HVAC Frequently Asked Questions

Why is my house so dusty?

Your A/C system has a lot to do with this because it is constantly circulating air through the house. If the filter for your A/C system is not properly installed dirt and dust can be bypassing the filter. Also a very low efficiency filter will cause the dirt and dust to go right through the filter.

The air in my house is humid-why?

The A/C system controls the humidity in the house. If the A/C system has not been properly maintained or is in need of repair the humidity in the home can be at an uncomfortable level. Also if the system is too big it will cool the home down too quickly and turn off not allowing the unit to run long enough to remove the humidity.

Why do my lights flicker when my system comes on?

The A/C unit pulls the most power during start up and this can cause the lights to flicker. It should only be for a split second, if the lights are dimming or you notice the condition is getting worse there may be an electrical problem with the unit.

Why are different rooms warmer/cooler in my house?

This condition is usually caused by a poor ductwork design, ductwork that is in poor condition, or someone has added excessive heat producing appliances to a room. Also the A/C system could be in need of a tune up by a professional service technician.

Why does it seem like the temp on my thermostat isn’t consistent?

Some thermostats can loose their calibration which can cause a big swing in the temperature reading. The thermostat is improperly located in the house. If air from a supply outlet is blowing on the thermostat this will cause the temperature on the thermostat to drop quickly giving a false reading of the actual room temperature.

What can cause tapping on my outside unit?

Something has fallen into the fan blade, the fan motor bearings are so loose causing the fan blade to come in contact with the fan shroud or the contactor is chattering which is a sign of a control voltage problem.

Why does my A/C unit ice over?

There are three reasons why the A/C unit will ice over. There is a restriction in the refrigerant line, the system is low on refrigerant and/or lack of air across the evaporator coil. The lack of air across the evaporator coil is caused by a dirty filter, a filter that is too restrictive, a dirty coil, a dirty blower wheel, incorrect blower motor and/or wheel, the inside unit is not matched properly to the outside unit, ductwork is not sized properly, too many supply registers are closed, the return are inlet is too small or restricted or the ductwork is restricted inside by a damper or ducting material that has come apart.

Why does my A/C stem overflow?

The drain line or drain pan gets clogged up. This is caused by dirt that has accumulated on the evaporator coil and has washed down into the drain pan and drain line. Also if water is sitting in the pan or drain line and does not drain out completely it can cause algae to grow causing the system to overflow. If the system pulls air through the evaporator coil the drain line must have a P-Trap installed in it, this prevents the blower from pulling air up through the drain line causing a negative pressure on the line which will allow the condensation to drain.

What is an electrostatic filter?

As air passes through the filter it causes an electrostatic charge causing dirt and dust to cling to it. Some manufactures do not recommend these to be installed in their A/C units because air restriction is to high.

Do UV lights work? What is a UV light?

UV lights work to purify the air in the home and help fight mold growth. When placed right before the evaporator coil it will change the molecular structure of the dirt and dust causing the coil to stay clean. A UV light is an air purifying system that greatly improves indoor air quality.

I have allergies, what filter system do you recommend?

I would recommend a combination of an electronic air cleaner with UV lights in the return air and in the supply air right before the evaporator coil.

What is the benefit of a programmable thermostat?

During the cooling or heating season you can program a higher or lower temperature when no one is home causing the unit to run less and save energy.

Why does my water heater make rustling noises?

This is caused by calcium and mineral deposits in tank that reach high temperatures and pop.

Why does HARP hard pipe water heaters instead of using flex connectors?

Flex connectors have the tendency to leak , after installation. By hard piping your water heater all joints are either threaded or soldered with very little chance of leaks appearing later.

Can I use anti-freeze to protect my system?

Anti-freeze can be used with our boilers. We recommend using an anti-freeze designed for hydronic systems, formulated with inhibited propylene glycol, a non-toxic antifreeze. A solution of up to 50% can be used. No compounds containing petroleum should ever be used in your heating system. Do not use automotive anti-freeze.

How do I clean the boiler?

Steam Boilers
To clean a steam boiler, use one pound of trisodium phosphate for every fifty gallons of water content. Heat the boiler to 180 degrees F; hold at 180 degrees F for two hours. Do not allow the boiler to make steam. After two hours, drain the boiler and fill with fresh makeup water. Water treatment chemicals should be thoroughly reviewed before they are introduced into the boiler. Foaming agents that will interfere with steam action are of particular concern. Sodium carbonate (one pound for every 30 gallons) or sodium hydroxide (lye) (one pound for every fifty gallons) may be used.

Check pH level after cleaning. It should be between 7 and 8.5. A small amount of cleaner may be added to adjust the pH up to the proper range.

DO NOT use petroleum based products in the boiler.

Water Boilers
Use one pound of trisodium phosphate for every fifty gallons of water content. Fill, vent and circulate the system with above mixture, allowing it to reach design or operating temperature, if possible. After circulating a few hours, drain the system completely and refill with fresh water. Usually, enough of the cleaner will adhere to the piping to give an alkaline solution satisfactory for operation; a pH reading between 7 to 8.5. Sodium carbonate (one pound for every 30 gallons of water content) or sodium hydroxide (lye) (one pound for every 50 gallons) may be used.

Check pH level after cleaning. It should be between 7 and 8.5. A small amount of cleaner maybe added to adjust the pH up to the proper range.

DO NOT use petroleum based products in the boiler.

Miscellaneous Tips

-Check the insulation levels in your attic, exterior and basement walls, ceilings, floors, and crawl spaces.
-Check for holes or cracks around your walls, ceilings, windows, doors, light and plumbing fixtures, switches, and electrical outlets that can leak air into or out of your home.
-Check for open fireplace dampers.
-Make sure your appliances and heating and cooling systems are properly maintained. Check your owner’s manuals for the recommended maintenance.
-Study your family’s lighting needs and use patterns, paying special attention to high-use areas such as the living room, kitchen, and outside lighting. Look for ways to use lighting controls—like occupancy sensors, dimmers, or timers—to reduce lighting energy use, and replace standard (also called incandescent) light bulbs and fixtures with compact or standard fluorescent lamps.

How often should I flush my water heater?

Some manufacturers suggest every month – while others say every 6 months. We suggest 2 times a year.

How often should the Temperature & Safety Valve be checked?

Manufacturers suggest check once a year & replaced every 3 years.

HARP Mechanical
483 Spring Street
Windsor Locks, CT 06096


Mon - Fri: 8:00am - 5:00pm
24-7 Emergency Service
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