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Merrimack, NH

Residential heating & air conditioning contractor in Merrimack, NH

GSMS is proud to serve the residents of Merrimack, NH, with top-quality heating and air conditioning services. As a family-owned business with over three decades of experience, we are dedicated to providing reliable, efficient, and professional HVAC solutions tailored to your home’s specific needs. 

GSMS is proud to be your Merrimack Lennox Premier Dealer!

Whether it's an emergency repair, a total replacement, or routine maintenance, we have you covered. Call 603-424-8258 today!

Air conditioner repair & replacement

  • AC Repair: We handle cooling problems big and small with speed and attention to detail. Our technicians are trained to troubleshoot and fix refrigerant leaks, thermostat issues, electrical failures, compressor problems, and more. 
  • AC Replacement and New Installation: Time for a cooling upgrade? We offer high-quality systems from Lennox and other leading manufacturers to improve efficiency, enhance comfort, and reduce homeowners' carbon footprint.

Furnace repair & replacement 

  • Furnace Repair: Dealing with a broken furnace? GSMS technicians work efficiently to track down even the smallest of problems and repair them in no time. Common furnace issues we repair include pilot light problems, thermostat malfunctions, ignition system failures, and blower motor problems. 
  • Furnace Replacement and New Installation: Upgrading your furnace takes your home's winter warmth to the next level. Our energy-efficient systems provide consistent heating, reduced maintenance, and enhanced safety. 

Boiler repair & replacement

  • Boiler Repair: Common boiler problems with pressure, thermostats, pilot lights, and leaks, can be a homeowner's nightmare. GSMS technicians work quickly to repair your boiler and get your home warm again in no time. 
  • Boiler Replacement and New Installation: Whether you are considering switching to a boiler system or it's time to replace your existing system, GSMS is here to help you increase efficiency and reliability with advanced units. 

Mini-split heat pumps

GSMS provides comprehensive services for mini-split heat pumps, including installation, maintenance, and repair. We specialize in Mitsubishi ductless units, known for their reliability and efficiency. Whether you’re looking to install a new system or need service for your existing mini-split heat pump, our technicians are here to ensure optimal performance and comfort in your home.

Ductwork cleaning & installation

  • Duct Cleaning: Regular duct cleaning helps improve air quality, increase HVAC efficiency, extend system lifespan, and eliminate odors. We use an advanced Roto Brush system to reach every corner of the ductwork and keep your home clean and comfortable. 
  • Duct Installation: Proper ductwork installation is crucial for airflow, efficiency, comfort, and durability. Choosing GSMS to install your ductwork gives you peace of mind that your new air ducts are safe and secure. 

Merrimack plumbing services

GSMS is proud to provide comprehensive plumbing services to homeowners in Merrimack, NH. Our experienced and professional team is dedicated to delivering reliable and efficient plumbing solutions tailored to your specific needs. 

Quick plumbing repairs, complete installations, and preventative maintenance are what we do best. Call 603-424-8258 today!

Water heater plumbers

  • Repair: Our skilled technicians can quickly diagnose and repair common water heater issues, including inconsistent temperature, leaks, and strange noises.
  • Replacement: When it’s time to replace your old water heater, we offer professional installation of both traditional tank models and modern tankless systems.
  • Maintenance: Regular maintenance is essential to keep your water heater running efficiently. Our comprehensive maintenance services include inspections, cleaning, and tune-ups.
  • Tankless Water Heaters: Upgrade to a tankless water heater for endless hot water, improved energy efficiency, and space savings. We provide expert installation and maintenance for these advanced systems.

Kitchen plumber services

  • Faucets: From repairing leaks to installing new faucets, we ensure your kitchen faucets are functioning perfectly.
  • Sinks: We handle all sink-related services, including installation, repair, and replacement, to keep your kitchen fully operational.
  • Garbage Disposals: Our team can install and repair garbage disposals, ensuring efficient waste management in your kitchen.
  • Dishwashers: We provide installation and repair services for dishwashers, making sure they are properly connected and running smoothly.
  • Water Lines: Whether you need new water lines installed or existing ones repaired, GSMS ensures a reliable water supply for your kitchen appliances.

Bathroom plumber services

  • Toilets: From fixing leaks and unclogging blockages to installing new toilets, we provide comprehensive toilet services.
  • Showers and Tubs: We offer repair, replacement, and installation services for showers and bathtubs to keep your bathroom comfortable and functional.
  • Sinks and Vanity Plumbing: Our team can install and repair bathroom sinks and vanity plumbing, ensuring everything operates seamlessly.
  • Pipe Repairs and Replacements: Whether it’s a minor leak or a major pipe replacement, GSMS provides expert pipe repair and replacement services to prevent water damage and maintain optimal plumbing performance.

Why choose GSMS in Merrimack?

  • Proven Track Record: With a long-standing presence in Merrimack, NH, GSMS has earned the trust of countless homeowners. Our dedication to excellence and reliability has made us a preferred choice for HVAC and plumbing services in the community. We are proud of our reputation and continually strive to uphold the high standards that have set us apart.
  • Local Expertise and Dedication: GSMS has been serving the Merrimack, NH community for over three decades, building a reputation for excellence and reliability. As a family-owned business, we are deeply committed to our local community and understand the unique needs of Merrimack homeowners. Our local expertise allows us to provide tailored solutions that keep your home comfortable and efficient year-round.
  • Comprehensive Range of Services: From HVAC to plumbing, GSMS offers a full spectrum of services to meet all your home comfort needs. Our skilled technicians are trained in the latest technologies and techniques, ensuring top-quality service for every job. Whether you need a quick repair, a new installation, or regular maintenance, we have the expertise to get the job done right.

Become a GSMS Home Club member today

Join the GSMS Home Club and enjoy exclusive benefits designed to keep your home’s HVAC and plumbing systems in top condition. Membership perks include:

  • Priority Service
  • No Diagnostic Fees
  • 10% Off Repairs
  • Home ID and Smart Monitoring
  • Monthly Credits Towards Major Purchases
  • Regular Maintenance
  • Labor Warranty Upgrades

Call today for great service in Merrimack.

Trust the experts at GSMS to provide reliable, efficient, and top-quality services tailored to your needs. Whether you need a quick repair, a new installation, or regular maintenance, our dedicated team is here to ensure your Merrimack home remains comfortable and functional year-round.

Call 603-424-8258 today or fill out our online contact form to book an appointment!

Recent Jobs and Reviews in Merrimack, NH

Rated 5.0 out of 5 stars based on 36 customer reviews

Customers say: The recent reviews exhibit a predominantly positive sentiment, with recurring themes of satisfaction, professionalism, and expertise. Customers express gratitude, recommend the company, and acknowledge the quality of the work performed. Positive reviews frequently mention friendly and knowledgeable technicians, timely responses, and efficient service. Negative reviews are minimal and do not represent a clear, recurring trend. Overall, the reviews suggest a positive experience with the company, with many customers expressing satisfaction with their HVAC and plumbing needs.

Job Locations and Reviews

Qwentin G.
Qwentin G. Checked in
Client was noticing that their single zone mini split unit was overheating and also under heating. I checked both of the thermistors and both were in spec. I called into tech-support and left my name and number but got no response for over an hour and a half, so I let the client know that we will come back and figure out the issue that it’s having. I turned the remote to act like the thermostat as well. I wanted to see if anything changes.
Merrimack, NH 03054
Review
Excellent service
Kathleen - Merrimack, NH 03054
I completed the gas furnace maintenance today. I started off with checking all the wiring connections and the capacitor, everything looked good. I pulled and cleaned the flame sensor. I replaced the air filter with a 20 x 25 x 5 air bear filter. I checked incoming and outgoing gas pressures and everything was according to manufacture specifications. Lastly, I ran the unit and performed a combustion analyzer test to check for CO, CO2 and oxygen levels and everything was running great!
I completed the gas furnace maintenance today. I started off with checking all the wiring connections and the capacitor, everything looked good. I pulled and cleaned the flame sensor. I replaced the air filter with a 20 x 25 x 5 air bear filter. I checked incoming and outgoing gas pressures and everything was according to manufacture specifications. Lastly, I ran the unit and performed a combustion analyzer test to check for CO, CO2 and oxygen levels and everything was running great!
Qwentin G.
Qwentin G. Checked in
I completed the gas furnace maintenance today. I started off with checking all the wiring connections and the capacitor, everything looked good. I pulled and cleaned the flame sensor. I replaced the air filter with a 20 x 25 x 5 air bear filter. I checked incoming and outgoing gas pressures and everything was according to manufacture specifications. Lastly, I ran the unit and performed a combustion analyzer test to check for CO, CO2 and oxygen levels and everything was running great!
Merrimack, NH 03054
Review
Excellent Service
Sharon - Merrimack, NH 03054
Mark D.
Mark D. Checked in
Install garbage disposal and humidifier shut off
Merrimack, NH 03054
Merrimack, NH - Pm on oil boiler,snaked master bath drain,replaced cartilage on hallway bath faucet (cold water side) Repaired drain on kitchen sink
Mark D.
Mark D. Checked in
Pm on oil boiler,snaked master bath drain,replaced cartilage on hallway bath faucet (cold water side) Repaired drain on kitchen sink
Merrimack, NH 03054
Review
Excellent
Sharon - Merrimack, NH 03054
Lennox gas furnace maintenance. Replace toilet fill valve. Fix humidifer. Install hole home sediment water filter. Gina from the office will call to schedule the garbage disposal and supply valve replacement. Thank you!
Lennox gas furnace maintenance. Replace toilet fill valve. Fix humidifer. Install hole home sediment water filter. Gina from the office will call to schedule the garbage disposal and supply valve replacement. Thank you!
Jack D.
Jack D. Checked in
Lennox gas furnace maintenance. Replace toilet fill valve. Fix humidifer. Install hole home sediment water filter. Gina from the office will call to schedule the garbage disposal and supply valve replacement. Thank you!
Merrimack, NH 03054
GSMS Homeclub heating visit. All heating systems were gone through. There were no repairs found today. The damper for garage zone seemed to have a loose wire at the zone panel. I cycled it a few times and it was opening and closing. I replaced the 16x25x3 filter for basement air handler. You're all set & thank you!
GSMS Homeclub heating visit. All heating systems were gone through. There were no repairs found today. The damper for garage zone seemed to have a loose wire at the zone panel. I cycled it a few times and it was opening and closing. I replaced the 16x25x3 filter for basement air handler. You're all set & thank you!
Jack D.
Jack D. Checked in
GSMS Homeclub heating visit. All heating systems were gone through. There were no repairs found today. The damper for garage zone seemed to have a loose wire at the zone panel. I cycled it a few times and it was opening and closing. I replaced the 16x25x3 filter for basement air handler. You're all set & thank you!
Merrimack, NH 03054
Adam P.
Adam P. Checked in
Bad condensation pump. Replaced
Merrimack, NH 03054
Completed the furnace maintenance today. Started off checking all electrical connections and the capacitor and everything looked good. I replaced the air filter that the client supplied. I pulled and cleaned the flame sensor. Flushed the condensate pump with cleaner. I checked incoming and outgoing gas pressures and everything was according to manufacture specifications. I performed a combustion analyzer test to check for CO, CO2 and oxygen levels and everything looked great. I replaced the humidifier pad and when I went to test the humidifier for operation, it was not working. I found that the solenoid valve had failed. We will get Mark on the schedule to come out here to figure out the water banging sound.
Completed the furnace maintenance today. Started off checking all electrical connections and the capacitor and everything looked good. I replaced the air filter that the client supplied. I pulled and cleaned the flame sensor. Flushed the condensate pump with cleaner. I checked incoming and outgoing gas pressures and everything was according to manufacture specifications. I performed a combustion analyzer test to check for CO, CO2 and oxygen levels and everything looked great. I replaced the humidifier pad and when I went to test the humidifier for operation, it was not working. I found that the solenoid valve had failed. We will get Mark on the schedule to come out here to figure out the water banging sound.
Qwentin G.
Qwentin G. Checked in
Completed the furnace maintenance today. Started off checking all electrical connections and the capacitor and everything looked good. I replaced the air filter that the client supplied. I pulled and cleaned the flame sensor. Flushed the condensate pump with cleaner. I checked incoming and outgoing gas pressures and everything was according to manufacture specifications. I performed a combustion analyzer test to check for CO, CO2 and oxygen levels and everything looked great. I replaced the humidifier pad and when I went to test the humidifier for operation, it was not working. I found that the solenoid valve had failed. We will get Mark on the schedule to come out here to figure out the water banging sound.
Merrimack, NH 03054
Gsms HomeClub furnace maintenance. Everything went great. I also replaced the upstairs thermostat.
Gsms HomeClub furnace maintenance. Everything went great. I also replaced the upstairs thermostat.
Jack D.
Jack D. Checked in
Gsms HomeClub furnace maintenance. Everything went great. I also replaced the upstairs thermostat.
Merrimack, NH 03054
Jack D.
Jack D. Checked in
Expansion tank small leak. I un-threaded it completely and reapplied Teflon tape and pipe dope. I tested for leaks and all is set. Covered under labor warranty. Thank you!
Merrimack, NH 03054
Jack D.
Jack D. Checked in
Replace Zone Damper.
Merrimack, NH 03054
Mark D.
Mark D. Checked in
Tighten expansion tank
Merrimack, NH 03054
Performed the furnace maintenance today. I started off with checking all the wiring connections and everything looked good. I replaced the 20 x 25 x 5 air bear filter and the humidifier pad. I pulled and cleaned the flame sensor. I checked the capacitors and those were both good. I checked the gas pressures and everything was within manufacturer specifications. Lastly, I ran the unit and performed a combustion analyzing test for CO, CO2 and oxygen levels and everything was running great.
Performed the furnace maintenance today. I started off with checking all the wiring connections and everything looked good. I replaced the 20 x 25 x 5 air bear filter and the humidifier pad. I pulled and cleaned the flame sensor. I checked the capacitors and those were both good. I checked the gas pressures and everything was within manufacturer specifications. Lastly, I ran the unit and performed a combustion analyzing test for CO, CO2 and oxygen levels and everything was running great.
Qwentin G.
Qwentin G. Checked in
Performed the furnace maintenance today. I started off with checking all the wiring connections and everything looked good. I replaced the 20 x 25 x 5 air bear filter and the humidifier pad. I pulled and cleaned the flame sensor. I checked the capacitors and those were both good. I checked the gas pressures and everything was within manufacturer specifications. Lastly, I ran the unit and performed a combustion analyzing test for CO, CO2 and oxygen levels and everything was running great.
Merrimack, NH 03054
Review
Quentin was awesome he was very professional, respectful and extremely knowledgeable and competent. Great personality. and exhibited interpersonal and communication skills.
Ronald - Merrimack, NH 03054
Qwentin G.
Qwentin G. Checked in
Completed the furnace maintenance. I replaced the humidifier pad and put it into winter mode. I cleaned the flame sensor. I checked all the wiring connections and everything looked good. I checked incoming and outgoing gas pressures and everything looked good. Lastly I ran the unit in low and high fire and I checked the CO, CO2 and oxygen levels and everything was according to manufacture specifications.
Merrimack, NH 03054
Merrimack, NH - We replaced the pressure reducing valve. Completed a furnace maintenance. Replaced the humidifier pad and put it in winter mode. The clients air filter was clean so he wanted me to leave a new one with him that he could replace. Checked all the wiring connection everything looked good. I cleaned the flame sensor. I checked incoming and outgoing gas pressures and everything looked good. Lastly, I ran the unit and performed a combustion analyzing test. I checked for CO, CO2 and oxygen levels and everything looked great.
Mark D.
Mark D. Checked in
We replaced the pressure reducing valve. Completed a furnace maintenance. Replaced the humidifier pad and put it in winter mode. The clients air filter was clean so he wanted me to leave a new one with him that he could replace. Checked all the wiring connection everything looked good. I cleaned the flame sensor. I checked incoming and outgoing gas pressures and everything looked good. Lastly, I ran the unit and performed a combustion analyzing test. I checked for CO, CO2 and oxygen levels and everything looked great.
Merrimack, NH 03054
Today I completed a maintenance on your Goodman propane furnace. I also completed a maintenance on your Rinnai tankles water heater. Everything went well and there were no repairs found at this time. Thank you! Please see maintenance for for details of what was done today.
Today I completed a maintenance on your Goodman propane furnace. I also completed a maintenance on your Rinnai tankles water heater. Everything went well and there were no repairs found at this time. Thank you! Please see maintenance for for details of what was done today.
Jack D.
Jack D. Checked in
Today I completed a maintenance on your Goodman propane furnace. I also completed a maintenance on your Rinnai tankles water heater. Everything went well and there were no repairs found at this time. Thank you! Please see maintenance for for details of what was done today.
Merrimack, NH 03054
Mark D.
Mark D. Checked in
Replaced hot water heater and pm on furnace
Merrimack, NH 03054
Review
Never problem with GSMS! They have installed and serviced my furnace and AC for 27 years. Over the years Mark has gone out of his way to fix problems and now crew is continuing his great service! I have recommended them to many people.
Joseph - Merrimack, NH 03054
Jack D.
Jack D. Checked in
Replace outdoor frost free water spigot.
Merrimack, NH 03054
Repaired 1/2" water line and 3" drain line
Repaired 1/2" water line and 3" drain line
Mark D.
Mark D. Checked in
Repaired 1/2" water line and 3" drain line
Merrimack, NH 03054
Review
Very good experience - good communication from Gina about scheduling. Techs (Jack and Qwentin) showed up on time and completed the job (new hot water heater and related cleanup) efficiently.
Ann - Merrimack, NH 03054
Review
Qwentin is a valued team member of GSMS (Granite State Mechanical Services). He is friendly and knowledgeable
Tom F - Merrimack, NH 03054
Review
Qwentin was on time and provided excellent service as always
Tom F - Merrimack, NH 03054
Replace 40 gallon power vented propane. Gina will call to schedule an estimate for a system replacement. Thank you!
Replace 40 gallon power vented propane. Gina will call to schedule an estimate for a system replacement. Thank you!
Jack D.
Jack D. Checked in
Replace 40 gallon power vented propane. Gina will call to schedule an estimate for a system replacement. Thank you!
Merrimack, NH 03054
Qwentin G.
Qwentin G. Checked in
Found the Mr. cool mini splits were low on charge so they wouldn’t turn on at all. Error code PC 03.
Merrimack, NH 03054
Mark D.
Mark D. Checked in
Replaced shower drain
Merrimack, NH 03054
I performed a furnace maintenance. I checked all electrical connections and everything looked good. I replaced the humidifier pad. I replaced the air filter that the client supplies. I checked the gas pressures and those were inspect. I ran the unit in high and low fire and performed a combustion analyzing test. I checked the CO, CO2 and oxygen levels and everything was within manufacturer specifications.
I performed a furnace maintenance. I checked all electrical connections and everything looked good. I replaced the humidifier pad. I replaced the air filter that the client supplies. I checked the gas pressures and those were inspect. I ran the unit in high and low fire and performed a combustion analyzing test. I checked the CO, CO2 and oxygen levels and everything was within manufacturer specifications.
Qwentin G.
Qwentin G. Checked in
I performed a furnace maintenance. I checked all electrical connections and everything looked good. I replaced the humidifier pad. I replaced the air filter that the client supplies. I checked the gas pressures and those were inspect. I ran the unit in high and low fire and performed a combustion analyzing test. I checked the CO, CO2 and oxygen levels and everything was within manufacturer specifications.
Merrimack, NH 03054
Jack D.
Jack D. Checked in
Replace 40 gallon natural gas atmospheric water heater.
Merrimack, NH 03054
I performed a furnace maintenance. I started off with checking all the wiring and tubing connections and everything looked good. I checked the inducer motor capacitor, and that was inspect. I replaced the air filter that the client supplies. I replaced the humidifier pad. I flushed the trap and the condensate pump with cleaner. I ran the unit and checked the gas pressures and they were inspect. I did a combustion analyzer test for CO,CO2 and oxygen levels and they were within manufacture specifications. Everything looks and runs great!
I performed a furnace maintenance. I started off with checking all the wiring and tubing connections and everything looked good. I checked the inducer motor capacitor, and that was inspect. I replaced the air filter that the client supplies. I replaced the humidifier pad. I flushed the trap and the condensate pump with cleaner. I ran the unit and checked the gas pressures and they were inspect. I did a combustion analyzer test for CO,CO2 and oxygen levels and they were within manufacture specifications. Everything looks and runs great!
Qwentin G.
Qwentin G. Checked in
I performed a furnace maintenance. I started off with checking all the wiring and tubing connections and everything looked good. I checked the inducer motor capacitor, and that was inspect. I replaced the air filter that the client supplies. I replaced the humidifier pad. I flushed the trap and the condensate pump with cleaner. I ran the unit and checked the gas pressures and they were inspect. I did a combustion analyzer test for CO,CO2 and oxygen levels and they were within manufacture specifications. Everything looks and runs great!
Merrimack, NH 03054
Review
Excellent in all areas of service. Punctual, courteous, kept us well informed of service progress. Upon completion of the furnace installation Adam explained all features of the new system , and addressed questions . The above statement can be said of all GSMS employees as we have used them over the years for several different systems installation. Excellent in all areas.
Bob M - Merrimack, NH 03054
Review
Excellent service
Sylvie - Merrimack, NH 03054
Review
Friendly and knowledgeable
Trevor - Merrimack, NH 03054
Review
Everything is working great!
Brendan - Merrimack, NH 03054
Review
GSMS helped us out after I discovered water surrounding the furnace. Qwentin quickly found the issue, explained what happened and what needed to be fixed. Great communication, excellent service, and he left the area cleaner than he found it. GSMS is always a pleasure to work with.
Sam - Merrimack, NH 03054
Review
Five Stars
Ellen - Merrimack, NH 03054
Review
Couldn’t have asked for a better installation of dishwasher/toilets. Mark was very personable and professional. Arrived on time and finished on time. Excellent experience
Wayne - Merrimack, NH 03054
Review
Very professional in all respects.
BJ - Merrimack, NH 03054
Review
I have been working with GSMS for close to 8 or 9 years now. Had them replace my entire HVAC system and on demand hot water heater installed. Today just had my annual service for my HVAC unit done. They really do great work and all their technicians are very skilled and knowledgeable. I highly recommend them for anybody for your HVAC and plumbing needs!
Scott - Merrimack, NH 03054
Review
Great overall service, always has done a great job for me!
Al - Merrimack, NH 03054
Review
Mark and his entire team do a wonderful job. Show up on time and treat your home with respect. Recommend them without reservations.
Tom - Merrimack, NH 03054
Review
Outstanding service
Al - Merrimack, NH 03054
Review
Granite State Mechanical Services has been serving our home for 30 years. They show up on time, complete the work and treat your home with respect. I recommend them to all our neighbors.
Tom - Merrimack, NH 03054
Review
Excellent service
Philip - Merrimack, NH 03054
Response from GSMS Air•Heating•Plumbing:

We count ourselves lucky for customers like you and look forward to working with you again in the future!

Review
Great service as always. Turned out grandchildren tired off the emergency gas shutoff when they were playing some game
Thomas - Merrimack, NH 03054
Response from GSMS Air•Heating•Plumbing:

Thank you for taking the time to leave such a positive review! We're glad to hear you had a great experience with us.

Review
Your GSMS team set the standard in your business area for integrity, honesty, performance and quality. They are courteous and we trust them being in our home.
Ronald - Merrimack, NH 03054
Review
claire lafond - Merrimack, NH 03054
Response from GSMS Air•Heating•Plumbing:

Thank you so much for the 5 stars, Claire! We’re grateful for your support and truly appreciate you choosing GSMS. It means a lot to our family and our entire team. – Zak D., Second-Generation Owner

Review
High recommend. Called GSMS because of a leak. Jack arrive and within minutes diagnosed the problem - and fixed it. Thank you
Ann - Merrimack, NH 03054
Review
As usual, Jack's work is stellar.
Bob Bedrosian - Merrimack, NH 03054
Response from GSMS Air•Heating•Plumbing:

We are so glad to hear that you had a good experience.

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