Soliciting opnions/thoughts on new plumbing setup

The old system is a gravity fed system that was modified in the 50's to a circulation system modified in the 2000's to a coal fired boiler. I've been kicking around the idea of installing a primary-secondary loop, however in looking at the setup and my situation, now would be the best time to junk what I have and start over.

I intend to convert the 2inch mains from a direct return two pipe system to a 1inch PEX reverse return system. From what I'm reading, this will eliminate a lot of the balancing issues that I have with the current setup without having to resort to balancing valves on each radiator. I will also no longer be smacking my head on 2 inch CI pipe hanging in the basement.

I'll be running a primary loop using 1 1/4 CI, tying in the old boiler to give me extra mass for the winter months. I'll be able to bypass the boiler for summertime hot water, reducing the amount of fuel I'll need when it's warmer out. The primary circulator is a 23gpm unit, I'll be hooking up a 10gpm unit for the secondary loop. Because of the extra mass, I'm not sure I'll need a three way valve in the primary loop, however that is an option that I'm considering.

The secondary loop will be fairly narrow, out and back is ~30 feet, and the loop will be ~2 feet apart. I'll run 3/4 inch PEX off the loop to all the radiator feeds and returns which will remain CI from the point where they joined the old mains. This is mainly for ease of installation.

That's the plan so far, I imagine it will be modified somewhat as I proceed. One major concern I have is that the coal boiler will be turned off for a substantial period of time. I can put a light bulb inside the burn chamber to keep the rust out, however I'm trying to think of how best to protect the wetted parts from corrosion. I'm leaning towards adding some corrosion inhibitor down the supply side, filling the chamber with water than shutting the valve and pressurizing it while I do the work on the plumbing. It could be out of service for 2 weeks or so, so I don't want any chance of rust building up on the inside.

Another issue I'l have is where to plumb in the expansion tank. I don't like the way it works now (the circulator is on the return side of the boiler and pressurizes the expansion tank every time it comes on). I'm wondering if I can plumb the expansion tank into the secondary loop, or if it needs to be on the primary loop for some reason. It's an old style tank without an air bladder.

Lastly, I assume the dump zone now has to be tied into the secondary circulator. That would mean the primary has to be wired in so that it runs continuously even when the triple aquastat is shut off by the hi limit circuit. I'm not sure how that will work, but it is something I'll have to make sure about.

As always, thanks for the advice.

It occurs to me that now would also be the time to setup the system for two zones. That's going to be one busy manifold back by the boilers....

Day one demo of old piping:

Rented a chain cutter, crushed the pipe (two inch) in two places. Cussed a bit.
Bought a Sawzall and a 15 dollar cast iron pipe cutting diamond grit blade that cut about 1/2 inch into the pipe. Cussed a whole lot more.

Finished that cut with my hacksaw and one of the three pack of 18tpi bi metallic blades.

Day two demo:

Cut everything out (two inch pipe) in 8 hours with the sawzall and a cheapo pack of bimetallic blades. Felt much better Sunday night.

See that, you're gaining on it

freetown fred wrote:See that, you're gaining on it

Well, I'm definitely committed to making it work at this point.

Sounds like you are piping in the old boiler as a buffer tank?

kstills wrote:Another issue I'l have is where to plumb in the expansion tank. I don't like the way it works now (the circulator is on the return side of the boiler and pressurizes the expansion tank every time it comes on). I'm wondering if I can plumb the expansion tank into the secondary loop, or if it needs to be on the primary loop for some reason. It's an old style tank without an air bladder.

Since you have a traditional compression tank, the idea is to have a take-off from the top of the boiler (or in the first run of piping exiting the boiler) so any air bubbles go into the tank, and not into the piping/radiators. If you want to move the circulator to the supply side, now is the time to do it.

kstills wrote:Lastly, I assume the dump zone now has to be tied into the secondary circulator. That would mean the primary has to be wired in so that it runs continuously even when the triple aquastat is shut off by the hi limit circuit. I'm not sure how that will work, but it is something I'll have to make sure about.

Just run a length of thermostat wire from your dump zone aquastat to the TT contacts on that zone relay...assuming that relay is tied into the triple aquastat, both circulators will run as needed. The triple aquastat will run the circulator on C1/C2 if there is a heat call even if the high limit setting has been exceeded.

Rob R. wrote:Sounds like you are piping in the old boiler as a buffer tank?

Yes.

Since you have a traditional compression tank, the idea is to have a take-off from the top of the boiler (or in the first run of piping exiting the boiler) so any air bubbles go into the tank, and not into the piping/radiators. If you want to move the circulator to the supply side, now is the time to do it.

I've been giving this a lot of thought. Yancy posted about how solid fuel boilers had to have the pump on the return side to avoid the boiler running dry. With the extra supply from the old boiler, I'm not sure if that would still be an issue.

Just run a length of thermostat wire from your dump zone aquastat to the TT contacts on that zone relay...assuming that relay is tied into the triple aquastat, both circulators will run as needed. The triple aquastat will run the circulator on C1/C2 if there is a heat call even if the high limit setting has been exceeded.

Day five update:

1) Boiler is totally disconnected from the old manifold, which is now gone.
2) New manifold will be 'pumping away' from the boiler.
3) New manifold will be black iron and will be the primary loop connecting the new and old boiler, with a PEX crossover for summertime hot water (eliminating the extra 40gallons of water in the old boiler from being heated).
4) Secondary loops (first and second floor zones) will be run in 1" PEX with 3/4" supply and return to the radiators.

2 weeks, and all is well.

I pressure tested the system last nite and chased down a few minor leaks (had 2 unions on one radiator that had worked loose and were pouring water out, but that was an easy fix) and will be putting the power back on tonite. I had one leak in a PEX crimp ring, and that was in the 1/2 inch supply to the boiler where I had crimped the ring over the burr on the fitting (doh!). Other than that, every other connection, 3/4 or 1 inch was tight.

Working with 1 inch PEX was a bitch, and it certainly does not look as pretty as it could. If I had given it a bit more thought, I would have run the long supply and returns with 1 inch black iron, than made my connections to the rads with the PEX. As it is, I'm going to be getting air out of the system for quite some time due to the up and down nature of how the pipe runs.

I have a air seperator on the primary line and I installed one on the downstairs zone (which will be the dump zone for the boiler) so I'm going to run the circulators continuously for a few days to remove as much of the air as I can. This weekend I'll fire up the boiler, make some hot water and test the rads for flow.

Overall, it has been fairly easy up till this point. If all the rads get hot, I'll be happy.

Ok, the primary line has been installed, but I'm air bound in the larger boiler. Unfortunately, I forgot I had an air purge so I didn't install it in the primary line. I have it in the secondary, so my plan is to hot wire the circulator in that line and run it until I get all the air out and movement in the primary.

I do have a boiler mate tied into the primary line, and atm that is acting as my extra mass (such as it is being not much more than a coil). Even with the smaller amount of water, I'm able to hold my set point almost exactly on the low limit of the boiler (and as a consequence, never run out of DHW).

My dump zone is improperly installed atm. I either needed a check valve between the supply and return line (which at this point would be a nightmare to pipe in) or to have the primary circulator continue to run when the dump zone kicks on. Which is how the system will be wired in this week. I doubt I'll ever hit the dump zone limit with the way the system is currently set up ( and even if I do the boiler fire will go out before any damage is done the way it works atm) however I don't want to take any chances with this part of the controls.

I won't be able to run the rads until I have a zone control installed, and that will take another week or so. But I am getting flow to them when the dump zone kicks in, so I'm optimistic.

If you're getting flow to them---you SHOULD be optimistic

If you have no way to easily vent air from the system, I would drain it and install a tee and boiler drain at the high point on that primary loop. There is nothing worse than having to take the system down on a subzero day and fighting to get the air out of it before something freezes...been there, done that.

Rob R. wrote:If you have no way to easily vent air from the system, I would drain it and install a tee and boiler drain at the high point on that primary loop. There is nothing worse than having to take the system down on a subzero day and fighting to get the air out of it before something freezes...been there, done that.

You know, I still have a fresh water supply hooked up to that old boiler. If I valve off the LL110k and fill the old boiler with the air vent open on the secondary, think that would purge that air pocket?

All you have to lose is some water.

Rob R. wrote:All you have to lose is some water.

And it's not like that hasn't happened more than once over the last 2 weeks....