I am new to this forum and from what I have seen you have a great community - a credit to all!

I have a few questions regarding baseboard heat in a retail space (open floorplan 2400 sq ft)

We are looking at changing from oil fired hot air to baseboard electric. It is a very well insulated space and completely open with 9 ft ceilings.

From what I can understand we would need about 22000 watts of energy to heat this space - does this sound correct?

What would be the max baseboard heater wattage allowed on a 20A/240V line.

What would be the max breaker size and load for baseboard heaters daisy chained together? I assume there is a limit to the number of heaters that can be daisy chained together by code?

Can I use one thermostat to control the heat in this space?

Thanks for any insight you can give.

John

I will ramble on here in no particular order:

Looks like your using 9 watts per square foot, which is typically used for residential with 6 inch insulated exterior walls and 8 foot ceilings, and average heat loss surfaces, i.e. windows. I am not sure of this, my gut tells me 10 or 11 watts per sq ft is needed, due to high ceiling, what is ceiling and exterior walls insualtion, large front windows?

22KW of heat at 240 volts will draw 92 amps, with a service rating of 115 amps alone. Be sure the electric service can handle this load. Most likely not, and a new larger electric service is called for.

I cannot imagine using baseboard heat in a retail space. 2400 sq ft works out to a 30 foot wide by 80 foot long space. 22 KW of heat would need 11 - 8 foot baseboard units at 2000 watts each.

A 20 amp 240 volt circuit for heat must be derated 80%, so one circuit can handle 3840 watts. Simple method will be to use 30 amp circuits, #10 wire, that would feed 2- 2000 watt units.

Sure, all the heat can be controlled by one stat, by having the stat control contactors that would control the heat circuits. One issuse with this is demand billing from the utility, having 22 KW of load slam on and off all at once. Better to zone out with multiple stats.

Baseboard heat is purely passive, creating convection currents by heating the air. This means the heat cannot be covered at all, one for safety reasons, two, to allow proper heating.

Since the existing system is hot air, would mean duct work is all in place already. Would it be more practical to replace the oil fired unti with an electric furnace?

Does any of this make sense to you? Are you sure you want baseboard heat?

Thanks for your input - I have made some notes below

Quote:

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Originally Posted by tkrussell

I will ramble on here in no particular order:

Looks like your using 9 watts per square foot, which is typicaly used for residential with 6 inch insulated exterior walls and 8 foot ceilings, and average heat loss surfaces, ie windows. I am not sure of this, my gut tells me 10 or 11 watts per sq ft is needed, due to high ceiling, what is ceiling and exterior walls insualtion, large front windows?

Space is 40 x 60 with 3 windows each 4ft by 4 ft. 2 x6 walls insulated/vapour barrier etc with R-31 in the ceiling.


22KW of heat at 240 volts will draw 92 amps, with a service rating of 115 amps alone. Be sure the electic service can handle this load. Most likely not, and a new larger electric service is called for.

The service is 200 Amp Federal Pioneer and major load on the service (excluding heat) is a 20 Gal HW boiler and 4 rows of 2 X 8 ft flourescent lights (each row 32 ft long) and 6 exterior sodium lights.

I cannot imagine using baseboard heat in a retail space. 2400 sq ft works out to a 30 foot wide by 80 foot long space. 22 KW of heat would need 11 - 8 foot baseboard units at 2000 watts each.

By retail I mean a hardware store

A 20 amp 240 volt circuit for heat must be derated 80%, so one circuit can handle 3840 watts. Simple method will be to use 30 amp circuits, #10 wire, that would feed 2- 2000 watt units.

Sure, all the heat can be controlled by one stat, by having the stat control contactors that would control the heat circuits. One issuse with this is demand billing from the utility, having 22 KW of load slam on and off all at once. Better to zone out with multiple stats.

Baseboard heat is purely passive, creating convection currents by heating the air. This means the heat cannot be covered at all, one for safety reasons, two, to allow proper heating.

Since the existing system is hot air, would mean duct work is all in place already. Would it be more practical to replace the oil fired unti with an electric furnace?


I was going to use a Air source heat pump (5 Ton) with an Air Handler c/w backup heating coils but the air handler uses 2 x 60 AMP breakers itself and the heat pump ues a 60 AMP breaker itself.

Wouldn't an electric furnace have the same load as baseboard heaters? The old oil furnace was around 80000 BTU's if I remember correctly.

Does any of this make sense to you? Are you sure you want baseboard heat?

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I don't really want baseboard but don't want to upgrade the main service if I don't have to either!!

It seems like you found the proverbial rock and hard place. Is air conditioning a part of this equation? With a heat pump it's taken care of. You might consider sticking with an oil fired furnace. Can you really give up 88 linear feet of wall space for baseboard heat in a retail setting. Any upgrades involving anything other than another oil furnace will probably force you to upgrade your electric service. I spent many years in a retail hardware environment. You need outlets for displays, exuipment, cash registers, computers... etc. Eventually you will need the larger service... trust me... and you haven't got enough light as it is... customers buy more when they can see what you are selling.

Quote:

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Originally Posted by Missouri Bound

It seems like you found the proverbial rock and hard place. Is air conditioning a part of this equation? With a heat pump it's taken care of. You might consider sticking with an oil fired furnace. Can you really give up 88 linear feet of wall space for baseboard heat in a retail setting. Any upgrades involving anything other than another oil furnace will probably force you to upgrade your electric service. I spent many years in a retail hardware environment. You need outlets for displays, exuipment, cash registers, computers....etc. Eventually you will need the larger service.....trust me....and you haven't got enough light as it is....customers buy more when they can see what you are selling.

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Rock and a hard place is right on the money!!

A/C is not important but oil ( I am in Eastern Canada) has been between $3.50 and $4.50 per gallon and the future for oil does not look bright!!!

One of the other options I am looking at is Electric Infra Red Radiant ceiling heat
(see http://www.brantradiant.com/brant.html)

Those breakers on the air handler are mainly for the backup electric heat. If you don't use the electric backup, you won't need all that current. Heat pumps are still more efficient than electric resistance heat until the outdoor temp gets below some number in the teens. In mild weather, they really shine.

What I would do is get the installer to set up the system so that if your electric heat is called, it cuts off the outdoor unit. This would at least allow you to limit your maximum demand to the electric backup requirements. Better yet, stage your electric backup so that the compressor and second stage (electric) don't exceed your electrical capacity. Then shut down the compressor when the third stage is called (heat pump can't keep up).

Stay away from electric resistance heat for the primary source of heat if you can. Heat pumps are more efficient and you get summer cooling to boot.

Just caught your last post. Ceiling radiant will save you the baseboard space and clearances, but a kW of electric heat is still a kW of electric heat. Radiant and convection will use the same amount of electricity for the same BTU heat output.

First, To size your heat correctly, a heat loss calculation is needed, to arrive at the amount of BTU's needed, and convert to wattage of electric heat. I am not convinced that 22 KW of electric heat is enough. Arriving at the total load of electric heat is important to sizing the electric service.

Here are a few:
Heat Loss Calculation Page

Room Heating Calculator - Chromalox Precision Heat and Control

Heat Selection Guide

The more accurate input about size, square footage, and R values of existing surfaces, along with desired interior temp, and typical coldest day, will help arrive at the minimum amount of heat needed.

My point of the electric furnace was to take advantage of any existing duct work. It will be easier to connect power to one furnace, rather than multiple unit heaters. One stat can control the furnace, and it will have a method of staging the heat for demand, rather than having all the heat come on at the same time.

One important factor with electric heat is it is very dry. Adding moisture to the interior air is very important with any heating system, esp electric heat. This is easily done using one heat unit by adding a humidifier to the ducted system.

If a furnace is not the answer, then multiple hanging fan forced unit heaters
will be better than baseboard heaters. Missouri Bound reinforces the point of baseboard heat, as I am sure you need the wall space for product display. EPMiller mentions a good alternative to baseboard with the radiant ceiling panels

If you use four 5000 watt unit heaters, each can have it's own stat, taking care of zoning and keeping the total load from coming on all at once.


While heat pumps are efficient, before investing in one, you must consult with a local heating expert to be sure what size is needed, and what size auxiliary heat is needed.

A heat pump may have nearly as much auxiliary electric heat built in as with a standard electric heat installation. This load is needed again to size your electric service.

Sizing your service must be per Canadian Electric Code. I do not know CEC, only NEC used here in USA, I suspect it will be similar.

Sizing the service is a bit complex, each type of load must be included, along with derating factors. I will list them best I can to give you a flavor, with some assumptions of actual loads, but explanation and accurate calculations must be done by someone qualified in your local area.

Noncontinuous loads- Each duplex outlet at 180 watts, I assume 20, totaling 3600 watts. Can derate this type of load over 10 K watts by 50%, does not apply here.

Outlets........................................... ...........................3600 watts
Interior Lighting 16- 8 Ft @ 190 watts each 3040 x 1.25=...3750
Exterior lights 6 150 W HPS 175 Watts each total..............1050
Water heater............................................ ..................4500
Signage........................................... ..........................1200
Show window(may not apply here,check local code)..........2400
Electric heat.............................................. ............. 22,000
Total calculated connected load..................................38,500 watts


38,500 watts / 240 volts = 160.42 amps

A 200 amp commercial service cannot be loaded more than 80%, the total max load allowed is 160 amps.

So you can see that with my assumptions of loads, and I am sure I missed something, this service calculation is right on the edge.

My suggestion to you is to get expert help from a local heating contractor to size the amount and type of heat best for you situation, and an electrical contractor to size the service.

Thanks everyone for your input!

I think the radiant ceiling heat is definitely a better alternative to baseboard but fan forced is certainly an option too! I am going to try and do a cost estimate of each.

I have another couple of questions if you don't mind?

I already have the heat pump and air handler for another site and was thinking of testing the capability of the air handling unit to heat the space without the heat pump - basically it is an electric furnace in it's own right.

The airhandler (Trane) for the secondary heat in the Air Handler has 2 x 60 AMP breakers built in. It is a 2 circuit single phase unit with a capacity of 15.36 KW(52400 BTU).
Heater AMPS per circuit are circuit 1 - 40 AMPS Circuit 2 -24 AMPs.

If I was to have this hooked up to the service (which is 40 ft away) what size wire would be required for each 60 Amp breaker and what size breaker would be needed in the main service? Is 25% over the rated air handler breaker correct?

Instead of running 2 wires from the main panel (1 to each breaker) could I use a 3 AWG
wire from the main service to a subpanel and then supply the airhandler from the subpanel?


Thanks again for your immense knowledge!!

John

Yes, one feeder can supply a electric furnace or heat pump.

The two 60 amp breakers builtin are to comply with 2008 NEC Section 424.22 (A), no unit shall have overcurrent protection for resistance heat elements larger than 60 amps.


While the max heat load is 15.36 KW, this is not the total load of the unit. You say it is an air handler, so that means there is a fan motor, along with control, and possibly other accessories or other load.

You need to find the nameplate that lists these other loads, or lists the total load, and increase by 25%, to arrive at the min size feeder.

I would run two smaller lines, one to each circuit breaker, which can be #6 copper NM-B cable, and be done with it.

Remember, I am using the NEC applicable to the USA, and not CEC, which you must refer to. Some of the info I have given may not be applicable in Canada.

Thanks TK

I was thinking 2 lines would be the best also. Our code is very similar to the US code.

I appreciate your in depth answers!!

John