Jan 23, 2012, 10:12 AM
Post #23 of 25
Re: [whynotwrite] Tankless water system
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Reading the manual to the OD heater is very important. It does explain the fact there is a flow sensor that must "see" water flowing before the gas is opened. No water flow, no gas, no hot water. In Mexico the problem is low pressure in almost all cases.
This turns out to be a do it yourself project since finding someone who will read the instruction manual and install the OD water heater per specs is not easy. Plus the fact the install is going to cost you more due to the water pressure problem. Rotoplas sells a booster pump, a neat little designed pump, that is made to correct the problem of low water pressure and will be part of the install cost in most cases.
On Demand water heaters use a fraction of the gas of tank type water heaters. Installation per the manual´s specs is more costly than you might wish but you will likely see the gas savings in less than 2 years. Getting someone to install it per spec. it seems is the hardest part of the project.
What specific OD water heater models and brands have you found work well and reliably?
sfmacaws experience is similar to the one we installed for a friend. His hydropneumatico is a large capacity, reliable system set to 25 - 30 psi of working pressure. The Bosch OD units sold in Mexico simply do not work as advertised, even when installed by a professional, precisely following the manufacturer's instructions.
As sfmacaws described, even when the official Bosch technicians come out and inspect and try to adjust - even with pressure systems - these systems simply do not work as expected. Do we imagine that 4 different official Bosch technicians do not know how to install or maintain their own hardware?
Continuing with other brands:
I've installed and worked on "Cinsa de Paso" and "Cal-O-Rex" units - where the manufacturer uses a high capacity burner and a cylindrical tank with special baffles for transferring heat - no flow sensors and no pressure sensors - and these work for about 6 months to a year - then they fill up on the bottom with solid sarro - scale - filling as much as 1/3 of the tank with a big block of near solid white crystalline CaCO3 that reduces capacity and causes the heater to shut off prematurely. Rinsing does not help. Adding a liter of muriatic acid helps a little - but may be hard on the copper tank. The best solution we've found is to remove the Zn rod, and ram a piece of 3/4 in PVC down the hole - over and over - to break up the block of crystallized scale - and also remove the drain valve to offer a drain hole big enough for chunks to come out, and then use a hooked wire to fish out the chunks through the drain cock hole, while flushing with water and chopping/poking with the PVC... The last one took 45 minutes of chipping and flushing to remove a substantial pile of sarro chunks.
Is this really a big savings, when it takes disassembly and 30-45 minutes of vigorous messy effort to keep an OD heater running and not shutting down prematurely?
Indugas's Splendid OD units have been the most reliable OD heaters we've found here - not finicky with low pressure - but their capacity is quite small.
Really, unless you know the specific brand of heater, how sensitive it is to flow or pressure, and how quickly they plug up (even the Bosch units plug up rapidly when they do work), then the advice of people who have not installed and maintained your specific unit for more than a year, probably does not fit the quirks of your specific OD heater.
I've only worked on about 9 OD units here in Mexico, and only one has worked as hoped for.
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