Pipe material for replumbing hydronic central heat...

Question for those that have done DIY work on their central heat-

I'm in a large and old farmhouse that currently has a very old Fitzgibbons 400 oil boiler and hydronic heat zoned into 2 main feed/return loops with branch lines for the cast iron radiators (comes off feed through radiator and onto the return line).

The plumbing is all 'black iron' pipe. Needless to say, I'd like to have more than 2 zones for about 3500 sq ft of floor space, plus the system I have is not well balanced. I'm sure the radiator and plumbing sizing was all done by rule of thumb. The radiator valves either leak through or don't turn at all.

I'm replacing the oil boiler this summer with a more efficient unit. Next year or the year following I plan on doing a gasifier install, followed by storage as time/budget permits.

To rezone the heat with the current plumbing would be at best extremely difficult, given how I plant to rezone.

About 1/2 of the plumbing is in a dirt crawlspace, and 1/2 in a stone basement. Is oxygen barrier pex suitable/practical/cost effective? Copper in the diameter and wall thickness I'd need (doing rough estimates of heat demand and flow requirements) would be insanely expensive, plus I'd have to use dielectric unions at every radiator... I'm not a big fan of cutting and threading steel pipe, but that might be my best choice.

Were you in my shoes, what material would you use for replacement?

Thanks for the feedback, NWM. What style connector did you use?

Sting said:

Leave the distribution system alone

Replace each radiator control valve in the areas you want to to maintain at a cooler temperature with Danfoss thermal reacting valves and relocate the house stat to the area that has the greatest heat loss.

Lost less work and lots less expense with a greater comfort and return on investment!

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I appreciate the feedback, and I have considered TRV's, but they're just not something that will meet all my needs going forward. This resto/renovation/upgrade is what I'd call medium grade... and trying my best not to sound like the guy teaching everyone a new game and adding rules as it becomes convenient, I'll be doing other things that will require more flexibility in the system, like adding radiant heat to the kitchen (when it gets redone in two or three years), the downstairs bathroom and the upstairs bathroom, I'll be adding panel radiators on the second floor, I'll be adding plumbing for the wood boiler and storage tanks when I eventually get there, plus I'm replacing the oil boiler at the same time.

I'd rather replumb and have the system designed for what I want it to do, and hence making it more efficient, rather than just adding flow restrictions to redistribute the heat. And now's the time to do it. It's a complicated house, and it will take more planning and design than what was originally put in to the system (which was none).

steam man said:

I am not convinced you need dielectric unions at every radiator. You can use yellow brass fittings between any ferrous metal and copper with minimal galvanic action. A lot of plumbers seem to not like dielectric unions which have there own issues.

Mike

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Thanks for that, and thank for the link Rick.

I had read some things in favor and against dielectric unions... I have seen some pretty aggresive water chemistry in the fire protection systems I work with, and typically pipe and fittings will corrode first, however, the water is completely different from boiler loop water since most of what I deal with is all oxygenated.

Regardless, I think copper is my last choice if only due to its price, and the inconvience (at best) of sweating connections in a dirt crawlspace, which I'd like to avoid if at all possible, so the point may be moot right now.

Sting said:

MarcM said:

I appreciate the feedback, and I have considered TRV's, but they're just not something that will meet all my needs going forward.

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HUMMMMMM!! each radiator can be upgraded in about an hour -- the area is then comfort modulated and will consume less energy - the system performance is enhanced. And this doesn't meet your needs?????

OK -- start by tearing the entire distribution system out of the basement - back to the last available fitting disappearing into the walls and construct home runs of 3/4 black to each loop left by the demolition - Place a thermostat in each of those areas and control either a zone valve or a dedicated (better) zone pump to each loop - add what ever baseboard ( YUCK ) or radiant system you want in any area and pipe home runs of that back to the boiler. Construct one or several temperature reducing manifolds and connect the home runs to these as or directly to the boiler temperature manifold as you heat loss calculation dictates per load loss of each zone. Add several ports to each distribution loop for planned expansion.

Still sound like a DIY project????

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Indeed it does. I knew pretty well what I was getting into when I started the project. I'll be using panel radiators, by the way, not baseboards.

Thanks for the info Sting.

If it makes you feel any better, I do actually have some background in this... not residential boiler loops in particular, but I've got a couple engineering degrees and have calculated flow demand and friction loss on more commercial sprinkler systems than I care to remember. Thank God for SprinkCalc. I'm tight with Hazen Williams. Plus I currently work in a lab that certifies fire protection equipment, so I'm good with sweating, threading, roll grooving, cut grooving, cementing, flanging, etc. etc.

DaveBP said:

Marc,
Sting's links are good info.
I don't think it's possible to over-endorse Siegenthaler's book, "Modern Hydronic Heating" for anyone who is willing to tackle a project like yours. It's not light reading. But if you have the courage of your convictions you'll find it a treasure of information and inspiration. If you can do fire suppresion sprinkler systems you can handle hydronics; just the mental flip of adding heat transfer to the flow calculations. Siegenthaler's book comes with some very useful software to do some of the basic drudgework. And if you speak Autocad, the Hydrosym software allows you to make really professional drawings of anything you can imagine hydronically.

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Thanks for the feedback Dave. After all the heat transfer work I did in college and since then, it doesn't yet intimidate me. Perhaps it will once I get into it, but I love a good challenge just the same.