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Slow Heating Radiator? With Thermal Images!

First, let me say thank you to Gerry Gill who has been a huge help to me. He has helped me to understand much about my system. I wanted to show these images to The Wall because I think they are really interesting, and to see if anyone else had thoughts on what we're seeing. Gerry after all is a busy guy just like the rest of us - so I figured it would be a good idea to pose my questions to many experts instead of just one.

Thanks again to Gerry and everyone here. This is a really great community.

About the system:

Mouat Vapor 2-pipe system (built in 1930)

Operates at about 2oz pressure (new vaporstat makes sure it's less than 6oz, but it has never stopped the boiler due to pressure - apparently the system just runs on low pressure all by itself!)

About the pictures:

Timestamps are valid, but temperature values are obviously not. I still believe the images show the correct temperature deltas, but the values are wrong due to calibration problem or a setting in the camera that I have not found yet.

All of these images are looking at the same radiator over a period of 21 minutes (from the time steam enters the supply pipe, until the thermostat shut off the boiler).

About the radiator:

American Radiator Company.

8 sections

4 columns

37 inches from floor to top, about 34 inch high sections

What I think these images are showing me:

I believe the Mouat valves are acting like orifices and allowing me to control how much steam enters each radiator. This radiator in particular seems to me to have a bit of a flow restriction. I believe this because in one image you can see the radiator in the next room with steam filling the radiator at a faster rate - this is assuming that the steam reached both of these radiators at the same time. I believe that I am happy about these valves acting as 'flow controls' because the trap seems to be broken in the open position. So I am controlling the 'entry door' instead of controlling the 'exit door' to borrow some phrases from Gerry Gill.

This is allowing me to essentially have no working traps, but not waste steam since the radiators never fill completely before the thermostat is satisfied.

My questions:

Assuming that my above thoughts are correct - please tell me if you disagree - my question is about the time to heat this radiator. Is there a way to calculate how quickly steam should fill a radiator given an open 1/2" supply pipe, 2oz of pressure, and no trap?

It seems to me that the radiator should be fully hot in less than 21 minutes given how quickly the steam gets from the floor to the valve (about 20 seconds) - so do I have a valve that isn't all the way open, or does it just take that long to heat this radiator?


  • air in the way?

    how is the air in the supplies [and boiler], getting out.

    maybe some main vents at the end of the suppies would enable the air to escape more quickly?--nbc
  • butlermog
    butlermog Member Posts: 50

    This picture shows my vents. I believe they are all Hoffman 75's. The single vent to the left in the picture is at the end of the supply main - as far away from the boiler as possible where the two mains meet (I think).

    The other two vents are on the end of the return - which I think is normally how a Mouat system was installed. The one vent on the main looks to have been added sometime later.

    At current, those two vents are not installed to give maximum venting. Instead the pipes are open to the air. We did this after we calculated the A and B dimensions and proved that it would take more than 1 pound of pressure to move the water that high. And since the vaporstat would shut the boiler down long before that we could live without them attached. It sounded crazy to me at the time, but we've never had an issue with the vents not attached.

    Obviously more venting could be added to the main, but since the steam is reaching my radiators pretty quickly I don't think it is needed - or am I convincing myself of things that aren't true?
This discussion has been closed.