if it doesnt work.....medium....than hi.

Dave_61

what speed setting for 3 speed hydroair handler

We have 3 speed air handlers (Trane) for our hydroair system. They are not variable speed. Changing speed basically means moving a wire from one terminal to another.
What should the fan speeds be for heating?
How about for A/C in the summer?
Thanks.
Dave

Tim_33

No right anwer

to your question. Are you setting up a new system for th first time? Is there a problem with the way it is operating? Just curious?

Typically, heating and cooling modes in a multispeed air handler/furnace require different fan speeds. The fan timer (control panel) may or may not support various speeds.

Bottom line, without alot more information, no one can answer your question.

Brad White_9

It depends on a number of things...

but my typical advice would be (and not to be a smart-a**), "as low a speed as will meet requirements".

By this I mean that in summer/cooling mode the airflow is not only sufficient to cool the space (meet the sensible cooling load) but also not so low that the coil frosts over. Slower coil face velocities enhance dehumidification too.

In winter, low fan speeds mean less propensity for drafts and warmer discharge air temperatures, both good things.

The cost of moving air should not be discounted. Low speed helps in a number of ways, summer and winter.

The fact that the system cannot be easily switched is a tad annoying, isn't it? Are manufacturers listening? I imagine a clever electrician or controls person could install a rotary multiple speed switch for you. Better yet, a micro-drive... cool. They have been out for a number of years.

Dave_61

Our system is about 5 years

old. It seems like it heats and cools OK. However, we added a 3rd air handler in our attic area and it was placed over a bedroom. It sounds like a dryer running above the room.
I know at one point, with our A/C, the installer had changed the air speed on one of the handlers. It was a manual moving of the wire to another spot. Inside each air handler, there is a terminal with 3 positions (low, med, hi).
I was just wondering what the general thoughts are on what speed a/c should be run at and what speed heating should have.
Our water temp that goes through coils is about 170 degrees.

Dave_61

So,

should I decrease speed to low in winter?

Brad White_9

I would

leave it at the lowest speed year round; see if it works for both. The variables are totally in your court; I can only guess what is comfortable for you.

From your subsequent posting, it seems you are in the unenviable position of having to choose between comfort and noise-instigated insanity.

My only concern about reducing the speed in winter is that, if you are heating with warm air from above, the discharge air may be too hot. If it leaves too hot you not only have a scorched effect (stuffiness overhead) but the buoyancy makes it hard for the air to get down low where you, the occupants, are. You might look at better temperature control if that is an issue; perhaps P/S circuiting to get a lower water temperature, hence air temperature.

It all has to heat and cool the space, however. That is your call.

Tim_33

Changing the speed

may or may not affect the transmission of noise into your bedroom. If is rigidly supported from the structure and/or the duct is not isolated by means of flexible connectors, it probably will not matter. There are vibration isolators made for suspending units to minimize the transmission of vibration to the structure, and your ears. Installation of a "canvas" at the supply and return connection to the unit is not typically a DIY project, but if you could find them, you could probably install them.

As far as the speeds go, Brad covered that well enough. I am much more familiar with gas furnaces than hydronic air handlers. They (furnaces) have four speed taps (typically) and cooling "uses" one speed, usually med-high or high, and heating "uses" one speed, usually med-low or low. Two stage units will use a different speed for each stage. The control board "tells" the fan which one to use, if it is wired for heating and cooling (thermostat wire connections, R, W and Y, maybe C).

burninben

Back up everyone. Dave, how many ton of cooling, what size is the supply air? Return? Is the duct in good shape? Insulated? Any flex on supply duct?

mtfallsmikey

Yes, the rotary switch to change speeds

Is one answer. The 'ole Honeywell heating/cooling relay, which I have long ago forgotten the model, provided for 2 speed switching between heating/cooling modes. I don't know this for sure, but I understand that there are small VFD's coming on the market for residential use. We have them in my buildings on the cooling tower fans, looking into grafting them on to the condenser water pumps as well.

Brad White_9

VFD's

are coming down in price so much that they become a default on most motors over 5 HP in our commercial work and down to 1/2 HP if we can get them on the job. It amortizes part of the cost of a starter so all the better.

Cheaper than a sheave change and can be set up for constant airflow as filters load (for example) or as the summer coil "wet pressure drop" shows up, all by using a Setra DP sensor across the fan.

We live in a great age, don't we?