# Indirect hwt



## OldSchool (Jan 30, 2010)

Yesterday we changed out an indirect hwt on a boiler system

The tank was only 4 years old

What was happening was the boiler pressure was increasing even with the boiler feed off

Drain boiler down to about 10lbs and in no time it was back to 30 lbs with the boiler not even running

There is a leak on the coil or heat exchanger with in the tank

This morning going to another job to replace heat exchanger on wall hung boiler at an apartment building .,, owner calls last night and describes the same thing that was happening to the other guys...., both tanks are under 5 years old

They both have indirect tanks

We were not the original installers of these systems but have since then took over these buildings

So my question is .... Is this happening to any one else where the indirect tanks are going prematurely. These are not tanks leaking on the out side they are leaking on the heat exchanger inside the tanks where the domestic water pressure is going into the boiler

Sent from my portable office....yes I am at work


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## MarkToo (Dec 17, 2011)

If the pressure is "only" going up to 30 PSI then I would question if the coil is compromised.

I'd be tempted to air test the coil and see the result on the boiler side with the rest of the system isolated.


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## BROOKLYN\PLUMB (May 21, 2010)

OldSchool said:


> Yesterday we changed out an indirect hwt on a boiler system
> 
> The tank was only 4 years old
> 
> ...


Did they have properly sized expansion tanks? I see this especially when thermal expansion is not being controlled


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## OldSchool (Jan 30, 2010)

It's only going to 30 psi because the relief valve on the boiler system starts to blow off

Expansion tanks are sized properly
And on the first one the day before the tank is actually over sized

The thing is even with out the boiler operating the pressure continually increases until the relief valve blows and the boiler feed is turned off

The water pressure can only be coming in from one other source and that would be the coil within the indirect hot water tank

We ran a few test on the first one

Boiler feed off pressure still rising

Then domestic hwt cold valve off and pressure remains constant

Then turn back on cold supply to tank and boiler pressure rises

Then shut off supply and return from boiler to indirect hwt and boiler pressure again remains constant

Therefore the source of additional water pressure is coming from indirect hwt

Sent from my portable office....yes I am at work


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## trick1 (Sep 18, 2008)

We had 2 this past year, both in apartment complexes.

One was a Bock 119 gallon and the other was a Super-Stor Contender.

These complexes were plagued with undersized expansion tanks and every now and again we'd have issues with discharging pressure relief valves.

In this case, an air pressure gauge can be your friend

After ruling out the usual suspects, we ended up with a coil issue.


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## Widdershins (Feb 5, 2011)

I had it happen about a year ago with a Triangle Tube storage tank. It created quite a mess at the manifolds when a couple of the o-rings on the manifolds unions failed.


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## pilot light (Apr 21, 2012)

OldSchool said:


> It's only going to 30 psi because the relief valve on the boiler system starts to blow off
> 
> Expansion tanks are sized properly
> And on the first one the day before the tank is actually over sized
> ...


 What kind of tank is it ?


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## GrumpyPlumber (Jun 12, 2008)

The reason the pressure stops at 30psi, the boiler PR is set for 30psi.

I use Superstor, 316 SS tank, lifetime warranty, and unlike Amtrol, the "guts" aren't hidden - I have had more than a few warranty's honored by Superstor, they don't bat an eye, regardless how old.


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## vinpadalino (Aug 27, 2010)

Had a problem with a John Wood. Do a water test make sure waters not corrosive..


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