multi meter bank question

Status
Not open for further replies.
M

mkgrady

Senior Member
Location
Massachusetts
I don't usually work in the city (Boston) so I'm not up on how to deal with a multi meter situation. A 14 unit apartment building has a 200 amp, 120/240v service. The main feeds 15 meters and breakers that feed student apartments upstairs. The only exception being one of the 15 meters feeds a house panel with a 40 amp main. This panel is clearly overloaded with about 16-1 pole 20's and a 2-pole 30, and needs to be upgraded. I can't tell what all these house circuits feed but the normal load must have been below 40 amps because it never tripped until recently (so I'm told). The reason I'm there is because a heating contractor installed a new oil burner that requires a 30 amp 230 volt circuit for a 3hp burner motor. They reused the existing 2-pole 30 cb in the house panel. Two things are happening. The 40 amp main on the house panel is tripping occasionally (no surprise but I don't know why it wasn't tripping on the old heat system) and the oil burner 3hp motor has failed twice in two weeks. The heating contractor has asked me to upgrade the house panel to 100 amps because he feels the new oil burner motor is failing because of a low voltage condition due to the inadequate house panel feed. I don't know if upgrading the panel to 100 amp will correct the failing motor problem but it seems necesssary regardless. So now finally to my question. Can I connect a 100 amp panel to the existing meter? How do I find out? My first thought was to look inside the meter socket to see if it will accept 100 amp wire. Sorry for such a long post.
 
Re: multi meter bank question

My first thought was to look inside the meter socket to see if it will accept 100 amp wire.
Click to expand...
That would be the place to start, the meter base should be labeled with its rating. :cool: :cool:
 
Re: multi meter bank question

Originally posted by mkgrady:
Can I connect a 100 amp panel to the existing meter?
Click to expand...
Maybe


Originally posted by mkgrady:
How do I find out? My first thought was to look inside the meter socket to see if it will accept 100 amp wire.
Click to expand...
As Jhr has said it should be labeled, although that may be inside as well.

My feeling here is you are about to open a can of worms.

If you can change landlord panel to 100 amps the question becomes are you now overloading the 200 amp service?

I work in and around Boston and I am fairly certain the smallest landlord panel meter position permitted is a 200 by the power companies.

This job may turn out to be never ending.
 
Re: multi meter bank question

I like what Bob has to say ;) I like all the information in your post too. Sounds as if you're most interested in doing what's best for your customer, not in just trying to sell them equipment. From 3000 miles I don't see how you can condemn the subpanel and not question the main service. For all I know, those 16 - 20A breakers are just individual smoke detector circuits. It's possible that the school, insurance carrier or the local jurisdiction has special rules for this type of tenancy and you would be opening pandora's box by altering the design. If you're going to upgrade, you will want to have time for plan checks, etc., and to have downtime during school breaks. What I would do, is change the arcing, worn out 30 and 40 amp breakers (pitting and worn springs are causing the problem, not an inadequate feed) first, to give them back power, and then approach the testing / load calc / capacity concerns.
 
Re: multi meter bank question

There is no labeling on the outside of the meter bank so I'll pull the meter and see if I can connect 100 amp wire. Since the 40 amp main is tripping it seems I have nothing to loose by upgrading the house panel to 100 amps. At that time the 30 amp burner cb will be changed. Somebody, I assume the heating contractor, changed the 40 amp before I got there.

It may be that the 200 amp main service is too small but if the main 200 amp fuses are not blowing (maybe they are)what would be an easy way to determine that? My first thought would be a recording amp meter but I don't have one.
 
Re: multi meter bank question

mkgrady, This may sound stupid but are you sure the house panel was originally protected by a 40 Amp. breaker. You state that someone has already changed it out. What size cable is feeding the house panel. I have seen maintenance types and A/C people use whatever they have handy. I would do what someone suggested and check this hole mess out before changing anything. Did you find any arcing at the breaker or buss, are the connection tight( everywhere including the meter base ). Have they added any loads other than the heating system ( more exterior lighting ). Just one more stupid question, when you say the motor fails are you saying that it shuts off when the breaker trips or is the motor not operating correctly even when the breaker is not tripped.

[ January 27, 2006, 05:08 PM: Message edited by: growler ]
 
Re: multi meter bank question

The wire from the meter to the house panel is #8 cu. I know the 40 amp main tripped more than once and has been replaced with a new 40. I know the motor has failed twice but they haven't told me what that means yet. The last time it failed it caused enough smoke to send the fire dept. The heating contractor called me after that. Thanks for all the input. I will look for loose connections. The building is currently running off the old oil burner that has a smaller motor. I will check voltage at that motor while it is running to see if it is low. The new motor has been running on the same circuit. Once the new burner motor is up and running I will disconnect the old boiler/burner. Any other ideas?
 
Re: multi meter bank question

sounds to me that you have a decent gameplan. assuming that meter is buss fed or fed by an adequate condctor, surely a 16 ckt panel is rated >40 amps, the "quick fix" would be a #3 Cu and a 100 amp breaker while keeping a check on the load to the 200 amp main.
Although, I must say, it would sure be interesting to see a load calculation on this entire set-up.
 
Re: multi meter bank question

---------------------------------------------
"Can I connect a 100 amp panel to the existing meter? How do I find out? My first thought was to look inside the meter socket to see if it will accept 100 amp wire."
---------------------------------------------

What is the rating on the breakers that feed the panels in the student apartments? That may give you a clue as to the rating of the meter stack. Just because the terminals may accept 100 amp wire does not mean it is rated for that. I would look very carefully for some labeling, maybe inside the meter. If you can get a manufacturers number then you should be able to find out the rating.
If you cannot get a 100 amp service from this equipment, you may be able to come out of the tap box before the meter stack ( if there is one). Then you would be actually originating a new service rather than upgrading the existing one. In my area this would require approval from the utility after you submit a load data sheet. I am currently involved in this exact situation. I am building a 200 amp service adjacent to a meter stack with a 125 amp branch circuit rating. I will come out of the tap box, and everything should work out fine.
 
Re: multi meter bank question

growler made the best point so far. Yes their heater worked before. No you have no clue what has happened since then. It looks as if the heating contractor added a larger motor which directly caused all but the first incident. Where did smoke come from, that motor by federal law must have an overload protector. By all means, as a couple people wiser than me have pointed out, digging into this will mean the utility getting involved.

[ January 27, 2006, 09:26 PM: Message edited by: peteo ]
 
Re: multi meter bank question

I plan to call the utility to get a utility authorization number for the city permit.

If the meter socket can not handle the new 100 amp panel I could tap into the trough ahead of all the meters. Thanks for that idea.

The motor had internal thermal protection. I don't know why it smoked enough to set of the fire alarms.

I would expect a load calculation would indicate a need for a building service larger than 200 amps but I don't think the owner would spring for the cost unless they had no choice. Does adding the larger house panel (to accomadate the larger motor)at 100 amps negate the grandfathering of the existing service???

My customer, the heating contractor is already sore about having to upgrade anything upstream of the boiler room. They will be even more unhappy if they have to eat a new building service. The landlord has indicated that they bought a new heat system, not a new electric service, so they expect the contractor to do whater is necessary at their own cost..
 
Re: multi meter bank question

First off let me say that I'm only asking questions. I don't know enough about the problem to make suggestions. I think a new house panel sounds great ( it's probably overloaded ). First question: How much bigger motor? Is the blower belt driven? Did you check drive belt( make sure it's not too tight )? Did you remove the belt and spin the blower manually to make sure it turns freely? Turn motor shaft and make sure the bearings are good ( I know it's new but they manufacture a lot of sub-standard products lately , the parts come from all over the world ). Check motor windings, make sure you don't have a short winding or short to ground. Motors shouldn't smoke like that it's bad for their health. If the Heating contractor didn't want to up-grade any of the electrical systems he should have installed a compatible system ( same size ). It's not the electricians fault when others do stupid things. He should have contracted the heating only and made the landlord responsible for providing correct power source.
 
Re: multi meter bank question

The existing burner motor is a little smaller than the new 3hp but I won't know exact size until I go back on Monday. I'm guessing 1.5 to 2hp. All your questions about the new motor are things I will check on Monday. Although I think upgrading the house panel to 100 is needed (because the 40 amp main trips) I will not be surprised if that does not fix the problem. An ideal situation would be for me to find the reason they have burned up two new motors and upgrade the panel. I dread the thought that I will change the panel and a third motor burns up. I have made it clear to the heating contractor that upgrading the panel might not fix the problem. Because they have experienced burner technicians he hasn't even asked me to look at the motor or other burner components.
 
Re: multi meter bank question

Found the problem. The new burner motor was connected to the old burner circuit. The circuit had a bad splice that allowed enough current to pass through to power the old 2hp motor but it was not good enough to power the 3hp motor. The spliced #10 solid wires were barely making contact inside the charred wire nut. The wire nut fell off when I touched it. The wires were held together more by the melted insulation than anything else. The only bright copper was where it had been melting within the wire nut. I took a picture of the splice but I don't know how to attach it to this message.

I assume the higher current on the new motor caused the bad splice to heat up to the point where it was delivering a reduced voltage to the motor causing the current to rise. I can see where this would overheat the motor but why wouldn't the thermally protected (internal) motor kick out on thermal overload before burning up? This happened to two new motors.
 
Re: multi meter bank question

Thanks for posting the update. Good to think those students are now warm and safe :)
I'm playing devil's advocate here: What it sounded like, is a terrific inductive load for that setup. Forget overheating at that point. There's an arcing fault, which means things do not behave nicely. Breaker contacts welded shut. Motor overheat could care less, it's useless with that going through it anyway. Just an idea, but obviously the breakers/ overload did give those 3HP motors protection. What did start smoking, by the way.

edit; 'did not'. Or 'gave those motors adequate, sufficient, etc protection'. Great typing today :D :D

[ February 02, 2006, 08:45 PM: Message edited by: peteo ]
 
Status
Not open for further replies.
Top