Good read........

[heaterman]

About a fundamental hydronic truth.

Designing a system to operate with a high T is a big factor in performance and efficiency.
Another great column from John Barba at Taco.

http://jbblog.flopro.taco-hvac.com/delta-t-dawn-2/

 

[__dan]

Along the same line, I've been encouraged every time I see you recommending the pellet boilers. There's a couple of recent threads here with owners having 4 zone oil hydronic baseboard. Anyone in that situation and no gas, I've also recommended the pellet boiler. The sweet setup would be outdoor reset for the secondary baseboard loops, then the pellet boiler could do a variable turndown of the firing rate and dial in to the load.

The oil boiler they have now is doing on/off and going right to high fire. The pellet boiler could be arranged to not short cycle, the load would be on longer at a lower maintenance temp and the boiler would run longer at a much lower firing rate. Keeping everything else the same, just that change to a modulating firing rate and outdoor reset loop temps yield a big efficiency savings by eliminating the short cycling at high fire. The article indicates another way modulate the load to demand with the fixed delta T circ, But with the pellet boilers the result would be the same, the boiler would turn down the firing rate to match demand. It cannot be said enough times what an efficiency gainer that is.

It shows the market still has a lot of maturing to do. In the future, the article will show how the load matching to demand took the oil bill from $1000 to $600, then yanking the oil boiler for a pellet boiler install took the fuel bill down again from $600 to $300.

 

[arbutus]

In the third of three linked articles he mentions the cost difference between ECM and standard pumps and gives an example that works out to $14 per year. Over the year, not a big deal. It becomes a bigger deal when several pumps are running in a primary/secondary arrangement.

 

[heaterman]

I know for a fact that outdoor reset will be available on the Windhager as an option at the least and possibly as standard equipment. These things are fully as sophisticated and capable of providing primary heating as any gas or oil boiler from what I have seen.

 

[AndrewChurchill]

I have a Grundfos Alpha pump on my new system. The user manual is very limited in explaining how it works. I don't see a way to set the Delta T. Does it operate on a different principle than the Taco's listed in the article?

 

[arbutus]

The Alpha pump can be set for various pressures, not temperatures.

 

[AndrewChurchill]

How does varying the pressure compare to setting a fixed delta t in terms of fuel savings.

 

[BoilerMan]

How does varying the pressure compare to setting a fixed delta t in terms of fuel savings.

This is a much debated topic. Personally I like the idea of delta-T over delta-P in a residential application.

TS

 

[heaterman]

Varying Delta P is good in a system containing zone valves or TRV's as it keeps constant flow to any open zone.
I like to use deltaT circs on residential apps that require very low flow. Such as a house full of iron rads. The BumbleBee can be dialed in all the way up to a 50* temp dif and goes as low as 9 watts of power.
Going to try one on a primary loop pump if the right system comes along one of these days.

 

[kuribo]

still waiting for a reverse acting bumblebee.....

 

[Bob Rohr]

Varying Delta P is good in a system containing zone valves or TRV's as it keeps constant flow to any open zone.
I like to use deltaT circs on residential apps that require very low flow. Such as a house full of iron rads. The BumbleBee can be dialed in all the way up to a 50* temp dif and goes as low as 9 watts of power.
Going to try one on a primary loop pump if the right system comes along one of these days.

But the sky is not the limit, or maybe the basement is not the limit

When you run wide delta T and reduce flow rates ie GPM and FPS, you get to a point where heat transfer drops very quickly. This happens in the boiler or heat generator, as well as heat emitters. It's's the point where the flow goes laminar. Locking in a fixed delta t can take you to that point if you are not careful. The universal BTU formula is a good guideline to design with but don't assume it will always define a "workable" system.

Look at the Alpha curves and notice they block out some of the low end to protect against low, low conditions. Also you should avoid running any pump at the top or bottom of it's curve. At least that is what the pump manufacturers have been teaching us.

Watch for the Sept issue of PM magazine www.pmmag.com. Siggy wrote an important article showing the use, or misuse of the hydronic formula and how to predict what happens in a radiant pex loop, or a baseboard fin tube loop when you run the numbers down to the low ends.

 

[heaterman]

Absolutely correct Hot Rod.
I should qualify what I said in the example I gave referencing the large T......In a situation where for instance you were running a series of baseboard, you wouldn't want to run a temp drop that large. The last pieces of BB would be very low output.
The system I had in my head was a house full of TRV equipped iron rads all running from a common manifold.

As you are famous for saying. "it depends".

 

[Bob Rohr]

Absolutely correct Hot Rod.
I should qualify what I said in the example I gave referencing the large T......In a situation where for instance you were running a series of baseboard, you wouldn't want to run a temp drop that large. The last pieces of BB would be very low output.
The system I had in my head was a house full of TRV equipped iron rads all running from a common manifold.

As you are famous for saying. "it depends".

True what you say, and I know you know about temperature drop through a string of heat emitters.

But also even on a short run or thru just one radiant loop, the flow needs to be sufficient to allow the fluid to be turbulent. Some of the "talk on the street" about a fixed delta T system may not, in reality, exchange any, or enough heat. So short cycling could in fact be caused by too much btu out of the boiler and not enough load, or not enough flow to transfer the energy from whatever the heat emitters are. The boiler or heat source becomes constipated due to insufficient flow to transfer the energy, via the fluid, to the heat emitter.

There needs to be some qualification around the concept of fixed delta T system operation. Just beacuse a pump or control can provide it, doesn't mean it is correct or always workable.

 

[huffdawg]

I have a loop that supplies heat to the loads in my house. The pump that is on that loop runs 24/7. this pump draws from a 150 gal. hydraulicseparator if the term is correct. The separator is heated by the boiler or my 1000 gallons of storage. Seems like a delta t type pump on the loop to the house would be a good upgrade to the system. What do you guys think.

Huff

 

[heaterman]

I have a loop that supplies heat to the loads in my house. The pump that is on that loop runs 24/7. this pump draws from a 150 gal. hydraulicseparator if the term is correct. The separator is heated by the boiler or my 1000 gallons of storage. Seems like a delta t type pump on the loop to the house would be a good upgrade to the system. What do you guys think.

Huff

At the very least, an ecm circ would likely cut the power consumption for that loop by half all other things being equal. Do you know what flow rate and head you're working with on that loop? What type of heat emitters are you working with in the house? Radiators, baseboard, fan/coil, radiant slab? Those factors will all make a difference in your target T. Of course with an ecm circ, that is very easy to play with and adjust.

 

[huffdawg]

At the very least, an ecm circ would likely cut the power consumption for that loop by half all other things being equal. Do you know what flow rate and head you're working with on that loop? What type of heat emitters are you working with in the house? Radiators, baseboard, fan/coil, radiant slab? Those factors will all make a difference in your target T. Of course with an ecm circ, that is very easy to play with and adjust.

That is the design summary for the main floor. The upper floor is the same square footage but a lot less heat load. It is heated by base board on a single loop, 7 -6ft. baseboards. I cant seem to find the paperwork on it though. The loop from my hydraulic separator is roughly 80 ft. total with 1-1/4 pex buried in the ground

Dale

 

[Bob Rohr]

That is the design summary for the main floor. The upper floor is the same square footage but a lot less heat load. It is heated by base board on a single loop, 7 -6ft. baseboards. I cant seem to find the paperwork on it though. The loop from my hydraulic separator is roughly 80 ft. total with 1-1/4 pex buried in the ground

Dale

Any way to turn the pump off when no heat or energy is needed? That would save pumping cost and limit heat loss to the ground. An ECM type of pump would save maybe 50% or more on electricial costs.


Here is a link to the article I mentioned. Sometimes we get hung up on a number, or formula while ignoring the actual reality of how the system operates. Nothing magic about a 20 degree ∆T. And forcing a system to work at a fixed ∆T may not always lead to better efficiency, comfort, or lower operating cost.

The understanding on how the energy transfers from the fluid stream, via the heat emitters, to the load is the key.

http://www.pmmag.com/articles/95877-nature-vs-math

 

[huffdawg]

I do go out and turn it off manually if I remember. I can run some thermistat wire out to the boiler room from the controller in the house through some conduit that I ran in the groung when burying the pex. Im just not sure how to wire it to my controller (honeywell AQ2000). I would like the controller to be able to shut that loops pump off when no call for heat. Would I have to have a 120v supply coming from the controller as well or could the 120v be picked up in the boiler room as it is now?

 

[Bob Rohr]

I do go out and turn it off manually if I remember. I can run some thermistat wire out to the boiler room from the controller in the house through some conduit that I ran in the groung when burying the pex. Im just not sure how to wire it to my controller (honeywell AQ2000). I would like the controller to be able to shut that loops pump off when no call for heat. Would I have to have a 120v supply coming from the controller as well or could the 120v be picked up in the boiler room as it is now?

Is this the control you have? If so it has an AUX set of contacts. I believe when a call for heat is present those outputs receive 120V. Use a meter to confirm that. Test those terminals without a heat call from a thermostat, then call a zone on and check them.

If it is in fact 120V run that out to the remote pump and power from that.

If you want to run just a signal out you could use a RIB relay with the 120V coil connected to AUX. Then send the contacts to another pump relay box out at the pump. This would require two more components however.

It will be simple and cleaner if you can run the 120V signal from AUX directly to the pump.

I like to leave a means to disconnect power to that pump. Generally I put a cord and plug on the pump, A disposal cord or old computer power cord works nicely. Mount a receptacle on the end of the wire you run out. merely pul the cord if you need to service that pump, without needing to co to the Honeywell control.

 

[huffdawg]

Bob , mine is the model without that digital display. But mine does have an aux set of contacts. I have a conduit I can push a 14/2 wire through. Thanx for the help I will get it dun when I get back home from my shift.

huff

 

[huffdawg]

Hi Bob I have tested the aux set of contacts , and no power when call for heat. Could I jump from the line voltage side of the ZR contacts, it powers up when there is a call for heat.

Huff

 

[huffdawg]

Got it figured out. DIP switches under centre panel cover.