Am I crazy or have some of you guys had to deal with this too?

[IrishRugger]

Custoomer is flipping a 2500 sq ft house, wants existing 200 A Wadsworth panel changed out to new panel. Tells me he is considering adding electric heat furnace 15 KW and maybe a heat pump but is not sure.

Using standard method from Mike Holt calculation freebee web site I do a load calc for these three senarios. 15KW electic heat furnace w/ 3 ton Cental Air
15KW electric heat furnace w/ 3 ton Heat Pump
Propane furncae w/ 3 ton heat pump.

I gave him all three load calculations and advised him if he wants to have the 15 KW electric furnace with AC or Heat pump he should add a second 200Amp panel and up grade existing service to 400 Amp to handle the heat load, or if he doesn't want to upgrade the service to use the propane/ heat pump option.

He said that his heating guy says that the one existing 200 amp service can handle the load.

My question is how often do you guys hear this from people and do you find it just as frustrating as I find it ?

I know the load demand for each calculations, I know that it is not prudent to put 100% of a 200Amp load or more on a 200 Amp service.

Why don't people realize this?

 

[IrishRugger]

P.S thanks for letting me vent

 

[augie47]

Without knowing the particulars, but using Mikes residential load calculator and the OPTIONAL method, I show that it is possible that a 200 amp panel will meet the minimum requirement.
I agree that I would not suggest a 200 only, but in inspecting, I am often surprised at how lenient the optional method is.
If it meets NEC and he has the $$, you might as well install what he wants or someone will for sure.

 

[ptonsparky]

Code calcs for homes SE are more than adequate. A 225 might be an easier sell. Big $$ jump to 400.

 

[GUNNING]

SECTION 220.83B

SECTION 220.83B

I hate flippers.

Locally our city inspectors make us do load calculations when a change out of an HVAC system is installed permitted and inspected. The city utility has a rebate and the city inspector makes sure all is up to snuff. It is a pain but after the first few is easy to do. Do a load calculation on the existing equipment and square footage and have the owner and inspector sign off on what is existing with your new service. WRITE the owner a note saying this is what is calculated for the given loads and anything extra will require a change order. Get your money up front.
I like using 220.83B. Its a load calculation for just adding a new a/c, quick and simple
Flippers look at the bottom line and the less they put in the more MONEY they make. The good news is the new a/c stuff is a lot more efficient which translates into smaller wire and $. Its very possible if a suitable sized a/c unit is installed (in tons) the service will be big enough. If the flipper is cramming you down he is also cramming down the a/c guy. I've seen where the a/c guy will put in minimum sized heat strips just to get the job and then come fall its a return trip and an extra. I have also seen where the same sized HVAC unit takes half the amperage.
Don't forget to add an outlet outside if none exists within 25 feet of the new condenser.
Remember the customer is always right. Educate and communicate, then cash the check before doing the work.
I would revisit my math on that original load calculation.
200 amps is a BIG electric house. Check out the examples given.

 

[renosteinke]

"HVAC guy says...." SO what? You're being paid for your professional opinion, not his employee. What you can 'get away with' and what is right are two different things.

Don't get me wrong; I have the greatest respect for the HVAC guys. Yet. I wonder if they didn't take so many short-cuts if they woul not be quite so busy in the summer. I mean, I offered three guys a NEW install at the beginning of June, and I'm still waiting for quotes. Must be nice to be that busy.

"200 is huge ..." Not really. An all-electric double-wide is often a 200-amp service. I do think the OP might want to be a bit more accepting of the concept of 'load diversity,' but the simple fact is that his load calc is what determines the meter base size. Maybe he does need 225 amps.

Flippers? I haven't heard that term for awhile. Personally, I have ZERO sympathy for those wanna-be slumlords. Perhaps my opinion is colored by the $6000 house I bought. I've had several 'flippers' and small-time 'landlords' advise me on how I need only throw on some paint, etc., and all will be ready for renting. They object to my complete-gut remodel. Yet, the moment I say I plan to live there myself, the opinion suddenly becomes 'don't buy this one.' IMO, if it's not good enough for me, it's not suitable to rent; but I wander.

So, I tell the OP: make your best call, and stand by it. Just tell the guy you'll give him what he needs, and your price. Your price is (say) $5000. For a 225-a service, $5000. For a 200-A service, $5000. For a 30-A service, $5000. For whatever he wants, $5000. If he can't decide on his heating methods, price for electric. If he can't tell you what he wants, tell him to call again when he can.

 

[iwire]

If it meets the NEC and it is what the client wants just do it, pocket the money and don't loose any sleep at all.

The power company assumes the actual load to be about 40% to 50% of the NEC calculations, they are overblown.

 

[iwire]

I know the load demand for each calculations, I know that it is not prudent to put 100% of a 200Amp load or more on a 200 Amp service.

Why don't people realize this?

Actually if you do the calculations as the NEC requires you have already accounted for continuous loads etc.

So if you had 160 amps of noncontinuous loads and 40 amps of continuous loads (with the 125% already factored in) that would be a total of 200 and a 200 amp service would be more than enough (and perfectly code compliant)

 

[readydave8]

"200 is huge ..." Not really. An all-electric double-wide is often a 200-amp service.

Mobile home services are often oversized, it may cost manufactorer the same for 150 as for 200 (panel price only--he doesn't have to pull wire to it). Many mobile homes had electric furnace instead of heat pump and I believe bigger heat strips than normal for heat pump? I've seem 'em with gas heat and still same 200 amp panel.

 

[hurk27]

Mobile home services are often oversized, it may cost manufacturer the same for 150 as for 200 (panel price only--he doesn't have to pull wire to it). Many mobile homes had electric furnace instead of heat pump and I believe bigger heat strips than normal for heat pump? I've seem 'em with gas heat and still same 200 amp panel.

Once in a great while we will get a park that buys a MH at a auction for "such a deal" only to find it is all electric and has an electric heat furnace, these have two 10.8kw heat strips in them and have two 60 amp two pole breakers in the 200 amp panel, then I get to tell them I can't hook it up to their 100 amp service, and most could not afford the electric bill here anyway using electric heat, so their "such a deal" turns into a new gas furnace, and new gas lines run to all new gas appliances.

But back to the OP, 15kw seems small to me, but either way, if you calculate the 15 KW with air you pick the largest of the two loads as both will never run at the same time, but with the heat pump you have to calculate them together as the electric strips will kick on if the heat pump can't keep up, not knowing all the loads, it sounds like Bob is right, a 200 should be fine.

Here is one bit of advice I give customers: even if they don't have a high costing electric rate such as one POCO south of here is not to bad, I tell them when making this choice of what type of heat they want remember this, if they ever want to do a generator back up for power failures the cost of larger generators can get real high after a 20kw and thats only 83.3 amps of generator power, so choose wisely now or you might paint yourself into a corner later.

 

[growler]

He said that his heating guy says that the one existing 200 amp service can handle the load.

The heating guy may be right but it's just his opinion until someone does a proper load calculation.


For a 2500 sq ft house I'm not sure a 3 ton unit is big enough. Did anyone do a calculation to see how much heating an cooling would be needed? Most 2500 sq ft homes have 2 units, one for up-stairs and one for the main level with a total of around 5 tons of cooling ( but that's here in the South where it's hotter ).

When I deal with HVAC people all I want is the total for the electric heat and that's hard to get out of them.

A 200 amp panel is probably big enough but what else is there. Water heater, washer & dryer, hot tub, pool heater, jetted tub heaters, range and ovens. What's the finished property going to be?

 

[Sparky555]

Just curious if you were paid a dime for doing three load calculations for a flipper?

 

[IrishRugger]

The heating guy may be right but it's just his opinion until someone does a proper load calculation.


For a 2500 sq ft house I'm not sure a 3 ton unit is big enough. Did anyone do a calculation to see how much heating an cooling would be needed? Most 2500 sq ft homes have 2 units, one for up-stairs and one for the main level with a total of around 5 tons of cooling ( but that's here in the South where it's hotter ).

When I deal with HVAC people all I want is the total for the electric heat and that's hard to get out of them.

A 200 amp panel is probably big enough but what else is there. Water heater, washer & dryer, hot tub, pool heater, jetted tub heaters, range and ovens. What's the finished property going to be?

I am uncertain if the HVAC guy calculated to see if a 3 ton HP and 15KW heat will be enough.

The dwelling does have electric WH, one Electric Range, Electric Dryer, dishwasher, Microwave, garbage disposal, washer, no pool, I wasn't told if there is a jacuzzi in the bath so I did'nt include that.

We live in an area where it can be below zero at night and sometimes during the day in the middle of the winter for up to a week or two. In the middle of summer and it can get over 100 for the same amount of time. Also it has been the case that down the road the home owner decides to purchase an outdoor spa that can require 50A overcurrent protection.

I have gone on calls where a 20KW electric furnace w/ a HP is on just a 200Amp service and the main has not been able to hold after a few years of the new HVAC being installed.

I just feel that a second 200 amp panel for just heat alone is a prudent choice based on load calcs and my experience with 200 mains not holding after some time has passed.

In a new dwelling with a Heat pump and a backup electric I will figure for a 400 Amp service.

Thanks for all of you post guys!

 

[renosteinke]

While it's not directly related to the OP, I thing that two 'basics' need to be repeated.

The first issue that need attention is: how does iit affect load calculations if the home is a 'trailer?' I want to stress that, if the home is a 'manufacturer' home witha HUD sticker, you need to provide service to match the rating of the main panel. Period. If there's a 200-A panel, you need a 200-A service, no matter your load calculations. I ran into this the hard way ....

The second topic relates to heat pumps. I'll make it real simple: a 'heat pump' is only an air conditioner running backwards. If that A/C will cool a house (say) 30 degrees, it will also only be able to heat the house 30 degrees. If you need more heat, supplimental heating is required. That's what the 'heat strips' are. It's also very possible that a completely separate furnace will be needed. This is one time you can't assume that the "A/C" and the furnace won't run at the same time!

We could get into the topic of flippers, ladnlords, etc .... but simple charity makes me decline that particular discussion. It's probably safe to assume the **** just wants the cheapest band-aid possible, to let him either pass on utility expenses to the tenant or kick the 'can' of inadequate design down the road, to the next buyer. Keep that in mind, and withold enough to prevent him from taking your advice and hiring some day laborer to patch it together.

 

[Strife]

I'll humbly disagree with the "lenient" comment.
I've seen hundreds services that wouldn't even provide HALF of what the code calcs would allow. Yet, they never tripped(blown fuses).
I've also seen several peak reports from POCO where, again, the peak wasn't even at half of what NEC would require.
Last, I have done several projects where our service was 750KVA and POCO had a 150KVA transformer.
In fact I had a job where my service for one warehouse was larger (based on NEC calculations) than the POCO's service for 40+ spaces in that whole complex.

Without knowing the particulars, but using Mikes residential load calculator and the OPTIONAL method, I show that it is possible that a 200 amp panel will meet the minimum requirement.
I agree that I would not suggest a 200 only, but in inspecting, I am often surprised at how lenient the optional method is.
If it meets NEC and he has the $$, you might as well install what he wants or someone will for sure.

 

[hurk27]

The second topic relates to heat pumps. I'll make it real simple: a 'heat pump' is only an air conditioner running backwards. If that A/C will cool a house (say) 30 degrees, it will also only be able to heat the house 30 degrees. If you need more heat, supplemental heating is required. That's what the 'heat strips' are. It's also very possible that a completely separate furnace will be needed. This is one time you can't assume that the "A/C" and the furnace won't run at the same time!

The above in red is not correct, remember an AC unit in cool can always remove more heat then in heat mode, because if the outside temperature gets below a certain point there will not be much heat to remove from the outside that can be expelled inside, this is the whole reason for the backup electric heat.

 

[renosteinke]

Hurk, I'll stand by my comment, but I understand yours. My model is, at best, the 'ideal;' that machine can only move a certain amount of heat.

When you're trying to make the 'cool' side colder, in order to move the heat to the warmer side, well, then the performance of the coolant becomes an issue. This issue is not as clear as it once was, simply because the latest "Freons" are actually blends of several different fluids. If it's cold enough outside, the fluids won't evaporate at all, and thus can't move any heat at all. If anything, this means the machine can 'heat' less than it can 'cool.'

Take my statement and look at it a bit closer. What's the usual winter thermostat setting? At what temperature does the auxilliary heating strips kick in? How many degrees difference is there?

Now, look at the summer use of that unit. What's the thermometer set at? What's the maximum temperature? How many degrees difference? I'll bet that number looks a lot like the first one you calculated.

I really object to the pure pablum put out by various writers about how heat pumps 'capture free heat' from the outside. That simply isn't true. It costs just as much to run the air conditioner in either direction. You can't even say it's a 'greener' way to heat, as the electricity to power the heat pump has to come from somewhere.

 

[bullheimer]

mtc: 1.. hvac guys know NOTHING about electrical requirements, even of the stuff they sell you. believe nothin they say. nothing.

2.. flippers will run the other way as soon as you tell them a service change is only $2400, and they will pass the "savings" on as a discount to the selling price.


3.. a power lineman told me when he hooked up a new 400A service to two homes, that it would be a miracle if the two of them together ever drew over 90 amps.

you my friend, OP, are in a Lose Lose situation.

ps, born and raised in reno, glad to see some form of life still exists there. i'll never move back there, but tha's another story. Love and Kisses, sb

 

[IrishRugger]

Okay this is funny,

just received a call from someone (totally different person) that wants a price on a 100amp to 200 amp service upgrade. Guess what? he's getting a new heat pump and electric backup furnace!

Guess what else, I asked what size HP and backup EH, he said he doesn't know, but the HVAC company said all he will need is a 150 Amp service. and one 80 amp breaker.

Then guess what? I asked if I could call the HVAC co and get the correct loads.

You know what he can't remember their name.

I then explained to him that a load calculation needs to be done to ensure proper sizing of the service. He said he wants to have an all electric house and wants to install an electric tankless WH. Okay now we need to find out the load of the tankless WH to ensure the correct load demand for the house.
I'm going to meet him in an hour to look over the job. Sounds like a nice guy but yet another example of HVAC outfits acting like they know everything.

I'm gonna look over the job, get the loads that I need from the HVAC company and the plumber, do a load calculation, and price a new service that is going to fit that application and not fail ! I'm gonna use the standard method because based on my experience and our enviornment I feel that the standard option best reflects what the true demand load will be.

If I get it then I know it will be done right and both the customer and I will be able to sleep well. Remember the NEC is the minimum requirement. There is nothing wrong with reasonably going beyond the minimum requirements.