Fix faulty split loop or convert to single loop?

peedee360

I have a 2 zone house 20'x40' footprint, upstairs and downstairs on zone valves, single pump on the return side, both were simple single loops but at one point during a renovation the downstairs loop was split into 2 loop with ball valves on the returns. The loops are very uneven and I don't get enough heat on one side (both sides have been purged). One loop is shorter and travels directly into the living area. the other loop is much longer and travels through an unconditioned crawlspace (zone 6A). Obviously they are unbalanced and I can't seem to get it right with the ball valves. I am going to repipe to remove the old polybutylene pipes. I am unsure if I should return the system to a single loop to simplify or keep the 2 loops and add the correct balancing valves. If I make a single loop, I am concerned the last sections will not get enough heat, and if I add balancing valves I am not sure which to get. I have driven myself crazy trying to figure this out and it is almost heating season again!

Jamie Hall

You really could go either way, and there are arguments for both. Single loop -- simplicity. Split -- control. As you have discovered, balancing is the key -- and ball valves, while not hopeless for balanacing (they're better than gates, but that isn't saying much) aren't that good. I'd get proper balancing valves and go that route if it were mine.

hot_rod

Go with a balance. With one long loop you tend to run out of heat output at the end and may not be comfortable.

Balance valves run from mild to wild. Ball type are very common, just don't close them more than 75-80%. B&G Circuit Setter is perhaps the most popular balance valve around, it is a ball valve style.

Globe valves are another option.

Any ball valve will work, if you want a specific balance valve you need a differential pressure gauge to connect to the ports to read what they are being adjusted to.

A nice compromise if you want to know the flow is a Quicksetter which has the flow reading on the valve.

Is this fin tube? How many emitters on the split? That would indicate what flow rate you are trying to adjust to. Above or below 2 gpm, for example.

mattmia2

You could also put a section of smaller pipe in the short loop to help restrict it without the balancing valve or put separate zone valves and t-stats on each section. If you go the zone valve route you could chose a higher and lower CV zone valve for each to help balance.

peedee360

hot_rod said:

Go with a balance. With one long loop you tend to run out of heat output at the end and may not be comfortable.

Balance valves run from mild to wild. Ball type are very common, just don't close them more than 75-80%. B&G Circuit Setter is perhaps the most popular balance valve around, it is a ball valve style.

Globe valves are another option.

Any ball valve will work, if you want a specific balance valve you need a differential pressure gauge to connect to the ports to read what they are being adjusted to.

A nice compromise if you want to know the flow is a Quicksetter which has the flow reading on the valve.

Is this fin tube? How many emitters on the split? That would indicate what flow rate you are trying to adjust to. Above or below 2 gpm, for example.

I hope you can follow this, its a little nutty, everything is piped 3/4" copper and polyb, with slant fin emitters.

First loop is a few feet up into a room and then 8' fin, 5' fin, 8' fin, then it returns to the boiler over the fins.
Approx 50' total run, 21' of emitters

Second loop: 30' in warmish basement, up to 8' fin, down into unconditioned crawlspace (non vented, encapsulated and insulated) 25', up into room 16' fin, returns over the fins 16', back into crawlspace for 21' and basement for 30' back to boiler.
Approx 145' total run, 24' of emitters

Let me also throw another wrench into the plan, I want to add a hydronic kickspace heater to this zone as well.

hot_rod

So a total currently of 45' of fin tube?
X 550 btu/ ft = 24,750 BTU/hr that you can transfer

24' = 13,200 BTU/ hr 1.3 gpm
21' = 11,550 BTU/ hr 1.1 gpm

The spec sheet on the kick space heater may show the equivalent feet of fin tube to add into that circuit. I'd guess 10', also the BTU/ hr it can move. Being a forced convector it will be higher that 10" of fin tube.

For my money I'd use two zone valves and a delta P circ like the Grundfos Alpha. Once dialed in it will move exactly the gpm each zone requires weather one or both are running. probably running about 20W or less power consumption while not over pumping.

If you add ball valves somewhere on both circuits you could manually balance also.

peedee360

hot_rod said:

For my money I'd use two zone valves and a delta P circ like the Grundfos Alpha. Once dialed in it will move exactly the gpm each zone requires weather one or both are running. probably running about 20W or less power consumption while not over pumping.

If you add ball valves somewhere on both circuits you could manually balance also.

Thanks Bob, Unfortunately adding a zone will not work, the entire first floor of my house is almost all open plan, so I am now planning to keep the 2 loops but add Quicksetter valves to help properly balance them. Unless you mean the 2 zone valves/pumps are used for one zone?

It looks like for me the Quicksetter+, 3/4" with a .5-1.75 gpm range is what I need?

pecmsg

peedee360 said:

I can't seem to get it right with the ball valves. I am going to repipe to remove the old polybutylene pipes.

Virtually imposable to balance with a ball valve, Open or closed no in-between!

hot_rod

here are some common ball valve style balance valves.
The main difference between these and plain ball valves are the PT ports to connect a differential meter on, with the B&G Circuit Setter.

The Quicksetter has the meter built on and you can balance within fractions of a gallon.

The Dahl mini ball valve has been used on radiant manifolds for many years, both as a basic ball valve and this balance style.

With a ball valve you do not want to choke too much, notice the B&G indicator goes to 50%. At some pont it is better to slow the circulator instead of a big reduction at the balance vale, regardless of the type of valve. Variable speed circulators are a great option.
Excessive chocking of flow can lead to cavitation.