Re-piping the main loop of a cast-iron radiator system

[jasonk823]

Hello all! I hope someone here can share their wisdom with me.

I have a monoflow radiator system that heats a basement and two above-ground floors. The main loop in the basement connects to 14 cast-iron radiators. The system gets the house nice and toasty in the winter.

Right now my basement is unfinished and I am looking to make it into a livable space. The ceilings are high enough (7') but the main loop of the radiator system hangs down 14" (!) from the ceiling. The loop also runs through the center of most rooms rather than pushed out towards the walls. All of this serves to make any renovations to the basement pointless. I'm a tall guy, I need head clearance!

I want to raise the main loop up to the ceiling and push it out towards the walls. Right now the system uses iron pipe.

Here is my question: can I replace the iron pipe in the main loop with copper? In some cases I would also like to replace the runs from the main loop to the individual radiators. In other cases I would like to connect the existing iron pipe runs to the new copper main.

Is this possible? Is it a bad idea?

Here are some things I have taken note of...

* The main loop appears the be the same size pipe from start to finish.
* There are a couple locations where it looks like work was done and the run from the main to the radiator is in copper already.
* The main loop looks to be pretty level throughout.

Any advice is appreciated. Thanks in advance!

[Mike Speed 30]

Yes, your can use copper.

[rbeck]

Mike you kinda left that open ended. The pipe can be moved but you must be careful of tee spacing and placement of the monoflow tees and the direction of the tee arrow.
Keep the pipe the same size as now and do not trap any of the pipes going to the radiation.

[jasonk823]

rbeck -

Thanks for the added insight. I would be copying the layout of the exisitng loop pretty much exactly, just higher and closer to the outer wall. Tee placement/direction would be the same.

So as not to go without heat for an extended period of time I was going to attempt this job in pieces. ie redo the piping in one room of the basement first, test, and then move on to another room. Is there any problem with transitioning from the iron pipe to copper and then back to iron? Assuming the pipe size is the same, my only worry is that there would be an uphill climb from the iron to the copper. Bad?

[Mike Speed 30]

Originally Posted by jasonk823

Is there any problem with transitioning from the iron pipe to copper and then back to iron? Assuming the pipe size is the same, my only worry is that there would be an uphill climb from the iron to the copper. Bad?

Not a problem. Your system flow is driven by a pump, not gravity.

[Mike Speed 30]

Originally Posted by jasonk823

I would be copying the layout of the exisitng loop pretty much exactly, just higher and closer to the outer wall. Tee placement/direction would be the same.

As rbeck mentioned, the spacing between the tees, supply and return to each service, is most important. They need to be spaced adequately for the monoflo system to work, typically a few feet, minimum. If the system has been functioning satisfactorily, then if you maintain the present tee spacing, you should be OK.

[Mike Speed 30]

Originally Posted by jasonk823

So as not to go without heat for an extended period of time I was going to attempt this job in pieces. ie redo the piping in one room of the basement first, test, and then move on to another room.

That approach is OK, but after each loop is completed, you'll probably have to drain the system, vent, etc. You might get tired of that?

The main thing to test for is leaks, right? If you do the whole shebang at once, and find more that one leak, you can drain the system once and fix the leaks.

By the way, this would be a good time to add any valves (isolation, balancing, or drain) to the system you've always wanted.

[jasonk823]

Mike -

What I have really always wanted to add was a couple of zones. Right now all three floors are on one zone. It would be ideal if I could have the second floor on one zone and the basement/1st floor on another.

How complicated is this? Is this the kind of thing where if I have to ask it's not for me to do?

[Mike Speed 30]

It can be done. But with your monoflo system, adding zone valves may be tricky, depending on how the system is configured. It sounds like from your description, both the 1st and 2nd floor convectors are fed off the same main monoflo loop in the basement.

[jasonk823]

Originally Posted by Mike Speed 30

It sounds like from your description, both the 1st and 2nd floor convectors are fed off the same main monoflo loop in the basement.

You are correct - everything is fed off of the same loop. In my mind it seems like it should be as simple as adding a tee after the loop leaves the boiler and putting a zone valve on each end of the tee. Then I run my two separate loops, each feeding the necessary radiators. The loops meet back up at the end with another tee and feed back into the system, same as it does now.

[Mike Speed 30]

That will work. But, the pipe size of each of the two new loops should be a bit smaller than the pipe size of your existing loop. You want the pressure drop across each of the diverter tees to be about the same as it is now, which will maintain approximately the same flow diverted to each radiator. If you post the size of your existing loop piping, I can look up in an old B&G manual and tell you what size to make the new loops.

And your circulator should have a relatively flat pump characterisic curve. That will keep the flow in each of the new loops nearly the same whether both or just one zone valve is open. If yours doesn't have a relatively flat curve, I'd probably replace it.

And you will need to find a chase to run thermostat wire from whatever floor doesn't have one. And redo the control wiring for the zone valves to coordinate with the pump and burner.

[NJ Trooper]

And redo the control wiring for the zone valves to coordinate with the pump and burner.

Which is actually a pretty easy task for a moderately skilled homeowner.

[jasonk823]

Mike -

The current iron pipe diamerter is 2".

I spent some time looking at the system this weekend and I realized that it is actually split into two loops. Each loops serves half of the house. I put together sketch of the basic layout:



The black blob is the boiler. Each of the blue dots represents a radiator.

If I was to set it up as two zones, naturally this layout wouldn't work. I would need two full loops going around the house.

NJ -

Glad to her the wiring isn't too difficult. Honestly, that was something that I was actually a little worried about. Heating control wiring has always scared me - so many little wires, so many colors.

[Mike Speed 30]

Assuming you were measuring the outside diameter, that would 1-1/2" black pipe. (Actually the o.d. of 1-1/2" pipe is 1.9". Based on B&G data, making two loops out of one, it says use 1-1/4" to maintain the the same pressure drop across the monoflo tees. That would go for either copper or black pipe.

I'm assuming, based on your diagram, that the pipe you measured is in the two loops, not the common piping, near the boiler, shared by both loops.

[jasonk823]

Mike -

Thanks for all your help. After considering how much pipe I'd need to do three zones and how much 1 1/4" costs, in addition to the pumps, joints, thermostats, etc. I realized that I'd be spending $2k + before even beginning work.

I brought in a highly reccomended plumber who specializes in this kind of work in my kind of house (ie: old). He reccomended using PEX and a three-manifold system. I like this idea - it completely opens up my basement ceiling. It will also only set me back a little over $4k and be done in a week. Seems worth the extra money to me!

I've heard lots of praise for PEX and a few negative things here and there. It seems especially well suited for this type of project. Any thoughts?

[Mike Speed 30]

Originally Posted by jasonk823

I've heard lots of praise for PEX and a few negative things here and there. It seems especially well suited for this type of project. Any thoughts?

Should be fine, but make sure he uses PEX with an oxygen barrier (PAP).

[jasonk823]

I wanted to post a quick followup to this thread.

We did have the pro come in and put in a three zone system using PEX. I can't complain about the work he did - the place heats up in 1/4 of the time it used to. And having a zone on each floor makes it much more comfortable. No more boiling 2nd floor just to have a comfortable 1st floor!

The one problem I did have was with the professionalism of the plumber. We had the same pro come out twice and both times (a week apart) he quoted us $4,500. Due to other jobs he had he was unable to start work on our place for almost three weeks. The evening before he was to start he called us and said that he was wrong in his quote and that the price would be $6,400. Not too happy about that. Due to the fact that it was now pretty cold out everyone else we called was booked for weeks (and their prices had all gone up now that they were busy). We felt that we had no choice but to go with the original guy in order to get heat and still have the timing of the job work within our travel plans for the rest of the year.

I found this behavior very, very unprofessional. We felt that we did our homework by having him come out a second time to double-check his initial estimate. I can't help but feel like he deliberately waited in order to force us to pay a higher price. I won't post the name of the company here but we are located in Hyattsville, MD. If anyone is interested PM me and I'll give you more info on the plumber.

Anyways, thanks to everyone on here that offered me advice. I appreciate it!

[NJ Trooper]

I most definitely would have shown him the door, and as long as there was no deposit money, torn up the contract, if there was one. I guess there wasn't one though, else how could he have jacked you up like that? You might as well have taken a walk in downtown Camden with hundred dollar bills hanging out of your pockets. The dude definitely fleeced you. Damn this pi55e5 me off!