Rainbow Services - HVAC-articles


One HVAC system, 2 or 3 thermostats ?

October 14, 2015

I've had a number of uneven temperature complaints this summer. Some of the problems involved loose wiring, bad damper motors or just poor ductwork installation.This is usual repair work, however the majority are from customers or clients who have only lived in their new homes for a few years The surprising thing is that these are newer homes and  the HVAC equipment is working perfectly. 

In my customer interview about how the systems are used, I've found that the zone damper system is not being used properly. No information about the HVAC zone system has been offered by whoever installed it. The customer is in the dark about how its supposed to work and so I'm left to explain why they can't keep one floor turned off and the other two at wildly different temperature settings.

I'm going to reprint one of the explanations I emailed to a client after a damper motor repair, which made it better but didn't solve it completely. The hope is that I won't have to apologize for another zone damper system which I don't advocate and did not install. If you know how it works you are better prepared to Save Your Money.

Mr. Client,

Zone damper systems as installed in Raleigh are problematic.The most common complaint is the one you just described.

One system big enough to cool the entire envelope of the structure is too big for any one zone by itself.

What the zone system was designed to do is compensate for temperature differences floor to floor.

 What it is misapplied to do is to give independent temperature control on each floor without respect for the whole envelope. Also without consideration for the fact that we have a one speed only unit. The equipment is designed to operate at its full capacity only, so various tricks are used to keep from starving the unit of air when only one zone calls for cooling.

It's like running a motor at high revolutions and controlling your speed with the clutch. It can work, but shifting to a different gear would be a better plan. This in equivalent would mean two or even three air conditioning units. It's easy to see why this isn't done by builders.

When codes caught up with the times in North Carolina, it was decided to use one unit per floor. This was cost prohibitive so a code buster was offered. Independent controls for each floor, all with one unit. 

The complaint  of hot upstairs and cold downstairs was addressed with controls rather than design.  You can tell I don't agree with this reverse engineering, but I'm a lowly furnace mechanic and do not get a vote.

The good news for contractors is that they do not have to make damper adjustments at the change of each season. Seasonal adjustment of dampers has been the only way to prevent stratification between floors.

The assumption was made that one temperature or small deviations around a common set point would be automatic. This is a workable solution for the hot upstairs problem if the floors are set fairly close together in temperature.

If you give people a control they will expect absolute control. If it can be adjusted we will stretch the ability of the control beyond its intention to the limit of its adjustment. If it shouldn't be set to 60 deg, then why does it go there? I don't have the answer, but it's a fair question.

The problem you described is real, and is exacerbated in direct proportion to the temperature set point difference between floors. The floors are not independent and there is no insulation between the separate areas anyway. The system works best when set points are close to each other and some spillage of air is expected between floors.

This may not be your case. I only describe a popular complaint. 

It shouldn't be your challenge to work around the systems design, and we aren't going to reinstall or reengineer the system so I think maybe I should try to tweak  the dampers resting positions around the way you use heating and cooling, insofar as possible of course.

I propose to do this very thing. If I invest a little of my time at no charge to you and get this thing working as close as possible to your requirement I will be a clever boy with a happy client. That's the big deal to me and is payment enough.

Results were that the homeowner didn't need me to come out again, once he understood what to expect he was comfortable with his system instead of worrying about some huge repair looming on the horizon.

At your service, Ed Cline


I want to clean my outdoor air conditioning coil.

September 3, 2015
This summer I've found a lot of air conditioning coils that need cleaning, and I've cleaned most of them. I've been too busy to keep track of the pollen counts, however I suspect that the unusually high outdoor temperatures simply revealed this problem and that the air conditioning coil problem was there all along, or at least a few cooling seasons.

Your air conditioner is oversized for most of the year, so if its not quite up to snuff you may not notice. When its 100 degrees outside you will ...
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I have a smell coming from my furnace, does it need service?

September 3, 2015
The cooling season is almost over. Whew! Soon the evening or morning will come when the heating cooling gets switched at the thermostat for occasional heating duty in the evening and cooling during the day.
You will very likely smell an odor from the ducts. At any other time of year I would recommend a service appointment right away, however not in this case.

During the summer we have used the furnace blower and the heating cooling fan and ductwork for cooling only. During this time a layer of ...
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Heat Pump 101

July 7, 2011

If you’ve just moved into a home with a heat pump, or never really understood how a heat pump works, or just want a solid base of knowledge about your heat pump before you discuss it with a service person or sales person, then this is for you. 

A heat pump - air conditioner heats your home during the winter, it also cools it during the summer. It does not burn fuel to produce heat nor does the electricity it consumes go through an electric element except during defrost. The compressor does...

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What can I do myself? DIY improvements.

November 26, 2010
The single most important thing you can do as the operator of a heating or air conditioning system is to change the filters every month. An air conditioner or heat pump needs to breathe! Your furnace or air handler is trying to distribute heating or cooling that you have bought and paid for already and you can help. There is no use in buying High Efficiency heating or cooling if you won't do your part. The useful life of a filter is about a month at my house, so I check the filter every time ...
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Should I buy a Service Agreement?

November 26, 2010

 Hiring someone to repair and maintain an Hvac system is as personal as choosing a friend almost. You'll need to trust this person to tell you "what's wrong and how much?" you should spend on a repair. You probably don't know too awful much about how the heating / cooling system works from a mechanical standpoint so, you're (in effect) trusting the repairman with your wallet.

When I look to have something fixed, I want to talk to the actual mechanic who will do the work first. Answering servic...

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How long will my system last?

November 26, 2010
  • A new, high efficiency, 13 SEER air conditioner uses about half the energy of a 15-year-old air conditioner. If your air conditioner is 10 years old or less, maintain it well and keep it. If it is between 10 to 15 years old, minor repairs and service are still acceptable. If the air conditioner is 10 to 15 years old or older and needs substantial repairs, your best alternative is to replace it with a new, high efficiency system.
  • Turn air conditioners to the highest comfortable setting. We re...

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About a New Thermostat?

November 26, 2010

What's a digital thermostat?

Digital thermostats are energy saving devices that are manually programmable to allow users to control temperature settings. They can be used with most heating and cooling devices.

How does a digital thermostat work?

A digital system can automatically store and repeat settings while still allowing for the option of manual override. These thermostats provide occupants with a more comfortable house temperature during waking and sleeping hours by automatically turning t...

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Should I have my ducts cleaned?

November 26, 2010
This is a question that may cause me a lot of grief personally, I have every thought that someone who runs a duct cleaning service will get together with the "duct cleaners of America" and show up under my balcony with torches. So let me say that I live to learn and will research further anywhere you tell me to look, except in your sales literature of course. I think I'll pause for a cup of tea from that kettle on my stove (I am the writer and the photographer on this website). My observation...
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How well do the new Air Cleaners work?

November 26, 2010
Air filters come in many flavors. There is only one kind with the potential to damage your system, I'll get to that one in a minute. Lets start with the one that comes in the furnace or air conditioner. This variety of filter has a job, it's to protect the equipment from relatively large hunks of dirt that will invade the air circulation wheel and motor eventually insulating it with a coat of dust and pet hair. It's better than no filter and thats all that can honestly be said for it. If you ...
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About Me, I'm building this in real time, meanwhile please go to contact page for answers..thanks ed cline

Have a question? Call 919-630-1776. Or write to me!



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Rainbow Services Raleigh NC at Chesterbrook Ct. Raleigh NC 27615 services these Raleigh Neighborhood Zips. 

Central Raleigh 27601, East Raleigh 27604, Falls of Neuse 27609, Five points 27608 and 27605,  Glenwood 27609, 27608, 27612, 27607, Hillsborough 27605, 27607, 27608 Mordecai 27604, North Raleigh 27609, 27613, 27615,  North Central Raleigh 27601, 27610, Northeast Raleigh 27604, 27616, Northwest Raleigh  27613, 27617, Six Forks 27609, 27612 South Raleigh 27610, South Central Raleigh 27610 Southeast Raleigh 27610, Southwest Raleigh  27606, Wade 27607, 27608 West Raleigh 27606, 27607. In 27603 we service the northern part a few miles past the 401 70 split, or a bit past the Walmart is our service area border. Any service coupon or quoted service is confined to these areas.

About Knightdale and Cary. Rainbow Services  27511, 27513 along the edges that border Raleigh and 27545 to within a few miles past 540. There are no discounts available for these areas, however just plain good repair work at a fair price is available for these zip codes  bordering our repair service area.