repiping options

Old 03-28-06, 01:06 PM
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repiping options

OK, considering (considering!) taking on a small repipe myself, to rid the system of its air/negative pressure problems.

The subject system is here:

Option1 photo provides a decent overview of the whole system.

Option 1: leave circulator where it is and relocate expansion tank (ET) and feed/backflow (FB) to return. Red box on vertical return shows likely spot to insert the tee. The ET would go in between the indirect and the boiler; top of ET about level with top of boiler. Joist-hung strap would go on pipe from ET to tee to provide support. FB would be cut in somewhere along that line.

Pros: Pretty simple to do. Minimal cutting and moving. Technically, it's pumping away, and with it go my problems.

Cons: 1) makes accessing the shutoff switch and more importantly the circulator rather difficult. 2) To solve that, the ET will stick out into basement, subject to bumping, kicking, etc. 3) although this would technically be a pumping away set up, it would not be on the (preferred) supply side, downstream of air separator, yada yada. Also a bit concerned about head loss through the boiler such that we still don’t create enough positive pressure upstairs to keep air entrained. This is probably not a big deal, though. In theory, it works.

Probably could also locate the ET above the indirect in between all the indirect piping, but I’m not sure what the “rules” are for piping the ET into the return using a vertical run before entering the tee. Is that OK? i.e., ET goes above indirect with a short horizontal run toward return line to get FB piped in there, then down to the red box entry point. Assuming here that the proper entry point is below the bottom-most (indirect) return in the return manifold.

Option 2: move circulator over to supply side, immediately downstream of spirovent (see option2a picture, red boxed area).

Pro: creates a genuine, supply-side pumping away set-up. Positive pressure throughout system, etc.

Cons: 1) space is t-i-g-h-t, tight (see option2b picture). Coming out of the spirovent, there’s only a couple inches before the tee for the indirect, then a couple more before the tee that splits out to the heating zones. Then a couple more inches before the zone valves. I would have to move the indirect tee toward the heating zone valves, cut back the approach piping to the zone valves, and if I can get a circ coupling flange butted up against the spirovent, it might all fit (and no room for isolation flanges?). 2) are there “rules” about lengths of approach piping (inches, # of pipe diameters, or similar?) before entering/leaving a tee or zone valve? In this configuration, the pump would almost literally be pumping right into a very tight intersection of indirect tee and heating zone split. Somehow I think that’s not a good thing…. There is a couple inches of straight pipe downstream of the heating zone valves, before they elbow up to begin their run along the basement ceiling. Could cut that back a bit, too, again assuming that there are rules about approach piping that I don’t want to violate. 3) should I be nervous about hanging a circulator directly over my boiler? 4) awful lot of cutting and dealing with small pieces, overheating zone valve bodies, etc.

For option 2, would also likely put a drain valve and a shutoff valve on the supply (Holohan-esque) to become the one and only needed valve/drain. Maybe install the drain at the elbow before the spirovent, with the valve in the approach piping to the spirovent. Then someday cut out all the extra valves on the returns.

Opinions and alternative suggestions appreciated. In an ideal world, I'd move the indirect tank left about a foot (all that's available) so I could do most of the piping/pumping on the wall. Not sure I want to go there, yet. Thanks.
Old 03-28-06, 04:48 PM
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I know you don't want to hear it but I'm going to say it anyway:
I wouldn't waste my time with a minor re-pipe unless you just want the practice & hopefully prove me wrong. I think there is a lot more to your problem than just pumping away will cure. Keeping in mind I have not seen the whole system, but I think you simply have too much, too small pipe. You know far more about the head on your system than I & probably more about head period than I do but I would almost bet if you split those zones via a couple of true manifolds, spirovent your problem would go away. If it is not too much trouble, maybe just splitting the troublesome zone into two, each with it's own circulator would do it. Something else which could help is to use long radius ells such as those used in the refrigeration trade. Long radius ells provide a smoother path thru which the fluid can travel. I looked at the head for the 570 series zone valves vs the ESP type & the ESP is considerably less restrictive. If you are as close as I recall, maybe a simple zone valve change?
Old 03-28-06, 10:04 PM
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I'd go option 1. Pumping away on the supply side is supposed to help because the air comes out of solution more when water is heated...

However, I'll bet you never get a huge gap between your supply and return temps. You aren't heating a big slab. If your delta-t is small, it matters little which side its on.
Old 03-29-06, 07:11 AM
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Thanks for the feedback. Grady, I understand completely. I'm numbers- and book-rich with little to no practical experience.

Turns out this can be as simple as a tee on the return and just move the tank. No need to move the feed valve.

Going to try this in the next day or so I hope. Will of course post back with results.

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