Good Day, I had issues with the Rheem 230 Volt Central A/C unit at my home. I asked questions relative to the blower motor inside and the compressor outside. Replacing the blower motor worked for the inside, however, replacing the push relay on the outside had no effect. HVAC1000, who was very helpful said something about checking the 24 volts on the coil to the push switch. Is there a schematic I can download or a theory of operations that I could review that would give me the source of that 24 volts and, someone told me about a freon level fault that could be a problem as to why the unit will turn on intermittently. Thanks in advance for your assistance.

The 24 volt source is located inside the unit in the home. It is a transformer that produces 24 volts which goes to the thermostat then back outside to the unit to energize the push relay as you call it or the contactor /starter as I call it.

Whenever there is a call for cooling a 24 volt signal will be available at the contactor to activate the coil and energise the 240 volts allowing it to pass through to the compressor and fan. NOW there is a possibility you are low on refrigerant causing a low pressure switch to open. That will not allow the 24 volts to pass and it stops the contactor from activating.

Thanks again for your responses. They are a great help.

Would frosting over of the cooling lines and the evaporator inside be an indication of low refrigerant? Is there a way to tell if there is a slow leak of refrigerant? The last two years mostly during spring and fall when the weather changes to where your are using A/C in the daytime and heat during the night, there has been a frosting condition. Please advise. Thanks again.

Yes frosting can be a indication of a low refrigerant charge but it can also be a sign of a outdoor low ambiant condition such as would be experienced when the outdoor temperature especially at night drops below a certain temperature level.

The only way to be sure is to have a professional do a ON SITE survey of the operating condition of your unit and if necessary add refrigerant OR a low ambiant kit which will cycle or slow down (variable speed) the outdoor fan during cool nights to maintain the proper head pressure.

I have such a kit on one of my central air units because the home will stay warm inside till morning and that caused the A/C unit outside to run when the outdoor temperature was 50-60 degrees. The ambiant kit solved the frost problem and allowed the A/C unit to operate normally.

FanHandler.com (http://www.fanhandler.com/)

Look under products for head pressure controler

Not these products are only sold to professionals since knowledge is necessary for the proper hook up and control adjustment.

There are other company that make similar design products.

Wow that is a snazy contraption. Very interesting.

A more economical solution would be a factory pre-set fan cycle switch. I have installed them on residential systems used to supply commercial buildings with good success. Wire it in series with the condensing fan and screw the switch onto the access port on the high side.

more economical solution would be a factory pre-set fan cycle switch

That works also but over the years I found that those systems will turn the fan off and on rapidly during the winter. Had a problem at the TV station computer room 30 years ago. The units were set up for low ambiant by the original installing company but we were called for service when they kept replacing condenser fan motors.

Started to use a fan speed control instead of a off/on type control and there problem went away. Never went back to the old style pressure cut outs.

In that application I can see why you would use such a device. A computer room will generate a pretty good heat load all season but on a residential system I don't see it running in the bitter cold lol.

Based solely on ease of installation and price and the given application I would suggest the fan cycle switch... again just my opinion.

I always over engineered my toys. Tankfully most of my work was commercial/industrial. Most of the residential was for the company owners that we already did there business and they wanted us to take care of there homes also.

I have used many expensive devices over the years to solve problems in the HVAC arena and some I have actually designed and built. There is no industry that offers more opportunity's than the HVAC trades. You can never know all of it.

Gentlemen, thank you very much for your responses. Your candor and insight is very valuable to us of limited financial means that have just enough skills and knowledge to be dangerous, but at least ask questions FIRST and shoot from the hip later. Frankly, the thing I was trying to avoid was the service call because the estimate I got was $200 plus parts. If that is what services calls in HVAC are running today, I need to get retrained. I do computer service and guess I don't have the brass ones to charge that much.

Sorry but prices for HVAC work can be expensive. It in some ways is a supply and demand thing plus many expenses that are not present in other trades. Just the cost of transportation today is a killer let alone 20 to 30 thousand invested in tools and a very small service stock. Below is a small list of costs associated with the HVAC industry.




As to mark up or costs of business, keep in mind a quality contractor that will be there for you when you need him may have some or all of the following business expenses:

Not limited to;

401K
Health Insurance
Holiday Pay
Office Benefits
Sick Pay
Uniforms
Vacation Pay
Air Conditioning Equipment Maintenance
Building Repairs
Cleaning Service
Electric Utilities
Facility Mortgage Payments
Furniture
Gas/Oil Bill
Landscaping
Office Rent
Parts Storage Racks
Security System
Shop Tools
Callbacks
Miscellaneous Hardware
Air Conditioning License
Answering Service
Bad Debt
Business Licenses
Cash Reserves
Certification Tests
Chamber of Commerce Dues
Collections
Dealer Meetings
Employment Testing
Help Wanted Advertising
Interest Expense
Internet Access
Inventory
Inventory Shrinkage
Invoices
Legal Services
Liability Insurance
Management Training
Mobile Phone Charges
Mobile Phones
Office Training
Pagers
Property Insurance
Recycling
Subscriptions
Tax preparation
Technician Training
Trade Association Membership
Brochures
Charitable Contributions
Customer Satisfaction Surveys
Door Hangers
Home And Garden Shows
Magnets
Newsletter
Newspaper Advertising
Other Advertising
Outdoor Advertising
Patches
Radio Advertising
Sales Commissions
Warranties
Website
Yellow Pages
Youth Sports Team Sponsorships
Accounting
Calculators And Adding Machines
Computer System Maintenance
Computers
Copier
Fax Machine
Files And File Cabinets
Office Supplies
Phone Bill
Phone System
Postage
Postal Equipment
Printing
Software
Stamps And Pads
Telephone Bill
Telephone Equipment
Training Equipment
Trash And Disposal
Water Bill
Call Taker
Dispatcher
Employee Incentives
Employee Pay
Management
Office Staff
Receptionist
Technician Pay
Federal Taxes
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Local Taxes
Municipal Property Tax
Other property Taxes
Sales Tax
Social Security Taxes
State Taxes
Unemployment Insurance
Worker's Comp
Gasoline
Ladders
Radios
Tires
Tools
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Truck Depreciation
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Truck Maintenance
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Trucks
Profit
Tool Insurance
Truck Plates
Life Insurance
Equipment Insurance
Warranty Expenses
Code updates
Other trade book updates
Permits
Dental / Vision Insurance
Equipment Consumables
Inventory Tax