Question for Brad..........

Unknown

On a constantly circulated zone with CI rads, with Pri/Sec boiler piping attached(through 2 closely spaced tees), do you think it makes any diff if the hotter boiler water is injected with the flow in the loop first, or against? I would think this way the "mixed" water will bring the boiler up to operating temp faster. This has been a debate up here for quite a while-now, what do you think?

Brad White_9

Hi Dave

Not sure if I grasp the condition entirely or what you mean by "against flow" versus "with flow". But let me try.

Diagramatically, the flow patterns would be in opposite directions, say the boiler loop is counter-clockwise and the radiation loop is clockwise. For the sake of discussion, let's say that each circuit circulates 5.0 GPM such that the secondary circuit can see anywhere between full boiler hot water temperature (100% boiler water) and room temperature return (0% boiler water). Sound ok?

Say 1.0 GPM of boiler water is called for so it enters the secondary (radiation) circuit upstream of the radiation circulator. It immediately mixes with 4.0 GPM the radiator return flow to achieve setpoint.

Round it goes, comes back to the closely.spaced.tees. That 1.0 GPM goes back to the boiler at return temperature. Mission accomplished.

Now, is your question, "where do I install the injection valve or circulator"?

In that case it would go on the hot water supply side, closest to the secondary (radiation) circulator.

If the question is, "I am using a 2-way modulating valve, where does it go?" I would say it could go on either bridge line between the circuits (flow will always enter from the hot water side anyway). My preference here is to put the valve in the supply side, not the return. Why, I cannot really tell you. I have done both but lately have picked that and stuck with it.

If the question is, "I am using a 3-way mixing valve, where does it go", I would say it takes the place of the tee just upstream of the secondary (radiation) circulator. (One always mixes upstream of a circulator for you have to pull through all ports. Otherwise you are diverting.)

Now, how badly did I mangle your question??

Cheers!

Brad

Unknown

Brad.............

Man, I had to read that-one a couple of times...... LOL! No mixing, injection or diverting valves here. What I meant was just a simple-loop constantly circulated to the rads, the boiler is tied to this loop with 2 closely spaced tees(4"), should the boiler water enter this loop first and return to the boiler in the same direction of the loop flow? or vice-versa. The VV way would bring-in cooler water to the boiler as it would`nt be mixed. (hope I said that right!)

Brad White_9

The BIM Conundrum....

Boiler Injection Module...

Same flow pattern, hottest water goes to the secondary (radiation) inlet tee first.

If you were to reverse this, injecting into the return side, there would be some rat-racing and a constant T-Mix happening at your closely.spaced.tees.

You would mix down, then lose some of that back to the boiler. Now, there is more to this than you are telling me. Is the goal to protect the boiler? Is there a boiler circulator (hope so)? Is this a conventional CI boiler?

Can you post a diagram, Dave?

Unknown

Yes...........

in this case it is just a bang-bang CI boiler, and of course it does have a boiler-pump to introduce this water to the loop. The HO complained about the rads "creaking" and when I looked at-it the boiler was starting to soot(its Gas fired), so I reversed the hot-tie-in point(at the 2 tees), from the boiler to introduce the hotter boiler water "with" the flow, and back to the boiler, and everything seems fine. As it seemed "tempered" better this way. By the way, I didn`t originally do this, I just "inherited-it".

Brad White_9

Your approach makes sense, Dave

from the perspective of protecting the boiler. There is no guarantee of course in that the flow rates are fixed (correct?)

So what you have is a jury-rigged bypass approach with "better than nothing" return water tempering. Hardly efficient or predictable control at either end but better than nothing.

No, Dave, it would never occur to me that you designed it that way. If you inherit systems like this, you need different relatives.

Here I was thinking I was helping to settle a debate raging north of the 45th parallel since Diefenbacher was PM....Back to hockey for you, eh?

Cheers,

Brad

Unknown

You did help...........

Brad, most 99% of what I see up here is not by-passed in any way, it`s just "rammed" right through and its very sad to see!
Yes I do watch hockey, and "Old Deif" has been dead along time! I know this isn`t really the way to solve the issue, but like you said "its better than nothing", and I see "nothing" everywhere here! PS- When I said "inherited", I meant the HO(not a relative), couldn`t get anyone to at least try to solve this. So she called me. I really appreciate your input!
Thanks.