Mike Dolt Enterprises
Mike Dolt Enterprises
User: busman, Location: Northern Virginia
Asked on: Monday, March 31, 2025 at 12:26 pm EDT
Answered on: Monday, March 31, 2025 at 12:26 pm EDT
Question: All,If you remember my post about the church with the single phase service and the three phase gear. Photos below show what I had expected all along. Details in words:No CT's in the CT cabinet200A service conductorsIllegal jumper in the MDPDidn't trace the red taps in the MDP mainsIt is pretty clear this used to be three phase service with CT. Is it possible the PoCo dropped the three phase for some reason? This church was probably a very low usage customer (only on Sundays). There is 3-phase along the road less than 80 yards away where this is fed from. I could try to get it back to 3-phase, but they may have appliances that won't like 208V (AC units).My question is, if I remove the clearly illegal jumper between A and C phases and replace with a three opening Polaris tap, will there be any other violations?Thanks,Mark
Okay, Mark, let's break this down and address your questions regarding the church's electrical service
Understanding the Situation
You've uncovered a messy situation: Single-Phase Service with Three-Phase Gear
You have a single-phase service feeding into equipment designed for three-phase. This is a recipe for confusion and potential code violations.
Missing CTs
The absence of current transformers (CTs) in the cabinet designed for them indicates a previous three-phase service that was likely metered using CTs.
Undersized Service Conductors
The 200A service conductors might be inadequate if the building's load actually requires a three-phase, larger service.
Illegal Jumper
The jumper between phases A and C is a clear violation. It effectively turns the three-phase panel into a single-phase panel, but in a dangerous and incorrect manner.
Possible Voltage Issues
The existing setup could be operating some three-phase appliances on the wrong voltage and/or using two legs from a three-phase service as single-phase.
Possible Reasons for Service Change
You're right to suspect the utility might have downgraded the service. Here are potential reasons: Low Demand
If the church's electrical consumption was consistently low (especially outside of Sunday services), the utility might have deemed the cost of maintaining a three-phase service excessive.
Cost Savings
Three-phase service often has higher monthly charges, even with low usage. The church might have requested a change to save money.
Utility Grid Changes
The utility may have made changes to their distribution system in that area.
Faulty Equipment
A fault in the service line might have triggered the PoCo to downgrade the service.
Addressing Your Question: Removing the Jumper
Your immediate question is about removing the jumper and replacing it with a three-opening Polaris tap. Here's why simply removing the jumper might not solve the problem, and what other issues you need to consider:1. If the Utility actually removed one phase, what you are left with is Single-Phase Service If they removed on phase, the panel will be fed with single-phase power.2. Service Size Adequacy
The 200A service may be sufficient for the current (reduced) load if the utility downgraded the service and the building's load is truly within that capacity. However, you need to
perform a load calculation to verify this. This is crucial.3. Incorrect Voltage Equipment
You mentioned that you have 208v appliances. If you remove the jumper, only one line of voltage will feed them, so they will probably not work.4.
Neutral/Grounding Issues
Make sure the grounding and bonding are correct for the current service configuration. Since the panel was originally designed for a three-phase service, the grounding might be tied to the enclosure in a way that is no longer compliant with the current single-phase configuration.
Before Anything Else: Contact the UtilityThe absolute first step is to contact the power company (PoCo). Ask them the following: Confirm Service Type
Verify whether the church is currently being billed as a single-phase or three-phase customer.
Service History
Inquire about the history of the service. Did they intentionally downgrade it? If so, why?
Voltage Availability
What voltage is actually present on each phase?
Cost of Upgrade
What would be involved in restoring three-phase service (if desired), including any costs associated with the upgrade.
If you can get back to 3-Phase1. Voltage Selection
If three-phase is restored, discuss voltage options with the utility. You can generally choose between 208v and 480v.2.
Equipment Compatibility
Ensure all existing and planned equipment is compatible with the chosen voltage. If you have 120V equipment in addition to 208V equipment, a 208V three-phase configuration is probably what you need.
Recommendations1. Stop Work
Halt any further modifications until you have a clear understanding of the service history and utility's input.2.
Contact the Utility
As stated above, this is critical.3.
Load Calculation
Perform a detailed load calculation to determine the building's electrical demand. This calculation will inform your decision about service size (whether single-phase is sufficient or if three-phase is required).4.
Consult an Electrical Engineer
Given the complexity of the situation, consider engaging a licensed electrical engineer. They can analyze the system, perform the load calculation, and provide recommendations for bringing the installation into compliance with the electrical code.5.
Inspect and Correct Grounding
Carefully inspect and correct the grounding and bonding system to ensure it meets code requirements for the current* service configuration.6.
Documentation
Document everything: the utility's input, load calculations, any modifications made, and the final system configuration.
In summary, removing the jumper without addressing the underlying issues could create a more dangerous situation. Start by gathering information from the utility, performing a load calculation, and consulting with a qualified professional before taking any further action. Flag for review