Boilers - Steam and Hot Water Systems - circulator pump sizing

I have two floor house where I installed radiant floor heat. Each floor consists of 3 loops (300'x1/2" tubing each loop) that are connected to a single pump (each floor is on separate pump). So when the thermostat calls that particular pump should push the water through 900' 1/2" tubing total. I am using the Grundfos UPS15-58 3 speed pumps and I am suspecting they are not strong enough to push the water into all 3 loops. When I close 2 of the 3 loops I am getting hot water back with about 15° temperature drop, with 2 loops open the drop is about 25° but when I leave open all 3 loops the temperature drop is about 40°.

Does anyone has a suggestion if my assumtion is correct and what pump to use. Should I go with Gunfos UPS26-99 or TACO 011?

Thanks,
Peter

That's with the pump on highest speed I presume?

Pushing 1800ft of line and getting a 40deg drop between supply and return isnt so much the problem, as far as heat-design would be.. the problem would be the actual return water temp back into your boiler.

What kind of boiler do you use ? Are the temps you posted at the supply and return headers, or at the boiler output and input points ? If there is a primary/secondary kind of loop, then the boiler may be protected anyhow in your setup.

Pics ? Diagrams ?

Thank you for your replies. I am using Munchkin 80M and it is set to 130°F while the return is about 90°F. Yes it is on the highest speed of the pump. The system is shown in the attached picture.

Each floor is operated by one of the UPS15-58 pump. Each floor consists of about 4' of 3/4" PEX tubing before and after the pump and then there is a split into 3 1/2" loops (each 300' long). Each of the loops has valve allowing me to close any of the loops if needed; however the plan is to have open all the loops all the time as they are under different part of the floor.

I installed this last year and then we experienced a little colder winter then we were used to with steam radiators. Since the house is about 70 years old I decided to re-do some of the insulation. I removed the ceiling once again and added 2" rigid foam insulation around the perimeter of the house assuring there is no unwanted draft. However since the piping was exposed I run the heating system and tried to figure out why I getting this temperature drop on return, and I found that the piping in each loop is warm roughly in 2/3 of of the length (200'), when all 3 loops are open, so I assume the problem is the size of the pump. I know now that essentially the problem is the design, I should probably have each loop on single pump, or make them shorter (200'). However the job is done now.

I was considering bigger pump like Grundfos 26/99FC 3-speed, but now I am confused, I think I need pump with higher head feet so maybe I should consider UP26-116F or UP26-120U. I tried to run the calculation using SelectingCirculators.pdf from TACO website; however I am getting pump head feet 46.

Thanks for advice.

http://sadlop.com/image_2.JPG
<br>
http://sadlop.com/image_3.JPG

Also I would like to point out that the pumps are on the return and they are pumping down. I hope this is not a problem.

I am getting pump head feet 46.

That's one of the problems. For the same reason you can't push your breath through 100 feet of garden hose, you can't push water through 1800 feet of tubing with less than a gargantuan commercial pump. There is too much resistance.

Some of the problems here:

1) you are probably not getting adequate flow through the boiler because the boiler is piped directly through the zones. There are only a couple situations where you are allowed to pipe a Munchkin direct, and this is not one of them. You will probably need to repipe this to primary/secondary depending on...

2) how you break up the loops. At 300 feet each, you may need a pump on each to get adequate flow and temperature drop to heat the space.

3) I'm guessing that you have some sort of bullhead tri-tee for each of the loops Coming off the 3/4". That won't do. Depending on the heat load calculation, you probably need 1" going to a real manifold, and will have to pump each loop to get the flow rate needed to deliver the heat needed.

3) the manner in which the gas line is secured is probably not to code.

What floor coverings are in the rooms, how did you install the radiant (e.g., pex in transfer plates), and what design temperature for what heat loss?

I'm not going to get into the details of the 'issues' with your install just yet, but wanted to talk a bit about your head calculation.

It sounds to me as though you added the length of all the piping? 1800' of 1/2"...

An easy example...

Let's say that you had 100' of 3/4" copper pipe. The head loss on that pipe would be appx 4'. (with appx 4 GPM flow rate)

Let's further say that you took another 100', and put it in SERIES with the first 100', for a total length of 200'... head loss 8', right? Yes, right.

Now, instead, let's put that second 100' in PARALLEL with the first, would the head loss now still be 8' ? answer: NO.

It would be LESS than 4'... probably approaching 2', (not quite because the relationship isn't exactly linear). This is because for the same GPM flow rate, the flow VELOCITY decreases. When velocity decreases, head decreases.

So, now you have TWO lengths of 3/4", each capable of flowing 4 GPM... and the flow through the parallel circuit can be increased to 8 GPM. When you increase the flow up to that figure, you are again back at 4' of head.

For 1/2" COPPER (I don't know much about PEX, but the numbers are similar), you want to flow appx 1.5 GPM for a proper VELOCITY (2-4 FPS) in the pipe.

If you parallel THREE 1/2" loops, then you need to flow appx 4.5 GPM into the manifold. 3/4" pipe will do 4.5 GPM but it's at the high end... you are probably OK with that.

Increasing the size of the pump is probably not the answer, and certainly not the answer you want to hear. You will end up forcing the water through the pipe WAY to fast... again, I know that with copper, 2-4 FPS is recommended, PEX I'm sure is different, but probably similar.

There's LOTS more to be said in this thread, but I'm getting the hairy eyeball from the spousal unit, and need to do my chores.

I will end now with one parting question: Why didn't you pipe per the diagrams in the Munchkin manual? I think their manuals are among the best in the business... all of their 'preferred piping' for the Munchkins show PRIMARY/SECONDARY setups... your's isn't...?

Hello Xiphias/NJ Trooper, thanks for your input. I did the under floor piping and then I have plumber to do the connecting. I am not sure why we did not follow the diagram as Munchkin manual suggested. I trusted to his experience with connecting the boiler. Now I looked the manual and I see what you mean by primary and secondary loops.

You are also guessing right about the "bullhead tri-tee" 1/2" tubing coming from 3/4" PEX. I got those WATTS Quick-Connect Solution manifolds Watts: Single Sided Manifolds | Quick-Connect Solutions (http://www.watts.com/pro/_products_sub.asp?catId=71&parCat=2973) and I thought they will do the job.

My understanding is that creating the primary loop is necessary, and I will call plumber to do so. It should be fairly easy on my configuration, as shown in red on the image below (I would use Grundfos UPS15-58 as suggested by Munchkin manual).

As a second step I thought I would add extra pump (same as on the return UPS15-58) to the feed side of the 3/4" PEX, so each floor (900' total, 3 parallel 300' loops) would use two pumps. I am trying to stick to my original design, simply because otherwise I would need to take apart some walls, etc. to extend the 1/2" PEX from 2nd floor all the way to the boiler room.

Do you guys think this is possible? How does the characteristic for the two pump change? Somewhere I was 2 parallel pump connection where the flow increases almost double, however this is not parallel connection so I am not sure.

The orignal Munchkin suggested connection
http://sadlop.com/munchkin.jpg

My setup with suggested modifications
http://sadlop.com/munchkin_my.jpg

All the floors are hardwood floors/no carpet with exception of bathrooms where I have tiles.

http://sadlop.com/floor.jpg

Also NJ Trooper, for the calculation I used formula HL = k x c x L x (f1.75) found in SelectingCirculators.pdf on the TACO website.
So HL = 0.0374 x 1.047 x 350 x 3.364 (where 0.0374 is value corresponding to 1/2" PEX, c is correction factor for water 120°F, L is total equivalent length of piping circuit in feet, I used 350 to accommodate the 3/4" PEX as well as 3 ball valves and 2 elbows, and f is flow rate to the 1.75 power, I used 2 gpm as desired flow rate). So I really did not added all the length I used one loop only.

Thanks

I believe that the 'manifold' system which you used is intended for potable water systems. I'm not sure that it is appropriate for a radiant heating system.

While I do not think that installing an extra set of circulators will solve your problem, I also do not think your proposed location is correct.

May I ask some more questions?

What type of tubing did you use? brand/model,etc

When you did the design of the system, did you know how many BTU each room would require in order to properly heat the room?

Was the tubing installation designed in such a way as to be able to deliver the correct amount of BTU to each room?

If the tubing design is not adequate to deliver the required BTU, there is no way that you will be able to 'FORCE' it to work, no matter how many pumps you install.

The 1st floor consists of 2 rooms each about 20'x12'x8'. According to the calculation I used I would need 9,144 BTU/hour to heat each room. So the whole 1st floor will need 18,288 BTU/hour. For calculated 20°F temperature drop, the desired flow rate is 1.82 gpm. 1/2" PEX tubing has min 1.2 and max 2.3 gpm flow rate. The tubing I used is PEX-B Tubing with O2 barrier.

I also have question. You mentioned that the proposed location of the circulators is not correct. Are you referring to the green circulators that I placed on the fee side of each circuit? If so what is wrong with the location?

I am considering two possible solutions:
1) Add the primary circuit and the two extra circulators (preferable for me since it does not require taking down some of the new walls)
2) Add the primary circuit and split all 6 loops each with separate circulator

Thank you for you reply

If you repipe to primary/secondary and use a properly sized set of closely-spaced tees to a properly-sized manifold, you might be able to do this without pumping in series (which you wouldn't do like you have, but one right after another).

Thank you for all your suggestions.

I have one more question, about my setup. I called couple of plumbers about re-piping the Munchkin and so far I had no luck setting this up. Before I have someone over for the work I would like to have an idea what he will be expected to do. The way how I think this could be done is to add couple of tees and circulator as shown in the attached picture below. Would this configuration satisfy the recommended connection? Thank you for your answer.

http://www.sadlop.com/boiler/images/Boiler%20side%20view%20with%20primary.jpg

No, that is not the way to set up a primary/secondary system.

You really need to find a contractor that knows WTH they are doing, and understands what a primary/secondary system IS, AND can read and understand the manual.

Go here:
http://www.htproducts.com/literature/lp-185.pdf

Drawing 2C, page 24.

HTP drawings are about as clear as they come.

Thanks again. Yes, my intention is to find someone who is experienced with Munchkin installation. I am not planning to fix this myself; however I am trying to understand it as well just to make sure that this time this will done right. I really appreciate all your help and suggestions.

I looked the drawings again as xiohias suggested, btw it is the same picture I posted above... and I cannot see any problem with my setup once the 1 1/4" return and feed to the boiler will be connected and added the extra pump. I am adding one more picture in order to show how the water feed is connected (seems to be matching the Drawings 2C).

http://sadlop.com/feed.jpg

So I still think that adding the pump and connecting the return/feed using two tees would satisfy the drawings. The manifolds I used are intended for radiant heating, at least the seller is it suggesting, see 2 - Circuit BRASS Deluxe PEX Manifold Radiant Heating - eBay (item 200398863029 end time Nov-25-09 11:34:24 PST) (http://cgi.ebay.com/2-Circuit-BRASS-Deluxe-PEX-Manifold-Radiant-Heating_W0QQitemZ200398863029QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item2ea8b3fab5).

I also searched internet for some installation samples and I actually found something very similar, see below. (obviously it does not mean it is correct)

http://sadlop.com/notmine.jpg

Lastly would you recommend someone in Boston area who is specialized in Munchkin installation?

I didn't mean the manifolds that are visible in the picture... when I said the 'manifolds' were possibly not appropriate, I was talking about the ones that you posted the link to at the Watts website. The ones that you used to split the 3/4 into the two 1/2" loops.

The example you show of a similar installation is ALSO wrong. Looks pretty with the pipes all painted, but it is not the way that a primary/secondary system is to be piped.

This:

http://www.comfort-calc.net/pictures/Measurements_for_P-S_Tees.JPG
photo courtesy comfort-calc.net

shows how the closely spaced tees must be set up.

You see, just because the points are technically 'connected', does not mean that just any setup will FUNCTION properly and provide the hydraulic separation required for P/S piping.

There may be other issues with the installation... I asked these questions before, and there was no answer:

When you did the design of the system, did you know how many BTU each room would require in order to properly heat the room?

Was the tubing installation designed in such a way as to be able to deliver the correct amount of BTU to each room?


You may well find that even with the proper piping at the boiler that you have no way to deliver enough heat to the home to meet the heat loss of the home.

Ohh, thank you. Now I see it. Thanks also for the clarification on the manifolds. Regarding to your question about the BTU requirement: I thought I mentioned it in my reply (#10) above. 1st floor has two larger rooms while 2nd floor has 3 smaller bedrooms. The two rooms on the 1st floor are roughly same size, about 20x12x8' and I calculated about 9,144 BTU/hour to heat each room. So the whole 1st floor will need 18,288 BTU/hour. For calculated 20°F temperature drop, the desired flow rate is 1.82 gpm. 1/2" PEX tubing has min 1.2 and max 2.3 gpm flow rate. The tubing I used is PEX-B Tubing with O2 barrier.

Thank you again for your patience with me.

That actually did answer the first question... but the second question not really.

Two rooms, 20x12 = appx 480 sq feet of floor space. Some of this space is not available for heat output, such as under kitchen cabinets, appliances, etc, but let's use 480 for the example.

Let's round down and say your heat loss is 18K BTU.

Dividing 18K by 480 tells us that your radiant floor assembly would need to OUTPUT 37.5 BTU per square foot. I doubt that it's possible to achieve that...

Click here and read this, especially #5 (http://www.houseneeds.com/shop/Heatingproducts/radiantheating/safelink/safelinkheatsources.htm)

So let's do the math: 25 X 480 = 12K BTU

There's a shortfall of appx 6000 BTU there. You probably will need to add some supplemental heat source to keep the building from cooling off during design temperature conditions.

The delta tee and flow rate really have little to do with the ability of the floor assembly to provide the required BTU output that you will need to properly heat the room.

Another point to consider:

How are you controlling the TEMPERATURE of the water going into the radiant loops?

You don't want the surface of the floor to be above say 85°F and in order to make this so, you should probably not supply too much more than 110° water to the radiant loops...

In the pics/diagrams, I don't see any means of 'tempering' the water to the loops. It appears that you will get full boiler temperature water through them, which could be as high as the high limit on the boiler.

The diagrams shown in the manual are for high temp heat sources, such as fin-tube baseboard and the like. They are pointed out as examples of the P/S piping that you need.

There is additional work needed to temper the water to the radiant loops by adding mixing valves, etc...

The main thing I would say here is.....Read and follow manufacturers directions!!!!!

I did use for the calculation of the heat loss very simple application I found at How much heat does that room need? (http://www.hearth.com/econtent/index.php/articles/how_much_heat_does_that_room_need), but now I see I should re-calculate the heat loss properly to get more accurate result, since with this calculator there is no way radiant floor can be used without supplemental heating.

Regarding the temperature control - the Munchkin boiler is taking care of it. The limit is set to 130°F (I played with setting between 110-130). The floor is about 75°F.

I will have the re-piping done within next two weeks so I will see if it helps. Thanks for all your help.