So much for the super beast.

[Smart $]

Spoiler Alert:
Highlight the "A:" line in your browser....

Did that already... :?

 

[GoldDigger]

Just a reference to the stereotype that their troubleshooting skills are limited to board replacement rather than root cause analysis.

Tapatalk!

 

[kwired]

Don't forget that a neutral voltage shift of the same size as the voltage drop in the ungrounded conductor is perfectly normal and not a sign of a high resistance neutral.
It is only if the neutral shift is higher than the drop in the ungrounded conductor for a single sided load or if both are excessive that you need to look at drop or transformer neutral issues rather than just overall sizing issues.
In fact in a circuit where a reduced neutral is allowed, you would expect the neutral voltage shift to be higher than the hot lead drop when an unbalanced test load is applied.

Tapatalk!

I kept reading through all the posts and was thinking about line length and size never being mentioned, sure sounds to me like voltage drop could be an issue, and is something I have encountered before making someone think they had a neutral problem.

 

[mbrooke]

Not certain if it has been mentioned because I did not read all the posts... but I believe a common cause of furnace board failure is power line surge.

The blunt truth is the electronics in a lot of appliances are complete garbage. They fail ALL the time even under none abusive conditions. Ive lived in many different houses, and over the years almost everything with electronics eventually loses a control board at some time. Some things like microwave ovens I have had luck with, but Ive had dishwashers, ovens, water softeners that would eat control boards even under warrantee. Techs have openly admitted electronic burn outs are common for certain brands or models.

Just recently I lost a control board on a direct vent heater still under warentee:roll:

nothing you buy today is the quality of 20 years ago:rant:

 

[mbrooke]

Just a reference to the stereotype that their troubleshooting skills are limited to board replacement rather than root cause analysis.

Tapatalk!

POCO are notorious for reusing severely outdated equipment or building it just to the point it wont burn up in the first 20 years of service. Municipal POCOs are usually different, they listen to their customers with the intent of above average service continuity, but when dealing with a behemoth POCO asking them to fix problems is like trying to ask your pets to clean your house. They just don't want to get it, claiming its ok because there the experts:happyno:

IN the OPs case sounds like hes got a POCO crew willing to listen.

 

[K8MHZ]

The blunt truth is the electronics in a lot of appliances are complete garbage. They fail ALL the time even under none abusive conditions. Ive lived in many different houses, and over the years almost everything with electronics eventually loses a control board at some time. Some things like microwave ovens I have had luck with, but Ive had dishwashers, ovens, water softeners that would eat control boards even under warrantee. Techs have openly admitted electronic burn outs are common for certain brands or models.

Just recently I lost a control board on a direct vent heater still under warentee:roll:

nothing you buy today is the quality of 20 years ago:rant:

The furnace tech said the same thing. So he installed an older, used board and only charged for labor. He said the older style boards were much more robust and he had one from a working tear out.

 

[dfmischler]

The blunt truth is the electronics in a lot of appliances are complete garbage. They fail ALL the time even under none abusive conditions. Ive lived in many different houses, and over the years almost everything with electronics eventually loses a control board at some time. Some things like microwave ovens I have had luck with, but Ive had dishwashers, ovens, water softeners that would eat control boards even under warrantee. Techs have openly admitted electronic burn outs are common for certain brands or models.

Half of all new designs are below average.

Part of the problem is that all manufacturers want to reduce their costs, and so they try to keep up with the chip manufacturers (each new generation is usually cheaper and higher performance than the previous one). Unfortunately, this means that the product cycles are very short and very little of what the engineers can learn is applicable to the next generation. By the time the field people have useful/statistical results to report back to the design engineers the product is no longer being manufactured.

Think about how horrible the safety and reliability of electrical wiring and devices would be if the industry did not update codes and practices regularly based on field experience. When a serious problem is recognized (e.g. residence fires from early use of aluminum wire) the problem is researched and the code and related practices are updated, and this information is widely deployed. That is overall a very good system that is not practiced as much anymore with manufactured goods.

 

[StarCat]

Good Info Thread

Good Info Thread

109 volts doesn't sound that low to me.

2 boards go bad. One cause is that they replaced with a defective board (no quality control) or there really is a problem with the furnace and the guy isn't smart enough to trouble-shoot.

If two guys say there isn't a ground and you know there is one that should tell you something. Sounds like standard BS when they don't know.

Zero, or improper ground usually does not destroy HVAC control boards, but can make them behave erratically.
Typically, if the power is not right the board will just behave strangely.
Some newer generation boards have some real strange and seemingly stupid attributes.
I know of an ice machine board that carries Tech warnings not to power the board up with the water pump disconnected.
That is bad Engineering.

Speaking as a Veteran HVACR Tech, this is correct moving along correct lines that real and correct troubleshooting is NOT happening in this case.
I'd like to know how the HVAC Tech came to start saying this line, exactly how, and how many times, and on what equipment OEM etc.
Sounds like " programming." Who told him this was the case? I'd like to know what OEM Tech support is saying about that series board....service bullitens, known problems....Tech Talk.
If I came back to change a second board, I would be taking the Fan Drive apart with a fine tooth comb and looking for an onboard ground fault, and not just on the 120V or 240V output side, but on the 24v side. Pinched wires, things miswired from the factory....etc.
Some very unusual things can happen with 24V side ground faults that are not enough to directly take out the transformer or transformer secondary fuse.
Something is sounding intermittent here, its creating stress and the board is receiving it.
Boards do get recalled sometimes as well.

I would totally rule out any weirdness on the machine end before pointing blame to the power supply, and even then I'd have some kind of meter readings or logical suspicions to back up my claim. I'd be curious to know if there are any visible burns or blown compoments on the board.
I'd then be asking for an electricians assistance to help me solve the matter as a team and stop blindly changing parts, AND tell the home owner I am not confortable leaving the system enabled until the root cause of the faulure has been found and corrected. I'd let them know that its an unusual case and will require a meeting of highly trained professionals to get through it.

As an attending electrician, I'd pull out my meter when HVAC man was there and read ground at the unit and then ask him to explain why he is " claiming " bad ground when the readings say otherwise and the wiring checks all the way back to the panel.

Lots of good DIAG information on this threaad.

 

[kwired]

Though I agree that things are generally made cheaper then they used to be, when it comes to electronics surges seem to be a big problem with about anything, and a whole house surge arrester does help with the cause. Surges can happen from normal operations of POCO switching operations.

 

[growler]

He pulls the meter and puts this cheesy thing called a 'Super Beast' on the tabs, turns it on and by looking at two crude analog meters.

Why would anyone use such a crude instrument for troubleshooting professionally? It looked like it was made from drain pipe and Radio Shack parts.

There is really nothing wrong with an analog meter for residential trouble-shooting.

A digital meter may impress the customers but an analog will give an accurate reading. They probably used pretty high quality meters for the beast.

 

[K8MHZ]

There is really nothing wrong with an analog meter for residential trouble-shooting.

A digital meter may impress the customers but an analog will give an accurate reading. They probably used pretty high quality meters for the beast.

My problem was the 0-150 range with 5 volt increments. The increments were about a millimeter apart. A variation of 4 volts would have been almost undetectable. The needle is about a volt wide. Also, moving it around made the needles move. You could get a 5 volt spike just by bumping it.

They accuracy may be the same, but the precision is not.

 

[GoldDigger]

There is really nothing wrong with an analog meter for residential trouble-shooting.

A digital meter may impress the customers but an analog will give an accurate reading. They probably used pretty high quality meters for the beast.

But the quality of an analog meter (as measured by damage resistance, accuracy and repeatability, for example) does not guarantee that other aspects of the design (such as precision and readability) are in the range needed for examining voltage differences in the several percent range.

 

[growler]

My problem was the 0-150 range with 5 volt increments. The increments were about a millimeter apart. A variation of 4 volts would have been almost undetectable. The needle is about a volt wide. Also, moving it around made the needles move. You could get a 5 volt spike just by bumping it.

They accuracy may be the same, but the precision is not.

But the quality of an analog meter (as measured by damage resistance, accuracy and repeatability, for example) does not guarantee that other aspects of the design (such as precision and readability) are in the range needed for examining voltage differences in the several percent range.

If you guys will take a look at the "new" super beast in the link provided by Mivey you will see they are still useing tha 0-150 volt analog meters.

The basic product has been around for 30 years and in that time digital meters would have been cheaper to buy so why did the engineers decide to use analog?

The product has been used by power companies all over the nation with good results. As they say the proof is in the pudding.

 

[meternerd]

Interesting discussion....right down my alley. As a former (now retired) meter/relay tech for the local POCO, I did this kind of diagnosis all the time. The newer Mega-Beast uses digital meters and adds up to 80A load on either side of the service, which locates most service problems pretty well. If the neutral is the only problem, then under load one side will go down and the opposite (unloaded) side will go up by a similar amount. Nearly every service side voltage problem is caused by too long of secondary runs for the service drop size, or an overloaded transformer. Many times the problem was not obvious when I got there because on transformers that are shared by several services, the max load doesn't show up until 5 or 6 PM, (after we've gotten off work) when everyone is home from work cooking, using hot water, kicking on the furnace, etc. The giveaway of service line drop or connection problems is when the loaded voltage readings at the transformer are much better than at the meter. A common connection problem comes when "insulink" crimp style connectors are used on the service conductors. They have a bad habit of filling with water over time, causing corrosion of the aluminum conductors that is not visible from the outside. We quit using 'em years ago and went to "one-bolt or two-bolt" connectors. One problem a lot of customers had with the POCO is that we weren't allowed to diagnose problems beyond the service point. They figured while we were there, we should rip into their sub-panels, water bonds, etc. Big no-no both from a liability standpoint and from local electricians who feel that we were taking their work (and I agree with them). The lineman did all he could without engineering approval of bigger wire or a bigger (or additional transformer to divide the load) and the associated costs. One other thing worth mentioning is that a service neutral or connection problem would likely cause other equipment damage as well. No mention of any blown fuses, burned out bulbs, flickering lights, half of the lights in the house going brighter when the other half go dim?

Just curious.

 

[K8MHZ]

Interesting discussion....right down my alley. As a former (now retired) meter/relay tech for the local POCO, I did this kind of diagnosis all the time. The newer Mega-Beast uses digital meters and adds up to 80A load on either side of the service, which locates most service problems pretty well. If the neutral is the only problem, then under load one side will go down and the opposite (unloaded) side will go up by a similar amount. Nearly every service side voltage problem is caused by too long of secondary runs for the service drop size, or an overloaded transformer. Many times the problem was not obvious when I got there because on transformers that are shared by several services, the max load doesn't show up until 5 or 6 PM, (after we've gotten off work) when everyone is home from work cooking, using hot water, kicking on the furnace, etc. The giveaway of service line drop or connection problems is when the loaded voltage readings at the transformer are much better than at the meter. A common connection problem comes when "insulink" crimp style connectors are used on the service conductors. They have a bad habit of filling with water over time, causing corrosion of the aluminum conductors that is not visible from the outside. We quit using 'em years ago and went to "one-bolt or two-bolt" connectors. One problem a lot of customers had with the POCO is that we weren't allowed to diagnose problems beyond the service point. They figured while we were there, we should rip into their sub-panels, water bonds, etc. Big no-no both from a liability standpoint and from local electricians who feel that we were taking their work (and I agree with them). The lineman did all he could without engineering approval of bigger wire or a bigger (or additional transformer to divide the load) and the associated costs. One other thing worth mentioning is that a service neutral or connection problem would likely cause other equipment damage as well. No mention of any blown fuses, burned out bulbs, flickering lights, half of the lights in the house going brighter when the other half go dim?

Just curious.

She trips a breaker once in a while and the lights do flicker. It was hard to tell if one side was getting brighter or not as it was a sunny day, but my meter read a rise on one side and a dip on the other.

Several of the inslulink connectors did get replaced with one-bolts.

 

[mbrooke]

Interesting discussion....right down my alley. As a former (now retired) meter/relay tech for the local POCO, I did this kind of diagnosis all the time. The newer Mega-Beast uses digital meters and adds up to 80A load on either side of the service, which locates most service problems pretty well. If the neutral is the only problem, then under load one side will go down and the opposite (unloaded) side will go up by a similar amount. Nearly every service side voltage problem is caused by too long of secondary runs for the service drop size, or an overloaded transformer. Many times the problem was not obvious when I got there because on transformers that are shared by several services, the max load doesn't show up until 5 or 6 PM, (after we've gotten off work) when everyone is home from work cooking, using hot water, kicking on the furnace, etc. The giveaway of service line drop or connection problems is when the loaded voltage readings at the transformer are much better than at the meter. A common connection problem comes when "insulink" crimp style connectors are used on the service conductors. They have a bad habit of filling with water over time, causing corrosion of the aluminum conductors that is not visible from the outside. We quit using 'em years ago and went to "one-bolt or two-bolt" connectors. One problem a lot of customers had with the POCO is that we weren't allowed to diagnose problems beyond the service point. They figured while we were there, we should rip into their sub-panels, water bonds, etc. Big no-no both from a liability standpoint and from local electricians who feel that we were taking their work (and I agree with them). The lineman did all he could without engineering approval of bigger wire or a bigger (or additional transformer to divide the load) and the associated costs. One other thing worth mentioning is that a service neutral or connection problem would likely cause other equipment damage as well. No mention of any blown fuses, burned out bulbs, flickering lights, half of the lights in the house going brighter when the other half go dim?

Just curious.

Uness its a full blown open neutral I don't find poor neutrals tripping breakers. Of course when they do the load tends to be burning up at that point.

But like the OP mentioned, 10kva is feeding multiple houses. 10kva is small even for some single houses now a days.

 

[K8MHZ]

Uness its a full blown open neutral I don't find poor neutrals tripping breakers. Of course when they do the load tends to be burning up at that point.

But like the OP mentioned, 10kva is feeding multiple houses. 10kva is small even for some single houses now a days.

Am I wrong in looking at it like the transformer has about the same capacity as a 10kW portable generator?

Or am I missing something?

 

[GoldDigger]

The only thing you are missing, IMHO, is that the generator has a hard limit on the power it can deliver longer than instantaneously, based on the engine power.
A transformer on the other hand can deliver almost unlimited overloads until the primary protection trips (if ever) or the temperature rises too high over a period of hours or more.
But during that time the voltage regulation will suffer. The neutral offset will only be that caused by the service wiring.

Tapatalk!

 

[PetrosA]

There is really nothing wrong with an analog meter for residential trouble-shooting.

A digital meter may impress the customers but an analog will give an accurate reading. They probably used pretty high quality meters for the beast.

I'd also add that for this particular type of measurement where you're looking for opposing trends on different legs, an analog readout will be much better. Digital numbers may seem more precise, but you don't need precision in this case, you need a very visual indication of how the voltage is changing and movement of needles does that very well.

 

[mbrooke]

Am I wrong in looking at it like the transformer has about the same capacity as a 10kW portable generator?

Or am I missing something?

Not missing to much. A 10kva transformer core is about the same as a 10kw generator voltage regulation wise. Only difference is the generator has less over load capacity, above 10kva the generator section will handle the overload poorly overheating and the engine will overheat or stall. Because the transformer core is immersed in oil it acts as a thermal buffer for when the core is overheating. Thus oil pole top units on average can handle short time overloads of 200% to brief overloads of 300% without failure or any significant loss of core life, assuming the oil was given significant time to cool after the last overload period. However, loading above 150% tends to start producing a noticeable voltage drop, and above 350% it will be heavily felt.


That however is on the LV terminals alone. Add an undersized or long run will add to voltage drop.

The only thing you are missing, IMHO, is that the generator has a hard limit on the power it can deliver longer than instantaneously, based on the engine power.
A transformer on the other hand can deliver almost unlimited overloads until the primary protection trips (if ever) or the temperature rises too high over a period of hours or more.
But during that time the voltage regulation will suffer. The neutral offset will only be that caused by the service wiring.

Tapatalk!

Well you did say almost, but I wouldn't say unlimited. The cooler the oil the heavier the overload the core can take, but there is a point where the core can be overloaded faster than the oil can take care of it. Generally overloads lasting more than a few seconds beyond 350% are a bad idea life wise.


If a transformer is a CSP it will shut down on a thermal overload should the oil get to hot (CSPs have a built in LV breaker) but a conventional unit does not have any thermal protection. Conventional units rely entirely on the fused cut out for protection. How much or little protection the cutout gives is entirely up to the engineers or what the line crews think is right. Some POCOs protect with a fuse ampacity and time current curve close to anticipated normal operating conditions so a heavy overload or short circuit will clear quickly. Other pocos will severely over fuse either to prevent nuisance blowing from lightning or just to keep fewer fuses in stock (a few oversized fuse to fit a number if applications).


A general rule of thumb for most pocos is to fuse 2 to 3 times the full load nameplate kva rating ampacity. IE, a 50kva unit connected phase to phase on a 12kv line will pull about 4.2 amps when loaded to its full name plate kva rating. A 10 or 12 fuse would be selected based on the rule of thumb. Fuse type K, T, H, K, ect is then chosen based on what speed and surge withstands are desired in the link.