Thanks for the input Yanche -
I'm not sure but I get the idea that my posts come off like I am asking for someone to tell me what to do and how to do it without the willingness on my part to do any of that research myself. I'm sorry if it seems that way. I have done quite a bit of reading and digging through this forum as well as the Heating Help site and the net in general for information, wisdom, ideas and so forth.
I have yet to run across a situation quite like mine. There are quite a few posters here on this forum who have dealt effectively with adding a boiler to their existing system. The primary difference is their existing system is not an old, non-pumped, gravity system. There are quite a few posters on the Heating Help site who deal with gravity systems in a number of ways, but finding ones that are adding on a boiler is not so common, and most are concerned with pumping the system as opposed to keeping the gravity system functioning.
Maybe I am not asking the right questions or don't know what to ask. I shall attempt to clarify. I wasn't planning on adding any more pictures, there had been a request for them a few posts back and I had thought there addition would bring additional commentary. And look it did
I haven't bothered to do a heat load calculation as I am not buying a new boiler, but have the boilers I already own so I can not size them to the HL of the house. Having said that, the Stelrad boiler rated at 110BTU was able to keep up with most heat demands except on the coldest of days, and this was run as an add-on gravity boiler. The coal-o-matic is rated at 130 so I am thinking I should be able to keep up with the heat demand on most days. There may still be a few cold ones that the gas needs to fire on, but it is clear I can use all 130k btu on the coldest day.
So - I need to move 130kBTU from coal-o-matic to main system.
Is that a sensible conclusion?
I think I can push this through a 1” pex pipe with an appropriately sized circulator. (And by pex, I do mean Pex-Al-Pex, I had mentioned it as PaP some posts ago, but then got lazy and referred to it as just pex.)
Will I be able to push all 130k btu’s through the 1” pipe?
The post from Sting a few posts back indicates that this is beyond the limits of the 1” pipe. In the posting he is referring to heat transfer.
Am I misunderstanding something here?
I have looked at the free calc site and what I get from that is that I gain about 9’ of head if I try and push 13gpm (using this figure based on the 130k boiler and a “rule of thumb” posted here). This is through 1” PVC (site doesn’t offer PEX as an option).
So, based on that number and the chart referenced http://www.builditsolar.com/References/ ... Curves.htm
below I could reasonably expect good performance from a Taco 0010.
Does this make sense?
Now I get confused though as I read things like http://www.heatinghelp.com/article/11/H ... ng-Systems
which indicates I should plan on flowing much more gpm to account for all the water in the system. Based on my look at the data plate on the gas boiler (which say 360kbtu) I need something in the neighborhood of 55gpm flow.
So, do I need to size the circulator for 55gpm or 13gpm?
What am I not thinking about?
Sting mentions the turbulence factor. Once that high preasure water coming from the circulator reaches those larger pipes it will create turbulence. Is this something that will cause me lots of trouble? Can I alleviate that by upsizing (1 ½” - 2”) the near-boiler piping on either end?
I don’t feel uncomfortable doing the analysis, but was hoping the expertise of the board could help me in figuring out what I need to know. I don’t have an infinite amount of time, but I really don’t think this is impossible. I would very much like to have this installed before the heating season gets really going. I find it very difficult to find a hydronic heating professional with experience in operational gravity systems, let alone adding a coal boiler to them, particularly as I am a fairly rural part of CT.
Thanks again for any and all help provided.