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Tankless Water Heater

Hi all:

During the summer of 2008 I installted a tankless water heater (Bosch Aquastar 1600H-NG) in my 102 year hold home. After some modifications to the water and gas lines it seemed to work rather well though it never delivered the savings on natural gas that it claimed.

When the weather here in PA began to get colder I noticed that my hotwater took longer to heat up and evenutally I had to turn the power on the unit to maximum (90* rise). However, for the past week or so I've had almost zero hot water output. I've traced the problem back to gas flow. When my gas furnace fires up I see a noticeable drop in the gas pressure to the water unit and if it is running the flames die down. All of the gas lines to the unit are run with 3/4" black iron as per the manufacturer's specifications, as are the rest of the gas lines in my home. I believe the problem stems from my gas meter restricting flow.

Currently, my main service comes in through 1 1/2" galvanized which is then shrunk down to 1/2" to the meter. The meter then expands to 3/4" for my lines. The meter itself has no restrictions and is connected to the downsized 1/2" pipe via a coupler which is 1".

My questions are as follows:

1) Can I simply convert the lines to the gas meter back to 3/4" (or 1" perferably)?

2) Has anyone else in the 19095 zip code (or surrounding area) installed a tankless unit and run into a gas flow problem?

3) Do these types of units really offering a savings over a tank? I like the idea of not storing excess water and would really like to make this unit work.

Any insight out there would be a huge help. Thanks!

Re: Tankless Water Heater

Just some thoughts ...

A couple of things that need to be verified when installing these systems are ...

1 - water flow and pressure

2 - gas flow and pressure.

Since this unit was installed in the summer no doubt it functioned well for a couple of reasons. The temperature of the incoming water is typically warmer than in the winter. As you know the colder the incoming water temperature and the greater the temperature rise of heating that water reduces the output from the unit. Simply it takes longer to warm cold water .... so the flow through the unit has to slow down.

The other reason it was working well during the summer was you weren't using gas for your heating system.

In your installation instruction manual it would describe the proceedure for testing to see if there is enough gas supply and checks for static and operation pressures.

As it will describe the sizing for the gas piping .... the 3/4 is the size of connection at the unit and would be the minimum size of piping ..... but that depends on how long a run of pipe. If it's 20 feet or shorter it should be fine.

However .... this is also dependant as to the supply to the home. In other words the total BTU demand from all gas appliances would have to be calculated along with the distance of run from the meter would determine the size of pipe from the meter.

Based on what you have described it sounds as though the size of pipe is undersized to supply all the BTU demand for all the gas appliances.
Depending on what your furnace input BTU and the input BTU of the water heater and any othe gas appliance may require a 1 inch line ..... depends.

As for cost efficiency ... the unit itself is in the neighborhood of 75-80% efficient while running. So ... around 20 cents for every dollar is going out the exhaust ..... which is better than a conventional tank type.
I would suspect during the winter it would probably be a little less saving since the unit has to run a little longer to output hotwater at a slower rate.

However .... because your system doesn't sound like it running properly you will probably see less saving until it's running properly.

Hope this helps.:)

Re: Tankless Water Heater

Hi, thanks for the reply!

I think we are own the same page. My concern is obviously that I'm not getting enough pressure to run all gas appliances. However, I think that this stems from 1/2" pipe on the gas main to the meter. This is definitley reducing the flow.

Can I simply re-pipe the meter?

Re: Tankless Water Heater

You are welcome.:)

As for the question ... I think the answer would likely come from your gas utility company. They should also be able to provide the size requirement based on the total BTU demand of all the gas appliances and even do a pressure test.

Good luck and let us know how you make out.

Re: Tankless Water Heater

Is there a regulator somewhere in the gas piping?

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