I need a plate style HX. I did the home heat load on alternitive heatings site it said 90,000 btu wich one do i need
How big of an HX do i need?
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Simple answer would be big enough to supply 90k btu at the target delta-T with the system (plus hx) pump head (flow rate) of the design. Study the approach tables for various plate hx's to help make this decision. Also, Plate HX is a good planning tool to help make this decision. Keep in mind that at approach temps less than 20 (supply input temp minus hx output temp), sizing increases rapidly. Also, that as flow rate increases, pump head goes up fast.
fabguy01 said:
What size tube are you going in and out with on both sides and how much flow rate do you have to work with. Low flow rates and close approach temperatures (approach = incoming boiler water temp compared to supply out temp) often mean a HX that is significantly larger than what is usually guessed at by a lot of installers.
Trust but verify, i would recommend you use any past heating bills to spot check the number for sanity. You would not want an incorrect assumption to lead you astray. That said, my heat load was 93,393 @ -15.
My case the house load is similar but I was planning on storage so the question became how to I save the practical maximum my boilier will deliver an EKO 60 says 210,000 so reality will be less. I was guessing 80% , wishfull thinking maybe but also better slightly higher than lower was the thought.
I put all I knew into the web site mentioned above and varied the temps and flow rates until I found something workable.
I landed at 10-12 Gal/min input of 50/50 water/glycol in at 185 degrees using a 5x12 80 plate was the smallest HX that would get it done. Start slowing the water down and I quickly moved into 10x20 size. I wound up bumping the source pump up a size to comfortably deliver , picked 3 speed grundfos 1/6 HP ( I think so I had some options if reality did not work out so well ) I am 75 feet away with the 1" so the Head was starting to climb at the faster flow rates that was about the top I was comfortable going.
In the end it did work well I used the smaller 3 speeds on the tank side and in the zones. I believe the reason I top out at 175 in my tank is as others have mentioned when the tank is 175 and the source is 185 I would need a much larger HX or very fast flow rates that I just cannot get with 1" pipe 150 feet long.
I guess I put this down so you can see that there is no single answer, you need to have some of the other info asked for here and plug it in , or discuss it here to get a good choice for you.
My case the house load is similar but I was planning on storage so the question became how to I save the practical maximum my boilier will deliver an EKO 60 says 210,000 so reality will be less. I was guessing 80% , wishfull thinking maybe but also better slightly higher than lower was the thought.
I put all I knew into the web site mentioned above and varied the temps and flow rates until I found something workable.
I landed at 10-12 Gal/min input of 50/50 water/glycol in at 185 degrees using a 5x12 80 plate was the smallest HX that would get it done. Start slowing the water down and I quickly moved into 10x20 size. I wound up bumping the source pump up a size to comfortably deliver , picked 3 speed grundfos 1/6 HP ( I think so I had some options if reality did not work out so well ) I am 75 feet away with the 1" so the Head was starting to climb at the faster flow rates that was about the top I was comfortable going.
In the end it did work well I used the smaller 3 speeds on the tank side and in the zones. I believe the reason I top out at 175 in my tank is as others have mentioned when the tank is 175 and the source is 185 I would need a much larger HX or very fast flow rates that I just cannot get with 1" pipe 150 feet long.
I guess I put this down so you can see that there is no single answer, you need to have some of the other info asked for here and plug it in , or discuss it here to get a good choice for you.
I landed at 10-12 Gal/min input of 50/50 water/glycol in at 185 degrees using a 5x12 80 plate was the smallest HX that would get it done. Start slowing the water down and I quickly moved into 10x20 size. I wound up bumping the source pump up a size to comfortably deliver , picked 3 speed grundfos 1/6 HP ( I think so I had some options if reality did not work out so well ) I am 75 feet away with the 1” so the Head was starting to climb at the faster flow rates that was about the top I was comfortable going.
Bingo!!
I can't begin to tell you guys how many times I have went to a lack of heat complaint on an OWB or indoor boiler and found a 5x12-30 or 40 plate HX that showed about 50* differential between the boiler side and the load side. After I tell them that the thing is too small the instantaneous comment is, " The other guy said this was plenty big"
Yeah right...........
On a lot of our Garn jobs where we are talking sometimes upward of 400 foot loops and loads of 150K plus, a 10x20-50 plate HX is the norm along with 1-1/4" or 1-1/2" pex. Using a small circ you can get the approach temps within a few degrees which allows a lot more leeway with either storage or boiler temp before you have to bring it back on.
Off the cuff I would probably recommend a 10x20-30 or a 5x12-80 or 90 plate for your application given that you have 1" tube which really limits the GPM you can push through the HX. It's all about flow and temp drop.........always.
PS: The thing to remember is that a lot of websites will say that the HX they have will transfer XX,XXX btu. But what they often don't say is at what flow rate, temp drop and differential from side A to side B. You can make a very small HX deliver a huge amount of btu's. In normal size residential heating applications i try to stay within 10* side A to side B and do it with 10 GPM flow rate. About the smallest HX I can remember installing is a 50 plate 5x12.
Bingo!!
I can't begin to tell you guys how many times I have went to a lack of heat complaint on an OWB or indoor boiler and found a 5x12-30 or 40 plate HX that showed about 50* differential between the boiler side and the load side. After I tell them that the thing is too small the instantaneous comment is, " The other guy said this was plenty big"
Yeah right...........
On a lot of our Garn jobs where we are talking sometimes upward of 400 foot loops and loads of 150K plus, a 10x20-50 plate HX is the norm along with 1-1/4" or 1-1/2" pex. Using a small circ you can get the approach temps within a few degrees which allows a lot more leeway with either storage or boiler temp before you have to bring it back on.
Off the cuff I would probably recommend a 10x20-30 or a 5x12-80 or 90 plate for your application given that you have 1" tube which really limits the GPM you can push through the HX. It's all about flow and temp drop.........always.
PS: The thing to remember is that a lot of websites will say that the HX they have will transfer XX,XXX btu. But what they often don't say is at what flow rate, temp drop and differential from side A to side B. You can make a very small HX deliver a huge amount of btu's. In normal size residential heating applications i try to stay within 10* side A to side B and do it with 10 GPM flow rate. About the smallest HX I can remember installing is a 50 plate 5x12.
Heaterman- It is interesting you referred to a 10x20-50 plate HX for a 1 1/2" pex 400 ft loop 150k+ btu load. I am currently looking for a pump and HX for a 300 ft loop with 1 1/2" pex for a 190k btu load. I'm new to all this, so I don't really know what kind of flow rate I'm working with, nor how to figure the approach temps. How do you figure these without having it actually hooked up? Sorry if this is a dumb question 
I've checked at pexsupply.com and they have a 10X20-40 plate 100 gpm with 1 1/2" thread for $2,756. They have a 10X20-50 plate 150 gpm for $3,243, but it has 2" thread. What is the deal with the thread on the HX? Do you recommend keeping everything the same, as in if I'm working with 1 1/2" pex, go with 1 1/2" thread on the HX and 1 1/2" pipe coming out on the other side? Also, This Warm House quoted me for a $500 70-plate HX when I originally bought the Garn, so the prices on the HX's I just mentioned are a bit shocking to me. I definitely wasn't expecting that after the HX quote from TWH. Any recommendations for my pump as well? I was quoted for a grundfos 3 speed 1/6 hp 145 psi with a connection size of 1/2" (I don't know if that connection size is ok or not, and I have no idea if this pump is adequate for my system). I really appreciate any help you or others can offer.
I've checked at pexsupply.com and they have a 10X20-40 plate 100 gpm with 1 1/2" thread for $2,756. They have a 10X20-50 plate 150 gpm for $3,243, but it has 2" thread. What is the deal with the thread on the HX? Do you recommend keeping everything the same, as in if I'm working with 1 1/2" pex, go with 1 1/2" thread on the HX and 1 1/2" pipe coming out on the other side? Also, This Warm House quoted me for a $500 70-plate HX when I originally bought the Garn, so the prices on the HX's I just mentioned are a bit shocking to me. I definitely wasn't expecting that after the HX quote from TWH. Any recommendations for my pump as well? I was quoted for a grundfos 3 speed 1/6 hp 145 psi with a connection size of 1/2" (I don't know if that connection size is ok or not, and I have no idea if this pump is adequate for my system). I really appreciate any help you or others can offer.
fabguy01 said:
This is exactly where a lot of guys get in trouble with HX sizing. Read the parameters for the HX listed in the McMaster link. Pay close attention to the fluid temps listed there. (They are shown for cooling use but for heating it would be the same) Briefly, the temp differential is around 70* from side A to side B and the in/out temp on the load side (B) is only 20*. True they are transferring gobs of btu's but the temp differentials listed are not even remotely close to what field heating circumstances dictate. In short, neither the item listed in the Grainger or the McMaster link will work for your app.
Another area that really messes up a lot of people is the flow rate/head rating. The Grainger item says it will handle 50GPM. Looking at that a person might think that with a max flow rate like that it will probably be very low restriction at say.....10GPM. Not really the case. My B&G software says 10 GPM through that HX will add about 8 ft of head or the equivalent of about 150' of 1" pex. While a persons calculations might show that their tube length and diameter is OK for their required flow rate, adding a HX like that will probably put you out in no man's land.
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