Adding a secondary pump to my radiant heating system

SilverCheetah

3/8 " tubing. 1000 feet of runs. 6 loops ranging from 140 feet to 180 feet. GPM flow average about .65 gpm per loop. My pump is after the mixing valve. Trying to get more flow through each loop. Have balancing valves to slow water flow if need be. The thermostat signal (24 volt) is sent to a control board which in turn starts the pump (120 volts) and the isolated switch turns on the boiler on same board. So here is the question:

Can I add another small pump right before the boiler? Can I hook up a second pump to the board? So both pumps will turn on at the same time. Will adding a second pump damage anything or even help out with the actual flow? I can post pictures if necessary, etc.

SilverCheetah

SCHEMATIC OF SYSTEM

Schematic of the system and pump

SWEI

a drawing will help

Pretty sure JPG, GIF, PNG, and PDF all will work.



Depending on the current layout and pump, there are several possible solutions.  Why do you feel you need more flow?

SilverCheetah

Attachment

Tried attaching 2X but nothing worked.

SilverCheetah

Why I feel that I need more flow

When the system starts up it takes quite a long time before the return side of the tubing is warm too hot to the touch, especially from a cold start. The system is in the subfloor in the basement. There is bubble wrap underneath and very well insulated with double layers of R15 insulation (tucked in nicely). After the system runs for at least one hour or a few hours (no more then 2 hours) and the room is up to temperature the heat will not kick on for at least 6-8 hours depending on how cold it is outside. Today it is 35 degrees. Heat really never goes above 70 degrees as this is very comfortable.

I understand that there is a pump curve to any water flow.  Luckily the first floor has radiators as well in the other part of the rooms and the largest room with high ceilings has both radiant and radiators. Unfortunately the subfloor has only one loop through each joist (some parts).

Once the system gets going the house and kitchen are very warm and stay warm for quite a while.  The situation is that the cold water automatically starts mixing with the hot water creating a very slow effect. I am assuming that creating more flow (slightly in each loop) will create heat faster. The heat will probably take a while to come up but not as long as before.

Sorry about JPEG pictures, they were not uploading. The PDF worked.

STEVEusaPA

little more info...

First, I don't think the second pump idea will work.

What pump do you have now?  What are the sizes of all the piping?

What water temp do you have running thru the radiant?

Where are the radiator loops on the diagram, and what temp are they running at.

How many btu's do you need for each loop.

Lets evaluate the design first to make sure it can do what you need it to do as far as flow, btus, right circulator, etc.

SWEI

radiant, radiators, and pumps

Radiant floors and radiators generally need rather different water temperatures.



Do floor loops and radiators share the same manifold port, or are there specific ports used for each type of radiation?



Looks like the boiler probably has an internal circulator, but just in case -- is there only one pump in the system?



Can we assume the two crosses shown in your drawing are do not represent four pipes connected together?

SilverCheetah

Update on the information: Please see answers after questions.

First, I don't think the second pump idea will work.What pump do you have now? B& G Series 100 1/12 HP Pump   What are the sizes of all the piping? 3/8" tubing pex for radiant heating only

What water temp do you have running thru the radiant? 120-140 (Mixing valve installed)

Where are the radiator loops on the diagram, and what temp are they running at. 180 for the radiators. 2 extra B&G pumps. 1st floor and 2nd floor. Radiators are zoned with Honeywell controllers, etc.

How many btu's do you need for each loop. Do not know, but boiler is 90% efficient 175,000 BTU.

Lets evaluate the design first to make sure it can do what you need it to do as far as flow, btus, right circulator, etc. steve

 

1. radiant, radiators, and pumpsRadiant floors and radiators generally need rather diferent water temperatures. They are at different temperatures. 180 for Radiators and 120-140 for radiant.
   
   
   
   Do floor loops and radiators share the same manifold port, or are there specific ports used for each type of radiation? specific ports for each zone. They do not share the manifold. The wirsbo uponor supply and return manifold (6 loops) is only for the radiant heat only.
   
   
   
   Looks like the boiler probably has an internal circulator, but just in case -- is there only one pump in the system? Boiler does not have an internal circulator. There are 4 circulators. There are 4 circuit boards with zone valve and priority zones (not used). End switches and Isolated switches. All the signals are sent from one board to another for the zoned areas with Honeywell valve controllers. For radiant and hot water wired directly to secondary boards. No zone valves only flow control valves. The signal then goes to aquastat and to electronic ignition. Only the isolated switches on the boards are wired to the aquastat.
   
   
   
   Can we assume the two crosses shown in your drawing are do not represent four pipes connected together?  No only the mixing valve connects the 2 pipes. Although the piping is still connected to all the other piping and zone valves. The controllers are closed not allowing water to move past a point in addition pumps are not moving the water, only the radiant heat pump pulls and pushes water through the system, etc.

SilverCheetah

Ultimate Goal

The ultimate goal here is to create more flow or GPM through each loop. Can only one pump for the section off radiant part pull/push water through or can 2 pumps be installed. If so, will the 2nd smaller pump create problems because the pump is trying to push water through faster then the bigger pump can handle? That is really the question. If so, then the only other option is to purchase a bigger pump. Thanks!

SWEI

the ultimate goal

is to make you system work properly.  If we don't understand how it was designed and installed, we stand precious little chance of improving it.



Photos of the boiler and associated piping, valves, etc. would help.



The Series 100 is a wonderful high flow low head pump.  I've never used one on floor loops so I'd really like to understand the rest of the design.

SilverCheetah

Pictures

First page: Pump for Holding Tank, Pump for First Floor and Pump for Second Floor. Empty line is where I possibly could add another small pump.

Second page: Open port before the boiler

3rd page and 4th page: Radiant close up

The loops are all being fixed and organized after the heating season.

SilverCheetah

REST OF THE DESIGN

The B&G Pump is only for the Radiant as you see in the pictures. The small Grundfos pump is for the holding tank. Looks like 30 gallons. The B&G Pump next to the small one is for the 2nd floor. The second floor has 4 bedrooms and 2 bathrooms. There are 3 zones all controlled by Honeywell zone valve controls and 2 circuit boards. The zone valves only open up when there is a call for heat and the pump circulates water through the system. The last B&G Pump is for the first floor. The first floor has 4 zones (not including the radiant). Same set up with 4 Honeywell zone valve controllers. The radiant and hot water holding tank only are isolated with 2 flow control valves next to the Air Purge and Vent Valve. Hopefully this answers your questions. Thank you

.

Paul48

Ain't Broke

Is there a specific problem, other than the fact you would like the system to heat up faster?

SilverCheetah

No specific problems

No, there are no specific problems. I have a little air in the system. I am not going to bleed at this point because we only have about 15 days left and the loops have to come down anyway. The pex tubing will be organized neatly and the copper tubing is leaking (very small) and plumber states no air is getting in. But with both the flow control valve leak along with other leak (this has to be fixed).

It just takes a while (Like 30-60 minutes) before return side is within 20-30 degrees of supply side. This is from a cold start because mixing valve is supplying cool water to keep the system from getting to 180. Also have radiators for other floors. Supply side runs @ 140 going in and return side fluctuates between 110-120.  The system has always run at 140 going in and I have never had any issues. Temperatures of tiles are between 75-80 degrees. I believe once I bleed the system of all air in the spring the temperature differences will become closer. 

I was looking at a TACO pump (2400-45) where the Max Flow is 55 and Max Head is 45.  The B&G is 33/8.  Because 3/8" tubing (kind of restricted). Looks like I am getting about 4.5 GPM. A lot of variables here. Maybe swapping out the pump may help and increase the flow.

SilverCheetah

CAN ANYONE TELL ME IF THIS IS A SUBSTITUTE FOR MY B&G PUMP (SWAPPING OUT)

I was looking @ the 0013 Variable Speed Delta-T Cast Iron Circulator Pump, 1/6 HP. It has a flat curve for GPM and Ft per head. 34/33 while the B&G is 33/8. This may do the trick. Please advise. Thank you.



Max Flow: 34

Max Head 33

This pumps adjusts based on tempeature swings between return and supply manifold and matches your system over time for errors.

http://www.pexsupply.com/Taco-0013-VDTF3-0013-Variable-Speed-Delta-T-Cast-Iron-Circulator-Pump-1-6-HP

SWEI

substitutes

The 0013 does not have a flat pump curve.  A 0010 does, and makes a pretty good replacement for a Series 100 in most applications.

SilverCheetah

TACO's Advice

I spoke to TACO and after a lengthy conversation with them they suggested the 0015 3 Speed Pump. This has a very flat curve of 21 gpm and 20 feet of head. Because of all this resistance in the system and the design, they suggested the 3 speed pump because I can find a happy medium to have a Delta T of 10 degrees. This is my next step. I will update once this is done.

SWEI

What is a flat curve?

When we refer to a circulator as having a flat curve, we are describing a pump which does not dramatically increase its head pressure as flow decreases.



Take a look at http://www.taco-hvac.com/uploads/FileLibrary/00-3speed_family_curves.pdf and you will see why the 007 and 0010 are said to have flat curves. http://jbblog.flopro.taco-hvac.com/watching-the-detectives/ and http://jbblog.flopro.taco-hvac.com/waiting-for-columbo/ explain why this characteristic is desirable for many heating applications.  High head pumps have their place, but they are not "flat curve" designs.

SilverCheetah

What TACO advised

I do not know if "flat curve" is what they used. Please accept my apology. I explained the situation of the supply and return temperatures and all the other characteristics. TACO stated that the 0015 or 00R pump would probably be best as I do not require a lot of GPM through each loop, but would have to increase the head pressure in order to overcome the resistance. Right now the system can operate at 4.0 GPM will all ports fully open. The difference of the supply and return temperature is between 25-40 degrees. Only on a few occasions has the Delta been 20. I have worked with the mixing valve from 110-140. There are 6 settings, while 6 allows less water to mix, in which I am assuming each increment is 5* under perfect conditions. The TACO 3 speed pump has the following characteristics at the highest setting # 3:

GPM                                        5                  6                   7                 8

Total Feet Head                    16               15                  14               13

At this point the B&G has a total of 8 feet per head whether you are at 5-6-7-8 GPM. From Zero GPM to 10 GPM, the head pressure remains pretty flat at around 8. Only at this point the head pressure decreases while the GPM increases. These pumps work great for the zoned radiator parts. I am assuming that is the reason why my flow whether one loop or all 6 loops are fully open changes very little, possibly .10 GPM in total.

 I am trying to get the Delta to 10 because of the layout. Unfortunately even the software provided by manufacturers can not plug in my number because 2/3 of the radiant heat through the subfloor has spacing of 16" apart instead of 8". Bad mistake on builders part. Luckily I have the radiators to compensate (different zone) the Foyer and Hallway. The Kitchen is the only area that has no other zones to compensate for.



The Taco 0015 and Grundfos 15-58 are so-called “steep-curve” pumps – lower flow, but higher head pressure.  These are great for radiant floor heating, and well-suited to be zone pumps for panel radiator or baseboard jobs using copper or PEX tubing.



If I am missing something, please help as it sounds to me that this is perfect for my Radiant Heat application. Thank you.

SWEI

so all this serves is the floor loops?

and there are no zone valves downstream of the pump?

SilverCheetah

All this serves is the floor loops

Swei, thank you for your continued support.

Yes, all this serves is the 6 floor loops on the first floor & nothing else. On the first floor I also have 3 other rooms with radiators. One of the rooms on the first floor (20 feet high and 400 sq. feet) has radiators and radiant heat (2 separate thermostats). The spacing is 8" in this room. So the heat is great. This TACO pump looks like it will use less electricity & circulate the water at constant temperatures resulting in better even heating.

SilverCheetah

All this serves is the floor loops

Swei, thank you for your continued support.

Yes, all this serves is the 6 floor loops on the first floor & nothing else. On the first floor I also have 3 other rooms with radiators. One of the rooms on the first floor (20 feet high and 400 sq. feet) has radiators and radiant heat (2 separate thermostats). The spacing is 8" in this room. So the heat is great. This TACO pump looks like it will use less electricity & circulate the water at constant temperatures resulting in better even heating.

SWEI

radiators and thermostats on the first floor

So the radiators on the first floor are fed by a different pump?



Is the tubing embedded in concrete, or is this a dry floor system?  If the former, you really can not rely on a conventional thermostat to regulate space temperature.   Outdoor reset control would be best, but a hydronic thermostat with a slab sensor would represent a major improvement.

SilverCheetah

BTUH Calculations

Based on the calculation I have done of 38,835 BTU's per hour/(10*500) = 7.767 GPM. Divided by 6 loops I would need 1.30 GPM through each loop. Assuming that I have to have the 6 loops at 1.30 GPM, at the lowest setting I would obtain 6 feet of head. At setting # 2, the head pressure increases to 10.5 feet per head, and at setting # 3, the head pressure would be 13 feet of head. Not that significantly more than the B&G Pump.

My concern after reading the articles is "Banging in the pipes". So is head pressure what is really needed here to achieve a lower delta T. ? Thank you.

SilverCheetah

The Radiators are Fed by a different Pump

Yes, the radiators are fed by a different pump and not through PEX, but copper tubing. I believe there is very little resistance and in addition there are zone valves that open and close to allow water through. Water goes in at 180 degrees and will come back at 130 through the copper. Works real well.

I have all the radiators on one thermostat as I find the house heats better. The other thermostat is for the radiant.

 The radiant system is through the subfloor in the basement 3/8" tubing joist aluminum tracks. Then bubble wrap is used to insulate the floor with 2 extra layers of insulation in the kitchen and one extra everywhere else. The subfloor is insulated extremely well.

IMO, the kitchen area is only operating at 50% efficiency because the spacing is 16" and not 8" for the loops.

SWEI

bubble wrap

is not a particularly effective insulating material.  How are your basement temps?



I would seriously consider an outdoor reset-driven mixing valve for those floor loops.

SilverCheetah

My basement temperature

My basement temperature is fine. The heat is not escaping into the basement. The heat is being contained in the subfloor. I was just curious to know if the pump will do the trick. I understand that it will take a while before the heat comes up. If I left the kitchen at 66 degrees, the radiant would probably run only 1X per day probably at 4-5 a.m. and this is when temperatures drop below 40 degrees F.  I do not really understand an outset reset switch.  

SWEI

outdoor reset

changes the temperature of your heating water based on the outdoor air temperature.  As the outdoor temp warms up, lower temperature water is supplied to the emitters.  http://heat-timer.com/En/EducationDetail.aspx?Id=3 explains pretty well.  While it's useful on almost any type of system, it's pretty much a requirement for maintaining a stable room temperature using in-floor radiant heat.  Given that you have a conventional boiler and a mixing valve, fluid temp for your floor loops could be controlled by replacing your existing mixing valve with something like http://flopro.taco-hvac.com/products/index.html?category=188



I should have asked if you are measuring those large ∆T numbers when the system starts up and if they drop later as the system comes up to temperature?  If so, adding ODR might be a better move than installing a larger pump.



You could also add outdoor reset to your boiler, which would vary the temperature in your main loop depending on weather, probably saving ~15% on your annual fuel bill.  The mixing valve controlling the floor loops would not be affected by this, but overall system comfort would increase.

SilverCheetah

What happens when the system starts up

I should have asked if you are measuring those large ∆T numbers when the system starts up and if they drop later as the system comes up to temperature?  If so, adding ODR might be a better move than installing a larger pump.





When the system starts up from a cold start, the surface temperature of the manifolds are 70* on the supply and return. Now the boiler starts and water is at 70*, slowly the temperature increases to 180* on the boiler and the supply temperature increases at a slower rate. Within 10 minutes the supply temp. is now @ 140-450 degrees. The return temp. is still at 90-100 degrees, so the initial difference is 40-50 degrees, and will not reach the difference of 30 degrees until system is running for at least 1 hour.  The water coming up from the boiler pipe is T off and I have the flow control valve that starts the cycle of water (pump still pulling at this point), then the next step is the mixing valve, circulator pump pulling and pushing down towards the supply side of the manifold. I am assuming the flow control valve creates resistance. I can sketch out the system if need be. All the other zones are shut down.

SilverCheetah

Radiant Sketch

Radiant Sketch

Gordy

D

Gordy

D

Gordy

D

Gordy

D

Gordy

D

Gordy

D

Gordy

Thorn in the design

Is 3/8" tubing 16" on center in a staple up configuration. It's not 50% less efficient it's just 50% less emitter.



The reason your delta is so wide is that the tubing is giving up twice the btus to the floor verses say an 8" oc layout by the time the return water gets back to the manifold it's plenty cold.



I doubt you will ever get a 10* delta t unless you use outdoor reset, and constant circulation. Less emitter is less BTUS a sf. With the present flow rates you might be getting 20-25 btus a sf.



The headloss for 180' of 3/8 tubing would be well over 20' for 1 GPM. Plus manifold, and supply return piping head losses.







Your not going to get what you think with the 0015





What are your floor coverings in the radiant areas?

Gordy

D

SilverCheetah

What are your floor coverings in the radiant areas?

I do not understand the question?  Please advise!

Gordy

Floor coverings

Carpet,tile,hardwood, engineered hardwood etc.

SWEI

supply temps

Are showing 170-190F on radiant loops?  If those are accurate, I'm wondering what the mixing valve is mixing down from...



Those big delta-T numbers you're seeing are a result of hot water hitting a cold floor.  Outdoor reset with constant circulation will stabilize those at a level perhaps a bit better than the 30F you are seeing after an hour of operation.



The way your system is currently configured and controlled is kind of like driving a car that has no accelerator or brakes -- your speed can only be controlled by depressing or releasing the clutch.  Imagine driving that car on varying terrain -- while only being able to see about 3 feet in front of your bumper.  That's roughly what an indoor thermostat controlling a fixed speed circulator or a zone valve can do.



Outdoor reset gives you an accelerator and brakes while increasing visibility to something like 200 yards.