How to replumb my hot water radiator heating system

pblackwood

I have a 60+/- year old, oil fired, two-pipe direct return, hot water heating system with three zones and 8 radiators in my house (albeit more radiators would be desirable) and one pump. The boiler itself is about ten years old and is rated for 180,000 BTU. The two storey house is about 2400 sq feet, a tad drafty, and marginal insulating levels. In the dead of winter and during high winds the system can more than heat the house. Over the years the system has been hacked to death….1-1/4” black iron which eventually reduces down to about 3/4” towards the end of the run, 1/2” & 3/4” copper, and 1/2” & 3/4” pex piping; three 1/2” zone valves, mostly basic cast iron heaters with manual valves (which are not used) one copper and alum fin baseboard radiator; some really hot and some marginally warm rads; and originally one zone system turned into three zones.

I want to raise my heating pipes in the basement and figure it’s a good time to replumb the basement portion of the piping system with pex (I.e. I’ll keep all the “vertical” steel piping that feed all the radiators, which are all on the upper floors) and install a manifold to better balance the system. I consider myself an advanced domestic handyman (lol) and have successfully replumbed my domestic water system over the years using a home run system. I figure I might try the heating system work myself.

Where’s the best place to go to get info on a proper system design. No one in my area is doing this anymore. All new installs are either in floor hot water via electric boiler, electric baseboard, or mini-splits. Is there a basic plumbing diagram I can refer to or a simplified design manual, etc. Any suggestions?

leonz

Any of Mr. Holohan's books on hot water heating will help you with your problem child of a heating system.

The issue for you is how much work are you willing to do and whether you want to correct the past plumbing errors to create a heating system with true balance using cast iron radiators to provide slow even heat with more thermal mass.

A heat loss study should be done and hiring a mechanical engineer affiliated with a large plumbing contractor after the heat study would save you work and money.

Snowmelt

where are you located ? You an do home run methods with pex and make a manifold at the boiler.

EdTheHeaterMan

start with this book. I has all the info you need to get the job done. Pipe sizing, piping design, circulator sizing, burner sizing how to convert gallons per minute to BTU per hour. https://s3.amazonaws.com/s3.supplyhouse.com/product_files/108119-Reference%20Guide.pdf

Once you understand the basics in this book, you will be able to design a working system. But read the book more than once. Each time I read it, I find another concept that I did not fully understand before. Not much has changed in the industry when it comes to proper design. Except perhaps the ECM circulator pump, that makes zoning with valves less problematic.

Dan Holohan wrote the book for us non-engineer types for the Bell & Gossett folks, so it is not signed by the author because it is owned by B&G. So it is not really his property, but you can see the writing style is definitely Dan's.

DCContrarian

What problem are you trying to solve? The purpose of a heating system is to provide comfort during the heating season. Is the system not providing comfort currently — are there spots that are too hot or too cold?

pblackwood

Thanks guys. I really have three objectives in mind. The first is to improve headroom in my basement as I want to do a total rebuild of my woodworking shop and the existing low pipes keeps me from rolling around some of my tools, like a bandsaw and drill press. The second objective is to straighten away the whole heating system so when I go to sell the house in 10-15 years my heating system doesn’t get trashed by the buyer’s home inspector…lol! A third objective really is to try and even out the heat throughout the house….too many hot and cold spots. I’m up to doing a total rebuild of the system if that is what it takes. I already did that for the electrical system and the plumbing system.

I’ll start with the book suggestions.

As to where I live, St. John’s, Newfoundland, Canada. (800 miles east of Maine….big island!) We have a 9-month heating season. Quite often damp, wind, and miserable 2-1/2seasons of the year because of the ocean currents, but never really frigid cold like in some of the northern states. Our January design temperature is -16C but I haven’t see that in a decade or more. Usually winter bounces around 2 to -10C.

Cheers, Paul

DCContrarian

The answer to comfort is zoning, as many thermostats and zone valves as you can stomach. It's also nice to have isolation valves so that if you do have to work on the system or add radiators you don't have to drain the whole thing.

I'd start by making a map of the existing system, where the radiators are and how they're connected. Probably where you want to end up is cutting out everything between the basement ceiling and the boiler, then putting a manifold on the supply and return of the boiler and reconnecting all those pipes to the manifold. But you want to draw it all out because you may find some of the lines are fine where they are.

EdTheHeaterMan

If you can make a floor plan with the locations of each radiator and the relative location of the boiler. A two story home with a basement might look like this:

On the floor plan mark it up something like the Blue = CI radiators, and the Red = Copper/Alum fin baseboard and there is a kick space convector under the kitchen sink, etc.

With something like that and perhaps the pipe size that feeds each radiator, I can offer some ideas for consideration.

Some ideas to consider are to use a manifold near the center of the home to have PEX home runs to a manifold. Many manifolds have adjustable valves to adjust water flow, or those valves can have motorized heads that are controlled by thermostats to zone each room separately.

Another thought is to have a constant flow to all the radiators with non electric thermostatic valves on each radiator. to maintain better comfort use Outdoor Reset to modulate the water temperature based on the outside temperature.

There are several other ways to do it with less work using only the basement risers to each heat emitter. Based on how those existing pipes are connected, that may be the best option.

JakeCK

180k btuh seems a tad big even for 2400sq ft, have you considered installing a buffer tank? Let the aquastat on the buffer call heat from the boiler and allow for nice long burns. And then feed the manifolds and rads from the buffer tank. When a t stat calls for heat, the zone valve opens, circulator kicks on and heat is delivered from the buffer to the zone calling for it. The boiler may or may not run during the cycle.

You can also do continuous circulation, and TRV's on each rad. Make sure to use the right type of circulator. There is also the possibility of ODR with TRV's and even with zone valves. These options, once dialed in, would provide for the best heat you could possibly experience short of in floor heating. You would set it to whatever temperature you desired and that is what you would have and your radiators would always be warmed to just the right temp to maintain equilibrium.

But do the math, it wont happen by accident.