Single supply, split return monoflo. Pumping away without zone valves?

sixplex

This is what i currently have and it works ok.
Needs air/dirt removal because the water gets black over time.
Also need to change gates valves (all gates broken off) on the zones to balancing valves.

Since i'll be doing major work anyway looking to improve the overall design, any way to pump away aside from using a single ciruclator with zone valves? i.e. could i use 1 expansion tank for each return?

If i used zone valves i'm not sure it would be a net benefit. It would add another component (2 circs vs 2 zone valves and 1 circ). Increase overall complexity. Add head, common zone valves are all low Cv.

EBEBRATT-Ed

One expansion tank is fine. Move the two pumps to the red supply line pumping away from the expansion tank and the boiler. Connect the city water make up into the expansion tank line. Add an air removal device on the suction side of the circs (between the circs and the boiler)

As far as zone control you can use 1 or two circulators with or without zone valves. It's your preference. More zones give you zone control but if the house heats evenly with one pump and no zone valves thet will save on future replacement and repair costs.

hot_rod

Looks like your circs are pumping away from the boiler return.?

A single ECM delta p on the red pipe with zone valves would work fine. Air sep before the circ as Ed mentioned of course. Expansion tank is ok where you show it, if that is a cast or low pressure drop boiler.

A mag sep on the return is a nice addition if you go with ECM circ.

sixplex

Update the pic. CI boiler yes.

Need control of those zones for sure.

As i mentioned pumping away adds complexity in this case unless there is a way around that.
What am i gaining in return? Static fill must be high enough in the system that pumping into the expansion tank never caused any obvious problems.


Will the micro bubble remover not to remove air/hydrogen from the top floor rads unless i pump away?

hot_rod

My take on zone pumps vs zone valves is the gpm required. If one pump can move the entire load, and modulate via ECM ∆P with zone valves, what do a zone pumps running at the bottom of their curves, moving a few gpm accomplish?

If the various zones require 6- 8 gpm, in the mid curve of most small circs, then perhaps a zone circs make some sense.

I see a wall of a mechanical room covered with zone circs moving a few gpm each, or under 1 gpm in some cases, hmm?

One 40W ECM to efficiently move the entire load or two 80 watt zone circs.

sixplex

would the following work, or some variation of it?

i want to pump away but not thrilled about zone valves.
the taco caleffi 1-1/4 zone valves are also solder only, adding complexity with my npt pipes.

hot_rod

that is a new one on my, two tanks, two PONPC?

As for zone valves, 1" threaded valves are available from most brands. The valve is sized by flow rate not pipe size. The Caleffi 1" and 1-1/4 are both 7.5 Cv, so you could use a 1" and a couple fitting reducers for the 1-1/4" line.

Any idea what the gpm requirement is for the two zones?

EBEBRATT-Ed

No that is not the best way. Also, the make-up water must feed the system on the same side of the circulators as the expansion tank.

mattmia2

You could do it with 4 zone valves, 2 on each zone, one on each half of the split return.
wire the zone valve coils in parallel per zone,
wire the end switches per zone in series,
wire each zone's end switch series in parallel to a pump relay at the boiler.


You could also use the high cv caleffi "motorized ball valve" and use a relay to power close it.
https://www.supplyhouse.com/Caleffi-644260A-1-NPT-Two-Way-Motorized-Ball-Zone-Valve

You can not use gate valves for balancing, the gate will be damaged from the flow and the screw will be damaged by the vibration. Use globe or ball valves. globe valves give better control but are more restrictive.

@hot_rod this is a monoflow system that they have had a lot of trouble getting everything to heat on so we are kind of guessing at the flow requirements.(although i think the lack of balancing valves on 1 supply that splits then splits again at the split then combines at the boiler in to 2 circulators is much of their issue with it heating)

sixplex

hot_rod said:

that is a new one on my, two tanks, two PONPC?

yes, no literature i could find covers it


As for zone valves, 1" threaded valves are available from most brands. The valve is sized by flow rate not pipe size. The Caleffi 1" and 1-1/4 are both 7.5 Cv, so you could use a 1" and a couple fitting reducers for the 1-1/4" line.

Any idea what the gpm requirement is for the two zones?

it's low, condensation if it's too low is more of a concern than the building not heating.

the original design has no restrictions at the boiler, gate valves. i'm afraid to mess things up by increasing the head too much with gate valves, balancing valves, etc.

sixplex

Looks like this is the only way redesign my system.
1 additional electrical component to fail, 0 circulator redundancy, a lot more HEAD.
Is it even a better design than original??

From what i understand with a high enough static fill pressure, and a low head circulator, pumping away isn't even necessary because the pressure won't drop too low.

mattmia2

sixplex said:

it's low, condensation if it's too low is more of a concern than the building not heating.

Where is this condensation you are worried about? At the boiler, the higher the flow rate the more likely it takes away enough heat to bring it below condensing temps.

sixplex

mattmia2 said:

sixplex said:

it's low, condensation if it's too low is more of a concern than the building not heating.

Where is this condensation you are worried about? At the boiler, the higher the flow rate the more likely it takes away enough heat to bring it below condensing temps.

return temp under <135F leads to condensation / boiler damage, no?

mattmia2

This is an option to get around the relatively low Cv that is available in common zone valves, move the zone valves to where i've circled in red:

hot_rod

sixplex said:

hot_rod said:

that is a new one on my, two tanks, two PONPC?

yes, no literature i could find covers it


As for zone valves, 1" threaded valves are available from most brands. The valve is sized by flow rate not pipe size. The Caleffi 1" and 1-1/4 are both 7.5 Cv, so you could use a 1" and a couple fitting reducers for the 1-1/4" line.

Any idea what the gpm requirement is for the two zones?

it's low, condensation if it's too low is more of a concern than the building not heating.

the original design has no restrictions at the boiler, gate valves. i'm afraid to mess things up by increasing the head too much with gate valves, balancing valves, etc.

With cast iron radiators you can end up with an air bubble at the top of them, this acts as a another "expansion" tank, maybe multiple. So determining or predicting the PONPC becomes almost impossible. No reason to purposely induce that condition by installing multiple tanks.

As for return temperature protection, it depends on how often and how long you operate at cold conditions, below the fuel dew point. And that dew point moves around a bit based on the fuel how the burner is adjusted, CO2 reading.

It would be best if the entire combustion side, boiler, flue, etc dried out each time the boiler fires. Rule of thumb is at least a 10 minute run time. You can watch your system on start up and see what the actual warm up time is and decide.