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System pressure and efficiency

Gary_31 Member Posts: 7
Ok I have no idea on this so I come, again, to the experts...

Installed a Weil McLain Ultra 105 two months back. It's been running ever since and I've saved a ton of money with our old cast iron radiator system. (Month one we saved 20% gas usage compared to a similar average temp day last winter, Month two we saved 30% gas usage compared to a similar month last winter).

System works wonderfully, been running constantly since install (running with no thermostat, just outdoor reset). Indoor temps have actually been several degrees too warm and I am looking forward to adding TRV's over the summer. I would recommend this solution to anyone with hot water and natural gas. The house is more comfortable than it's ever been.

Today, a fairly cold day, I went down to turn down the temperature a little more (70 deg at 70 / 180 deg at -10). While looking at the panel I noticed the system water pressure has dropped a bit, so I looked around for leaks.

When the system was installed, one of the flanges on the supply side circulator could stand to be tightened a bit more and it drips (has since install). I get (maybe) one drop per minute or two. So over 2 months the system has dropped it's pressure quite a few pounds. (I am not concerned about the pressure drop, I'm confident we'll tighten the flange when the season ends if the minerals have not stopped the drop by then). (I could just pour a little salt on it to expedite the corrosive process).

I am not going to tighten the flange anymore now because I risk fracturing the flange or cast iron it feeds into. That would be very bad in the middle of winter.

The house is 4 stories so we set the expansion tank and system initially to 28 lbs and filled it up, then bled all the radiators. With two exceptions (bathrooms) all the radiators above the second floor are turned off at the valve (we don't use the space).

The system pressure has dropped over two months, due to the slow drip, to about 15psi but we still get all the heat we need (even on the forth floor). I have no reason to believe their is any air in the system, it's just running at a lower pressure than it did on day one.

So here's the question:
Would I gain any efficiency by adding water to the system to get the pressure back up? Is there any reason to top off the system?


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    You need...

    1/2 PSI pressure at the boiler for each foot fo vertical elevation, PLUS 5 PSI to keep it from boiling on top.

    THere is no real corelation between water pressure and efficiency provided you follow the above guidelines. Your decrease in fuel consumption has more to do with the boiler working longer cycles as it gets cooler outside.

    NO leak is a good leak....

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Gary_31
    Gary_31 Member Posts: 7

This discussion has been closed.