PRV Leak w/Indirect Fire Oil Water Coil Tank

Steamhead (in transit)

is called an indirect water heater. The coil is the weakness of this type of heater..... if the entire tank needs replacing I'd go with the Triangle Tube Phase 3, which is a tank-in-tank design.

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Jim_150

When this year's heating season started in earnest, the pressure relief valve on the back of our oil burner started leaking. Pressure is routinely at 30-36psi and water temp at 190-220 degrees F. The max temp in the control unit is set for 180.

Our service guy replaced the whole PRV and assembly, but the situation stayed the same. He then replaced our overflow tank because it was waterlogged. Still, the problem remains. His next move will be to replace our water tank, as he thinks there may be a crack in the coil. That will run us about $1700+.

The tank in question is a 30-gallon Bock Turbo-Storr 30CT indirect-fired coil water tank that's probably around 10 years old.

Is our guy on the right track in replacing the tank? I don't understand how the water temp can get as high as high as 220 degrees when the control unit max is set for 180. Doesn't it sound like the water is simply getting too hot and causing the higher pressure?

We've even shut the supply to the water tank off, drained some water out of the boiler to get the pressure down to 15psi, and left it overnight. In the morning, the pressure was back up to 30psi and the PRV was leaking. Doesn't this prove it's not the water tank?

Our guy seems to be very knowledgeable and has over 30 experience, but before I shell out $1700 for what MIGHT fix the problem, I'd like another opinion.

Thanks for any help and info!

Steamhead (in transit)

Sounds like

this is a water-heater being used as a boiler. This is not the best setup IMHO, although the coil does separate the heating system water from the hot faucet water.

Not sure if the coil can be replaced as a separate part from the tank, if not and the coil is definitely bad, you'd have to replace the tank.

Why not consider putting in a proper boiler, using the Bock just for hot faucet water, and simply capping off the bad coil- if that is indeed the problem? Then, when the Bock tank starts to leak, you can put in an indirect tank that is heated from the boiler.

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Jim_150

Oh it's a proper setup...we have the oil burner and boiler units that provide forced hot water to the heating system. The Bock tank provides just the hot water for the kitchen, bathrrooms, and tubs. Sorry, I didn't do a very good job in making that clear.

bruce_21

Sounds like the water feeder to the boiler is letting in extra water. Either it is misadjusted, or the "fast-fill" lever is up, or the diaphram inside it is leaking. Try shutting off the boiler water supply completely (usually a little stop valve in the feed line ahead of the pressure reducing valve, water feeder), use a pair or pliers to make sure you get it tight. Drain water out of the boiler to get the pressur down to 12-15 lbs. Heat expansion od the water is only good for 5-8 lbs. If the water feed to the boiler is closed only a hole between the domestic hot water and the boiler water can be raising the pressure.