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.