Parallel Pumps instead of VFD

[Mid Michigan]

Well I am still looking for away to have a secondary pump and have it run proportionally to the load on the loop.

In Taco Technical Document 10 page 5 it states to run two pump parallel and you will double your GPM. This has me interested.
I can possible run 5 small pumps if I want and stage them on in proportion to the load as zone valves open.
Even use a step controller with a signal going to it.

Has anyone done this before?


(broken link removed to http://www.taco-hvac.com/uploads/FileLibrary/SelectingCirculators.pdf)

 

[Gooserider]

Might work, be sure to put flow checks in all the pumps so that you can't get backflow through the ones that are off...

However my suspicion is that you would be paying far more for that many pumps and associated control setups as you would for one pump with VFD or one of the new temperature / pressure responsive ECM motor pumps.

Gooserider

 

[jebatty]

...run two pump parallel and you will double your GPM.

Doesn't pass the smell test for me. Other things being equal, double the flow and head increases by 3-4 times. Flow will increase over one pump, but not by a factor of 2, IMO.

I already do this somewhat, not based on demand, but based on boiler output, as storage is loaded. Grundfos 15-58 on M is the main circ, but when boiler output reaches 185F a Taco 007 kicks in to increase gpm's. Purpose is to reduce idling, which starts to occur as return temp rises above 160F. It is effective.

 

[kabbott]

Might work, be sure to put flow checks in all the pumps so that you can't get backflow through the ones that are off...

However my suspicion is that you would be paying far more for that many pumps and associated control setups as you would for one pump with VFD or one of the new temperature / pressure responsive ECM motor pumps.

Gooserider

Agreed, by the time you buy all the pumps and controls I think you might as well spring for the the more exspensive vfd/ecm setup.

On the positive side multiple "cheap" pumps may be easier to maintain. I tend to shy away from the fancy setups, if a pump goes south in the dead of
winter on a Sunday I have a much better chance of finding a replacement at cheap/reasonable price.

An example: a variable speed injection mixing setup....works great but unless you HAVE to have it it adds a lot of "pieces" to the system that will need to
be maintained.

I like the KISS principle(keep it stupid simple) when it comes to the mechanical.

 

[kabbott]

...run two pump parallel and you will double your GPM.

Doesn't pass the smell test for me. Other things being equal, double the flow and head increases by 3-4 times. Flow will increase over one pump, but not by a factor of 2, IMO.

I already do this somewhat, not based on demand, but based on boiler output, as storage is loaded. Grundfos 15-58 on M is the main circ, but when boiler output reaches 185F a Taco 007 kicks in to increase gpm's. Purpose is to reduce idling, which starts to occur as return temp rises above 160F. It is effective.

Yes and No

If the loop is sized for low head with all pumps running there will be a small increase in head as each pump comes on, however keep in mind
he will be opening zone valves as the extra pumps come on line which will counteract this to some degree.

My question is why? If this is a new setup it would seem much more simple to zone with pumps. I know many frown upon this but I can buy the pump
for about the same price as the zone valve. Instead of using 5 parallel pumps just eliminate the zone valves and use the 5 pumps on five
zones. (or however many zones you have)

 

[jebatty]

Good points -- a little more complex than it appears.

 

[Mid Michigan]

Nice input guys.

Here is a drawing of my set up: http: //www.hearth.com/econtent/index.php?ACT=24&fid=21&aid=26406_S7s2Uni30g7yTGqMeqCz&board_id=1

I have changed things a bit and brought my GPM down to 18 and the head down to 26'.

At 26' of head I can use 3 Taco 0011 to reach 21 GPM or 5 Taco 009 to reach the 21 GPM as my zone open up. I am thinking less power consumption and cheaper installation as far as compared to a pump with a VFD that pushes 18 GPM at 26'. Honestly, I haven't even been able to find a pump/VFD that size that is not 3 phase.

As far as controls, that is not an issue for me as I do BMS for a living. That's the fun part to me. Its getting the most efficient mechanical system I can that concerns me right now.

If I interpret TD-10 right only the GPM goes up not the head???????
Also I agree with the idea of having a 009 or a 0011 laying around for a spare. Maybe one will go out but not all of them at the same time.

Thanks for your input and keep it coming.

 

[kabbott]

OK a lot going on there....
Hopefully a few of the pros will give some input, You have quite the mix of loads, some high temp some low.
I know you say you have reduced flow somewhat, but as it is drawn in the link the flow on the right side of the hyd separator is much more then
the left, which in itself is not a problem, but it will cause mixing which may be a problem when heating from storage(lower temps as storage drains)
esp with the furnace exchangers which I presume need fairly high temp water.

Can you post the file so it can be opened with the actual taco software?

That is a big load but The head seems painfully high. Glad I don't have to feed the monster.

 

[Mid Michigan]

Can't send file through Hearth.
Kabbott, did you get PM?
Thanks,

 

[kabbott]

Got it, Email sent

 

[Mid Michigan]

Anyone else running or even tried running parallel pumps for variable GPM?
Seems like a possible efficient way to get the most out of this system.

 

[kabbott]

Got a chance to look at the file you sent me. While I think you could do this with staged multiple pumps I can't help but think there may be
a better way.

I have no idea on the layout of the system, shop to house distance and such, storage open/pressurized and so on.

I believe I would try to treat the house/shop separately. How about a large low head loop from the separator to the house and
shop(or maybe 2 loops one for each) and then pull off that loop with close tee's and separate pumps for house and shop?
This will drop the head on your main loop dramatically and you should be able to use a much more efficient pump.

On the boiler side you could use a setup similar to the "simplest pressurized system" sticky and maybe eliminate the separator completely.

Something like DonL used but instead of the primary loop you could come off the separator or right out of storage tank if pressurized.
https://www.hearth.com/econtent/index.php?ACT=24&fid=21&aid=26570_boyuLyLSqgPshMAz5aZh&board_id=1

Can you stage some of the loads? Maybe the DHW in the shop and house are not used at the same time, that would cut the load some.

I also would check all the head figures in the software, Taco HSS inserts some unrealistic numbers for some things. Storage for instance shows
8.6 ft in the file you sent me which does not seem right, I think it's showing it pumping in series with the boiler pump.

Sorry this does not answer the original question, I have a bad habit of creating more questions... :coolgrin:
I suppose if you were to stage multiple pumps that would be just as efficient as long as they are sized correctly and you can control them well enough????

Kris

 

[Mid Michigan]

Kris,
Thanks for the time spent,

My house is 30' away from shop that will be built next spring. I have 1" pex going to house from OWB right now. Shop floor will go over were OWB is now, so I am trying to reuse same pex for house.
As far as loads you are right. How often will they all be on at the same time and if so for how long. Shop DHW probably is not all that important. I could design the system without in and not even notice when I do use it.
I have been really looking at a Garn. If I go that way that throws the hole storage issue out the window.

I am use to lots of controls on a heating system as that is what I do with commercial buildings. Many of them have VFD's. Matter of fact we are in the process of changing out AHU's to VFD in a hospital. All to save power. But when it comes down to a small system like this one of mine I can't see where a VFD will ever pay its self off. Thus staging some cheaper pumps.
20' of heat I can move 5 gpm with a 009. That means I need 4 pumps to stage. I think I would have that many circ. pumps if I go the other way.

I originally had a pump on each load. I though after getting some advice from this forum of trying to use zone valves and stack all those pumps in one place for variable speed. I think it would work.

I am definitely learning a lot and will have it figure out by next heating season. I will look into your other ideas!

Thanks for the input

 

[kabbott]

You may very well be right about it being better with staging the pumps. My biggest thought is trying to isolate the high head
loads so you only need a few pumps capable of high head and the rest could all be low head, cheaper pumps. As it stands now it seems
most if not all pumps needed are going to be medium/high head and if you can eliminate some of that it seems it would be more efficient.

Either way I would look into incorporating the simplest pressurized system in the sticky, you may be able to eliminate the hyd. sep. and a pump
if not a few more pieces. Basically use the tank/near tank plumbing as the Separator. There is a recent thread on the subject.(last day or so).

As far as the Garn, If you have the room I would give very serious thought to it, Can't get much easier plumbing the storage with a Garn. ;-)

 

[Mid Michigan]

You bring up the hi head and it takes me to my other post. If I may merge into that one.

In order to get the right amount of water (gpm) through each zone, regardless of when or how many are opened, would this be correct?

Figure head pressure on all zones.
Take highest one to base all your calcs on.
Put circuit setters in all other zones so they match the high zone.
Now each zone will get the right gpm regardless of when or what order they are opened because they are all the same head.
I stage the 4 pumps off of pressure.
Does this even sound close to being correct?
I can see there will be some possible problems with the system when it comes to pump staging on and the pressure jumping up. The dead band for the pressure would have to be played with and run threw all the possibilities to see what works best.