Tankless water heaters

[tspear]

A typical house furnace is 60-80K BTU. So a 200K water heater a larger pipe going it than the furnace.

Wow, that small? My boiler is 350K BTU (installed by previous owner, they did not fix the insulation and just pumped heat). I have a 2in pipe

Tim

 

[Gary Ward]

Wow, that small? My boiler is 350K BTU (installed by previous owner, they did not fix the insulation and just pumped heat). I have a 2in pipe

Tim

I live in a small house, 60K is good for 1000sq ft roughly.
How many sq ft is the 350K boiler heating? Would love to sell you gas for something that big. lol

 

[tspear]

How many sq ft is the 350K boiler heating? Would love to sell you gas for something that big. lol

Good size, 3600sqr ft above ground, and 1200 sqr ft 3/4 basement below grade.
We actually have fixed a lot of the insulation problems (installed double pane windows, added R16 insulation with new siding....) since we bought the house ten years ago. Even though we finished the basement, and gas prices have gone up, our gas bills are down 60% from when we moved in.

Tim1

 

[Sac Arrow]

I have been a LP gas supplier for 35 years.
I have fielded many calls( just hung up with another customer) from customers claiming that the pressure regulator is putting out low pressure causing problems with their tankless water heaters.
It's not the reg, it's the pipe size from the low pressure reg outside the home to the water heater inside the home. Most tankless I have seen are 199000 BTU. When they try to use 3/4 pipe that I see in so many pictures above and the same size they used on their tank water( that is 50,000 BTU) there isn't enough volume to keep your tankless water heater healthy. It will work at first, but will have a shorter life span.

Then add on other gas appliances the over all inlet piping coming into your home must be increased in size to be able to supply 200K btu to the tankless water heater.
It will also damage the house furnace because it is starving for gas too especially when the water heater is running when you have too small of piping.
Can't use the same size piping that you used for a tank water heater on a tankless water heater. People don't believe me but it's true. A typical house furnace is 60-80-100K BTU. So a 200K water heater needs a larger pipe going it than the furnace.

You need a large reservoir of gas right at the water heater inlet valve to supply 199K BTU to keep that water heater happy and 3/4 pipe is not going to do it with propane. Nat gas needs even larger piping.

The tankless water heater manufactures sell a reservoir that goes in the piping right in front of the gas valve to help have enough volume when the heater comes on. But if the over all piping is too small then you will still have problems.
Most of my customers have been putting parts into their 4-5 year old heaters before they call me because they don't have enough gas volume.

My gas piping got reworked so the 1/2" feeds the furnace, and the 3/4" feeds the tankless.

 

[Gary Ward]

My gas piping got reworked so the 1/2" feeds the furnace, and the 3/4" feeds the tankless.

How many btu is your water heater?

If a 2 pound system is used then smaller piping can be used.
But normally 2# systems are for larger cammerical setups.
I don’t know how they do it Cal.
Edit I see your on the east coast.

 

[Sac Arrow]

How many btu is your water heater?

If a 2 pound system is used then smaller piping can be used.
But normally 2# systems are for larger cammerical setups.
I don’t know how they do it Cal.
Edit I see your on the east coast.

The model is Navien MPE 210 A2, which is I guess 180,000 btu looking at the spec sheet. I'm in California - eman1200 and I have switched locations. In any case both seem to work just fine.