Flat Plate Heat Exchangers - Differences?

Here is the brand that I purchased: http://www.radiantheatproducts.com/store/cart.php?m=product_list&c=14 It appears to be the exact same construction and material as the more expensive ones I have seen in other systems. I am about to hook it up and try it in the next few days. I will let you know how it operates when I do.

I called them and talked it over with their tech. He was very helpful. The 30 plate will transfer the 140,000 btus that my Tarm 40 puts out if the water moves at 15 gpm. You can probably go up or down in size based on your btu rating using mine as a baseline. Take a look at the tank design page on my website (in my signature).

I started with (approx) 8" x 3" x 2" - 20 plate and found in my setup that did not seem to be able to carry the full Tarm 40 output; in other words, idling occurred more frequently than I thought desirable.

I changed that out to a (approx) 12" x 4" x 3" - 30 plate, with 1" inlets and outlets, and performance greatly improved.

Checkout ebay prices. Last summer got mine for just over $200. The brand was AIC, which appears to be an established mfr.

Just for reference my 30 plate was $197 from radiantheatproducts. See link in my first post.

We've had the best luck with Swep and Alfa Laval, but they are usually rather expensive.

Chris

Like any product there are good better and best options. If you find a price to good to be true, there may be a reason. I have seen some very low quality import components on the market these days. Material quality and workmanship suffer when you shop for lowest price, many times.

But some of the big name manufactures are going overseas for production and assembly. Usually a big name company will own or operate the overseas factory to assure the quality stays high. Viessmann is one example of a top line product that produces some components in China, as does B&G;. But they do control the product carefully.

I'd shop a reputable brand from a company that can answer questions and support the product should a problem arise. You won't know until it is all piped in as to the performance and quality, often times.

hr

Number of plates, size of plates, port size, psi pressure drops Side A and Side B at various flow rates; approach temperatures -- all are critical information. You need to make this choice carefully. I have seen people choosing a plate hx of, for example, 230,000 btuh rating, but this being based on, for example, 30 or more gpm's. Pressure drop at these flow rates is astronomical and highly probable that such a plate hx would not work in a typical wood boiler application.

I'm not saying what you plan will not work. All I am saying is that picking a plate hx is more involved than what might be apparent.

Agree completely with jebatty. Choosing the HX that "fits" take some study of pressure drops, flows, delta Ts, and etc. I found a very nice fit for my job at Outdoor Furnace Supply earlier this year for a brazed plate HX in 5" x 12", 50 plate and 1 1/4" MPT connections. The exchanger is not yet installed but is soon to be. After reading the posts here I thought the prices at OFS would beat those I saw, but went back to their site and can't find the same HX I bought for about $283 free shipping. Inflation I guess.

see

Ten plates and the overall size of the HX can make a fairly large difference in specs between HXs. Material of manufacture, pressure specs, methods of brazing/welding all have large parts to play in costs. The HX I bought earlier this year has been replaced with another at a price increase of over $140.

I just got my system up and running this past weekend i went with a 70 Plate Brazed Heat Exchanger, 5" x 12", 1-1/4" MNPT ports.

Really good delta T on the unit which is what i was going after.

I paid 340.00 for it.

Wicked good price, nice exchanger, and good results. You sure did make a good choice.

One thing to consider is the temperature approach on both sides, i.e. if you have boiler water at 140, how warm will you get on the other side? 130? 125? 135? With my Garn and radiant heat, I wanted to be sure to be able to get very close, that way I can keep heating the floors when the Garn drops down to 130...120...in that range. I wound up with an 80 plate 5x12 with the 1 1/4" fittings....GEA is it? I think that's the right company..... I think it was $425 or so, so the above 70 plate is in the same ballpark. My approach temperatures are 3 degrees....so I get 127 on the house side when the temp in is 130. I'm happy with that!

Don't forget to plan on insulating the beast when you do the install....I bet I'm losing heat there as I have it enclosed in a 2" polystyrene "box" very losely held together....wrapped in R30 fiberglass. Not a good job at all....I bet some mice might have a really nice, warm home!

Also, don't forget the strainers....and better yet, install fittings so you can easily purge the strainers and run "outside" water through the exchanger itself to flush it out. I say that....but I've been online for 13.5 months, and I have yet to flush! Though I did measure the 3 degree approach last week....so I know I'm still doing good.

I have an 00R feeding both sides of the exhanger....not much pump really. To me this, like buried lines, isn't a place to skimp....an extra $100 can get you everything you could want...and you don't have to do it again!

Marginal flat plate sizes are touted by the same salesmen that say the 1" pipe is enough to feed adequate heat to a big old house and shop 300' away.

Short money up front often (but not always) means less performance for the life of the system.

Makes a tough call for the system owner that has to pay for it.

The first plate hx I ought was about 3" x 8" x 30 plate, 3/4" ports, with statement that it could move 240,000 btuh. Well it could, with about a 100F delta-T and 40 gpm, pressure drop 20 psi, might be exaggerating a little, but to make the point. Picking a plate hx takes careful research, learning, or dealing with someone who really understands how they work and how to size them in a hydronic system.

BPirger and Jbeatty have hit the nails on the head......or heads........as there are several factors to consider when selecting a HX. Hot Rod also has an excellent "buyer beware" piece of advise. There is a LOT of really low quality junk hitting the market as people figure out who and how to deal with companies in China. I saw one supposedly stainless steel HX that rotted out in a little over a year. I don't remember the brand but I do remember that the "stainless steel" sparked when the owner touched it with an angle grinder.

I generally use AIC but have also installed GEA and Swep units. Flat Plate is the industry standard but there is no good source of supply near me.
The claims of 140,000 out of a 10 plate 5" x 12" model are true but as Jim pointed out, at what temp drop, flow rate and pressure drop. I'll just say that the smallest I recall installing was a 5x12-50 and that was for a fairly small house. Maybe 1,500 sq ft + domestic hot water. I like to shoot for temp differential from side A to B of less than 10* and preferably closer to 5. I have a few jobs out there on the commercial or very large residential side of things running with 10x20-50 or more. Loads on those are over 400,000btu peak demand.