DIY? Replace low hanging boiler lines with pex?


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Old 10-28-14, 12:33 PM
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DIY? Replace low hanging boiler lines with pex?

Awesome site. Appreciate ideas, comments on my issue.

We are in a 100 year old modest character home, 625sq ft per floor, 2 floors and an unfinished basement, with a 25-30 year old Burnham water boiler with newer circulation pump, attached to large dia(2.5" reducing to 1" at the end of the run) iron(?) supply/return lines that may be from the 1930's. These supply cast iron rads (approx 2'x3'each), one per room. Basement is heated only by the exposed heating lines. It all works fine at this point, reasonable heating bills, no concerns.
Time to finish the basement, so those low hanging (approx 5' 10" off the floor) heating pipes have to be raised to the joists. A neighbour told me about his friend having it done with pex. I am handy and would take this on if it can be a
diy job. We would be happy to simply replace the basement lines at this point, and add some basement rads, and do nothing else.

Can we simply run basement pex and connect to the iron lines that come from the rads thru the main floor into the basement (from both levels)? I don't want to get into fishing pex thru walls/floors to get to the upper level at this
point if i don't have to.

Is it necessary (i imagine advisable) to ensure the supply/return pex is always at or below the level of old rad pipe connection point in the basement, to avoid air locks, or is this really a concern? Some of these pipe fittings occur (not
more than 3") below the joist level, so to connect the pex, it would run the few inches down from the joist to the current rad-pipe fitting.

More questions:
-Should we expect to notice changes by switching out the old supply lines? More/less heating costs?

-Is boiler water temp a concern with pex?

-Fittings to go from pex to iron?

-Rads have original single-valve flow control and manual air bleeders. If these flow valves work, should they be adequate to adjust with the new pex system, if necessary? Right now the upstairs valves are slightly throttled to reduce heat to upstairs bedrooms for comfort (too much heat).

-Same diameter pex used for main lines vs branches to rads? Can i just copy the pipe layout that is currently there: 2 supply/return runs from copper fittings at the boiler; one run on each side of the house that feeds the upper and lower level rads on that side of the house. (3 bedrms and 1 bathrm upstairs)

-Will need to heat basement rooms, but won't have heavy daily use (12x10 secondary family rm, 9x9 bedrm, 10x10 laundry/furnace rm, 8x10 bathrm/sauna area, small workshop area, and indirectly heated storage area). Add 1 rad per main rooms?

So its a smallish house, with a simple system that works to our satisfaction currently. Basement will now be insulated so perhaps the new basement heating requirements will be offset slightly?

Anybody diy'ed this, or had it done? Costs?
Thanks so much!
 
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Old 10-28-14, 12:38 PM
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First thing, you MUST use a PEX with an oxygen barrier. Using standard PEX will allow oxygen diffusion into the boiler water and severely corrode any iron or steel.

Second thing is to keep from installing "dips" in the new piping as the dips will act as air traps and stop circulation.

If you could post several dozen pictures (only a slight exaggeration, more picture are always better than fewer) of your existing installation we have many talented people here that can advise you. Pictures do need to be well lit and in focus.
 
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Old 10-29-14, 08:43 AM
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pics

Thanks for the quick response! Hard to get good pics. Let me know if more are needed. Boiler is rated for 104 K BTUs.
 
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Old 10-29-14, 08:51 AM
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more pics

There is a main line dia reduction at each branch fitting.
Thanks!
 
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Old 10-30-14, 05:05 PM
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It appears that you have a pretty typical two pipe (supply and return) system. Yes, it is definitely a DIY job is you have reasonable skills. You DO need to avoid any dips in the replacement piping so it may be necessary to do something with those vertical pipes where the connection is below the bottom of the floor joists.

Use oxygen barrier PEX of he same size or perhaps one size larger for the pipes being replaced. I mention one size larger because the internal diameter of PEX is slightly small than an equivalent steel (not iron) pipe.

For the basement heating I would strongly suggest a new zone with a separate circulator. This would be controlled by a separate thermostat and if necessary the individual spaces (rooms) in the basement could be zoned with either zone valve or with mechanical thermostatic valves. Depending on the construction of these rooms you might want baseboard convectors, cast iron radiators or even a fan-forced unit heater.
 
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Old 11-01-14, 11:41 AM
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Thanks Furd. So any ideas on diameter pex used for main lines vs branches to rads? Like i say it starts out quite large from the boiler (3" OD) and has a reduction fitting at each branch, ending up 1" to final rad on line; i've read a bit here about pex used currently for supply/return is 1" for the entire line, branches maybe 3/4".
-This will supply enough hot water to heat the rads (approx 2'x3'x6" cast iron) as they are heated now? Or will the pump/furnace need to run longer/ heat come slower?
-Should i plan on having a control valve on each branch near supply/rtn to control flow to the rad as a backup for the old rad valves?

We like the old rads. Is there any reason to consider replacing them?
Thanks!
 
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Old 11-01-14, 12:57 PM
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In my opinion a supply manifold and a return manifold at or near boiler, one inch copper or black iron . Run 1/2 inch oxygen barrier pex to and from each cast rad as closes and most convenient place to attach . Zone valve on supply manifold so that each room that you want to accurately control its temperature . Rule of thumb , if the room has a door in it than it needs a thermostat. The old black iron pipe can be removed and sold. Make pex as neat as possible for looks .
 
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Old 11-05-14, 09:24 AM
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Thanks for that. The manifold route makes sense, would be an upgrade, more control, etc.
If i go that route any suggestions on threads here, or literature elsewhere on the design/install specifics? ie, Buying manifolds, valves, thermostats? Recommendations on quality products?

Need an extra circulation pump for basement, or maybe just a larger capacity single pump, or not really? What are the issues?
 
 

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