Boiler Heating Mystery for you to solve

My house was built in 1930 - I'm not sure how old the boiler system is, but based on my research trying to get some questions answered, I think it must be quite old since I don't have all the bells and whistles in the equipment on my system.

I have a New Yorker Boiler, model FR. It looks like an FR-122 except for that there are no digital controls, so maybe the earlier model of that? Coming from the top of the boiler is a single pipe which then tees to provide hot water to two loops.

The first loop provides heat to my 8 radiators in the house. The second loop provides heat to 4 floor radiators in a room that was added on around 30 years ago. Each loop has its own thermostat-controlled valve. For the return piping, both loops come back together, then travel through an old Grundfos circ pump and back to the boiler.

Here are my current symptoms:

1 - If the main part of the house is cold enough so that its thermostat relay is energized, I can trace hot water from the boiler to the first loop, to the attic, down the wall, through all 4 radiators upstairs and to the 4 radiators downstairs. However, the heat in 2 of the downstairs radiators stop about halfway down the radiator and the outlet pipe is not hot. The other 2 downstairs radiators are hot all the way to the floor. However, the return piping to the boiler is not hot either (both in the crawl space and directly next to the boiler). Additionally, the add-on room floor radiators do not have any heat whatsoever.

2 - If the main part of the house is warm enough so that its thermostat relay is not energized, the add-on room starts to warm up. The return water into the boiler is at least warm. It is uncommon for me to be in this scenario for too long since the main part of the house cools off so I find myself back in the first situation.

I have been troubleshooting my system for weeks, so I have much more information to offer if it will be valuable, but I can sure use some help heading down the right track. I can even draw a sketch of my system or post pictures if necessary.

Thank you,
Brian

So, you have two zone valves and a single circulator? Does the circulator run when only the added on section is calling for heat, or only the zone valve open? Are there drain valves on any/all of the radiators? Have you tried to see if you get any air out of the system there? Are the individual radiators in series or are they on monoflow T's or branches? Depending on the layout of the loops, there may not be enough head to ensure good circulation to all radiators. You might need separate circulators, each triggered by its respective thermostat.

A little more description and maybe a picture or two would help the pros try to help.

Sure thing - I will take pictures and post them when I get home (should be by tomorrow evening).

To answer a few of your questions, there are 2 zone valves and only one circ pump. The two loops join back together upstream of the circ pump, which is just about 2 feet before the return piping goes back into the boiler.

The circulator pump runs whenever either zone calls for heat. I have verified this by measuring voltage across the leads going to the pump - it's 110 VAC anytime either zone wants heat. If both zones are "happy" with the amount of heat, there is no electrical signal being sent to the circ pump. I claim the circ pump runs, but all I know for sure is that the electrical signal is being sent. There is no noise coming from the pump - no banging or anything, and it does feel as if there is some heat in the return piping at least when the add-on zone is the only zone calling for heat.

I have bled the system on multiple occassions. I have bled every radiator and am relatively confident there is no air in them. Each loop also has it's own vent thumbscrew which I have opened on a daily basis to let out any additional air. It has been 2 days since any air has come out, but it came out regularly for about 4 days prior to that.

Regarding the exact radiator makeup - I'm afraid that is one thing I don't know or understand. I will also try to post a rough sketch of how I think they system is put together but it'd be tough to explain in words I think.

I should also say that the system worked last year. But, since then I drained the system to clean out the radiators and I then reinstalled them.

I very much appreciate all the help. My wife and new baby sure enjoy the heat as well! Thank you again,
Brian

Good evening,

I am attaching a rough sketch of my system. The only thing I am not 100% certain of is if there are 4 sets of radiators in series. It is possible that there is a parallel branch so that the downstairs radiators (D) can operate normally even if the upstairs radiator (U) is isolated.

I did not include the isolation valves for each radiator, but they all have a Watts globe valve that is not thermally regulated or anything. The drawing does not reflect elevation, but the vents are physically at the highest point for each successive loop. Each zone valve is controlled by a separate thermostat.

My camera battery is charging right now - I will post pictures later tonight or tomorrow. Thanks again for the help!

Brian

Here are a few pictures of the valves and circ pump

What is the boiler pressure when it is running?