repiping hot water radiators

Mike T., Swampeast MO

Use thermostatic radiator valves (TRVs) and EVERY radiator becomes it's own completely independent <I>proportionally controlled</I> "zone". Will cost MUCH less than re-piping the system. Comfort will be exceptional. Barring an exceptionally poor original system or really fu¢%ed up modifications, temperature imbalances will disappear.

joe_61

repiping hot water radiators

two story house, cast iron raditors one zone. Want to repipe to three zone house. What is best way to pipe. Hot water.Want to make two zones on second floor one on first. Should I use monoflow tee's???????

Mike T., Swampeast MO

If you don't use TRVs

And presuming this is currently a two-pipe system, monoflow tees are likely the WORST way to go. First, you'll need an accurate room-by-room heat loss. Then you have to completely engineer a multi-zone, one-pipe, mono-flow tee system. This will COMPLETELY re-piping AND re-sizing much or all of the radiation AND a near-boiler piping strategy that can actually deal with a multi-zoned, one-pipe monoflow system.

The alternative of "home running" supply AND return from each radiator to manifolds that serve each zone is not so difficult to engineer, but will still be MUCH more expensive and less versatile than TRVs.

joe_61

The problem is three family house one zone one stat.The time the heat reaches the last radiator, the rest of the house is over heated. Also if I used trv's would my circulator have to run constant. And what about a bypass.Plus all the piping to be heated on the supply and the return plus all the volume of water in the system. The circulator is constantly going off on low limit. Would a bypass help.

Mike T., Swampeast MO

The problem is three family house one zone one stat.

Even more reason to use TRVs. Even the simplest can be set to allow limited adjustment while still taking some brain power to defeat. Highly tamper-resistant models are available. The key is to allow a high limit about 3 degrees above the highest reasonable setting. With a 3 degree differential the valve will be WIDE open and turning up higher won't increase heating speed to any degree--in fact limiting will help prevent overshoot with iron radiators.

If I used trv's would my circulator have to run constant?

YES! Circulator will run ANY time heat is required in the structure. With a simple system, add a warm-weather shutdown that stops ALL heat and circulation in moderate weather.

And what about a bypass.

YES, you will need a differential pressure bypass.

Plus all the piping to be heated on the supply and the return plus all the volume of water in the system

All of that piping and volume will become your FRIEND in a constantly circulating system with proportional control. If the basement is unoccupied, do insulate everything accessible. (You should be doing this REGARDLESS!)

Occupants will have an EXTREME increase in comfort. Whoever is paying the energy bill can expect some reduction. How much? Mainly depends on how much the current boiler is oversized. Go first-class, use a condensing/modulating boiler and expect EXTREME reductions in fuel consumption.

joe_61

What I planned on doing was, split the heat into three zones. Repipe the bouiler and get rid of the two inch pipe all over the place.One apt. upstairs has 4 radiators, which probably over sized. The other second floor apt. has 5 radiators, oversized to. The main floor has 9 raditors, oversized.I was going to pipe them maybe a one or two pipe system. Also I have three White Rodgers stats. with remote sensors. Stats locked in basment room. All apt. set at one temp.

lekpeter

repiping hot water radiators

If it's a 2-pipe system, just build a header/manifold at the supply side of the boiler (pumping away) with 3 circulators, one for each zone, with integral flow checks and a similar manifold to grab the returns, with the bypass that you mentioned. Use a Taco or Argo multi-zone relay control to individually control the circs and you'll be in business. I've done a number of these old radiator systems this way; radiators are very forgiving.

lekpeter

repiping hot water radiators

If it's a 2-pipe system, just build a header/manifold at the supply side of the boiler (pumping away) with 3 circulators, one for each zone, with integral flow checks and a similar manifold to grab the returns, with the bypass that you mentioned. Use a Taco or Argo multi-zone relay control to individually control the circs and you'll be in business. I've done a number of these old radiator systems this way; radiators are very forgiving.

joe_61

Can I pipe in radiators with a supply going to one side, using monoflow tees. And have the return going to a return line with reglar tees.

joe_61

or should I make it a one pipe system

lekpeter

repiping hot water radiators

If it's currently a 2-pipe system, you need to determine which supply and return pipes go to the radiators of the respective zones you want to create. With that info, you will then have to cut, cap, hang some new pipe and tie the respective supplies and returns together. You now have 3 newly created zones.
Now you would go back to the boiler and build the supply manifold/header with the 3 circulators and the return header and connect your zones.

joe_61

Do I need to us MONOFLOW TEES.On a one pipe system

Mike T., Swampeast MO

With standing iron radiator? Most certainly yes! But again be VERY, VERY careful. Iron radiators are quite forgiving, but the ones in this system were designed for a two-pipe system where each radiator received nearly identical supply temperature! One-pipe systems with monoflow tees will reduce the supply temp as each radiator is taken off. May by OK, may be tolerable, may be awful. You MUST do the calculations to get an idea what to expect (and to even see if it's feasible).

The design of monoflow systems is HIGHLY dependent upon flow rate. For that reason, and especially in this application where your three "zones" are actually three different apartments, each should be SEPARATELY engineered with its own main piping and circulator. If you try to use zone valves and drive with a single circulator, flow will go completely out of whack as the different apartments call for heat (likely at quite different levels).

You'll also need to use primary-secondary piping with a separate boiler loop circulator.

See why I keep suggesting TRVs? Not only is cost likely to be significantly lower, but comfort will be higher!

Mike T., Swampeast MO

Almost sounds to me like you're wanting to use much or all of the existing return piping and then just throw in three different supply lines with monoflow tees to the radiators served by each.

If so, I'd rate the chance of complete failure as extremely high with the chance of even moderate success extremely low.

While I certainly haven't seen everything, I've never seen anything similar.

Monoflow tees are used on one-pipe systems. One-pipe monoflow systems require VERY careful engineering.

Two-pipe systems do not need monoflow tees. There is however VERY good reason that two-pipe mains travel in closely-spaced, parallel pairs! You'll need to either create three completely separate two-pipe systems with properly sized mains, or "home run" the supply AND return of EACH radiator to manifolds to serve each apartment (zone).

John Di Lauro

Sorry, don't mean to hijack the thread but this is closely
related to another thread I started.

If one were to split the existing sytem as you describe, would there be a need to increase the diameter of the header where the circ are mounted?

Mike T., Swampeast MO

Sorry to give the same suggestion.

"Zoning" an existing multi-floor, hot water system with iron radiators is extremely labor intensive and much of the existing piping will have to be replaced (or at least recycled and relocated).

Provided the system is reasonable to begin with, thermostatic radiator valves (TRVs) will require much less labor, far fewer materials and produce superior comfort. Some minor near-boiler piping changes will be required, but nothing like primary-secondary with multiple circulators or zone valves.

You'll also be able to take best advantage of condensing/modulating boilers and add exceptional efficiency to your exceptional comfort!