Air handler with 10kw (actually 9.6kw) heat strip. Circuits to run to it.

[Hank33161]

Hi guys, I am a little rusty on some things. I was out of the trade for awhile.

I am doing a residential job and have a 3 ton air handler with a 10 kw heat strip to run the circuits to.

Now, this is a Chinese made unit (Haier) and the instructions are indicative that the person who wrote the manual was not a native English language speaker. The diagram is crazy and everything else. I think it was a mistake getting this unit ( I am installing it in a rental house I own). Buttt..

Anyway.....The air handler states on the label max 15 amp over current protection (at *230 volts - has anyone else seen things labeled for 230?)- it draws 2.5 min running ampacity. The heat strips calls for MOPD 60A and MCA 52.9A 75deg.

My question...I know we have to follow the manufactures specs..
When I install the heat strip (hvac work is not my thing) and its circuit I am pretty sure that becomes the circuit that powers the air handler and of course heat strips, despite the fact it says maximum ocp of 15 amps. Is this right or am I supposed to run a separate 15 amp circuit and a 60 amp circuit??

And please only answer if you have installed air handlers with heat strips.

Thanks,
Hank

 

[masterinbama]

I usually set a 4 circuit panel to allow for the max ocpd for the fan and the strips

 

[Besoeker]

Anyway.....The air handler states on the label max 15 amp over current protection (at *230 volts - has anyone else seen things labeled for 230?)-Thanks,

Just a passing thought.
I'm from UK and 230V is standard here and throughout most of Europe.
Is your AHU designed to a US spec?

 

[jumper]

Just a passing thought.
I'm from UK and 230V is standard here and throughout most of Europe.
Is your AHU designed to a US spec?

Bes, most likely that is the motor nameplate voltage spec.

In general, the US does not use your 230V single phase type of system.

 

[augie47]

Most of the units I have seen, the 15 amp circuit would be an air handler with no heat strips.
Your 60 amp circuit would handle the strips and the motor.
There is often an internal connection to facilitate that.

 

[Besoeker]

Bes, most likely that is the motor nameplate voltage spec.

In general, the US does not use your 230V single phase type of system.

Yes, I was aware of that and that's why I asked the question.

Thanks for the data on voltages and limits.

 

[Daja7]

Most of the units I have seen, the 15 amp circuit would be an air handler with no heat strips.
Your 60 amp circuit would handle the strips and the motor.
There is often an internal connection to facilitate that.

Yep, air handler with 10 KW strip. Standard, 60 amp Circuit. 240V. Disconnect at unit

 

[stew]

If the entire unit uses one 60 amp circuit as you have indicated does the internal circuitry of the are handler provide the 115 for the fan?

 

[stew]

Is there any way you can post the diagram . also if the nameplate shows 2 individual MCAs it probably needs both circuits. one at 115 with a 15 amp ocd and anothe at 60 amps ocd.

 

[GoldDigger]

Sometimes, when the electric heat is combined with A/C, the fan and controls are powered from the same breaker as the A/C condenser instead of the breaker for the heat strips.
If the air handler unit has a required maximum OCPD, then it would have to be a tap with its own OCPD to be fed from either of the high power circuits.


Sent from my XT1080 using Tapatalk

 

[kwired]

Most of the units I have seen, the 15 amp circuit would be an air handler with no heat strips.
Your 60 amp circuit would handle the strips and the motor.
There is often an internal connection to facilitate that.

That is what I usually see. Often there is a new label/nameplate to replace the old one or you have to mark the original with which heat strip is installed and then go by the MCA and other data marked for that combination. So the data changes depending on what accessories are installed.

If the entire unit uses one 60 amp circuit as you have indicated does the internal circuitry of the are handler provide the 115 for the fan?

115 volts was never mentioned, and these units are always 230 volt, but I won't say it is impossible to run into a 115 volt.

 

[Gregg Harris]

That is what I usually see. Often there is a new label/nameplate to replace the old one or you have to mark the original with which heat strip is installed and then go by the MCA and other data marked for that combination. So the data changes depending on what accessories are installed.


115 volts was never mentioned, and these units are always 230 volt, but I won't say it is impossible to run into a 115 volt.

It is 230 nameplate with a 230 motor and strip heat rated at 240

 

[Dennis Alwon]

I am wondering if this is a combination unit where the a/c, blower and heat strips are one unit. We used to see these alot as gas packs but this one may be that with electric heat- not gas.

 

[kwired]

It is 230 nameplate with a 230 motor and strip heat rated at 240

When all else fails, read the instructions.

It is very likely the system you have there (and many are this way) is a basic air handler with a refrigerant coil and a blower.

It has a nameplate rating of its own as a basic unit.

Then there are usually a few available add on heat strip options for this unit. When you add a heat strip the heat strip kit you usually supply power to the add on kit (either single or multiple circuits) and there is usually a fairly simple molded plug that supplies the air handler from the heat strip kit, and the thing effectively becomes a single listed unit when installed according to instructions. Those instructions will also usually give you a new "nameplate" or the original nameplate on the air handler will have data related to all the possible listed heat strips that can be installed and all you need to do is mark which heat strip is installed and follow that data when determining what to supply for branch circuit(s).

 

[augie47]

.................... all you need to do is mark which heat strip is installed and follow that data when determining what to supply for branch circuit(s).

or, as usually happens in my area:
(a) leave the new data tag with the instructions hidden somewhere in the unit
or
(b) trash it.

 

[Ragin Cajun]

HVAC nameplates are a real PIA! There are supposed to be standards but rarely followed properly. Yeah, I'm on a rant!

This is typical of many I have run into. The best advice I can give is to trace it out. Being "foreign" made, you never really know what the clowns did!

I will design to the specs from my mechanical engineering counterpart. Then the shop drawings come in and they in no way match what was speced. Then, what hits the site is anybodies guess!

RC

 

[kwired]

HVAC nameplates are a real PIA! There are supposed to be standards but rarely followed properly. Yeah, I'm on a rant!

This is typical of many I have run into. The best advice I can give is to trace it out. Being "foreign" made, you never really know what the clowns did!

I will design to the specs from my mechanical engineering counterpart. Then the shop drawings come in and they in no way match what was speced. Then, what hits the site is anybodies guess!

RC

I seldom have any problem with the accuracy of data on the nameplate matching the abilities of the unit. There may be problems with a plan showing a particular unit, and they give you data for that unit, but when it gets installed it is not what was on the plan. Maybe the HVAC received the designers blessing on some comparable unit, but nobody informs the other trades that it will not be the same unit that was specified. That is what I find to be a pain sometimes.

 

[StarCat]

208-240 V FCUs

208-240 V FCUs

The fan motors on electric fan coils are typically 208-240 not 115V. Some of these weird, off brand. 3rd rate OEMs that are now flooding the market may be trying to reinvent the wheel in. Standard is ONE power feed.
IN the refrigeration world Haier is very undesirable from a quality standpoint.
Often times on the old school units there are onboard fuse blocks for the heat acessory or a built on circuit breaker.
Carrier of which I have seen more than a few are set up this way.
THe confusion seems to come in because one may select different KW heat packages for the same CFM size fan drive over a range available for that model. Historically in the HVAC trade, there is typically only one breaker feeding the AHU on a residential unit. The breaker being sized for the Heat pack chosen.


All the best

 

[kwired]

The fan motors on electric fan coils are typically 208-240 not 115V. Some of these weird, off brand. 3rd rate OEMs that are now flooding the market may be trying to reinvent the wheel in. Standard is ONE power feed.
IN the refrigeration world Haier is very undesirable from a quality standpoint.
Often times on the old school units there are onboard fuse blocks for the heat acessory or a built on circuit breaker.
Carrier of which I have seen more than a few are set up this way.
THe confusion seems to come in because one may select different KW heat packages for the same CFM size fan drive over a range available for that model. Historically in the HVAC trade, there is typically only one breaker feeding the AHU on a residential unit. The breaker being sized for the Heat pack chosen.


All the best

If the circuit would need to be over 60 amps, it is very common for them to be split up into 60 amp or less circuits. This is an NEC requirement also that they can only be 60 amp max, or sub divided into 60 amp max components and probably part of listing requirements also.

See 424.22(B).