Another tankless water heater replacing boiler thread

[2Biz]

Heres a pic of my floor heat control panel. Basically I have 3 systems running off output 2 of the weepmiser. The floor heat system, the trough heat tape, and the LP hose blowdown/washerfluid injection system. The weepmiser output only see's about 10 watts. The bottom relay actually powers all three systems. The top relay is powered by the bottom relay which in turns powers the trough heat tape...Its not pretty but it works and with the terminal strips, makes it easier to trouble shoot if you ever needed to or expand. I don't like using wire nuts on things like this. I repurposed the old boiler panel that was already in the ER...

 

[OurTown]

Are you playin' with me?!

"If the temperature is 1° below the LL setting it will remain on until the temperature rises to 1° above the LL setting"

Edited to take out the HL stuff....CBChevy said it...If setpoint is 33°, It comes on at 32° and turns back off at 1° above LL which is 34°, a 2° diferential!

I'm not sure why my mind skipped over that. Lol. I think I need more sleep. This whole remodel is really taking a toll on me.

 

[2Biz]

I'm not sure why my mind skipped over that. Lol. I think I need more sleep. This whole remodel is really taking a toll on me.

I totally understand!! Sometimes it helps to get another perspective...Just trying to save you some time and un-needed work/expense.

 

[OurTown]

I totally understand!! Sometimes it helps to get another perspective...Just trying to save you some time and un-needed work/expense.

How do I verify that an 0013 pump is the correct size? I looked at an online calculator but it seemed over my head. We have 16 loops with 1/2" PEX. I have no idea how long the original loops are but I think the longest loop on the newly poured concrete is about 200'.

 

[OurTown]

Three of those pumps are close to $1,500 so I want to get it right the first time.

 

[OurTown]

I didn't think I'm going to use the buffer tank because we have little space for it without making it a difficult install. The air eliminators of course come in different sizes. The pump flanges come in many sizes also. The old copper is currently 2" and the manifolds are 1 1/2" which seem very large when I start looking at pumps, pump flanges, and air eliminators.

 

[OurTown]

 

[2Biz]

How do I verify that an 0013 pump is the correct size? I looked at an online calculator but it seemed over my head. We have 16 loops with 1/2" PEX. I have no idea how long the original loops are but I think the longest loop on the newly poured concrete is about 200'.

Yea, thats the million dollar question...There are mathmatical formulas that you can use, but you are right, it can get complicated. You can start by checking flow rates of the pumps and calculate capacity and head pressure of each zone. I remember you want about 2-3 ft per minute flow rate through each of the loops to get the proper heat transfer...There are online calculators that tell you how much fluid volume the 1/2" pex has per foot...Yes it gets complex...You need to start with the bays and work backwards to figure out the pump size....It sounds like you have a lot more surface you are heating compared to my cw...I only have (4) bay zones and a trough zone connected to 1" manifolds. The trough loop barely has any load once it gets warm and it also has the heat tape to help. It stays at about 110° since its insullated....Plus you have 2" supplies...A taco 013 will probably not be big enough to handle the load you have. 2 in parallel might, it will give you about 60gpm with no head restrictions. But I would probably size the pump for 2" and the gpm you need after calculating....Going to get expensive?! BTW, are the slotted screw fittings like ball valves? You only need to adjust/throttle the zones going out to the bay. The return manifold fittings need to be wide open. Good luck!

 

[2Biz]

BTW, when I installed my system, (2) 013 Tacos supplying pressure to my demand heaters was the cheapest route. I think they were less than $300 each. There might be a single pump design now that will give you the pressure you are looking for and save money? The research can take longer than putting the system together if you are engineering it yourself...

 

[OurTown]

Yea, thats the million dollar question...There are mathmatical formulas that you can use, but you are right, it can get complicated. You can start by checking flow rates of the pumps and calculate capacity and head pressure of each zone. I remember you want about 2-3 ft per minute flow rate through each of the loops to get the proper heat transfer...There are online calculators that tell you how much fluid volume the 1/2" pex has per foot...Yes it gets complex...You need to start with the bays and work backwards to figure out the pump size....It sounds like you have a lot more surface you are heating compared to my cw...I only have (4) bay zones and a trough zone connected to 1" manifolds. The trough loop barely has any load once it gets warm and it also has the heat tape to help. It stays at about 110° since its insullated....Plus you have 2" supplies...A taco 013 will probably not be big enough to handle the load you have. 2 in parallel might, it will give you about 60gpm with no head restrictions. But I would probably size the pump for 2" and the gpm you need after calculating....Going to get expensive?! BTW, are the slotted screw fittings like ball valves? You only need to adjust/throttle the zones going out to the bay. The return manifold fittings need to be wide open. Good luck!

On the secondary loop I calculated just the tubing runs and came up with about 23 GPM and 15 of head pressure. The 0013 is perfect for that if I don't count the extra head pressure for the manifolds and elbows.

 

[OurTown]

BTW, when I installed my system, (2) 013 Tacos supplying pressure to my demand heaters was the cheapest route. I think they were less than $300 each. There might be a single pump design now that will give you the pressure you are looking for and save money? The research can take longer than putting the system together if you are engineering it yourself...

I did some more calculations and I'm going to go with a Taco 2400-45-3P on the primary loop and one on the secondary loop. It's about the same cost as going with three 0013 pumps. I'm into this about $5K so far without the fittings that I'll buy locally as I put it all together. I'm sure I'll have at least five trips to Menards before I'm finished.

 

[2Biz]

Are you sure you calculated correctly? Check the graphs on the attached links. If I am looking at it right, the 2400-45-3P puts out about 39ft of head pressure at 5-6 gpm. Converted to psi, thats 17psi....Not near enough pressure for your demand heaters running only one pump...The larger pump might be better for the zone pumps than an 013...But take a look at the graphs and make sure you calculated right for the heater pumps. Just because it says its rated at 150psi, that means the pump will run in a system pressurized to 150psi....Not that it will develop 150psi...Thats how I interpret it comparing to the graphs and what I experienced with my system.

Taco-2400-45-3P-Product-Overview.pdf

79582_PROD_FILE.pdf

 

[2Biz]

Watch this video, maybe it will help you understand GPM and head pressure when it comes to reading these charts.

(1690) How to Read Pump Chart and Select Pump - YouTube

 

[OurTown]

Are you sure you calculated correctly? Check the graphs on the attached links. If I am looking at it right, the 2400-45-3P puts out about 39ft of head pressure at 5-6 gpm. Converted to psi, thats 17psi....Not near enough pressure for your demand heaters running only one pump...The larger pump might be better for the zone pumps than an 013...But take a look at the graphs and make sure you calculated right for the heater pumps. Just because it says its rated at 150psi, that means the pump will run in a system pressurized to 150psi....Not that it will develop 150psi...Thats how I interpret it comparing to the graphs and what I experienced with my system.

Taco-2400-45-3P-Product-Overview.pdf

79582_PROD_FILE.pdf

I understand the pump curve charts but don't comprehend the heater pressure drop curve very well. Isn't the pressure drop going to change with demand? The chart shows only 8 psi drop @ 5 GPM. It goes up to 12 @ 6 GPM. At 7 GPM it is still only about 12 psi or so. I need to regroup.

 

[OurTown]

Am I looking for 15-20 psi after the heaters to somewhat match the secondary loop? How do I know how much temperature rise my heaters will be running? You set the output to 105F but do you know the temp going into your heater? I'm guessing it is around 55F based on 7 GPM.

 

[OurTown]

The 0013 chart shows 29 feet of head at 7 GPM. Two of those would only be 58 feet of head and that is only about 25 psi, right? I'm really getting confused.

 

[2Biz]

You are taxing my 'ol brain! LOL....On my Takagi, I know I get 40psi at the inlet using (2) 013's in series. I have a pressure guage attached to check it. Maybe its a bonus running them in series? When setting the output temp to 105°, the heater regulates flow based on inlet pressure and temperature and maximises througput to get 105° output temp. Which in my case is 6gpm give or take a few tenths. If it allowed more than 6gpm through, then it couldn't maintain 105° output temp. So basically the gpm is the variable. It does what ever it needs to in order to maintain the output set temp.

As for the output flow of the heater....It needs to be about half that of the main loop flow....If the main loop is lower than 6gpm, the glycol will back feed back to the inlet to the heater....Thats why pump sizing on the main loop is so critical. It has to be about twice that of the heater through put...Ideally...Hope that makes sense. You'll need a minimum of 12 gpm which it sounds like you have.

AS for flows of an 013 at 60ft of head....Maybe I have ones made on Wednesday and they are better than ones made on Friday or Monday! LOL

I forget, are you using Takagis or another flavor?

 

[OurTown]

You are taxing my 'ol brain! LOL....On my Takagi, I know I get 40psi at the inlet using (2) 013's in series. I have a pressure guage attached to check it. Maybe its a bonus running them in series? When setting the output temp to 105°, the heater regulates flow based on inlet pressure and temperature and maximises througput to get 105° output temp. Which in my case is 6gpm give or take a few tenths. If it allowed more than 6gpm through, then it couldn't maintain 105° output temp. So basically the gpm is the variable. It does what ever it needs to in order to maintain the output set temp.

As for the output flow of the heater....It needs to be about half that of the main loop flow....If the main loop is lower than 6gpm, the glycol will back feed back to the inlet to the heater....Thats why pump sizing on the main loop is so critical. It has to be about twice that of the heater through put...Ideally...Hope that makes sense. You'll need a minimum of 12 gpm which it sounds like you have.

AS for flows of an 013 at 60ft of head....Maybe I have ones made on Wednesday and they are better than ones made on Friday or Monday! LOL

I forget, are you using Takagis or another flavor?

Two Takagi T-H3-DV-N units. Okay so if I use another 2400-45-3P in series on the primary loop it might work out fine. At 15 GPM they add up to 66 feet of head pressure. Maybe I'll get the bonus psi too. Lol.

 

[2Biz]

Since you are running 2 heaters, you'll get more flow and pressure with the 2400-45-3P than I'm getting with my (2) 013's....Did you check amperage on the 2400 series pump? Its 3.6a at 115v. Make sure your relays and aquastats handle the extra load. The 013's are only 2.0a. You'd think almost double the amps, you'd get double the volume and pressure!? LOL.....Probably like a boat, double the horse power and get a few more mph!

 

[OurTown]

Since you are running 2 heaters, you'll get more flow and pressure with the 2400-45-3P than I'm getting with my (2) 013's....Did you check amperage on the 2400 series pump? Its 3.6a at 115v. Make sure your relays and aquastats handle the extra load. The 013's are only 2.0a. You'd think almost double the amps, you'd get double the volume and pressure!? LOL.....Probably like a boat, double the horse power and get a few more mph!

Since you guys showed me that the Weep Mizer output 2 has a 2 degree differential I'm going to use that with a contactor for the secondary loop. The aquastat will have the two pumps on it and it's rated for twice that. Thanks for all your help and preventing me many times in this thread from making mistakes.