Yes, you can close in a furnace and water heater, but ensure proper ventilation and access for maintenance and safety compliance with local codes.
Many homeowners wonder if it’s safe to install a furnace and water heater in the same enclosed space. While possible under specific conditions, this setup requires careful planning to avoid safety hazards and ensure proper operation of both appliances.
Key Considerations for Shared Utility Closets
When placing a furnace and water heater in the same closet, several critical factors must be addressed:
Combustion Air Requirements
Both appliances need adequate combustion air to operate safely. The International Fuel Gas Code specifies minimum air supply requirements based on appliance BTU ratings. High-efficiency appliances may have different needs than standard models.
Venting Compatibility
Never combine natural draft (atmospheric vent) appliances with power-vented or direct-vent units in the same flue. As noted in forum discussions: “The natural draft appliance should not be connected into the portion of the mechanical draft system operating under positive pressure.”
Clearance and Service Access
Maintain proper clearances (typically 30 inches front, 6 inches sides/rear) for servicing. One forum user observed: “Water Heater has to be removed to service the HVAC (Closet Install with a 30 inch bifold door).”
Potential Safety Hazards
Carbon Monoxide Risks
A major concern is CO backdrafting from the water heater into furnace return air. As one professional warned: “The return on the furnace will draw CO from the flue of the Water heater when ever both are operating at the same time.”
Rust and Corrosion
Forum participants noted rust on appliances in shared spaces, indicating potential moisture issues. Proper venting and combustion air can prevent this.
Service Difficulties
Tight spaces make maintenance challenging. One inspector reported: “I could not open the furnace, tight behind a bifold door which I was not willing to remove.”
Code Requirements and Best Practices
| Requirement | Details |
|---|---|
| Combustion Air | 50 cu. in. per 1,000 BTU input for standard appliances |
| Clearance | Minimum 30″ front, 6″ sides/rear for service access |
| Venting | No mixing of natural draft and power-vented appliances |
For optimal safety, consider installing a CO detector near the enclosure and maintaining proper documentation of all installations.
When to Call a Professional
Consult an HVAC technician if you notice:
- Rust on appliance surfaces
- Soot accumulation
- Difficulty accessing units for service
- Unusual noises during operation
As noted in the forum discussion, many professionals recommend evaluation when appliances share tight spaces, especially if service access is compromised.
Alternative Solutions
If space constraints prevent proper installation:
- Consider tankless water heaters that can be wall-mounted
- Explore direct-vent furnace options
- Create separate compartments within the utility space
Proper installation ensures both safety and efficiency for your home’s heating systems.
