Heat Exchanger from Alternative Heating and Supplies

[emesine]

Is there anything wrong with the heat exchanger sold for $250?

http://estore.websitepros.com/1313539/Detail.bok?no=477

Is there any reason why it costs so much less than this one (same size) for $1100?

http://www.pexsupply.com/FlatPlate-...Thread-60-GPM-Heat-Exchanger-5-x-12-5791000-p

Andrew

 

[julien]

Hi Andrew, i am suppose the first is a 1" inlet and low cost made, the second is a 1 1/4" and is «Rated at 450 psi working pressure, both sides. U.L. Listed, European TUV and optional ASME code construction».

You have another choice at Cozy, LB31-50 at 385$, 1 1/4 " thread size

http://www.cozyheat.net/plate.html


And performance tables, is rated 300,000 btu/hr at 30 gpm !

http://www.cozyheat.net/exchangers/BRAZED_PERFORMANCE_TABLES.pdf

 

[rowerwet]

My CB dealer had 5x12" HX for almost triple what I found them for on EBay, I ended up doing the Ebay route, much cheaper price and am on my second year of use. mine is rated for 435 psi, and has the 1" bungs, since my thermopex is 1" it works for me.
the dealer I found on Ebay was freeheat4u they have good ratings and there are more people on here who used them and had good results also.

 

[dirtryder]

I also bought my HX's (2 water to air 3 water to water), my underground pex, pex for the house, and circulator pumps from freeheat4u on e-bay. I am very good at searching on Google and no one even came close to their prices. I got free shipping too. Other than a satisfied customer, I have no relationship with this company.

 

[DaveBP]

There's more to these things than just the number of plates. Those different pipe sizes on the ports are not just for the convenience of plumbing hookup.

If you look at the specs for the different models you notice that there are, say, 30 plate models that have a wide range of BTU/hr capacities, some more than double. Then notice that the higher rated models have the larger ports. That means they can cram more GPM through there to get those BTUs across. With the smaller ports the pressure drop will get you at the higher flow rates. You'll need a lot more pump energy and probably a bigger, more expensive pump. I don't know how the internal construction is different and whether it costs that much more to build them. They do cost a lot more, though.

And remember those BTU/hr ratings are under ideal conditions. They assume the maximum difference in temperature between the two sides of the system and usually use very high flow rates (GPM).
If you want to get your storage tank anywhere near the boiler output temp then the BTU exchange rate will plummet the closer you get. In other words you'll need a larger HX at those last top-off-the-tank stages that are really important if you're using high temp emitters like typical baseboards.

This forum is littered with tales of systems having trouble getting enough heat through underground pipes that are just too small. Flat plate heat exchangers can be a troublesome bottleneck, too. When you find the best price get the next size larger model than you think you need. You'll get long term efficiency gains that will probably save pumping money and improved performance for the life of the system.

 

[dirtryder]

Believe me, I know the difference from apples to apples and apples to oranges........I have been an ASE certified Master Auto tech for over 18 years and grew up with a wrench in my hand. Although it is not a car or truck.....HVAC, Hydraulics, electrical, pressures, flow rates.......are all the same once you know them.

 

[emesine]

Based on my calculations, I need about 20 gallons per minute running through the hot side of my exchanger in order to get excellent heat transfer. I have checked flatplate.com, which is an excellent resource for sizing a heat exchanger..... if you want to pay $$$$$$$$$ for the HX. According to flatplate, I can easily get 20 gpm with a 1.25 inch port 12 X 5 X 40.

Does anyone know what the pressure loss will be, running at 20 gpm, for a 12 X 5 X 80 with 1 inch ports? I can get one of those pretty cheap, the heat transfer would be excellent, but I am concerned about pressure loss and the ability to get 20 GPM.

The HX is not the problem; with 40 flow channels the pressure loss is bound to be very low. However, the 1" ports are going to be a big problem. Perhaps I could model and just assume the two 1" ports amount to about 3-4 feet of 1" pipe?

Andrew

 

[heaterman]

Based on my calculations, I need about 20 gallons per minute running through the hot side of my exchanger in order to get excellent heat transfer. I have checked flatplate.com, which is an excellent resource for sizing a heat exchanger..... if you want to pay $$$$$$$$$ for the HX. According to flatplate, I can easily get 20 gpm with a 1.25 inch port 12 X 5 X 40.

Does anyone know what the pressure loss will be, running at 20 gpm, for a 12 X 5 X 80 with 1 inch ports? I can get one of those pretty cheap, the heat transfer would be excellent, but I am concerned about pressure loss and the ability to get 20 GPM.

The HX is not the problem; with 40 flow channels the pressure loss is bound to be very low. However, the 1" ports are going to be a big problem. Perhaps I could model and just assume the two 1" ports amount to about 3-4 feet of 1" pipe?

Andrew

Does anyone know what the pressure loss will be, running at 20 gpm, for a 12 X 5 X 80 with 1 inch ports

There's the rub my friend. In a typical open system there is no physical way to get 20GPM through any length of 1" pex and that heat exchanger. You would be looking at head in the neighborhood of 40-50 feet which translates to a minimum of about 7-9psi mandatory at the suction inlet of the circ. Can't be done unless you put the boiler on a platform about 12 feet in the air.

You have to compensate for low flow by going about double on the size of the HX. As an example, we just finished an install which used a 10 x 20 - 50plate model with 1-1/2" tappings for a 250,000 btu load. That HX is rated for up to nearly a million btu but that's with max temperature drop and 50GPM sloshing through it.

 

[emesine]

Yes, that is the rub.....

The boiler piping is 1.5 inch, so no problem there. Even at 20 gpm the head loss is very low (about 5 ft water) over the boiler run. Let's assume the 1" fittings are approximately equivalent to 10 feet total of 1" pipe. at 20 gpm that would mean about 3 feet of heat loss over the fittings, not counting the exchanger itself. I would estimate the HX itself would be pretty low resistance with 40 separate channels to carry water, probably 3-5 feet of head loss. So..... running from the boiler through the HX would be a total head of about 13 feet. This side is pressurized, I haven't thought the other side of the HX through (it is to an unpressurized storage tank.)

Andrew

 

[emesine]

Where and for how much $$$ did you find a 10 X 20 X 50 heat exchanger?

Andrew

 

[emesine]

I did some research. First off, you can contact Advanced Industrial Components (make fairly cheap HX) directly and they will give you a HX size based on the info you give them. They sent a fully sheet on what they would recommend. GEA (flat plate) has the same service at www.flatplateselect.com.

A GEA 12 X 5 X 40 HX has a total transfer capacity of 1105 btu/hftF

An AIC 12 X 5 X 40 HX has a total transfer capacity of 1219 btu/hftF

AIC is, of course, a lot cheaper, but it looks from their literature that their HXs are good quality.

Andrew