If a tankless water heater is installed in an older home with existing gas lines that serve the furnace and stove, how do you determine if the line is sufficient to supply or if it needs upgrading before the install? Potential problems if the gas line is not large enough: reduced equipment life, increased CO and flue gas condensation, delayed ignition, and reduced performance. Are there any safety concerns if all systems (hot water, stove and furnace) run at the same time?

Views: 210

Reply to This

Replies to This Discussion

The answer is it depends - check the manufacturers specs, they will tell you the size of line needed, etc... if it isn't large enough or you ae not receiving enough through said line you won't get the BTU's needed to bring the temperature up to where you may need it an it can also downgrade the other components also.

I would say generally no on safety concerns though it will impact the burn though in most cases most by-products are caused by incomplete burn do to too little air. My biggest concern would be the stove as most people don't use the exhaust hood

This makes sense, thanks Sean!

Whe I personally installed my gas demand unit in 2010, they had to bring a 3/4 inch line to it, instead of the 1.2 inch line.    I had a 1 1./4 service entering the house, was not a serious issue.  Installed the same day the meter reader was there.   Usage went from 3 MCF per month in summer to 0.5 MCF per month.

Gas design should always take in consideration of all appliances running at the same time.

If all lines are proper size and delivery is normal then there should be no issues These items are normally overspeced. 

I would think net free air to gas fired appliances more of an issue as I have seen water heaters and furnaces slammed into tight spaces clearly not following specs countless times

First the problems - increased CO due to poor combustion, flue condensation delayed ignition, etc. Many potential safety issues.

The plumbing and mechanical code books show a method to size gas lines.The method assumes ALL combustion appliance are operating because that is the most critical condition. The method uses the longest length of gas line, pressure available and gas demand to size gas lines from the table. It is pretty easy to use this method compared to the "friction loss" method found in most fluids engineering text books. Since most plan reviewers and inspectors will compare to this method, it is usually easier to give them what they expect.


Forum Discussions

Indoor Air Quality Monitors and Meters

Started by Rob Madden in General Forum. Last reply by Al Tibbs 17 hours ago. 13 Replies

70 unit building rehab

Started by Jerry Needham in Multifamily. Last reply by Sean Lintow Sr on Saturday. 2 Replies

Linda Wigington Leadership Award Nominations

Started by Diane Chojnowski in General Forum. Last reply by Diane Chojnowski on Friday. 1 Reply

Latest Activity

Laurie DiDonato posted an event

RESNET HERS Rater Hybrid Training (Classroom Section in NH) at Online/ Classroom Component in Manchester, NH

April 29, 2019 at 9am to May 24, 2019 at 5pm
Online Component: NEW- On-Demand Training Modules (with Live Office Hours) Office Hours: April…See More
13 hours ago
Emily Ambrose posted a blog post

City Pages: What They Are & How to Use Them Right

Recently, we have been talking a lot about…See More
17 hours ago
Al Tibbs replied to Rob Madden's discussion Indoor Air Quality Monitors and Meters
"I would take a look at Gray Wolf products. They are the best I have used. I have tried most over…"
17 hours ago
Tommie John added a discussion to the group Energy Auditing Equipment for Sale, Trade or to Purchase

Blower Door and Duct Blaster!

Hey everyone, I have some great items for sale a Minneapolis blower door with dg-700. I also have a…See More
18 hours ago
Tommie John joined allen p tanner's group

Energy Auditing Equipment for Sale, Trade or to Purchase

Discuss the pros and cons of the equipment you are interested in prior to purchase. Post equipment…See More
18 hours ago
Kelly Caplenas posted a blog post

Technology and Customer Service

I read this line in a Forbes article … "Time and technology wait for no one, and customer loyalty…See More
19 hours ago
Diane Chojnowski posted a discussion

EERE Request for Information Concerning Efficient & Flexible Building Loads

The DOE Building Technologies Office has issued a Request for Information to solicit feedback from…See More
19 hours ago

© 2019   Created by Home Performance Coalition (HPC)   Powered by

Badges  |  Report an Issue  |  Terms of Service