Bypass Heater with Automation System

[stever]

I'm putting together all of the final pieces for our pool -- should start construction in 6 weeks or so (rain permitting).

Being in Southern California (and possibly putting in a solar system) we will not use the heater much -- except for heating the spa. Looking at the way heaters are made -- with a lot of small capilary tubes to aid in heat transfer -- they appear to create a lot of back-pressure. Why pump water through this restrictive system if not needed?

I am planning to put in an Intel-7 Automation system and thought it should be easy to put an automatic valve in to only have the water flow through the heater when in spa or pool heat modes.

Has anybody done this -- thought of this -- or any comments?

- does the additional valve cause the same amount of elevated head as the heater?
- is this not a problem at all?

A secondary benefit is to keep the saline water out of as much equipment as possible -- I have read that salt pools destroy equipment (or is this a myth?). I guess even if I bypass the heater saline water is still sitting in the heater. Bringing up another issue -- I don't like the idea of water sitting in the heater for 6 months turning green. I'd have to keep a small flow through the heater -- maybe 5 GPM -- just to flush it out.

Thanks for the input!

Steve

 

[waste]

Steve, welcome to TFP :!:

You seem to realize the potential for damage to the heat exchanger from simply bypassing it I think your idea of circulating a little water through it daily is a good idea!!. Please remember to keep the pH high enough (over 7.0) for any water running through the heat exchange!

Just an educated guess on my part, the 3-way valve should reduce the head on the system.

I just want to remind you that without a good test kit, you're 'guessing' at where your chem numbers are - if you don't already have one, get a good test kit (Taylor 2006-k is one or www.tftestkits.com is another).

Again, welcome here - and there will always be someone knowledgeable to address your questions. Hope you get the pool of your dreams -- and that it is always 'Trouble Free'

 

[mas985]

I have a salt system and never really considered bypassing my heater. Most heaters built today should not have an issue with a salt system. Here is what Hayward says about salt systems:

In addition, all Hayward H-Series heaters are all equipped with a Cupro Nickel Heat Exchanger for efficient heating and superior durability. Cupro Nickel provides improved durability and longevity against the damaging effects of erosion that can occur under high-flow conditions, corrosion from occasional pool chemical imbalances, and is ideal for salt-water based pool systems.

A reference for cupronickel: http://en.wikipedia.org/wiki/Cupronickel

Some heaters use titanium which is even stronger. You might want to check with your manufacture to see if the heat exchanger is vulnerable to salt.

Also, I believe most heaters a few large tubes in the exchanger rather than a lot little tubes. Mine has 8-1" tubes. So while the heater adds a little bit of head loss, I'm not sure it is really worth it to bypass it. It might be worthwhile to check with the manufacture on the estimated head loss of the heater. It might be that much of a gain adding a bypass valves which are a little worse than 90s for the branch port.

 

[Titanium]

stever,

I am planning to put in an Intel-7 Automation system...

I have not heard of this system before for pool automation. I even came up blank with a quick Google search.

Can you give us more information regarding this system? It sounds interesting.

Titanium

 

[stever]

stever,

I am planning to put in an Intel-7 Automation system...

I have not heard of this system before for pool automation. I even came up blank with a quick Google search.

Can you give us more information regarding this system? It sounds interesting.

Titanium

I meant the Pentair IntelliTouch i7+3 -- Seems to be able to do most everything. I am opting for the wired in-house controller (don't see the need for the wireless controller) and a spa-side 4 button remote.

 

[repair_guy]

Stever,

Keep in mind that a branch fitting (valve) will add up to 12' of head.

With your i7, you can program that valve to open when the heater circuit is enabled. The only issue I see is if you forget it at freeze time. You would have to enable that valve at freeze protect.

I'm in Murrieta and we have hit 34 last week and if you're sheltered in Escondido, you could have been lower. We lost a lot of Pentair NT heater headers last February from freeze when we hit those upper teens. Granted, you're not going to put in an NT, but the same situation exists. You're talking about a small of sitting water that can freeze and expand quickly.

 

[stever]

Stever,

Keep in mind that a branch fitting (valve) will add up to 12' of head.

With your i7, you can program that valve to open when the heater circuit is enabled. The only issue I see is if you forget it at freeze time. You would have to enable that valve at freeze protect.

I'm in Murrieta and we have hit 34 last week and if you're sheltered in Escondido, you could have been lower. We lost a lot of Pentair NT heater headers last February from freeze when we hit those upper teens. Granted, you're not going to put in an NT, but the same situation exists. You're talking about a small of sitting water that can freeze and expand quickly.

I guess the question is if the heater adds more than 12' of head... Ideas?

I see your point on the freeze -- we'll see 3-4 nights a year in the 28-32 range (last year had a few weeks of mid-twenties). (Yes -- I know how lucky I am). If I do this, I'll set the valve to route all water through heater or 90% bypass heater (10% through heater). This will keep the water fresh in the heater off-season and hopefully allow the freeze-protection in the i7 to do its job (even at 10% there's some water moving).

Thanks,

Steve

 

[repair_guy]

I just threw that one out there to indicate a plumb around could actually work against what you're trying to do in the long run. Per Pentair, the head loss on a MAX E THERM 400 heater at 60 gpm is about 14ft.

 

[mas985]

I disagree that the branch side of a valve would add up to 12' of head. The branch side of a 2" tee has the equivalent head loss of about 12' of PIPE (not head). 12' of pipe is not the same as 12' of head. In order to get 12' of head out of 12' of pipe, flow rates need to above 280 GPM. Not likely.

Most heaters have a bit more head loss than a filter. Based upon measurements made on my equipment, my filter has the equivalent head loss of about 70' of 2" pipe and a heater about 110 feet of 2" pipe. To compare the 110 feet of pipe with a bypass, you have to consider all of the fitting components. Here are a few fitting estimates in terms of equivalent pipe.

90s = 5.7' of 2" pipe
45s = 2.7' of 2" pipe
Branch Tee = 12' of 2" pipe
Through Tee = 4.3' of 2" pipe

Valves are somewhere between a 90 and a tee because the unused port is closed off. Equivalent head loss of valves built today are hard to come by.

Also, be aware that most heaters have built-in flow bypass which regulates how much water actually goes through the heat exchanger. So heater head loss can be somewhat difficult to pin down exactly. That is why you really need to talk with the manufacture to know for sure what your heater head loss is.

[Edit] 14 feet of head loss @ 60 GPM is about 245' of equivalent 2" pipe. Quite a bit more than what mine is.

 

[waste]

Mark, thank you for the 'head loss vs. fittings' mini chart! It's as I suspected, that the bypass would reduce the total head when the heater was bypassed . AS per previous posts, I'm aware of the 'cupronickel' heat exchangers, but wanted to mention the possible damage to even them as a result of the pH being too low, They may be of sturdier material, but they can not withstand months of water with a pH lower than 7.0, no metal can (As for the titanium exchangers, it's my understanding that the strength of the metal reduces the efficiency of the heater, ie, titanium doesn't exchange heat very well -- FWIW -- my wedding ring is titanium[it's handsome and simple just like me], I thought it would hold up better than gold )

One other thing to mention, is that the 'auto control' Jandy valves can only 'understand' 2 positions --- ie they will be open or closed depending on how the valve is actuated -- in other words, there is no way to have an actuated valve only be partially open when using the automation (one can partially open one if they use the toggle switch on the unit)

 

[Titanium]

waste,

As for the titanium exchangers, it's my understanding that the strength of the metal reduces the efficiency of the heater, ie, titanium doesn't exchange heat very well

Titanium does not transmit heat very well, but it is not because of the strength of the metal. Titanium's low thermal conductivity is just an inherent property of titanium. But since titanium is extremely corrosion-resistant, the titanium tubes can often be made thinner than tubes made of other materials (titanium doesn't need a corrosion allowance). Thinner tubes transmit heat better than thicker tubes.

A zero corrosion allowance can often be specified for titanium. This, coupled with adequate strength, permits titanium tubing to be used with unusually thin walls.
The high resistance of titanium to corrosion prevents buildup of corrosion products which rob other metals of heat transfer efficiency. Titanium's hard, smooth surface also minimizes buildup of external fouling films and makes cleaning and maintenance easier.

http://www.titaniummetals.com/fab-p09.htm

As long as the listed efficiency of a titanium gas heater or the COP of a titanium heat pump is the same as a gas heater/heat pump with a different heat exchanger/coil material, it should not matter which material is used. The manufacturer using titanium will either use more heat exchanger surface or coil length, along with thinner titanium material, to make up for titanium's lower thermal conductivity.

We tested at 100°F with a pH of 4.75 and chlorine levels 50000 parts per million (10000 times greater than normal pool water). Although this is a severe test, it simulates realistic possible conditions such as chlorine tablets in skimmers and out of balance pool water.

http://www.heatsiphon.com/2006website/w ... proof.html

If I were in the market for a new gas heater or a new heat pump, I would not buy one without titanium as the material which is in contact with the pool water.

Titanium

 

[mas985]

One other thing to mention, is that the 'auto control' Jandy valves can only 'understand' 2 positions --- ie they will be open or closed depending on how the valve is actuated -- in other words, there is no way to have an actuated valve only be partially open when using the automation (one can partially open one if they use the toggle switch on the unit)

While there are only two positions, cams on the Jandy valves can be set for positions other than 0, 90 or 180 degrees. So you can have partially off/on ports for either position.

Also, one configuration that might also work if head loss is the only concern is to use two Tees with a 2-port valve connecting them on the branch ports to allow bypass. With the valve open, most of the flow would bypass the heater but a very small amount would still make it through the heater since that direction is not entirely blocked. With the valve closed, all of the flow would be forced through the heater.

 

[mas985]

One more comment. I looked at the plumbing set up I mentioned in my previous post and came up with about 40' of equivalent pipe in bypass mode, if I substitute that for my heater in my system, my head loss would drop about 3.4' and flow rate would increase about 4.5 GPM from 88 GPM. It is something but not a big difference and not sure it is worth the extra trouble.

 

[stever]

Thank you all,

It's a challenge to make things as efficient as possible.... but that having been said, this may not net out to a real (measurable) advantage. I'm glad I got you all thinking -- I learned a bunch. The goal it to hit the requred GPM at the lowest pump speed (planning on an Intelliflo VS unless somebody can convince be the VF is that much better). Toying (probably a long shot) with the idea of PV panels to power the pump and the more efficient the better.

Steve

 

[JasonLion]

The VF has two advantages. First, if you haven't done the complete calculation of how much dynamic head there is in your system you need to run the VS at a higher speed to be sure you are hitting the design flow rate. The VF model knows the actual flow rate, so you don't need to add any headroom for possible errors in your calculations. Second, the VF adjusts it's speed to compensate for how dirty your filter is. Without the VF you should be setting the pump speed for something close to a fully dirty filter, so the system still works correctly even with the filter dirty. With the VF you save electricity because it automatically reduces the speed when the filter is clean.

How much you save in electricity because of those two factors varies quite a bit. The more accurately you calculate your systems dynamic head the less you can save with the VF. Normally very little effort is put into calculating the dynamic head and the pump is run at a higher speed than required "just in case". In that situation, the savings from the VF can be significant. Pentair makes some fairly dramatic claims of the possible savings. As far as I can tell those claims apply to the common case where no one has paid much attention to figuring out the ideal motor speed for a VS system.

Both the VS and the VF have additional advantages over a non-variable speed pump. The largest one is that they can run at very low speeds which would be impractical with a single or dual speed pump. For example, a single speed pump that corresponded to one of the lower speeds on the IntelliFlo would frequently have problems priming the system and would be hopeless for manual vacuuming. The IntelliFlo takes care of this by priming the system at a higher speed and then slowing down to the low speed. The speed can also be increased for manual vacuuming.

 

[mas985]

Based upon a recent post by Chemgeek:

Mark,

Take a look at this thread on another forum and note the posts a little more than halfway down by tmoss and others that seem to imply that the IntelliFlo calculates the flow rate and doesn't actually measure it. If that's true, then that might explain the anomalous GPM results I was seeing that didn't seem to fit the affinity equations very well.

Richard

It doesn't look like the VF actually measures the flow rate but infers it so I am not sure how accurate it is. Having a flow meter inside the pump form factor would be very difficult which tends to indicate that it probably doesn't. Based upon some numbers Chemgeek posted on his pool, it doesn't look like the reading is very accurate at lower speeds/flow. Up to 100% error when going from 78 GPM down to 15 GPM while the PSI change has less than 7% error from the affinity equations so it is clear that the GPM value is incorrect. The 15 GPM should be closer to 28 GPM based upon the change in RPM.

It isn't exactly clear what the VF uses to determine flow although theoretically, you can use the current draw to estimate flow rates for a given RPM but that requires calibration. The error tends to be more flow than the setting so you may end up more flow than the target which is certainly better than less flow but it does mean you may be wasting a little energy.

 

[repair_guy]

The VF gpm is calculated, not measured. The purpose of setting the temp on the pump is how this works. The logic on the pump knows that at a given temp, water molecules have a given resistance. The calculated amount is the expressed as gpm.

I've strapped flowmeters on the pumps and they are pretty accurate.

 

[mas985]

The VF gpm is calculated, not measured. The purpose of setting the temp on the pump is how this works. The logic on the pump knows that at a given temp, water molecules have a given resistance. The calculated amount is the expressed as gpm.

I've strapped flowmeters on the pumps and they are pretty accurate.

Yes, I noticed that was discussed in the Gardenweb post as well. The only flow meter that I know of that requires temperature readings are Calorimetric Flowmeters. Here is a decent description of one and matches what you are saying.

However, it still doesn't explain why the data Chemgeek collected in this post shows that the GPM values are not tracking RPM values when there should be a linear relationship according to pump affinity laws. It could be as simple as a calibration error or poor temperature reading.

Based upon some of the articles I read on these types of meters, they tend to be more accurate at lower flow rates than higher flow rates since the temp difference between the sensor locations is larger at lower flow rates. This is probably where the Intelliflo needs the accuracy anyway.

With a the separate flow meter you mentioned, did you happen to collect data over a wide range of flow rates (15 -> 80+ GPM)?

I would also be interested in hearing from others who have an Intelliflo with a flow rate meter to see if their systems track.

[EDIT] Have to add one more thing. Based upon the manual:

Enter the current water temperature from 68° F - 104° F (Default 75° F.) The “Water
Temp” is only for the accuracy of the flow sensor. Temperature accuracy is not
critical, just enter an approximate temperature. When the IntelliFlo is connected to an
IntelliTouch system, water and air temperature information is provided by the system
sensors. The flow reading on the IntelliFlo is –0 / +2 GPM. The closer the
temperature to the actual temperature, the more accurate the flow reading on the
IntelliFlo control panel LCD will be while it’s running.

It indicates that if you don't have an IntelliTouch system, it uses a programed value for the reference temperature which is probably why the error could be high if this were not set properly.

 

[repair_guy]

I was involved in that other thread. That guys specs were way out of whack and I'm not sure what he ended up finding. It may have been a bad drive. The pump defaults to 75 degrees. Even if you neglect to correct it, the gpm would not be off by more than a few gallons. There is no flowmeter in the pump. The pump measures resistance as you know and with a preprogrammed system that says water molecules resist at this rate at this temp, it's just an equation at that point.

 

[stever]

I understand that the VF can also detect blockage and shut down. The VS does not have the flow sensor (calculator) and just pumps away, even if there is an obstruction. I don't know really how important this would be -- not likely there would be a blockage as there are required so many drain locaitons they would all have to be blocked.

Dows anybody here have the VF?