Commercial heat pump w/aux heat - 2 separate branch circuits?

[bryanbdp]

I am working on a wiring plan which includes a number of modine heat pumps with aux heat (EFV036). Heat pumps are spec'd at 208 3ph, 18 FLA, 21A MCA, 30 MOP
Aux 10kW heater is 208 1ph, 34.6 FLA, 34.6 MCA, 45 MOP.

I haven't seen these units yet, and the information I have found isn't real helpful. Do these units typically have two breakers built into the control box, and you run one branch circuit? Or do you have to run two branch circuits normally? Is there an option to add a small 2 breaker box on the unit, and a single branch circuit? If you can combine the loads, how do you calculate the branch MCA and MOP?
:?
Thanks,
Bryan

 

[JFletcher]

I havent seen this particular model but we frequently run 2 circuits for heat pumps w/backup elec heat, usually a 30A on #10 and a 50A on #6.

You cannot combine the loads onto one circuit.

 

[Fnewman]

When the distance from the distribution panel is fairly long, i've typically seen a feeder run to a sub panel near the unit to provide the two circuits and serve as the local disconnect as well.

 

[JFletcher]

When the distance from the distribution panel is fairly long, i've typically seen a feeder run to a sub panel near the unit to provide the two circuits and serve as the local disconnect as well.

True. The above "cant combine loads on one circuit" was meaning to the unit, as there will likely not be breakers/fuses, just 2 different sized sets of lugs.

 

[Fnewman]

True. The above "cant combine loads on one circuit" was meaning to the unit, as there will likely not be breakers/fuses, just 2 different sized sets of lugs.

Sure-wasn't intending to disagree with you - just offering another way to get it done!

 

[JFletcher]

Sure-wasn't intending to disagree with you - just offering another way to get it done!

It's all good. and you're correct, you could run a feeder to a subpanel near/next to the unit.

 

[mgookin]

At a minimum you need disconnects at the equipment plus you also need a workmen's receptacle.
And if you want to do a nice job some lighting in the area would be nice but I don't think that's required.

 

[kwired]

Haven't seen the Modine units before, but all the geothermal units I have seen are pretty similar. The aux heat is an add - on component that is field installed. It always has had breakers included with it, around here they are usually 15 or 20 kw and do need two aux heat circuits, but the "heat pump" itself requires an additional circuit and has no integral circuit breaker or other disconnecting means.

The one in my house has three circuits run to it, one for the heat pump, and two aux heat circuits, but the unit is in same room as service panel so the branch circuit devices are within sight of the unit and are the local disconnecting means as well.

 

[bryanbdp]

suitable subpanel

suitable subpanel

The units are ceiling hung and accessible. Is a small subpanel cost effective, or should I just run two feeds?

 

[Fnewman]

The units are ceiling hung and accessible. Is a small subpanel cost effective, or should I just run two feeds?

Unless the distance from the distribution panel is great, two circuits are probably the easiest and lowest cost, especially if the unit has built-in disconnects.

 

[kwired]

The units are ceiling hung and accessible. Is a small subpanel cost effective, or should I just run two feeds?

depends on circumstances.

There used to be a pretty common 19.6 kW, 240 volt single phase air handling unit being installed around this area that could easily be converted from one circuit to two circuit installation.

If you ran one circuit it required a 110 amp circuit breaker which was pretty expensive compared to using two 60 amp circuit breakers that it called for if using two circuits. We had run some off a 100 amp breaker and never had any false tripping, but if it were to be inspected and they caught that the 110 amp was a lot more cost then a 100. We generally just ran two 60 amp circuits to these units for completely new installs.

 

[peter d]

I am working on a wiring plan which includes a number of modine heat pumps with aux heat (EFV036). Heat pumps are spec'd at 208 3ph, 18 FLA, 21A MCA, 30 MOP
Aux 10kW heater is 208 1ph, 34.6 FLA, 34.6 MCA, 45 MOP.

I haven't seen these units yet, and the information I have found isn't real helpful. Do these units typically have two breakers built into the control box, and you run one branch circuit? Or do you have to run two branch circuits normally? Is there an option to add a small 2 breaker box on the unit, and a single branch circuit? If you can combine the loads, how do you calculate the branch MCA and MOP?
:?
Thanks,
Bryan

This is not directly related, but who designed this? Heat pumps with electric heat in Connecticut? I hope the building owners realize they will be paying massive electric bills with this system. I'm sure you're just wiring it, but sounds like it was not designed by someone familiar with our climate and cost of electricity.

 

[iwire]

This is not directly related, but who designed this? Heat pumps with electric heat in Connecticut?

It sounds like exactly what a developer would do.

Low install cost and no concern with the running cost.

 

[kwired]

This is not directly related, but who designed this? Heat pumps with electric heat in Connecticut? I hope the building owners realize they will be paying massive electric bills with this system. I'm sure you're just wiring it, but sounds like it was not designed by someone familiar with our climate and cost of electricity.

From what he attached as the spec sheet indicates it is a geothermal unit. Back up heat should rarely be necessary, and probably mostly only runs if the heat pump has failed, of course that may not be discovered until the higher then usual electric bill shows up.

 

[peter d]

It sounds like exactly what a developer would do.

Low install cost and no concern with the running cost.

Yes, like cheaply built rental property.

 

[peter d]

From what he attached as the spec sheet indicates it is a geothermal unit. Back up heat should rarely be necessary, and probably mostly only runs if the heat pump has failed, of course that may not be discovered until the higher then usual electric bill shows up.

Even so, that still requires a large motor load to operate the system. Electricity in this region hovers around the .20-.22 / kwHr range. The bottom line is that we steer clear from electricity powered heating in any form in this region. With cooling we have no choice obviously.

 

[bryanbdp]

Cost of heating

Cost of heating

Yeah, by choice I'd never use electric heat. But, the building has an offsite boiler/chiller, and heat source water pipes for HVAC needs in the building.
I'd love to put in a number of split systems, and gas heat, but it is a historic building, and I really can't make changes to the outside, like multiple flues and the like.
It will cost me like 70 cents per sf per year JUST to tap into the system, PLUS whatever electricity for the heat pumps and aux heat. Water is supposed to be between 60 and 90 degrees, although even in the summer the pipes seem to be near room temperature.

We're building out 17,000 sf of space for our Makerspace on the first ground level floor. Ceiling abuts conditioned space above, slab on grade should be around 55 degrees all year long. Walls are two foot thick brick and masonry. Windows are new double pane. Building was steam powered at one time, so it is about 60 feet deep and 500 feet long.
Fresh air exchange is a challenge, due to limited areas louvers can be installed. I am hoping our energy usage won't be insane...

I'd like to be able to calculate the energy usage based on the average yearly heating and cooling loads. I would think the heat pump energy usage would be proportional to the amount of heat produced or removed. Anyone have a method to calculate energy usage like this?

Thanks
Bryan

 

[kwired]

Even so, that still requires a large motor load to operate the system. Electricity in this region hovers around the .20-.22 / kwHr range. The bottom line is that we steer clear from electricity powered heating in any form in this region. With cooling we have no choice obviously.

May not be as attractive now, but when oil and gas prices were higher that heat pump may have cost less to operate then oil or gas sources.

It is not using it's input energy to create heat, it is using it to move heat from within the earth. These things also do not necessarily draw anywhere close to nameplate amps when in heating mode. My 3 ton unit only pulls about 6 amps when in heating mode, nameplate amps is probably close to 20.