Plumbing help in the Garn Barn

[Sawyer]

My piping requirements seem rather simple, perhaps I am too naive. High temperature for the house which is the largest volume (max 10gpm if Wirsbo is correct 65gpm), low temperature requirements for the shop which is in-floor heat only (max 35gpm). I do not anticipate any further buildings or loads.

Is it necessary to use Primary and secondary piping for these needs using the Garn?

Please advise me in the right direction, I have been reading the archives so much that I feel you are all my neighbors! It is time I make some decisions. I picked up my black pipe Monday and finished insulating my overhang ceiling last night. I will start on the OSB today.

I have attached a sketch of roughly how I plan to plumb the system using Isolation valves to utilize the existing pumps. This diagram does not show all valves, strainers, unions, relays, etc. I do realize I may be better off isolating the boilers but I am not that far in the planning stage today to address that topic. My main concern is piping the lines in the Garn barn at this time.

Thanks for the help, George

 

[Jim K in PA]

George, it looks fine. I see no reason you can't plumb it with simple manifolds. You have one less pump this way. Just make sure that both main supply pumps have integral flow check valves, and size them appropriately. Use a full 2" main on the supply manifold.

 

[Sawyer]

George, it looks fine. I see no reason you can't plumb it with simple manifolds. You have one less pump this way. Just make sure that both main supply pumps have integral flow check valves, and size them appropriately. Use a full 2" main on the supply manifold.

Jim, I bought my black pipe for the initial set up. I bought 1 ½” for supply and return :red: . I have a load max of 93,000 & 32,000 BTU on the two circuits. I had thought that 1 ½” would more than carry this load. Did I screw up? Should I have stayed with 2” on the supply side? It would be better for me to know now than later. I did not pick up on the 2" supply in diagrams and thought that was for systems much larger than mine. I probably should have asked before I had the pipe cut and threaded.

Thanks again, George

 

[Jim K in PA]

You should be fine, but I suggested 2" so that you have the highest NPSH above the pumps. Depending on your actual flow rates, you might induce suction boiling in the supply manifold when both pumps are running and the water temp is over 200. Keep your pumps as low as possible. I used 1.5" piping in my primary loop before the pump, and if I were to do it over again I would use 2".

 

[Sawyer]

Thanks Jim, following your reasoning, if i had to do it over, I would go 2" also. I just focused on the BTU capacity when considering size. I had the pipe cut and threaded so my tees will be 8” off the floor. I will check when I have my pumps chosen and my system design finalized. The warm weather that arrived here is sure nice for working in the elements, didn't even need a sweatshirt under the coveralls today!

George

 

[heaterman]

Looks good to me.

1-1/2" piping will probably do the trick for you. Try to keep the pump(s) on the open side of the HX's as low as possible and if it's feasible, orient them with the flanges vertical to aloow them to naturally purge any air.

 

[jebatty]

Your diagram shows the plate HX are plumbed parallel flow rather than counter flow, and counter flow will provide more effective (higher efficiency) heat transfer. The house HX coil likely needs water as hot as you can provide, unlike the in floor radiant. Is it possible to feed the HX coil before rather than after the radiant? For the same reason, due to btu line loss + hx btu transfer loss (approach temp target usually is 10F), you may want to plumb the HX coil first to provide it with the hottest water. Last, for the same reason, you may want to fire the Garn hot (190F) to provide maximum heat to the HX coil.

 

[Sawyer]

Looks good to me.

1-1/2" piping will probably do the trick for you. Try to keep the pump(s) on the open side of the HX's as low as possible and if it's feasible, orient them with the flanges vertical to aloow them to naturally purge any air.

Thanks HM,

Pumps on open side low as possible relative to HX, Garn, LP Boiler,.....?

Do you mean pump/pumps mounted vertical? (I am thinking flanges vertical would make pump horizontal. I am new to this strategy)

Learning as I go, George

 

[Sawyer]

Your diagram shows the plate HX are plumbed parallel flow rather than counter flow, and counter flow will provide more effective (higher efficiency) heat transfer. The house HX coil likely needs water as hot as you can provide, unlike the in floor radiant. Is it possible to feed the HX coil before rather than after the radiant? For the same reason, due to btu line loss + hx btu transfer loss (approach temp target usually is 10F), you may want to plumb the HX coil first to provide it with the hottest water. Last, for the same reason, you may want to fire the Garn hot (190F) to provide maximum heat to the HX coil.

Thanks for the suggestions Jim.
You have a good point on the Coil and I will put this as #1 heat draw. We have an extremely well insulated home. Unfortunately the views demanded many windows that are not well insulated even with triple pane glass. The lower level has 2250’ of in floor with 4 zones. The upper level, other than the master bath (in floor) is off the coil in the plenum, divided in two zones. I have noticed when the entire in floor heat is turned on the plenum fan hardly runs, even at -20. I am hoping this is the case when the Garn is connected. It seems that the lower level heat works it way up through the floors to the upper level.
I do plan to run the pumps at the Garn priority to the house as the shop is a workshop.

Hope this Hx plan looks better.

George

 

[pybyr]

Looks good to me.

1-1/2" piping will probably do the trick for you. Try to keep the pump(s) on the open side of the HX's as low as possible and if it's feasible, orient them with the flanges vertical to aloow them to naturally purge any air.

Thanks HM,

Pumps on open side low as possible relative to HX, Garn, LP Boiler,.....?

Do you mean pump/pumps mounted vertical? (I am thinking flanges vertical would make pump horizontal. I am new to this strategy)

Learning as I go, George

Pumps on the open side should be as low as possible compared to the highest point of 'open water' which I expect will be the top of the Garn's water. The reason for this is that since the open side will have no pressure other than the weight of the water, you want a location that will maximize the "NPSH" (net pressure suction head) at the inlet to the pump. Pressurized systems can boost NPSH with their internal pressure, unpressurized systems can only achieve it by savvy location of the pump at the lowest feasible point, to maximize the height of the water column above. Pumps pulling from a situation with inadequate NPSH for their design often end up experiencing 'cavitation' which is when the reduced pressure of the water going through the pump (due to the pump's own suction) causes small pockets of water to violently flash to steam within the pump. The result is noise, and in some circumstances where cavitation is frequent and significant, damage to and eventual possible destruction of the pump's innards (which at least potentially could release bits of disintegrating impeller into the flow- probably not good for your plate HX).

If you haven't bought pumps yet, you may want to look not only at the flow rate and head capability, but also the NPSH ratings for the pumps that you intend to use on the open side; they're generally available, though seemingly not headlined as prominently within the manufacturers' literature.

With regard to mounting of the pump, it should always be done in a manner in which the pump's shaft is horizontal-- anything else is bad for the innards- so the reference above is to flanges at top and bottom, with the motor pointing horizontally out the side.

Happy installing! and enjoying your progress reports.

 

[heaterman]

Looks good to me.

1-1/2" piping will probably do the trick for you. Try to keep the pump(s) on the open side of the HX's as low as possible and if it's feasible, orient them with the flanges vertical to aloow them to naturally purge any air.

Thanks HM,

Pumps on open side low as possible relative to HX, Garn, LP Boiler,.....?

Do you mean pump/pumps mounted vertical? (I am thinking flanges vertical would make pump horizontal. I am new to this strategy)

Learning as I go, George

Let me rephrase; any pumps on the garn side of the HX should be a low as possible and the water flow should be vertical through them, preferably upward.

 

[Sawyer]

Thanks Trevor,
I haven’t purchased pumps yet, I will study the specs. As you and others have mentioned, I will be aware of the NPSH and place my pumps accordingly. I would have made a big mistake without this information.

Thanks Heaterman, I now understand clearly.

More to come!