Hot water zone added to steam system is a total bust

gilead1234

With Boston in a deep freeze, it's become impossible to avoid dealing with the shortcomings of the (gas) heating system I inherited when moving into my home, and I'm looking for advice on how to proceed.

In short, it's an old house with a gas boiler, and while most of the house is heated by a one-pipe steam system going to old radiators, a second zone was added at some point. The radiators were pulled out of the large living room, and replaced with a hot-water baseboard system — with two glaring problems:

First, when both zones are running at the same time, the hot water system starts gyrating and loudly clanking, I assume because the water is too hot and flashing to steam, creating air gaps (steam gaps?) that shake the tubing.

Second, especially when I run only the hot water zone (to avoid the problem listed above), the baseboard isn't able to sufficiently heat the room. I had it on for several hours, and it never broke 60, though the baseboard was warm the whole time and the thermostat was set to 68.

Not sure if those two problems are related. I know there is a way to do this setup correctly (https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler), but clearly mine isn't, considering the sounds and the weak heat, and the fact that there's no heat exchanger, though the link above suggests that would be good.

Bottom line, I'm wondering if there's a way to fix the current system so that it runs quietly and gets the baseboard room warm enough? Or if it is even worth turning that room to steam-heated baseboards? And especially, if there's anyone can recommend an expert in the Boston area that really understands this kind of stuff inside and out, so I can feel confident taking their suggestions. Any help is much appreciated!

KC_Jones

@Charlie from wmass I can never remember if you service Boston.

If he services your area Charles should be able to help you out.

Jamie Hall

It probably can be done; most things can be. Whether it can be done simply is another question. Is this living room hot water zone above the boiler? If so, you almost certainly will need a heat exchanger -- for the simple reason that the pressure in that hot water zone will be too low, and indeed the hot boiler water will flash into steam and collapse and make noises. If you run a separate hot water system through the heat exchanger, you can run it at enough pressure to calm it down. If they are on the same level, you should be able to do it without the heat exchanger.

The other problem is -- how much baseboard radiation do you have, and is it even capable of putting out enough heat to heat the space? It might not be.

Mark N

If these zones are installed properly they'll work fine. I have one off of my steam boiler that uses a heat exchanger to heat 2 rooms and my front entrance way. I used cast iron baseboard when i installed mine. Also be aware the zone should never exceed the pickup factor of the steam boiler. If it does it will affect the ability of the boiler to make steam when both zones run at the same time.

EBEBRATT-Ed

Yes it can be made to work. And yes as @Mark N pointed out the hot water zone cannot exceed your pick-up factor

j a_2

Post some pictures of your boiler and most importantly the piping around the boiler...what side of Boston are you on?

gilead1234

Many thanks for all the replies. So it sounds like I definitely need a heat exchanger, because the living room is on the main floor, above the basement. The room is about 12x26 feet, and there is about 21 feet of baseboard along one wall. How do I figure out the pickup factor, and whether it's exceeded?
Some pics of the (Medford, MA) rig:

AnthraciteEnergetics

It will work fine without a heat exchanger as long as there is a bypass installed to keep the water in the zone below 200 degrees. I have the boiler in the basement feeding a zone on the 2nd floor with no issues. And I am running 200 degree water through a toekick heater for a large bathroom (need those BTUs especially right now)

Air might be trapped up at the top of the zone, a lot of smaller pumps cant generate the static head to get water up two floors to purge that air out, necessitating filling with a hose from the city water supply via the purge valve that should be installed.

AnthraciteEnergetics

You have to figure out the EDR of the steam radiators and compare with the value on the boiler. The value on the boiler already includes a 33% factor.

If you found you had 500 sq. ft. of radiators, that's 500 sq. ft. * 240 BTUh/sq. ft. = 120,000 BTUh of steam radiators.

If your boiler has a "DOE Output" of 180,000 BTUh, your pickuo would be 120,000/180,000 = 0.66 or 66% of the boiler is utilized, leaving 33% as your pickup factor. That's 180,000 - 120,00 = 60,000 BTUh left for your water zones (including that indirect tank). You can put more water on than that, but the steam flow to your rads will be lowered when the water zones are calling and the system will be under vacuum.

j a_2

You got a few things going on there with that boiler. Not a lot of steam guys like Indirects off gas steam in these parts...at least I did not...secondly I am as sure as one could be from where I sit that your condensate loop needs to be up graded properly...I saw very few if any undersized steam boilers so I venture to say it’s doable.... who and how they do it is the question.....not a project for the wannabes and I think cans, or in fact one that says I need to call the tech department...sorry for carrying on...if I think of someone I know of round these parts I’ll pass them along

STEAM DOCTOR

What @AnthraciteEnergetics said. Also, I would remove the Flo check. I typically set these systems up without any sort of check valve or flow check. Don't usually see any issues with gravity flow. Maybe because of the low pressure in a steam boiler. The flow check creates extra resistance. Just a thought. The heat exchanger is more of a foolproof method but not necessarily needed. You definitely would benefit from having an expert like Charlie fixing it up. Definitely could be fixed up. Switching back to steam will be a costly and unnecessary undertaking

Charlie from wmass

Flow checks are very important for the system not installing it leads to Runaway water temperatures it can also lead to the water flowing back to the boiler and flooding it. Proper selection of circulator pump is important it seems that nobody wants to tell the people that they need a three piece stainless steel pump. I have dozens of these systems out there without any issue but they are piped properly.

STEAM DOCTOR

@Charlie from wmass. I am certainly in no position to argue with someone of your experience and expertise. Just my personal experience. My earlier "water loop off steam boiler" systems all had flow checks. I think that i had one troublemaker that I attributed to pressure drop. I eliminated the flow check on later systems and have not had ghost flow or gravity glow issues or any other issues. Not quite sure why. Maybe because the steam system is open and boiler and steam pipes are much larger then the water loop pipes? Maybe because low pressure in steam systems compared to true hot water systems? I have not put in many of these systems. Just my .02