My PEX heating project

Hi Guys,

I'm not a plumber so I hope you can give me some advice.
Right now I own a house that's about 75 years old, a 2 story center hall colonial. It currently has a convection flow steam system installed. I think the furnace is the original one. It's an old coal-fired monster and someone pulled out the coal grates and stuffed in an oil gun. I have 10 Aero steam/water radiators, each with one 1.25" feed/return pipe and a pressure relief valve.

My problem is that the oil bill to keep this dinosaur running is killing me, the upstairs is too hot, the downstairs is too cold, I don't think the old steam trunking system can be zoned and some of the cast iron fittings on the furnace itself are rusting. I think I need to put this thing out of my misery.
My overall plan is to rip out the entire existing system including the feeds to the radiators (but not the radiators themselves), the furnace and the oil tank. I want to bring in a natural gas line from the feeder line across the street and put in a new gas furnace.

I want to have 3 zones, one for upstairs, one downstairs and one for an indirect hot water tank.

For the distribution piping to the radiators I am thinking of running 1 PEX trunks and 3/4 PEX feed/returns to each radiator i.e. not home-running all the lines to a manifold. No trunk would support more than 3 radiators. Hopefully using PEX will allow me to avoid putting joints in the walls or ceilings and minimize the amount of sheetrock I have to hack up to get the piping in. Also, copper is crazy expensive these days and I am not a pro at sweating copper joints. I want to run ¾ PEX for better flow to the radiators (1/2 is too small once you account for the fittings I think).

I am thinking of using the Watts fittings and either the Watts SS cinch rings or the standard brass crimp rings (which is better?). Also, I would have to find a source for the oxygen-barrier PEX pipe (any good source?).

For the radiators themselves I have a bit of a problem. The side of the radiator that is currently hooked up to the steam system should be ok, I think I can break the union and reduce down to ¾ pex. The other end has been sealed with the factory plug since they were new and after 75 years of steam they WILL NOT move. The cast material the plug is made of won't hold enough pressure to break the rusted in seal, the metal just deforms. My plan is to drill through the face of the plug and tap it for 1 NTP, from there I can attach ¾ pex fitting. I tried this on a spare radiator that I removed last 1/2 it seems to work, although I haven't pressure tested it yet. Then I would have to drill and tap for the air bleeder valves and plug the hole where the steam pressure relief valve was attached.

I would have to pay someone to install the furnace unit itself along with the water heater tank, circulation pumps, expansion tank, connect to existing water lines, run the gas line and due any necessary system tuning. I would do all the plumbing for the trunk lines and up to the radiators (I just can't afford 85$/hour for that many hours).

OK, that's the plan. Please tell me what's wrong with it.

Thanks for your help.

David

I went through a similar project as you.

I have a 3 story colonial (100yrs old) was all one zone.

Now I'm at 8 zones all with circ pumps. I did it all with Wirsbo/Uponor pex with oxy barrier. HePeX. I bought the pipe from pexsupply.com

I did all mine with 1/2" pex. I also thought about doing larger but since i was breaking it down into so many small zones the smaller pipe was enough.

My third floor has stand up cast iron rads, the second has cast iron baseboard, and the first floor is a mix of cast iron baseboard and recessed cast iron rads.

I'll post more info up in the morning, got to get some sleep now.

I have seen a lot of steam Rad's leak when filled with water. I would rethink keeping the Rad's. I have gotten many flood calls caused by a steam Rad leaking because the boiler was over filled.

You can remove the union and the brass piece so you can bush it down with little effort. The other end might be a bit harder.

I think you would find it simpler to goto baseboard or replace your rads.

BTW, when heating water, it's called a boiler, not a furnace. A furnace is used to heat air in a residential situation.

I know it would add to the costs, but probably not to the labor...I'd chuck those old radiators, get some nice flat panel, unobtrusive new ones, and maybe even relocate them if the old positions aren't great. You'll have one huge rust mess once you circulate water through those old radiators that will take awhile to clear out, if you ever do.

The size of the pex you run would depend on the amount of heat you need to supply. Uphonor stuff has a good rep. Depending on the controls you choose, you may not need to buy their expansion tool as some of the fittings use o-rings and compression.

Just be extra careful when using the "o"ring/compression,or "QS",type fittings from Uponor.....the o-ring can get pinched really easy and if the PEX isn't cut square and fully inserted into the QS fitting you WILL have a leak...take it from experience!!!!

heat

75 years ago? You could have 3 column steam radiators which cannot be converted to hot water. I am not sure how you plan to pipe these radiators because you cannot loop from one to the other using the size pipe you indicate. And tapping the radiator with 1/2" ips and then increasing to 3/4" is also counterproductive. $85.00 per hour is expensive, until after you have done the entire system and it doesn't work right and you have to pay that to have it done over, which is the way it appears you are heading.

My system was a bit different as I already had a hot water circulating system except it was all on one big loop.

I didn't change out my boiler but it is on the list.

I did pipe the system with enough valves to make working on it, draining, purging, or swapping out components like circulators, expansion tank and the boiler itself without having to drain down the whole system.

I also did not want to deal with the complexity of zone valves in combination with circulators, so I zoned my entire system with circulators. I used a Taco zone controller so I can just wire a thermostat to each zone and then to it's circulator.

here are some pics. these are first round. more circs have been added since and I cleaned up the pex runs above to make it look cleaner. (as much as possible with pex)

rmelo99 said:

here are some pics. these are first round. more circs have been added since and I cleaned up the pex runs above to make it look cleaner. (as much as possible with pex)

Click to expand...

It looks like you are using cast iron pumps with non barrier pex.

I had to change to a brass/bronze pump since it kept rusting regardless of how much of the "protector" I added. Note: everything else in my system was PEX, copper, or stainless.

Dave-

Another issue with keeping the original steam radiators is matching the heat delivered by the lower temperature hot water to the heat load of the house. As others have advised, you may be better off replacing the radiators with something properly sized for your heat loss when using hot water. In fact, if you oversize the radiation, you can run lower temperature water and possibly consider a modulating/condensing boiler with outdoor reset and achieve a large energy efficiency gain.

Bill Arden said:

It looks like you are using cast iron pumps with non barrier pex.

I had to change to a brass/bronze pump since it kept rusting regardless of how much of the "protector" I added. Note: everything else in my system was PEX, copper, or stainless.

Click to expand...

Sorry, that is incorrect, my pex is Wirsbo HePex, it has an oxygen barrier. It isn't the aluminum type of pex, but does have an oxy barrier and can be used with cast iron, other wise I'd have more problems than my pumps all my rads are cast iron.

Any Pipe Corrosion?

I know this is an old thread, but hopefully someone is still around.
I am wandering if there is any corrosion due to dissimilar metals.
I am hooking up cast iron radiators and I ran pex to each one, then I want to change to iron pipe before I come through the wall or the floor. However, I can only find brass fittings to make the PEX crimp connection. Then, if I connect brass to iron pipe, I probably should use a dielectric union.
Does anyone know a better way, or a way around this? I just don't want my plastic pipe exposed in a 90 year old house...tacky!

brass to steel pipe is the correct way there will be no dielectric issues

ALL the gas CSST manufacturers state that their material is NOT to be used as a "flexible connector" connected to the appliance.

Yea but who reads directions these days

hj said:

ALL the gas CSST manufacturers state that their material is NOT to be used as a "flexible connector" connected to the appliance.

Click to expand...

Was this misposted? I don't see any mention of GAS piping or CSST or flexible connectors in this thread. Just pex / iron pipe and brass for hydronic heating.

To answer the question yes you can do brass to iron pipe, not an issue. Perfectly fine.

rmelo99 said:

Was this misposted? I don't see any mention of GAS piping or CSST or flexible connectors in this thread. Just pex / iron pipe and brass for hydronic heating.

To answer the question yes you can do brass to iron pipe, not an issue. Perfectly fine.

Click to expand...

I believe this picture brought the comment about CSST...

Gotcha! Didn't even realize the CSST being referred to was the CSST in my picture!

To clarify if it isn't visible there is Black pipe below that shutoff valve and that is what goes into the boiler. Same setup exists on the NatGas HW Heater behind in the pic. This was done by a licensed plumber and inspected when we bought the house. The house was winterized. When they unwinterized it for our inspection they had a gas leak that couldn't be located. A plumber ran new gas lines all CSST from the meter to the 2 gas appliances. The city inspections were done right after we closed on the house. So as far as the Building department is concerned my setup is ok in their books.

I have read about flexible or CSST connectors passing through the metal appliance jacket. But like I said about the last part of the appliance connection is actually black pipe.

Six zones, cast iron radiators, no bypass, no tempered return. I see a new boiler in the near future. Who does this stuff and why?

Wally Hays said:

Six zones, cast iron radiators, no bypass, no tempered return. I see a new boiler in the near future. Who does this stuff and why?

Click to expand...

If you're refering to mine there is a tempered return in place now. Not shown in those old pics but it is a bypass in place to protect the boiler from cold return temps.

I would sell that house and buy one with in floor PEX heating and plastic manifolds. Leave that threaded time bomb for someone else.