We are your complete commercial air conditioning and mechanical contractor. We have been serving the Maryland, DC, and Virginia metropolitan area since 2001. Our master technicians are trained and licensed to service several brands of air and water cooled chillers, pneumatic and direct digital control (DDC) systems, cooling towers, and more. We specialize in servicing units built by major manufacturers including Trane, Carrier, York, and many others.

We can prove that ensuring your satisfaction drives us to serve you with the highest level of promptness, courtesy and efficiency. At Horizon Mechanical Services, your comfort is our success.

Professional Associations & Certifications

  • ASHRAE, U.S. Green Building Council

Serviced Areas

  • Wshington, D.C., Northern VA and Maryland

Payment Options

  • American Express, Debit Cards, MasterCard, VISA, Discover Card

Contact Details

  City Upper Marlboro, MD
  Zip Code 20772
  Address 8039 Penn Randall Pl
  Phone Number (301) 669-6501

Products & Services



Our various services offered are repair, installation, and maintenance agreements.

Maintenance Agreements:
Our maintenance agreements are custom tailored to our clients facility and equipment life cycle which help prevent unforeseen equipment downtime, offers predictive analysis of potential equipment failure, and ensures maximum effciency of equipment operation. Examples of our predictive analysis are megging of motors for trending purposes, oil analysis of centrifugal and rotary screw chillers, combustion analysis of gas fired equipment with customer provided receipts, Measurement of air side equipment total CFM using digital anemometer for proper superheat and humidity control. Other examplesof preventive maintenance measures are chemical cleaning of water-side components such as water tube condensors, water side of firetube boilers, and cooling towers.

Repair Services:
Our scheduled and emergency repair services for all makes of air conditioning equipment including rooftop units up to 120 ton, centrifugal and rotary screw chillers, refrigeration equipment and boilers are performed skillfully and in a efficient manner by our factory trained technicians that reduce down time of equipment. We take pride in our highly skilled staff to offer building solutions as chiller problems, Variable air volume system performance issues, package cooling equipment and control systems. Our service technicians have all completed a 5 year training program through local 602 with training in all phases of commercial/industrial heating and cooling service. We offer 24 hour emergency service to all customers year round. Some of our repair services have included centrifugal chiller overhauls, compressor replacements, and disassembly and resealing of burner sections with new rope.

Rerofit / Installation Services:
Our retrofit and installation services have included replacement of water-cooled chillers, steam and hot water boilers, and cooling towers. We value engineer existing building systems for best equipment retrofit and replacement solutions to provide highest equipment utility payback on investment for our customers. Our skilled staff have over 30 years field experience which is an invaluable tool to our customers benefit.

  • I would not recommend this business
  • None.
  • Unprofessional, uneducated, faulty work, sketchy manager.


*Background* I live in a 8 story, high-rise condo in DC. My unit is equip with a "Retroaire" vertical standing HVAC. I've been living in my unit for about a year and a half and had issues with my drain pan getting clogged and not draining properly in the past. Back in April, after a little research online and taking things into my own hands, I noticed that after cleaning the drip pan (it had a NASTY amount of built up gunk growing in it) the pan began to drain properly again. I fixed the issue and decided to have the unit professionally looked during the summer when I'd be using the AC more often.

I was finally able to set up an appointment with Horizon Mechanical Services on July 18th 2011 - not because anything was wrong with the unit, but because building management recommends having the units looked at every 6 months or so. Not an issue. Or so I thought.

Now, prior to this day I had never had an issue dealing with Horizon. I actually had two great experiences when they sent Jack Santacroce out to fix my unit when I first moved in. And you can believe I made sure the manager was well aware of how much I appreciated Jack's service and that he often went out of his way to help explain to me what he was doing while he was working on the unit. He was fair and honest and I had no reserves about his work or knowledge. However, to my surprise, the latest experience with Horizon was, by far, the worst service I've ever had. And you can better believe I'm going to spread the word, as a consumer and fellow resident of the building, to as many people here as possible.

On the 18th Horizon sent out their technician, ISEMANN (last name), to my unit around 10AM. I told him (and the manager ZENOBIA) that nothing was wrong with my unit but that I had had issues in the past with it not draining properly because of all that built up gunk; all I needed was a check-up. Knowing that they charged $108/hour, I was more than willing to dish out the cash knowing that my unit was up-to-date. Especially considering how apt the upright units are to having issues.

A few minutes in ISEMANN noticed that the rubber condensate tube attached to the horizontal drip pan drain nozzle is kinked. According to him: because the building drain pipe, that drains all the water outside the building, is located underneath my HVAC, connecting the two is creating a harsh angle and therefore kinking the rubber tube that is attached to the drip pan nozzle. Okay, sounds legitimate. Still I figured it would be a quick fix.

An hour goes by. He's been tinkering away at my unit, not really letting me know what's going on and then he calmly asks if he can put a hole in my wall. 'A hole in my wall?! Why do you need to put a hole in my wall?!', I ask. He tells me he can't reach the drip pan nozzle because it's behind one of the metal supporting bars lining the interior wall housing my HVAC. I told him no, he couldn't put a hole in my wall and that Jack never had an issue accessing my unit when he worked on it. So then he asked if he could cut 'a small piece off' of one of the metal support bars. I told him to show me what he meant and then gave him permission.

Three hours, who knows how many buckets of water, 'to test to see if it's draining', now leaking on my carpet, a stained carpet due to his navy work pants and two to three bloody fingers later he's still tinkering away. And now he's frustrated. Oh, and why the bloody fingers? Because, without me knowing he actually cut the metal bar IN HALF AND ripped it off my interior wall AKA it was sharp as hell. Of course, by then, I helped him bandage his fingers and put a towel down so that he'd stop getting blood and ink from his pants on my carpet. I honestly felt bad for the guy but didn't understand why it was taking so long.

PS: While this is going on, I'm asking him questions regarding regular maintenance, where he's at in the process of fixing my unit, etc. and the man never seemed to have an answer. He was obviously clueless. And unfortunately I only realized this after FOUR hours ... and $432 later! I was left with a unit that was now leaking into my surrounding carpet (thanks to all the water he put in the drip pan to make sure it was draining), a cut metal support bar hanging off the ceiling, blood stains, dye stains, a rubber condensate tube still attached to the drip pan nozzle exactly how he found it and he even had the nerve to tell me to keep checking it to make sure it's not continuing to leak.

Oh, and he was serious.

You can better believe I got right on the phone with ZENOBIA and told her I would not be paying for his lack of service. By this time he had left and, unbeknownst to me was still in the building. ZENOBIA said she would call ISEMANN back and see what the issue was. Next thing I know he's knocking on my door an hour later. He starts tinkering with my unit again ... pouring more water in the pan and then goes out to his bag and grabs a zip-tie. I kid you not - when I went over to look at what he'd done, I saw the zip-tie around the rubber tube with the other end hooked around a flat head nail (one that used to be in my wall) on the hanging metal bar he had cut. His argument was that the zip-tie was supporting the tube enough so it wouldn't kink.

I had had enough. I got BACK on the phone with ZENOBIA and told her to get someone else out here. She told me she could have someone out by 7PM. After dealing with these people all day, I just wanted my unit fixed.

Long(er) story short(er): the serviceman who came out at 7PM (did not get his name), diagnosed the issue, slapped an elbow piece onto the drip pan nozzle (so that the rubber tube was now running straight down and didn't have to curve), poured some water in to show me it was draining properly, recommended that I put a capful of bleach into the drain pan to keep the algae from growing and was finished before Jeopardy was over.

Done & Done.

I told ZENOBIA I'd gladly pay for his service but that I expected for them to pay to fix the metal support bar ISEMANN cut in half and ripped off my wall. She said she'd call me back with a date.

**UPDATE** I never got a call. Now, to be fair I was out of town from July 30th to August 7th ... but I never got a call. I called two days ago. And after being told, by ZENOBIA, that she'll have to call me back because she was on hold and that 'she didn't want to loose her place in line' - oh, she was not on the phone with another customer, by the way, I asked - Horizon will once again be coming out to my condo to fix what ISEMANN broke this Wednesday the 24th.

CONCLUSION: From one customer to another, I would HIGHLY, HIGHLY recommend you NOT use Horizon Mechanical Services.

**UPDATE 8.24.11**

Well, as of today Horizon Mechanical Services has done nothing to clean up it's reputation, in my opinion.

Two days ago I set up an appointment through ZENOBIA, who claims to be the manager, for a different technician to fix the broken support bar their technician ISEMANN cut and ripped off my wall back in July (read my previous post for details). The appointment was supposed to be with a gentleman named Ural Payton - who I was told was the technician who ended up fixing my unit (in under an hour) in July.

The appointment time of 8AM came ... and went.

I called ZENOBIA at 9:10 and she said she'd call around and try to find out where the technician was. She called back about 10 minutes later and informed me that he was on his way. About 15 minutes later there was a knock on my door. 'FINALLY', I thought, 'we're going to get this taken care of'! I opened the door. And to my surprise ISEMANN was standing there - the SAME technician who broke my unit to begin with; the SAME technician who I SPECIFICALLY told ZENOBIA not to send back. I told him I had requested someone else and that I was calling ZENOBIA.

Her answer was that she was trying to resolve my issue as quick as possible and that he was the only one available. When I asked what happened to Ural Payton, who she originally told me was coming, she stated that he was not available.

Honestly, I can't say I was surprised by any of this nonsense. But you can better believe that I'm tired of dealing with this company. The only reason I continue to deal with them is because they are entitled to fix the mess they made.

Once again, ZENOBIA is supposed to be sending Ural Payton out at 9AM tomorrow (8.25.11) morning.


Value for money$432 for BREAKING not fixing my HVAC?!
Service & supportSame problems over and over and over ... (read review).
QualityA jimmy-rigged condensation tube? Laughable.
LocationThey're never on time.
Overall ratingPoor

  • I would not recommend this business
  • Out $6000 and still no A/C.

Our А/C unit went out. Horizon told us we needed a new unit. We bought a Carrier unit and it did not work. The following year Horizon replaced that unit because it was "defective." A year later it still doesn't work and now they tell us it is out of warranty. Another defective unit or a defective installer?

Beware - this company does not stand behind its product nor its workmanship. We are out almost $6,000 and still have no A/C. They do not return phone calls and they do not show up (until after the warranty expires) when they say they will.

Value for moneyA/C not working.
Service & supportA/C not working and response is horrible.
QualityA/C not working.
Overall ratingPoor

Customer Testimonials

After some miscommunication about arrival time Ural arrived and worked continuously until he found and resolved a very difficult problem in an older house where many who had come before had worked unable to resolve the problem.

Friendly service, knowledgeable technician (who's also the owner of the company). Reasonable rates.

From Our Website

Established in 2001, Horizon Mechanical Services LLC provides solutions to clients facing problems with their heating and cooling systems. As factory-certified technicians, we're capable of performing boiler repair, new installations, and chiller servicing to Washington D.C./Baltimore and Northern VA area customers. We're certified to work with numerous manufacturers of HVAC systems, including Honeywell, Carrier, WattMaster, and Stulz. Airports, Ice arenas, and schools can't afford interruptions to their air conditioning.

Horizon Mechanical Services LLC has over 30 years of experience providing retrofitted and replacement chillers to the Washington metropolitan area. Our clients have come to respect our ability to work within existing engineering plans to find the best solutions for inefficient and broken commercial HVAC equipment. Our goal is to more efficiently cool or heat your building and to do it for the best value possible. Most business owners and property managers are aware when their energy costs are going up or when their building is warmer than it should be, but may not be aware that it's time to consider a new or retrofitted system.

Horizon Mechanical Services LLC understands that no two clients or buildings are alike. Your HVAC system serves vastly different roles. Airport property managers must keep a large, sprawling building cool for travelers, while hospitals perform vital services which require cool rooms for medical sample storage. Regardless of whether you need to keep a server room cool or university lecture halls warm during the winter, we devise custom HVAC maintenance agreements for your Washington D.C./Baltimore and Northern VA area building.