Stainless pump for DHW
Hello, I am having trouble getting an answer no matter how much I search. I am using my water heater to heat a small basement. I am using a heat exchanger to separate the radiant floor from the DHW heater. So double duty…
Do I need to use a stainless circulating pump on the water heater side ? I am using copper pipe for this loop.
thanks
Comments
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Yes, you do unless you want a corroded pump leaking iron into your DHW!!
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yes, a stainless, bronze, or composite circ on the water side
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Thank you guys ! Much appreciated . A composite circ ? I haven't heard of them, are they cheaper ? any better or worse ?, brand name so I can look into them please ?
Otherwise I can use cast iron for the floor side , such as a Taco 007 ?
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Composite pump blocks is what they use in most of the combi boilers for the DHW heat exchanger module. Common in Europe, with union body connections, the composite body pumps may just be OEM versions in the US.
Depending on your distribution, is it zoned? I would look at one of the ECM type circs for the heating loop. More adjustability and less power consumption.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Thanks , Just one zone…
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I'm using a Taco 006 for my recirculating domestic hot water.
I do run the pump on an aquastat, but just to give some perspective that pump running 24/7 would cost about $7 a month.
Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.
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A composite circ, mostly used for DHW recirculation systems is an option over stainless or bronze casings. different strokes for different folks on how they connect to the system. Composite bodies will be a union connection, stainless can be threaded, flanged, or union. Bronze bodies typically are sweat versions.
So yes, on the heating side of the heat exchanger, you can use a cast iron flanged circ. Just remember to add air elimination, expansion tank and all the accruements on a heating system.
Dave Holdorf
Technical Training Manager - East
Taco Comfort Solutions
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Thanks, I was just looking at that. Haven't looked at an aquastat yet..
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Great, thanks, I'll have some questions about that, Like filling and pressurization but I'll wait until I'm ready for that part of the project.
You guys have been very helpful, It can be hard to find answers by searching the internet sometimes. Sure glad I found this place…
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Shop around for non ferrous options. Deals on E-bay but they could be out of date code and warranty.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Thank you for that !!
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Sample of one, but I've had good luck with a budget stainless circulator off your favorite on-line retailer.
Make sure to include a check valve/IFC or a heat trap on the loop to your plate HX to prevent thermosyphon when heat is off.
You also want to cycle the pump daily even during the summer to prevent it from seizing up and keeping the water from stagnating in the heating loop. Some controllers allow you
Also watch your flow rates. You want pretty high delta T (that is low flow rate) to prevent mixing your water tank. Too much mixing can cause excessive short cycling on the burner. Make sure to add a flow setter valve on the loop.
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High flow rate wi transfer more heat energy , more quickly. If the pump can then be turned off the tank will stratify for the next heat call
If the water side pump also serves as the dhw recirc pump, that complicates itThe recirculating flow is based on the temperature drop of the dhw recirc loop, usually 7-10 degrees. That may take a very low flow rate. So the two tasks may be at odds with one another
Im curious what the heat load is and the water heater btu. Those hydronic combicor tanks were 65,000 or larger
You may need to turn off the heat loop to get a hot shower on cold days?
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Here's what I have so far , do I need a pressure relief valve on the floor side ?
Going to add temperature gauges.
This is not necessarily how it will be physically laid out but it will be connected this way.
Oh I just noticed I have the heat exchanger flopped. I know it should feed from opposite ends.I'll fix that on the water heater side.
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yes the HX work best with counter flow piping . The heating circ wants to be downstream of the expansion tank
Pump away not at the expansion tank
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Ok I will move it , in fact I was thinking of putting it close to the mix valve between that and the manifold. So it draws the output of the mix and feeds right into the manifold. Will that work?
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I was thinking of putting it on a timer to run ten minutes a day
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Make sure to include a check valve/IFC or a heat trap on the loop to your plate HX to prevent thermosyphon when heat is off.
Not understanding this part..0 -
On your drawing, the stainless pump should have an IFC or a check valve in series with it. The bit of cracking pressure a check valve stops convective flow when the pump is not running.
Add a drain connection to the domestic hot water in of your HX so you can easily descale it if needed.
You need some fill setup (back flow preventer and regulator) and pressure relief valve on the heat side.
Not diagram specific, but pumps should be somewhere physically lower down, pumping sideways or up, so gravity will help in priming it.
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I would leave off the mixing valve unless you run your water heater higher than 140F.
Make sure you size your pumps for the pressure drop of the heat exchanger and flow, especially on the radiant side.8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab0 -
Here's a new drawing, not my best work , and I am an armature. lol
I'm unclear why a regulator is needed on the heat loop as well as a check valve ?
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If you are going to install a mixing valve, the pump goes on the outlet side.
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab0 -
right, my bad… I'll fix that later, don't know why I didn't that as I was aware.
left out temp gauges as well. Hard to draw on such a small screen.
Thank for the advice everyone. Please keep it coming, I'm a green horn but I am learning.
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Just so you know, Taco makes an X-Pump Block that can make assembly a lot easier and takes up less room. You still have to install all the accessories. It’s also expensive, but I’ve used them in a pinch.
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab0 -
thank you
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Here is the diagram you want.
About the only thing wrong with it is the expansion tank and water feed should be on the bottom just before the speace heat pump and needs a pressure releif valve.
As @Alan (California Radiant) Forbes said, you don't need a mix valve. Adjust the flow rate form you water tank until you get the right temp on the space heat side.
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it depends on how accurately you want the radiant temperature controlled. A typical water heater could have a 20 degree differential. For comfortable radiant a 10- 15 degree temperature drop is desireable. A mixing valve would regulate the SWT to the radiant within 2-4 degrees.Regardless of the WH temperature
In. Perfect world, all the info, gpm. Flow rate and temperature drops. Both on the A and B side of the HX would be entered into the sizing software, then the exact HX spec would be available.
Without this step you could measure temperature drops and add a balance valve to trial and error your way to the results you want.
KISS as Alan mentioned would be to run it without the mix valve, see what you get.
I would either add two valves or a Webstone purge ball valve on the potable side to acid flush it, or make the HX removable to descale it.
Webstone valves on the radiantside to fill into and purge out of.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
thank you I will study that
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Webstone valves on the radiantside to fill into and purge out of.
Yep on my list…
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Hi guys, any advice on heat exchangers, Pex Universe has them at the cheapest prices I have seen.
They are not potable rated but PU says they are made with the correct materials that would make them potable.
Saw a brand on Amazon for a bit more. They all look the same to me.
What do you guys think??0 -
I wouldn't use anything that doesn't say it's rated for potable use regardless of what it says it's made from.
Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.
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Right, I found a product on Amazon, UL listed, says for domestic hot water. Does that mean potable?
Also 403 or 316L , does it matter, I have conditioned well water..
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Hi @hunter29 , By 'conditioned" do you mean salt-softened, or? If salt-softened, how much calcium/magnesium hardness is left in the water? You want to leave 60-120 ppm, or the water gets aggressive and hungry. That's not the sort of water you want touching metals. 🐲
Yours, Larry
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they are less $$ because they are not paying for the testing and the right to use the UPC and NSF shields.
Without those certifications I suppose they can say whatever they want as far as “similar to”
Installing a non hello hlisted device is against code and opens you up to a liability issue for the life of that product to future owners. Is it worth it?
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Nope, not worth it, I just haven't found anything that says potable. I do have an email into one company to clarify. Then there are the ones listed for beer wort..
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Hi Larry, yes salt softened, whats left in the water I don't know. However its fine on all my fixtures and has caused no problems in over thirty years. If its going to be hard on a exchanger I can replace it however often..
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Hi, A simple observation is that if you have copper plumbing and are not seeing any blue staining in sinks, it suggests the copper is not being degraded. This is good and suggests you are not oversoftening the water. 👍️ Stainless steel doesn't like salt much, but if the water isn't particularly salty, you're probably okay. I have good experience with 316 L, so would choose that.
Yours, Larry
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No, Never seen anything like that. I'll likely go with the UL listed EX I saw on Amazon, it had a reasonable price. Supply House product is way expensive. This is not a critical system…
Thanks everyone..
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the NSF website shows NSF 61 compliant heat exchangers
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0
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