Help - my pump is still not pumping!

malconium

I have designed and installed a small radiant heating system in the floor of a 1973 31' Airstream travel trailer. The design is an open loop system. There are two radiant heating loops of 1/2" PEX tubing that run in parallel with each other. The tubing runs at about 6" on center. There is a single TACO pump (model Taco

006-ST4 in Stainless Steel) that services both loops at the same time. There is one 1-way valve that is designed to allow water to flow from the hot water side of the system to a point just in front of the pump to allow water to circulate around the heating loop. You can see the arrangement of the various parts of the system in the attached drawing and the photograph. The photograph is looking into the space under the kitchen sink where the pumps and valves are all arranged. If you look closely you can also see a simple flow meter that I have installed temporarily to help with trouble shooting the system.



I can get some flow to register on the flow meter when I turn on a hot water faucet in either the kitchen sink or the bathroom sink. I can use these faucets to make sure all of the air is bled from the system. The cold water input is currently supplied by a garden hose attached to the water input connection on the side of the trailer - shown at the middle top of my drawing. I have more or less normal city water pressure to the cold water side of my system. The fact that hot water successfully flows out of the kitchen and bath faucets verifies the entire hot water path through the open loop system except for the 1-way valve. I carefully checked the 1-way valve when I installed it making sure that the arrow was pointing in the right direction. I also tested its function by blowing into both ends before installing it. It is a 3/4" paddle type 1-valve that offers very little resistance to water flow in the right direction. Of course I also very carefully checked to make sure my pump was pointing in the right direction too. My pump seems to be turning on just fine.



My problem is that even after carefully bleeding the system when I turn on the pump I do not get any visible flow of water. The flow meter does not register <span style="text-decoration:underline;">any</span> movement and I do not see any movement of water in either the meter or the clear lines I am temporarily using to hook in the flow meter. Even when I also turn on a hot water faucet when the pump is running the only flow that registers is the amount that shows when just the faucet is running.



So what can I possibly be doing wrong? Is my installation somehow allowing an air bubble to form around the pump impeller? My system is implemented mostly on the horizontal plane. Does the pump have to be higher or lower than the rest of the system? Is the pump orientation somehow the problem?  As near as I can tell from the installation instructions I have the pump installed in an OK orientation but maybe not. My power connection does not seem suspect either. Right now I am plugging it directly into a 110 volt outlet and I am using about 6' of 16 gauge wire. The pump should be the right size for driving the amount of PEX tubing that I have too.



I really need some help with this problem. I have tried everything I can think of without success. At this point any suggestions would be very much appreciated. This is the last part of my Airstream plumbing system that needs completion and I really want to be able to test out how well the radiant heating system works.



Thanks for your help,



Malcolm

Alan (California Radiant) Forbes

It seems

that the pump could be circulating water, but not though the flow meter.  Could it be flowing through the black filter or pump in the middle of the picture?



How long are your heating loops?

malconium

The black pump and the heat loops

The black pump in the middle of the photo is the pump that supplies fresh water from the holding tank when I am not hooked up to city water. It has a built in check valve that prevents water from flowing back to the holding tank. The hot water pump could not possibly be pumping water back through it to the holding tank. If that were even possible the connection to city water would force water back into the holding tank which would of course be a disaster.



My heating loops are in the range of 140' each. They run in parallel with each other as my diagram indicates.



Thanks,



Malcolm

malconium

Are my calculations wrong?

I am completely stumped with this problem and could really use some help.



What kind of conditions are there that could prevent a circulation pump of this type from pumping? I though that I had picked the right pump. Besides if I picked a pump that was a little too small would that just mean that the flow would be less rather than none at all?



Did I perhaps completely blow the calculation? I am shooting for around 4 to 6 gallons per minute of flow through two parallel loops that are about 140 feet long. I was told that to calculate the head for my 1/2" PEX that I should use the following formula:



0.0402 x feet of 1/2" PEX



This would give me about 5.628 feet of head. The pump I am using has a head range of from 0 to 9 feet and a flow rate from 0 to 10 gallons per minute. I bought it from www.pexuniverse.com and I did ask their technical people if they thought it was an OK size - and they did. Is the calculation OK or did I do something fundamentally wrong here?



Does anyone have any suggestions for kinds of test I could do to help trouble shoot the problem?



Thanks,



Malcolm

NH03865

Pump Curve

Assuming that your calculations are correct, they still don't account for the total head as seen by the pump.  The biggest thing that I see missing is what is the head loss through whatever you are using as a heat source?  What is the total distance that the water has to be lifted by the pump?



If you look at the attached datasheet, the 006B series has a total head of 10 ft, the non 006B pumps only have a total head of 8 feet.  It is quite probable that the head presented by the pex plus the head presented by your heat source and other components in the system and the head presented by the maximum height the water needs to be pumped exceeds the head rating of the pump.

malconium

I am using a tankless water heater...

You are correct in that my calculation does not take into account the water heater. I am using a tankless water heater. Most of the plumbing in my system is on the same level as the radiant heating loops. The top of the water heater is a maximum of about 2 feet above the floor level. I assume that means that the amount of head added by the water heater is in the range of 2 feet plus whatever the internal tubing length is. If that was say 20' then that would be an additional about 0.8' of head. That takes me up to maybe 9' of head which does get close to the upper end of the pump's range. One test I can try is to bypass the water heater and see what happens. I can do that at the floor level so that there is virtually no head except the radiant heating loops. I will give that a try and see what happens.



Thanks,



Malcolm

NH03865

Pump Curve

If you look at the document attached in my previous post it gives you the performance curve of the pump.  Look at the table labelled Performance Field - 60Hz.  Your pump is curve #3.  At just over 8 ft of head the pump will have 0 GPM.  You state that you have approximately 9 ft of head.  That means that the pump will not pump any water, you have exceeded the capability of the pump.

malconium

Yes - it looks like I have the wrong pump...

Unfortunately it would appear that you are right that I have the wrong pump. Also unfortunately I don't think I can return it for credit since I have installed it. I may just have to try to find someone that is interested in buying it.



Meanwhile I am looking at replacing the pump with a Grundfos UP15-18B5 pump. Here is a link to its performance curve:



http://www.pexuniverse.com/docs/pdf/59896114-grundfos-up15-18b5.pdf



If my total head is around 9' then it looks like this pump would produce about 5 gallons per minute of flow which would be fine. If I am off on the total head calculation then I would still get 3 gallons per minute at 13' of head which does seem to give me some margin for error. I only want to order one more pump. Does this choice seem like a good one or is there a better choice for my application?



Thanks,



Malcolm

Gordan

You're confusing static pressure with head loss

Head loss, which is what a circulator in a closed loop has to overcome, is a characteristic of the heating circuit itself, not of its elevation. Just like the head loss through the PEX loops depends (for each type of tubing) upon the length of the circuit and the water velocity (which translates to gpm.)



The tankless heater you've got will almost certainly have a LOT more pressure drop than 1' at 5 gpm, or even at 3 gpm. You need to figure this from its manufacturer published specifications.

malconium

Is there a simple way to measure total head?

OK - I see what you mean about the head loss calculations. I am looking into what the manufacturers spec says about that.



In the meantime I am wondering if there is a simple way to measure the total head in a given system? Or perhaps I should have asked if there is an economical way to measure the total head?



Thanks,



Malcolm

Gordy

Piping issue

Maybe or is it my tired eyes? How is any hot water going to get into the radiant loops? I see the cold water going through both radiant loops then through the water heater which comes out into the hot water supply for the sink, and shower. Unless arrows in the drawing are wrong.





Gordy

CMadatMe

In Way Over

Your head. There is a huge pressure drop across the hx that you must overcome on top of the 16' of head you have to overcome based on 2gpm of 120 degree water thru 140' of 1/2" pex. Wanna move 3gpm then that head is 35' moving at 5ft sec.



Now let's talk reality. In no way will you move 2gpm thru each loop. Adding in the pressure drop of the hx is going to put you in a pump that probably cost more then the tankless heater. Your velocity will be so high that you may then begin to attack the hx.



Now moving 1gpm on the preferred 10 degree delta-t for radiant we can move 5,000 btu's thru each of those loops @ 5' of head. 1.5gpm we can move 7,500 btu's thru each loop at j10' of head. Take these head figures add to the head of the hx and pick the right pump. More likley a Grundfoss UPS26-99. Your only heating approx 175 sqft based on your total loop length and centers provided.

malconium

There is a one-way valve...

Gordy,



Thanks for looking at the diagram. There is a one-way valve that connects from the hot water line back to the cold water line near the input to the hot water pump. When the pump is running that one-way valve will open and water from the hot water side will move to the input of the hot water pump and around the loop that has been created by the one-way valve.



Malcolm

CMadatMe

How Did You

Come up with you have to move xx amount of gpm?

malconium

The flow guestimate was based on the water heater...

The water heater is capable of heating water at up to something like 4.4 gallons per minute. I rather naively thought that it made sense to move water through the water heater at that rate to minimize the amount of time that the water heater and the pump were running. If a smaller flow rate will get the heating job done then that is fine with me. The water heater does need a flow rate of at least  1 gpm to turn it on for heating though so I would want to have a little margin on that flow rate to make sure that it turns on reliably.



Malcolm

CMadatMe

That's Why

You should be piping primary secondary. Primary pumps job is to take care of the head in the tankless and move total gpm needed. The secondary's pump job is to move the gpm required for the system side. Think your in over your head and should contact a pro in your area before you get yourself in trouble.

cattledog

"Did I perhaps completely blow the calculation?"

Malcolm--



"Did I perhaps completely blow the calculation? I am shooting for around 4 to 6 gallons per minute of flow through two parallel loops that are about 140 feet long. I was told that to calculate the head for my 1/2" PEX that I should use the following formula:



0.0402 x feet of 1/2" PEX"



This looks like the calculation for a little over 1 gpm, so the answer to your question is yes if you were shooting for 4-6 gpm.



Chris's numbers for the pex loops are good, and you will need to add the flow rates together for the flow through the tankless heater. You might realistically achieve 1 and 1 gpm in the loops for a flow of 2 gpm through the water heater and have reliable turn on.



You will need the pressure loss data for your specific tankless water heater before you can size the pump. Remember that they are designed to work with incoming domestic water pressure and high temperature gain, so the passages are tight and head losses are high.

malconium

I did have a discusson with a local consultant...

I was able to find a local radiant heating consultant that I could bounce some questions off of. I think I now know about how much head loss there is in my system and which pump I am going to need based on the calculations. He was also able to tell me how I could make a simple measurement of what the actual head loss is before I commit to a new pump. What he told me was that I needed to have a pressure gauge at the output of the pump and another one at the end of the hot water loops - basically close to the input side of the pump. I can then run the faucets in my trailer, watch the flow meter until I get a flow range around 2 gallons per minute or so and compare the readings on the two pressure gauges. The difference in pressure will represent the head loss. All I have to do is convert psi back to head and I have a value that I can use for comparing with the performance curves of the pumps I am considering. It will not cost all that much for two pressure gauges and I don't mind having them in the system anyway.



Does anyone see any problems with this approach?



Thanks,



Malcolm

CMadatMe

I Gave

You the head loss in the tubing and his method still will not tell you the pressure drop across the hx.

malconium

Perhaps I am missing something...

Chris,



Did you somehow conclude from what I said that the water heater would not be included in the test? When I turn on a faucet water has to flow from the city water input through the hot water pump, around through the floor heating loops, through the water heater and back to where the faucets tap off their hot water. This means that the test would have water flowing through everything in the system - with the exception of the one-way valve. My intent was to measure the entire system for pressure drop. Am I still missing something with the approach that I just described?



Thanks,

Malcolm

CMadatMe

Are We Trying

To do this?



http://www.noritz.com/u/plumbing_diagrams/nrc111/6a_nrc111_dhw_hyd_ps.pdf

malconium

It is like this...

Chris,



What I am doing is somewhat like the diagram that you referred to except that I have radiant heat tubing in the floor. The basic diagram that I have been working from is shown below. I only have one heating zone that is split two ways and serviced by one pump. Otherwise my design is very similar. I have simplified somewhat in that I did not add as many isolation valves. This is, after all, a heating system in a travel trailer not a house. It is pretty easy for me to turn of all the water flow to the whole system if I need to service something. The internet site where I originally found it is the following where there is more explanation about the approach:



http://www.radiantcompany.com/system/open.shtml



Malcolm

malconium

I took some measurements...

Today I followed through on my plan to take some flow measurements. I added two pressure gauges to my system - one just past the output of the hot water pump and the other just before where the water is tapped off for the hot water faucets. I was able to turn on one or more faucets in the Airstream to get different levels of flow through the hot water loops and the water heater. My flow meter measures in Liters per Hour so I had to convert to gallons per minute for the chart below. I also converted the delta in psi to feet of head as well. Here are the measurements that I took - with cold water:



Static pressure in the system from the city water supply: 61 psi



Flow (gpm)        Input psi        Output psi        delta psi          head (ft)

1.1                          38                      25                     13                    29

1.76                        33                      13                     20                    46

1.98                        31                       9                       22                    50.6



The pump that seems to best meet my needs given the above information is the following:



Taco 009-SF5

Stainless Steel



I would have been happy to go with a brass model but evidently Taco has discontinued their brass versions of this pump in favor of stainless steel. This pump is designed to service systems that have a high head pressure but need a somewhat lower flow rate. The curve for this pump is show below.



It looks like I am near the top of the the 009 pumps curve. I am anticipating a flow rate a little above 1 gpm which should be enough to turn on my hot water heater.



Does anyone see any significant errors in my assumptions, tests or calculations relative to picking this specific pump?



Thanks,



Malcolm

Gordy

Question

Being an owner of some campers previously. Is this going to sit where AC electric, and municipal water is always accessible? Or will there be times on DC power, or generator?

malconium

Shore power mosly available...

I think that most of the time we will be using the Airstream in places where we can hook up to electricity. I do however have a plan in mind to add an inverter that would allow me to run some 110 volt things from my RV battery if we decide to go camping off the grid. I may or may not implement the plan depending on what we decide. We are relatively new to travel trailer camping so we have not yet made up our minds on some things like that. My Airstream has a 30 amp power system and that is split two ways - one breaker connecting only to the air conditioner and the other powering everything else. My thought is to install an inverter that could handle the everything else part of the circuit. Running the AC unit would be a bit much from the battery. In general we are also intending not to camp in places that are excessively cold. I had hoped to be able to find a suitable pump that was powered by 12 volt DC but that appears to be hard to do given the amount of head that my system seems to require. I also have a 1973 factory original propane powered 12 volt generator that is capable of recharging my on board battery if that were to become necessary.



Malcolm

Gordy

009

alone draws 168 watts. I thought maybe this was going to sit at a year around site going through the trouble of RFH.



Gordy

malconium

The Taco 009 does the job...

Yesterday I was finally able to install the Taco 009 pump that I had previously ordered. Sure enough it is beefy enough to pump water around the system. Not very fast mind you but I do get a flow rate around 1gpm that is sufficient to reliably trigger the hot water heater to stay on and running which is the major hurdle I was trying to get past. So I consider that part of my system development effort to have finally been successful. Now I will be able to do some testing to see how well the system can perform otherwise. For one thing I do not yet know how long it would take to get the system fully up to room temperature. Temps have been down close to the freezing point lately so I have just filled up my Airstream's water system with RV antifreeze for the winter. I have to come to some conclusions about whether to test the system with the antifreeze or to wait until I put water back in the system. The thing is testing the system in cold weather makes some sense to me. What I am not sure is how much different the RV antifreeze would behave relative to plain water for my testing. It does not appear to be any thinker than water but I do not know if its composition would make it work better or worse for testing compared to water. Does anyone have a thought on this?



Thanks,



Malcolm

Gordy

antifreeze

    It would seem to me you would want to test with out it. You can not possibly use it with antifreeze being an open system. The heat transfer is also different.



Gordy

malconium

How much different?

Gordy,



Sure, I understand that the antifreeze is different than plain water and that I will not be able to use antifreeze in the system for normal use. What I was wondering was how different the antifreeze is compared to plain water. If I knew how it would behave compared to water I could still conduct a test with the antifreeze to get an overall idea of performance. I could understand that the results would be better or worse depending on how the antifreeze differs.



Malcolm

Gordy

antifreeze the difference

Add a factor of 1.4 for head, and the same for average water temperature. The multiplier would be for 50% (glycol mixture).



 You are probably using RV antifreeze for the camper to winterize it. What I'm getting at is anti freeze is more viscous, and its flow characteristics are laminar where 100% water is more turbulent. The heat transfer characteristics are also different than 100% water. At any rate it takes more energy to pump, and heat antifreeze mixtures, the higher the concentration the more drastic the effects.



One question is this. If you went to the trouble to install radiant heat in your camper with an open system What temps do you plan on hanging up the season? Seems you could be caught in a prediciment if you don't winterize the system for the ride home after camping IF you are going to be out in sub freezing temps. Thinking wind chill effect also while towing at 60MPH to get home. Do you carry the antifreeze, and fill the system before parting home?



Gordy



Gordy

malconium

Shutting down for the winter...

Gordy,



OK - you have convinced me that I should do my heating experiments with just plain water.



You also raise several good concerns about how to handle my heating system. I have not yet had the opportunity to actually use the heating system in a real camping situation so I am not yet sure how I will do different things. Several thoughts come to mind relative to the issues as follows:



1.) It takes just shy of 4 gallons of RV antifreeze to entirely fill my plumbing system. While it is not at all hard to put in I do need to blow out the water first. I have only done that once so far and it is easy enough but it does require my air compressor. If I decide that a quick way of winterizing is needed I could probably figure out a way to use a small 12 volt air compressor and maybe I could even plumb it into the system. I could also conceive of somehow catching most of the antifreeze for reuse.



2.) The only part of my plumbing system that is not inside the Airstream is the water heater and a short amount of plumbing leading up to it. I think it would be a very good idea to create an insulated blanket covering of some sort to put over it while driving in very cold weather. That would protect it from freezing but would also protect it from dirt, bugs and flying rocks. As a practical matter it would be relatively easy to disconnect the water heater and drain it without having to do anything to the rest of the system.



3.) I suppose that while I am driving I could also set things up to allow the hot water pump to run without allowing the water heater to come on. It seems like that would go a long way toward keeping the water heater from freezing up if the water is moving through it. I am going to be installing an inverter soon that will allow me to run the pump from my 12 volt system which would be fine while I am driving and hooked up to my tow vehicle. The 12 volt system of the trailer connects to the 12 volt system of my pickup while towing. I have more battery capacity in my one ton diesel pickup than I do in the trailer. Of course while I am driving everything keeps nicely charged up too. I have also wondered if the water heater would work OK while I am driving. I suspect that it might have problems with wind at freeway speeds but I do not know that for a fact at the moment.



4.) I wonder if I could find some sort of small electric heating element that could be used to help keep the system from freezing when I did not have antifreeze in it? It would be kind of interesting to to be able to run the pump and have the water that is being pumped around be at least a little warm. I wonder what approach would be a good one for that?



Malcolm