My system works, but why?

jim armstrong_2

I have a single story house with a monoflo system installed. The main is 1-1/4" with two 1' branches. I installed a Lochinvar Knight boiler on the main, piping it Primary/Secondary. The tees are 1-1/4" x 1" and are 5-1/4" c to c. I left the existing cast iron boiler on the system using the B & G pump as the primary pump. Originally intended to bypass and use it as a back up, (have not done so to date). I have however disconnected the primary pump, (No power but the pump is still in place) and the boiler is set to pilot only. When my wife wanted to turn on the heat I told her to just turn it up, and to my surprise it started heating immediately. The Knight is running between 20 and 30 percent. The main floor is heating fine, the only drawback is the convector"s in the basement aren't producing much heat. They also use monoflo tees. The water is flowing in the proper direction. Because of piping arrangement I wouldn't think it is working like a gravity system. I have no complaints, I just can't figure out why it is working so well.

Mark Eatherton

It may be working now, but...

When it gets colder outside, it most probably will not be adequate.



For the distribution pump you need to emulate the performance curve of the series 100 pump as close as possible (flat curved pump).



At present, you have gravity working in your favor in the cases of the convectors being higher than the mains. You obviously have been exposed to and understand the reason why the elements below the main don't work so well. Hot water WANTS to rise, naturally, and must be forced downward to heat the basement elements. Typically, convectors below the main require two mono flow tees. One on the gozinta and one on the gozouta. On convectors above the main, there is usually just one monoflow tee on the convectors outlet, unless it is a big pressure drop convector (like a fan coil unit toe space heater).



What is currently being used for a distribution pump? In other words, what size/type/brand pump is being used to move water around the loop, but not through the boiler?



The common urge is to use a high head pump, but my experience in the field goes counter to that...



(EDIT) After rereading your post, the system is most probably working on gravity. My home is set up the same way. I called it my Y2K system, because I piped it mono flow (venture actually) in anticipation of the great electrical failure that never happened. It works marginally, but that was all I was looking for. Freeze protection, but not human comfort. As it gets colder outside, the gravity will become inadequate. Get the series 100 wired in before it gets cold or you WILL be hearing from your wife and kids :-)



ME

jim armstrong_2

More info on My system works, but why?

On my Knight boiler there is a Grundfos UPS 26 99 FC, main floor heating is 3/4" fin tube and as stated convetors in the basement. I have a power switch installed on the B & G pump so it can be powered up at any time. A couple of things about this baffle me. One is the speed at which the water circulates through the system, although not so fast that it will travel through the convectors in the basement. I've worked on a number of gravity systems and never had the water move so fast though one, but I've also never had a boiler piped up primary/secondary on a gravity system. Second is the fact that the direction of flow is in the proper direction. I expected that the secondary piping would have been the path of least resistance and just circulate through the boiler or create flow in the opposite direction. The water travels out of the secondary piping and through the primary loop rather than taking the path of least resistance and immediately returning to the boiler. Also I don't expect this to continue to work once we get real winter temps so far the coldest night we've had is 32f.

Thanks M.E. I needed someone to run this by.

Mark Eatherton

Induced flow...

Some times, our minds eye can't see all the dynamics at work. I've had situations whereby I was "seeing flow" in parts of a system that in my minds eye SHOULDN'T have been seeing flow, but as you said, it was WAY to fast to have simply been gravity induced, or so my minds eye thought...



Gravity is actually quite powerful, and with the low mass/quick recovery boilers of today, it IS entirely possible that what you are seeing is strictly gravity induced. Could be a combination of gravity and mechanical induction.



Got pictures?





PS, You are welcome. We are here to help.



ME