piping suggestions

IZZY

Need suggestions for extending heating system into an addition. I've included a sketch to try to clarify.  Hope it opens properly.

The system is a single zone hot water monoflo system.  The house is 2 stories, plus basement, with attached garage.  Basement mostly below grade, addition to be built above garage.  Sketch shows the monoflo loop, and I drew 1 radiator on 1st and 1 on 2nd floors to illustrate typical piping of system.  Incidentally, all tees are 1" x 1/2".

Plan is to add sunrads in addition in order to match rest of existing house.  New piping has to run from basement to 2nd floor, and then to new rads, and that's a pretty long run for a monoflo tee (huge pressure drop I think).

I want to keep the new rads on the same zone, and I'm shooting for simplicity.

Any ideas would be appreciated.  Thanks.

JStar

I would...

...use standard tees, and set up a secondary loop with it's own circulator.

Gordan

Is that diagram correct?

It shows TWO monoflo circuits piped in parallel. If that's correct, then adding more diverter tees, or anything else that adds appreciable pressure drop, to one side could affect the flow on that branch, unless you have a way to rebalance. Running the new circuit off of a pair of closely spaced tees with their own circulator, as JStar suggests, would seem like the least treacherous path; then the only thing you've got to worry about is temperature drop in the main. Since all other radiators are already sized the way they are sized, you might be best off teeing in AFTER all the other emitters on the branch, and sizing the radiators in the addition for whatever supply temperature will be available at that point.

IZZY

wiring?

How do I control the circ?  Do I wire it in parallel with the main circ?

IZZY

pipng

The system is in fact piped this way, although there are many take-offs on the loop.  Each radiator has a standard tee on the supply side and a monoflo tee on the return side.  I'm not that farmiliar with monoflo systems, but I thought that this was the way it is supposed to be done.  I can say that the system works fine and the rads at the ends of the 2 split loops are about the same temp (to the touch).  If it can be refined, I'm open to ideas.  Thanks.

Gordan

Now I'm even more confused...

When you say "supply side" and "return side", do you mean relative to the radiator, or relative to the boiler?



In a diverter tee circuit, also called one-pipe hot water, radiator risers are piped in series to each other to a common main that goes from boiler supply to boiler return - supply 1, return 1, supply 2, return 2, etc. Occasionally you could see an arrangement like supply1, supply 2, return 1, return 2 - this is to create a higher drop along the main between supply 2 and return 2, and force more flow into that branch, if necessary (typically only used for radiation below the main.)



Is that how yours is piped - two of these circuits in parallel?

IZZY

piping

Yes, the pipe leaves the boiler, loops around the basement ceiling and returns to the boiler.  Along the way, there will be a standard tee, whose branch supplies a radiator (supply 1) and whose run continues on into a diverter tee, whose branch recieves the return from that radiator (return 1), then on to the next standard tee to supply the next radiator (supply 2), and the into the next diverter tee to recieve the return from the next radiator (return 2), and so on until the main loop returns to the boiler.  The only difference from this is that there are parts of the house where the rad on the 2nd floor (rad 1) is directly above the rad on the 1st floor (rad 2).  Here, the piping along the main is supply 1, supply 2, return 2, return 1. 

Gordan

Ok, all's right with the world

That radiators at the ends of both runs feel equally warm means that the two circuits are probably balanced well enough. Don't do anything to imbalance them. The closely spaced tees/separate circulator at the return end of one of the branches would be least likely to cause problems with existing stuff.

IZZY

thanks

Thanks a lot.

JStar

Wiring.

You can wire a switching relay to a new thermostat in the addition to control the pump. Might as well set it up on its own zone while you're doing the work, and have the open framing. If not, you should have a dedicated switching relay for it anyway. You can use the dry contacts on the new relay to turn the boiler on at T+T. Or use the dry contacts on the aquastat to turn the secondary relay on.

IZZY

wiring

Thanks for the help.

Mark Eatherton

How's he going to keep from overheating the rest of the house???

If the addition is a higher loss appendage, it will probably call more than the core of the existing house...



ME

IZZY

good point

I'm assuming the addition will have less of a heat loss due to the fact that the existing house is approx. 60 yrs old, where the addition will have the proper insulation, house wrap, etc.

I was trying to keep the addition on the existing thermostat, but now that you brought that up, it might be better putting it on it's own zone.

Incidentally, somebody suggested cutting in a tee after the circ pump on the supply side of the monoflo loop (at the boiler) and a tee at the return side of the loop (also at the boiler) to make it like a split zone.

Any thoughts?

Gordan

Right...

I think a single zone approach, with the emitters in the addition being appropriately sized, would avoid those issues. The circulator for the addition runs when the system circulator runs. Simple control, enabled by appropriate design.