Is a high tech variable pump worth it?

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JP11

JP11

Minister of Fire
May 15, 2011
1,452
Central Maine
One of these fancy constant pressure pumps SOUNDS like it would be best. Not sure if you can justify the money.

I of course will have a constant pump to supply the storage tank from the WB. That amount of heat is pretty constant. So no need there.

The variable is from the storage to my loads.

I currently have 5 zones of radiant, and one zone that's a Indirect DHW tank. Those are supplied by 4 Taco 00R pumps. As for head on them.. I guess lowest would be one that feeds basement (pump is above load, and feeds 7 loops of 300' to 350 feet of 1/2pex) max GPM of the 00Ris about 14 with zero head. So I guess that the MAX possible output of the 4 would be 56GPM. I think that number is no where near realistic.. as some of the zones go 80 feet of 3/4 out to the end of the house to a manifold, then 5 to 7 runs of the 300feet or so of 1/2 pex. All the upstairs zones are 8' or so above the level of the pumps.

My question, or my thought is that why size the pump from the top of storage to input of load circs so oversize? You'd need to plan for all 6 zones open and calling. But in reality many times it would be only DHW circ calling. Or only a zone or two.

One of these variable pumps that maintain pressure SOUNDS ideal. It could be as small as a 1/25HP.. or as big as 3/4HP.

The distance from the top of storage to load circs is going to be less than 15 feet. Since tanks are going to be vertical it's downhill 6' or so.

Thoughts? I enjoy the research and planning. Learning a lot along the way.

JP
 
JP11 said:
One of these fancy constant pressure pumps SOUNDS like it would be best. Not sure if you can justify the money.

I of course will have a constant pump to supply the storage tank from the WB. That amount of heat is pretty constant. So no need there.

The variable is from the storage to my loads.

I currently have 5 zones of radiant, and one zone that's a Indirect DHW tank. Those are supplied by 4 Taco 00R pumps. As for head on them.. I guess lowest would be one that feeds basement (pump is above load, and feeds 7 loops of 300' to 350 feet of 1/2pex) max GPM of the 00Ris about 14 with zero head. . . .

JP
Click to expand...

I'm responding, but don't have an answer yet. I have 5 "hot" zones upstairs and 1 "hot" in the cellar (on a modine-style fan forced heater) a a single radiant zone with 4 x 200' loops for the first floor, with all water moved by a single Taco 0012 delta T variable pump. I know that if I "lose" the pump, I'm out of heat, so I'll probably buy a cartridge for that model for emergencies. I'll set the sensors on the hot supply and cold return lines and play with the delta T rheostat until I get what I want, but haven't tried it yet because we haven't had the first fire. Taco says it'll be quieter and more economical than multiple single or 3 speed pumps, so I'm hoping for the best.

JD
 
Smokeater..

That's a valid concern. I have 4 identical pumps. I should have a spare pump on the shelf.. or at least one of those drop in kits.

If I do put in this high tech pump... I guess the "plan" would be to replace it with my off the shelf one in a heating emergency, until I could get another fancy one.

I'll have 6 pumps in all in my system. I like having a spare kicking around. I'm looking at the Viridian line from Taco. Haven't seen any costs yet. I guess I'll make a call to the supply house this morning.

JP
 
I want to get one to run my house. The one I was looking at is $200.00. I think it will replace two pumps or a pump and zone valve. So it really isn't much more than 2 circulators. In the long run it will be cheaper due to electric savings. It will also
make for a better system.
 
Thanks

I have used Patriot in the past.

Now.. I guess it really comes down to flow. The 4 current 00R pumps.. One doesn't go far.. as it's only feeding the DHW the boiler sits on. Others all feed radiant zones. I would imagine it's pretty low GPM due to long runs. The 4 pumps if they were 3gpm could be fed by an ALPHA.

I'm looking at the MAGNA. More gpm.. but more than twice the money though. I think either should have a internal check valve.. as I don't want to let the oil boiler backfeed into the storage tank.

I tell you what.. I'm geeky enough that I'm planning a bunch of manual temp gauges, as well as one of those internet enabled X300s with the sensors in tank tops and bottoms.

:) If nothing else.. I'll have good data to put on here to have all you guys help me tweak. It's probably all foolish anyway.. as I have confidence in Mark from AHONA. But what can I say.. I'm a professional button pusher. Gauges are my thing!

JP
 
Ok.. worst case (DHW) circulator is 8ft of head, so 8gpm.

The other ones run a max of 70 feet of 3/4 pipe out to the manifold.. Ok.. so I was a little numb at first figuring out the head.. :) but the manifold and having 7 runs of pipe is LOW head, as there's little resistance with no elbows, and essentially a BIG pipe for the loops. I think 3gpm is probably realistic for the zones. So call it 3x3 9gpm, plus domestic 8gpm. 17 total GPM.

I don't think the alpha can do it.

JP
 
2 things to consider. What is the likely hood that all zones would be calling for water at the same time ? That would allow for the smaller pump. Also would there be any benefit in a Taco Zone priority control incorporated into system ? This is usually set so you have priority for the DHW. Once that is satisfied control goes to other load.
Rob
 
Rob

I gotta say it's likely, at least it has been the past 4 winters. But maybe that was just because the boiler is JUST BARELY big enough. Partly my fault, as I am firing it on a 70% biodiesel mix that I make.

That brings down the punch of the flame.. but it's a buck a gallon!!!

Now maybe it will be different with lots of 190 degree water there from the Vigas. Max temp on the radiant is 140.. so there's a lot of mixing going on there.

I guess I don't want to buy a 200 dollar pump, then need to replace it with the 400 dollar one. The part I'm not really calculating is I don't know how the pumps will work TOGETHER..

What I mean is.. the current circs do all the work. sucking it back from return, thru boiler and out to radiant. When I add in the pump from storage tank.. those pumps will now be fed water at pressure.

I don't know.. out of my depth here. :)

JP
 
JP11 said:
One of these fancy constant pressure pumps SOUNDS like it would be best. Not sure if you can justify the money.

I of course will have a constant pump to supply the storage tank from the WB. That amount of heat is pretty constant. So no need there.

The variable is from the storage to my loads.

I currently have 5 zones of radiant, and one zone that's a Indirect DHW tank. Those are supplied by 4 Taco 00R pumps. As for head on them.. I guess lowest would be one that feeds basement (pump is above load, and feeds 7 loops of 300' to 350 feet of 1/2pex) max GPM of the 00Ris about 14 with zero head. So I guess that the MAX possible output of the 4 would be 56GPM. I think that number is no where near realistic.. as some of the zones go 80 feet of 3/4 out to the end of the house to a manifold, then 5 to 7 runs of the 300feet or so of 1/2 pex. All the upstairs zones are 8' or so above the level of the pumps.

My question, or my thought is that why size the pump from the top of storage to input of load circs so oversize? You'd need to plan for all 6 zones open and calling. But in reality many times it would be only DHW circ calling. Or only a zone or two.

One of these variable pumps that maintain pressure SOUNDS ideal. It could be as small as a 1/25HP.. or as big as 3/4HP.

The distance from the top of storage to load circs is going to be less than 15 feet. Since tanks are going to be vertical it's downhill 6' or so.

Thoughts? I enjoy the research and planning. Learning a lot along the way.

The ECM or delta P pumps make sense if they are properly applied. Using an Alpha as a fixed speed will save @ 40% electrical energy. I suspect that pump will last 20 years if properly installed. so calculate how many hours you pumps are running and see if that savings works out.

But the better installation is to use the delta P function. This allows the distribution system to operate at a near perfect pumping condition AND save electrical energy.

With the huge price decrease they are starting to look good in either application as fixed speed and as a delta P.

JP
Click to expand...
 
Have you posted a pipe layout. Sounds like your adding storage and therefore are adding another pump. That is not always necessary because water will move at path of least resistance. Are you using a HX or something that makes the new pump necessary ?
Here is my set up and I have a return circulator shown. Circulator has no check valve. However, that only comes on when the return from storage water temp is above 165. This aides in keeping my boiler temps down so boiler doesn't cycle during burn.
As far as the flow goes, my lay out would work fine with out the return circulator.
I do get some minimal ghost flow through the OB but I close ball valves to isolate anyway.
Rob
 

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Head has nothing to do with how high elevation change is, unless your entire system is open loop. head is a reference to piping head losses. If you got the taco website and look into the flow pro university short video's there's a good explanation of headloss and how circulators work. if it goes up it must come down and these negate the head your thinking of, similar to a sump pump. If your thinking of a variable pump the pressure series is not a good idea, the variable temp ones are the correct pumps to use. Since its not pressure your trying to control but the amount of btu's given off with a delta T of 20 degrees. Variable pressure pumps can be misleading as they only adjust to the headloss of the piping system and have no regard for the tamp or number of btu being given off.

http://flopro.taco-hvac.com/flopro_u_courses.html

If you've never calculated your actual headloss TDL x HL you have no idea of how to choose the right pump. This is one of the most popular mistakes I come across.
 
Yes... learning along the way. :)

elevation change doesn't matter.. makes sense that uphill losses would equal downhill gains.

But, wouldn't a variable output pump, that is left in it's default ramp up pressure mode work best? It would vary pump output as the load circulators open and additional zone's head was introduced? Or are you saying that the zone valves and ciculators would NOT introduce their head to the system?

JP
 
If you are zoning by zone valves then yes it would adjust to the added head for each zone, when using a single primary pump to heat all zones. However each zone will have different head losses, so will it provide the correct gpm to heat the zone ??? One problem I have come across with these were adding too much flow and making the zone noisy, banging pipes, etc. A perfect example was an IDWH that did not have a full port zone valve like was called for by manufacturer. When that zone opened it sent the whole system out of whack. A VDT pump while better still might not fit the zone valve system correctly.Its asking a single pump to cover each zone perfectly. I prefer to zone with pumps and then each zone gets the perfect btu its supposed to. The goal is to have controllable , even, comfortable heat.
 
I guess I'm still a bit confused then.. sorry.

Fluid from storage will need to go thru two pumps.

one at the storage tank that will supply pressure to the hot manifold that comes off the current Oil Boiler.

THEN, from there.. each zone that calls for heat has it's own circulator. (not entirely correct, as two of the pumps have zone valves and supply two zones each)

Zone 1. Circulator that goes to IDHW
Zone 2&3. Basement/Garage -share a pump. Zone valves downstream of pump to control which zone heat goes to.
Zone 4&5. Home/Bedroom -share a pump. Same type zone valves downstream.
Zone 6- Wife's Photo Studio

I thought the variable pump would be better.. so it would use small current for when just a single zone was calling for heat. Then ramp up if there are lots of zones open.

Do I have the operation wrong? I figured if I sized it for the GPM that is needed to supply all 6 zones at once, it would create excessive stirring of my storage tanks when a few zones were calling for heat.

JP
 
JP11 said:
THEN, from there.. each zone that calls for heat has it's own circulator. (not entirely correct, as two of the pumps have zone valves and supply two zones each)

Zone 1. Circulator that goes to IDHW
Zone 2&3. Basement/Garage -share a pump. Zone valves downstream of pump to control which zone heat goes to.
Zone 4&5. Home/Bedroom -share a pump. Same type zone valves downstream.
Zone 6- Wife's Photo Studio

I thought the variable pump would be better.. so it would use small current for when just a single zone was calling for heat. Then ramp up if there are lots of zones open.
Click to expand...
The DHW and the radiant will most likely need to be pumped separately. Don't the radiant zones recirculate through mixing valves?

Do I have the operation wrong? I figured if I sized it for the GPM that is needed to supply all 6 zones at once, it would create excessive stirring of my storage tanks when a few zones were calling for heat.
Click to expand...

But how much flow do you really need 'all at once'? With radiant I expect you would need low flows for hours on end, and a constant head pump would do a nice job of adjusting flow as zones come on and off.

It's hard to go wrong with a constant head pump like the Wilo Stratos or Grundfos Alpha if the zones are reasonably similar in resistance. Since pressure drop increases as the 1.75 power of flow rate, it is hard for the relatively low resistance circuits to hog all the flow.

If your radiant zones are recirculating through mixing valves then you shouldn't have to worry about stirring storage, the radiant returns will automatically be low temperature.

How many mixing valves do you have now? Are you planning on using one constant head pump pulling through all your existing mixing valves in parallel?

--ewd
 
Yes, all radiant zones have mixing valves. DHW is it's own "zone" and has its own circulator that sends boiler water to the indirect tank.. which boiler is sitting on.

I would think that if only one zone is calling for heat... and the pump (pump at WB storage tank) was a simple on/off type.. that the excess fluid from the pump output that is NOT being used by that one zone would be sending my hottest water back to storage at the bottom of the tank. Wouldn't that mess up my stratification of the tank.

Of course the water coming back from the one zone in use would be quite cool, as it is mixed to go out to radiant at 140 or 100 (depending on upstairs staple up, or downstairs in slab). That return water is used with a bit of new/hot water to make 150 water to go back out.

Guess I'm not doing a good job explaining how I THINK it's going to work.

JP
 
I'm really slow sometimes..... but if each zone has a circulator that is drawing water from a hot water source. WB, OB, or storage why, when you add storage, do you need another circulator ?
 
Variable speed circ basics.....

First of all, it would be good to remember and realize that VS circs were designed and perfected in Europe for a very particular reason. Over there, the most common source of heating is the panel radiator. Almost invariably, they are controlled by a thermostatic radiator valve. To really appreciate what this means you have to understand how a TRV works.

The fundamental difference between what is normally encountered here in North America (zone valves or zone pumps) and a TRV controlled system is that the TRV system is never "off". Heat demand is usually triggered via an outdoor temperature sensor in a European system rather than an indoor thermostat. The pump in a TRV system runs nearly all the time except for periods of setback.
The room control is done individually by the TRV which simply "throttles" water/heat flow until heat supplied matches heat lost. It is never off in the sense of a closed zone valve or a de-energized pump. So the folks at Wilo and Grunfos attacked the problems of over capacity pumping by inventing VS pumps, that can match a given parameter for head/flow in a system which is capable of demanding nearly nothing at all to the max capacity of the pump.

This is far different than our normal systems here which run in an all or nothing mode.

So is there an advantage in using a VS pump on a typical North American system? Kinda depends on what you are dealing with...

If you currently have a system that uses zone pumps it would make little sense to replace them all with VS circs the way it seems to me. Other than the fact that you could dial each circ down to match the particular zone it was on, there is little other advantage. Energy payback would be waaaay down the road.
If you have a zone valve system, that introduces a difference in flow requirement that can have a pretty significant variation. In that case a VS circ would be worthy of consideration.
If you are fortunate enough to have a system controlled by TRV's it's a no brainer. That is exactly what those little wonders are designed to do.

We routinely use them on zone valve systems and they work exceedingly well. A person can dial them in pretty darn close to whatever temp drop you want to work with across the circuit. You want a 15* drop? Dial it in. 25*? just turn the knob (Wilo) The only thing you have to watch is getting enough oomph to overcome the head in the longest zone.

For customers that we are doing a system using any kind of radiators, controlled by TRV's, it's automatic. I spec the system with a VS pump and don't even bring up tha fact that it can be done a different way.
 
JP11 said:
Yes, all radiant zones have mixing valves. DHW is it's own "zone" and has its own circulator that sends boiler water to the indirect tank.. which boiler is sitting on.

I would think that if only one zone is calling for heat... and the pump (pump at WB storage tank) was a simple on/off type.. that the excess fluid from the pump output that is NOT being used by that one zone would be sending my hottest water back to storage at the bottom of the tank. Wouldn't that mess up my stratification of the tank.

Of course the water coming back from the one zone in use would be quite cool, as it is mixed to go out to radiant at 140 or 100 (depending on upstairs staple up, or downstairs in slab). That return water is used with a bit of new/hot water to make 150 water to go back out.

Guess I'm not doing a good job explaining how I THINK it's going to work.

JP
Click to expand...

With radiant zones the circulator pulls through the mixing valve. The entire mixed flow goes through the loop and heads back around to the mixing valve where it comes to a tee. One leg of the tee goes to system return and the other leg goes to the mixing valve. The mixing valve will recirculate most of the water back around the loop, but first it will pull in just enough hot water to bring the mixed flow up to the mixing valve setpoint, e.g., 125 degF.

As whatever amount of hot water is mixed into the radiant loop, the same amount will leave the loop at the tee. The water leaving the loop will necessarily be less than the mix setpoint temperature, 90, 100, 115 degF, whatever. So storage and radiant work perfectly together, the mixing valve sips hot water from storage and returns the same amount at a nice low temperature.
 
RobC said:
I'm really slow sometimes..... but if each zone has a circulator that is drawing water from a hot water source. WB, OB, or storage why, when you add storage, do you need another circulator ?
Click to expand...


Rob.. I fear it is I that am slow. I don't know if the extra head on the suction side of the pump is why I would need an additional circulator to pressurize what is currently suction.

I would not replace the taco 00R pumps that are currently in the system. I thought I needed to ADD two pumps to my setup. One on the return side of the WB to supply flow on the 1.5 inch pipe from the WB to the two 500gal vertical storage tanks.

The other is on the top of the 500s. They would be T'd together and the pump there to supply hot water from the top of storage tanks to the hot side of my current oil boiler.

I'm in a hotel. but will log into PC at home and see what I can find for pics of current setup. The rest is all in my head so far.

I should just give up and have Mark tell me what to buy. :)

JP
 
JP11 said:
Of course the water coming back from the one zone in use would be quite cool, as it is mixed to go out to radiant at 140 or 100 (depending on upstairs staple up, or downstairs in slab). That return water is used with a bit of new/hot water to make 150 water to go back out.
Click to expand...

Back to your original question, since you have differing mix temperatures you need a separate pump for each. And since you have a small number of zones for each mix temperature, and since they are recirculating radiant zones, variable speed pumps would take a long time to pay off, although you probably should do some analysis to be sure whatever single speed pumps you're using aren't way over-sized.
 
Dudley..

Sorry, you misunderstood my question.. or I've just been laying around this hotel for TOO LONG. I go home tomorrow.

The constant taco 00R pumps are staying. I was questioning a variable pump to supply THEM from the new 1000 gal of WB heated storage.

here's the oil setup, quite simplified as it was in process during this pic. there's a wall of copper there now. My idea is that the new, variable pump would supply hot water from storage to a point just before the spirovent on top of boiler.

JP
 

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I have a panel systym with TRVs It currently has a grundfos 15 -58 that I keep on low. Where the pex enters the radiaters there is a bypass so if the valve is closed the water will still circulate. I was thinking of removing the bypasses and installing a variable speed pump. I was thinking it would cut transmission losses in the crawl space and save electric. Would this be worth doing or should I leave well enough alone ?
 
woodsmaster said:
I have a panel systym with TRVs It currently has a grundfos 15 -58 that I keep on low. Where the pex enters the radiaters there is a bypass so if the valve is closed the water will still circulate. I was thinking of removing the bypasses and installing a variable speed pump. I was thinking it would cut transmission losses in the crawl space and save electric. Would this be worth doing or should I leave well enough alone ?
Click to expand...

Woodmaster, that Grundfos 15-58 draws 60Watts on the low setting. A little calculation say that if you run it constantly, it'll use about $4.30 per month of use. You'll wear it out faster, but a VDT pump is pretty expensive and the Grundfos is only about $85 new.

JD
 
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