Before and After Photos

Andrew Stern

Thank you Dan, and the wealth of information this site makes available.

Originally...
Gravity, natural gas system (nee coal) circa late 1920’s
175 gallon and lots of heavy iron
It went "free to good home"

Upgraded with (a used but cheap) 125K Slant-Fin Galaxy
4-speed B&G circ pump
System bypass
Throttle valves, isolation valves, test pots and gauges out the wazoo

Sort of a test-bed to prove the size, maybe get a few years and then change-out easily when need be.

A great site. Thanks all !!!!


Andy

Mike T., Swampeast MO

Looks Nice!

...and eerily familiar in the way the mains arrive at the boiler...

I noticed that you brought your supply and return main pairs together in "bullhead fashion" to the boiler supply & return lines. Supposedly this doesn't have a prayer of evenly balancing the flow between the two branches. But for the life of me, I don't see how the alternative of using the straight flow path for one and the branch for the other could be much or any better.

I did mine similarly and didn't seem to have any balance problems for the year without the TRVs and certainly none after. Perhaps this is another "oddity" about old gravity systems due to their nearly non-existant head loss. Dunno.

Comments?

Andrew Stern

Before & After: Balancing

Mike...

I was concerned about balancing too, so I added three old style gate valves to act as variable restrictors that are easy to adjust. You can see them if you look close. I put one on each of the return lines and one on the by-pass. So far I haven’t needed to adjust them as the flow seems to want to distribute evenly. I did throttle the bypass down, but I’m not sure I’m done finding the best setting. When cold weather hits I anticipated playing with the return valves (probably just one of them if needed to balance the flow), and by-pass then leave them forever.

I’m not an HVAC guy, just a homeowner. The biggest issue I have is if I should leave the pump on all the time (I have been advised to do that) and if I can do anything about the fact that the house warms up before the supply temp gets above 120 this time of the year. I can keep a delta-T to about 20 degrees, but even opening the by-pass fully and slowing down the pump doesn’t drive the boiler temp up too quickly. Overall, I’m happy with the project and it’s a BIG change.

Andy

Mike T., Swampeast MO

Have always been told and read that gate valves should only be used fully open or fully closed--not exactly certain why, but one guess would be that with the gate in the flowpath it might erode a bit and no longer close fully; other would be that it leads to "freezing" of the valve into position. Since you're not using it as a shut-off the first problem shouldn't be of concern, but the second? Have also been told and read that gate valves should be "exercised" by fully opening and closing them at least once a year.

Regarding your circulator: in all honesty I think you're just wasting electricity and even some heat by operating it constantly on your system. Why? 1) The piping and radiation have LOTS of mass and LOTS of water content--they continue to give off the heat nice and gently LONG after the circulator stops. 2) With the circulator constantly operating your boiler is now continually supplied with the BTUs that would normally stay in the piping and radiation--it'll just become an extremely effective radiator right up the flue.

Number 2 was my problem with constant circulation and TRVs. In moderate weather I'm quite confident that at least 80‰ of the boiler input was being wasted--much of it during the burner "off time" between cycles.

Not at all surprised at your low temperatures--you're probably in a cooler climate as such seems higher than I'd suspect!

Really hard to get much delta-t in the system itself in a gravity conversion--you have to keep the flow rate quite high to ensure full circulation--only sure way I know to get the delta-t back is to use TRVs.

Have fun with your measurements! You'll likely find things that just seem weird--such appears the norm with gravity conversions.

I started down nearly the same path towards understanding and efficiency 10 years ago. First it was insulation/weatherization, then bypass (none was on the 1970s Weil-McLain plain iron boiler), then TRVs, and now finally a Vitodens. Each step improved some things and made others worse. In "adjusted" money however, and even if I hadn't done most of the work myself, the final system was proportionatly MUCH less expensive than the original in the 1920s! An old kit house catalog I have shows that materials alone for a two-pipe gravity hot water system were easily 25% of the total material cost for the complete home!

Andrew Stern

Before & After

Mike…

I agree with what you have heard about gate valves and have some first hand experience to verify that you definitely want to “exercise the valve” and leave it in the full open/closed position. I used to work in coal mines and the water quality could eat a bronze impeller in a week and typically the stems would corrode. I suspect the valve will do OK in this application for a long time though. Probably longer than me. Basically I was looking for a good (and cheap) regulator with full flow capability. I would have used an orifice plate restriction if I knew what size to go with ahead of time. I marked the valve handwheel recorded the turns. Also intend to remove them.

I am inclined to agree with you also about the circulator not running all the time. From a power cost, the loss is negligible, but I’m not so sure about the flue losses as you say. If this was a low mass system and the convectors came down in temp quick, I could possibly argue that leaving the circ pump on would even the temp out around the house, but with a high mass system, I don’t think it is all that important also. I may run a test.

I wish I could put an auto-damper in the exhaust, but unless I lower the draft-hood (not I good idea I’d suspect) and put it above the hood before the elbow, there isn’t enough room between the elbow and the breaching (unless there is a “low profile” model. I should have put the boiler further into the room. Maximizing floor space was a mistake.

Keep warm
Andy