Something Just Doesn't sound right about this

scatgo · December 13

I am going to install a weil mclain aqua balance 120 heat only condensing burner. I got the manifold for the unit that has a 1 inch supply and return pipe. The plumbing on my 90 year old furnace has a return pipe of about 1 and a half inch. The supply pipe looks like it is as big as 3 inches. To jump from 1 to 3 inch on the supply doesn't sound right. Will this cause problems?

Jamie Hall · December 13

I wonder if the original system was gravity hot water and later converted to pumped?

No, the change in pipe size by itself won't cause any problems. But… if it was originally gravity and is now pumped, by may have some balancing problems.

JMWHVAC · December 13

I have seen many systems with 1.5" on up to 3" old iron piping going down to 1"or 1.25 at a new boiler and it heats well. As mentioned, some of these may have been gravity flow originally, but another thing is that some of these old buildings have much less heat loss than they did originally due to improvements.

mattmia2 · December 13

your heat loss calculations will tell you. you need about 1 gpm for each 10,000 btu/hr of load. once you know the flow you can use this table to get the pipe size:

https://s3.amazonaws.com/s3.supplyhouse.com/product_files/A1140750-flow%20rate%20chart.pdf

if that was a converted gravity system the pipes will be much larger than needed for pumped circulation

EBEBRATT-Ed · December 13

Good to see the McDonalds Coffee. That's the most important thing before starting work No coffee I go home.

hot_rod · December 13

That boiler with about a 100,000 BTU output needs about 10 gpm at 20∆. Probably connected through a hydraulic sep into the system.

If the secondary side is also designed around 10 gpm, in a 3" pipe that is around .5 fps velocity.

So flow under 2 fps sometimes is tough to get air removed from. The slow fluid speed prevents the air from being carried along with the fluid.

The downfall of old gravity systems was the horizontal branches could not be too long as the gravity driven, slow flow, would not carry heat out. So B&G developed the "booster pump" concept to aid those type of challenges.

It will be interesting to hear what capacity circulator will assure all the rads heat.

Steamhead · December 13

@hot_rod said "It will be interesting to hear what capacity circulator will assure all the rads heat."

Try this:

https://www.heatinghelp.com/systems-help-center/sizing-circulators-for-old-gravity-hot-water-heating-systems/

scatgo · December 14

https://forum.heatinghelp.com/discussion/comment/1877130#Comment_1877130

LOL. If someone should ask me how long do I think it will take to get a job done ill say about three coffees and a pack of smokes.

Ironman · December 14

That looks like an old gravity flow system that’s been/being converted to forced flow. We do a lot of these and the basic rule of thumb that Dan taught us has always worked: divide the size of the gravity piping by half, then go one size smaller for your new, near boiler piping.

One thing that’s very important and that you must address: the old piping and radiators can contain a lot of sludge and rust. You must get it out because it can destroy modern circulators and clog water tube heat exchangers and other components.

We start by flushing the system with water until it returns clear. Expect to use a lot, maybe hundreds of gallons.

Install a Dirt Mag or Sep4 LLH. Add a cleaner like Fernox and check the system after a couple of weeks of running. Repeat flushing as needed.

A standing cast iron radiator is the best natural air separation device. Caleffi has a small air vent that will replace the coin vent on each radiator and can manually and automatically vent the radiator which is where the air in the system will naturally go to and remain until vented.

scatgo · December 14

I do have a gallon of Sentinel X400 System Restorer and a dirt mag on order. Any opinions on the Sentinel X400 System Restorer would be appreciated. The one gallon set me back 150 bucks and I might need to use two gallons.

scatgo · December 14

So the bottom line is the only problem I am more than likely to run into is having a circulator pump that has to low of GPM flow?

scatgo · December 14

https://forum.heatinghelp.com/discussion/comment/1877117#Comment_1877117

Can you give me more detail on what you mean by balancing problems

Steamhead · December 14

If you add a circulator to an old gravity system, and the circ is too big, the water can short-circuit through the rads and they won't heat well. Check this out:

https://www.heatinghelp.com/systems-help-center/sizing-circulators-for-old-gravity-hot-water-heating-systems/

and here's an example of one that was over-pumped:

https://www.heatinghelp.com/systems-help-center/adjusting-the-flow-rate-for-an-old-gravity-hot-water-system/

Jamie Hall · December 15

The hydraulics driving a gravity system are completely different. The usual problem is that the pumped system tends to preferentially flow through the lower radiators, and the upper floors get little or no heat, whereas in a gravity system the hot water preferentially migrated to the upper floors.

Some balancing valves to persuade the water to go where wanted solve the problem.

Intplm. · December 15

And FYI… from here, the first picture above, that pipe looks like it's 2" inside diameter (ID), and the second pipe appears to be 1-1/2" (ID)

scatgo · December 15

https://forum.heatinghelp.com/discussion/comment/1877328#Comment_1877328

Thanks. I just hit the basement and took a closer look. It was the huge nuts on the union that is on both ends of the flow control valve that threw me off. First chance I get I am going to remove some of the insulation so I can get a more accurate measurement. And the circulator pump that is on there now is a taco 007-f3. The specs on it are 23 GPM and everything is keeping me toasty warm. Its possible that things might even get a little better once I dump a couple of gallons of Sentinel X400 System Restorer in the present setup. The only reason I am dealing with this whole situation is because the last couple of winters I got gas bills that were 500+ bucks for at least 4 months during the heating season and not much lower than that for the rest of the winter. That's not going to jive with my retirement plans and is somewhat kicking my azz right now. While we are on the subject of plumbing PB blaster has always worked great for me on automotive situations but i did notice when you spray it on a hot pipe int tends to evaporate kind of fast. I do plan on spraying everything I am going to have to touch at least once a day for about a week or two, but I never had to deal with 98 year old iron pipes. am I heading for a major nightmare when I try to patch into the old pipes?

mattmia2 · December 15

big wrenches will usually unscrew it if you put the wrench on such that it doesn't crush the pipe. if you can't unscrew it, you can cut or shatter the fitting depending on type or cut the nipple out of a fitting and build back from there.

that insulation looks like it is aircell asbestos.

Ironman · December 15

https://forum.heatinghelp.com/discussion/comment/1877317#Comment_1877317

Along with this: the old radiators that were upstairs often had field fabricated orifice plates inside the radiator valves to force flow to downstairs radiators. These plates should have been moved to the downstairs radiators when the system was converted to forced flow.

Something Just Doesn't sound right about this

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