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hot water on demand system

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Posted by: from Fort Saskatchewan
2/26/2011 at 6:43:18 PM

I have had trouble with my hot water on demand system since moving in to a new home 2 years ago. Made many calls on the one year builder warranty. A plumber would come out ( a day or two later) and it would be a temporary fix. The hot water goes totally off. You can imagine getting in a shower and it goes frigid. Then you spend the next half hour in the basement or ouside trying to fix it. I have learned how to remove the lint from the trap by removing the fan, how to check for ice build up outside, and how to restart the system. One or the other has worked until this winter. With extended -20 and colder weather the hot water shut off totally. I called the manufacturer, it has a 15 yr. parts waranty. They said its condensation freezing in the line inside the house somewhere. Nothing to do with their system. I have to call a plumber to remedy. In the meantime they said to remove the unit cover so the system could suck air from the house rather than the line outside. This worked initially, but shut off again in a couple days. Then when I tried to restart it, it sounded like a train and started shaking, but started up. Since then the weather is better, the cover is back on and it works again. However, it is harder to get a tub full of hot water. The hot is on full blast and it fluctuates from cold to hot. This unit has really been an inconvenience. Question 1: I heard of someone that had some kind of a box installed on the ouside of the house to prevent the pipes freezing up inside. Does anyone know what this is, and how it's installed and if it will even fix the problem? Question 2: Should the builder have some responsibility since the problem was never fixed.

REPLIES (1)
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Dave in Oshawa
Date/Time3/21/2011 at 11:49:01 PM

I have installed several on demand water heater systems along with troubleshooting existing systems.

There are several things that are required to make them run properly.

First off some units normally require around 60 psi water pressure, which is a city water pressure system. Some do work on well water but most units work on a "water differential switch", so low water pressure means no heat. Some units also require at least 3/4 inch water lines to and from the unit to get the proper pressure differential.

Secondly, depending on the units BTU input/output, it may require at least a 1 inch gas line. In other words the unit is "starving for fuel". I have found, sometimes the gas meter is not large enough to handle the required amount of fuel to operate.

Next check the venting. I kept the venting as short as possible according to the manufacturers installation specs.

All of these things should be in the installation manual. If you don't have one check with the manufacturer. In Ontario we are required to leave the installation manual with the appliance.

I have found that running the unit without the cover on, could end up freezing the unit on a cold night. If your unit is in the basement, the basement could end up in a negative air pressure causing cold air to freeze the water heater. This could cause some serious damage! Some units come with a cold air intake flap. Check with your manufacturer regards this, as this maybe the outside box you are talking about.

I hope this helps your problem. In my opinion, when these water heaters are installed properly, they are wonderful, well worth it.

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