Modular Furniture Demand (Heaters)

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GaTech04

Member
I'm working on a remodeled office building that will have 20 modular furniture units (cubicles). The engineered drawings put 1 or 2 units per circuit with a demand of 6.8 kVA total (all 20 units).

The owner is concerned, as pretty much every cubicle currently has a 1500W space heater that the employees like to use in the winter months. Im going to a meeting tomorrow to discuss options. I think putting each cubicle on its own dedicated circuit would solve the end-user portion of the problem - if the employee trips a breaker, they would only affect themselves, and if the problem is chronic perhaps they would by a smaller heater/not set it on max. However, Im not sure on sizing the panel.

The plans currently have a 45 kVA transformer feeding a 150A 3 phase 120/208V panel with a demand of 31.5 kVA. If I give each piece of furniture a new demand of 1800 (1500+300 for the computer) - that pretty much doubles the total to 60.7 kVa. However, it seems absurd to me to size this on a worst case scenario.

I have already quoted increasing the transformer to 75kVa and the 120/208V panel, but I was wondering if an increase would really be necessary.

Thanks for any advice.
 

rr

Member
Location
Georgia
I'm working on a remodeled office building that will have 20 modular furniture units (cubicles). The engineered drawings put 1 or 2 units per circuit with a demand of 6.8 kVA total (all 20 units).

The owner is concerned, as pretty much every cubicle currently has a 1500W space heater that the employees like to use in the winter months. Im going to a meeting tomorrow to discuss options. I think putting each cubicle on its own dedicated circuit would solve the end-user portion of the problem - if the employee trips a breaker, they would only affect themselves, and if the problem is chronic perhaps they would by a smaller heater/not set it on max. However, Im not sure on sizing the panel.

The plans currently have a 45 kVA transformer feeding a 150A 3 phase 120/208V panel with a demand of 31.5 kVA. If I give each piece of furniture a new demand of 1800 (1500+300 for the computer) - that pretty much doubles the total to 60.7 kVa. However, it seems absurd to me to size this on a worst case scenario.

I have already quoted increasing the transformer to 75kVa and the 120/208V panel, but I was wondering if an increase would really be necessary.

Thanks for any advice.

Ugggh. I hate dealing with modular furniture calculations. So many different variables.

Could you get an idea from the owner on how many people actually use a space heater in the winter? A quick employee survey might help you. With that being said, a branch circuit per cubicle would solve the problem, but might be overkill.
 

GaTech04

Member
Yeah I called the GC today - the furniture is actually being relocated (with employees!) from one building to another, and he said he looked at every piece of furniture and every one had a 1500W heater.

The furniture is currently engineered for 12 circuits total once it's all relocated (Im not sure how many circuits they are on in the building they are currently in), and the panel only has 8 spares/spaces - so it would completely fill up the 120/208 panel. I priced options to increase the transformer to 75 kVA, increase the 150A panel to 225A MCB and to add a second section.

As much as I'd appreciate the change order, I really dont want to upsell anything. But I really dont want to have the whole panel trip come December heh.
 

wireguru

Senior Member
UGH! I hate cubicles with employees who think theyre entitled to use heaters. I have seen more than one melted power strip from these. I would have a chat with the owner about the electricity cost from running these, the potential liability, etc, etc.

And the energy use....theyre trying to take away my light bulbs and make me unplug my cell phone charger when im not charging my phone -but its ok for someone to have 1500w of electric heat under their desk. :mad:
 

ptrip

Senior Member
Yeah I called the GC today - the furniture is actually being relocated (with employees!) from one building to another, and he said he looked at every piece of furniture and every one had a 1500W heater.

The furniture is currently engineered for 12 circuits total once it's all relocated (Im not sure how many circuits they are on in the building they are currently in), and the panel only has 8 spares/spaces - so it would completely fill up the 120/208 panel. I priced options to increase the transformer to 75 kVA, increase the 150A panel to 225A MCB and to add a second section.

As much as I'd appreciate the change order, I really dont want to upsell anything. But I really dont want to have the whole panel trip come December heh.

Personally, I wouldn't worry about it. They're moving from one building to another ... one HVAC system to another ... one set of insulated walls to a different set of insulated walls. Who's to say that the employees will have heaters any more? They may all have to switch to fans! :roll:

I've done these cube designs before and would typically put two "desks" per circuit. On one job the owner actually wanted two circuits per desk because of how many "things" were plugged in! I told him he didn't have enough money for that many circuits (state agency) and that he just had to have a formal conversation with the employees if it became an issue!

BTW ... it's not been an issue.

Good luck!
 

MNWildcat

Member
Location
MN
Yikes

Yikes

Our office does not officially allow the heaters. They are ineficient and mess with the HVAC system as it tries to ballance the actual loads. One cube per circuit is overkill. I have never designed an office like that. Two per circuit seams plenty.
I agree with the rest, discuss with the onwer. If they have a mech maint guy, I am sure he would chime in as well.
Though if they are really going to allow that amout of load, one per circuit is right. Plus with the multiwire circuit, it will requrie handle ties or multi pole CBs.
 

techntrek

Member
Location
MD
UGH! I hate cubicles with employees who think theyre entitled to use heaters.

Has nothing to do with entitlement, obviously the building enclosure and/or the HVAC system isn't doing its job. I once worked in an office space where half of my floor was underground and the other half had single-pane windows almost from floor to ceiling. The thermostat was in the middle, set to 72F in the winter. The people that sat around it were comfortable. The people in the back with no windows and 50F earth on the other side of the walls were roasting near 80F and always needed fans, those of us by the windows with 20F air outside were always freezing with temps around 64F. We wore sweaters, sometimes coats and yes... we often needed space heaters.

Once we moved to a remodeled building with a high-efficiency enclosure (including double-pane windows), almost nobody needed their heater anymore. Depending on the new building conditions, the OP may find the employees no longer need their heaters.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
The owner is concerned, as pretty much every cubicle currently has a 1500W space heater that the employees like to use in the winter months. Im going to a meeting tomorrow to discuss options.
My suggestion: tell the customer he's better off setting the thermostat high enough to eliminate the need for the heaters.

He's paying for the power anyway, but that way, he wouldn't have to put money into the partition wiring.

Sorry if that bites you in the wallet, though.
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
This was brought up at a recent energy efficency seminar.

In one study that surveyed several office buildings, the largest electric loads were space heaters. Larger than lighting, larger than computers, copiers, etc.

But the presenter also made a good point: you can't just blame the employees. Many offices that expect men to wear wool suits also expect women to wear skirts and hose. And the thermostat isn't usually set with the women in mind.

The Pentagon was used as one example where the thermostat is set really low for the men in dress uniforms, and the women are just expected to tough it out.
 

GaTech04

Member
Thank you for all the input everyone. I'll update you after the meeting tomorrow.

I think it will turn out that the managers/employees/maintainence guys are going to want a lot of change orders (like all these dedicated circuits, and the IT guy is mentioning IG receptacles everywhere....heh), but when it comes down to what the owner is willing to pay for things will be deemed extravagent as many of them are. I think the design of the remodeled and expanded facility was done well, and for the most part we will end up building to plans.

Either way, this should be a good project for us and we aren't reliant on CO's to post a profit. If we can make some changes that truly confer some benefits to the client, that would be great, but I dont want to enable some of the "wants" that crop up just to make a buck.
 

GaTech04

Member
This was brought up at a recent energy efficency seminar.

In one study that surveyed several office buildings, the largest electric loads were space heaters. Larger than lighting, larger than computers, copiers, etc.

But the presenter also made a good point: you can't just blame the employees. Many offices that expect men to wear wool suits also expect women to wear skirts and hose. And the thermostat isn't usually set with the women in mind.

The Pentagon was used as one example where the thermostat is set really low for the men in dress uniforms, and the women are just expected to tough it out.

Point well made.

I do believe the GC said 95% (19 of the 20) cubicle workers were saleswomen. Im not sure wool socks+skirts would make a great impression on people coming to buy a $100k+ car!

The room temperatures are probably set to make the clients comfortable while the saleswomen get to freeze.
 

techntrek

Member
Location
MD
My suggestion: tell the customer he's better off setting the thermostat high enough to eliminate the need for the heaters.

He's paying for the power anyway, but that way, he wouldn't have to put money into the partition wiring.

Not to mention that it will be far more efficient to generate the heat in bulk in the HVAC system, so he would be paying for far less power overall that way. Especially if the HVAC is gas-based or heat-pump-based. Resistive heating is always the most expensive option with a 1:1 efficiency ratio.
 

GaTech04

Member
Well we looked at several things on Friday, and Im giving him pricing to show the owner in a meeting tomorrow.

Adding 8 circuits to have each piece of modular furniture on a dedicated circuit isnt too large of an adder, but it uses up all the spares in the panel so it will probably lead to adding a two section panel. This makes things a bit pricier, but I have a feeling they will opt for the upgrade.


They also wanted to add some offices in another building and I have a small dilemma there. Every 120/208 panel in the electrical room is completely full, and there is no more room to add another transformer/panel (480y service). They only panel with spares/spaces is a 240 Delta 3 phase panel. They are wanting to add a couple offices with about 3 120V branch circuits and then 2 split systems for heating and air. I know I could get the 120V out of the 240 Delta panel (just avoiding the high leg) for the convenience outlets, but is there an option for feeding the split systems? We were given the options from the HVAC guy of 208 single phase or three phase - I'll ask him if he can get 240 3 phase.

I would prefer to run a new 480D circuit to feed a 480D - 208Y 75kVA transformer on the mezzanine (where the offices will be) and set a new panel so we have room for more growth in the building, but I want to make sure I give them all the options and let them decide. I have a feeling they would go for a new panel since they have had problems in the past adding on to the area.
 

GaTech04

Member
Update:

Things turned out well!

They just approved a C/O to:

*add 8 circuits for the modular furniture (so each has its on dedicated circuit)
*increase the transformer/panel (plus make it a 2 section panel)

*add a new 480/277 panel + reuse 45kva transformer from above work + add 208/120 panel for the mezzanine in the service building
 
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