HX might not be plugged... new info..

[Pat53]

Well, in the ongoing saga of trying to figure out why my HX is kettling, I found out today that the Delta T in the HX is probably normal. I had ordered a K type thermocouple to doublecheck my supply and return temps and lo-and-behold the thermocouple has confirmed that my storage tank temperature gauge that is on the bottom of the tank is off by a whopping 15-16 degrees !! I put a sensor probe on the outlet return pipe from the storage tank (which is right on the bottom of the tank) and one on the same line just before the boiler and they both read within 1 degree of each other. My temp gauge on the bottom of the tank was reading 162F and the thermocouples were reading 177-178F and my supply temp coming out of the boiler was reading 192F, so a 15 degree Delta T with a 400+F stack temp. And that was with the circulator on low speed. I still have the kettling going on, so now I'm even more confused than before !! LOL

Pat

 

[2.beans]

i never thought your hx was plugged. do you know what your draft is? could you slow the draft down with a damper to lower your stack temps and then run run pump on low speed. this may help with the idling times. just a thought.

 

[Pat53]

i never thought your hx was plugged. do you know what your draft is? could you slow the draft down with a damper to lower your stack temps and then run run pump on low speed. this may help with the idling times. just a thought.

I don't know what the draft is, but I only have about 15 feet of chimney, all Class A 8" metalbestos. I can live with running smaller fires for this season, but not indefinitely. I need to get this figured out one way or the other. I will definitely take the HX out during the off season and inspect it.

right now, I need to try to come up with some way to get my startification back into my storage tank. I destroyed that when I removed the diffuser pipe 2 weeks ago. I'll have to shut down everything I guess and re-install it, but that will take someone with a welder to tack it in place and I don't want to have to bother someone to do that. I'm trying to figure out if I can drop something down from the 2" port on top of the tank to deflect the incoming flow up and and stop the circualar type flow I must be getting now.

I am going to run the pump on low for a while, I get less kettling on low speed than on high speed, and I'm going to let my tank get down to about 145F before refiring the boiler, that may help the stratification for now.

Pat

 

[Singed Eyebrows]

Pat, Have you ever seen the water tube exchanger in a hot water pressure washer? They are one piece of pipe formed in a coil. I have never seen different. They work flawlessly, no banging no kettling. They cannot trap air, they cannot circulate internally & steam. No one in their right mind would put a parallel exchanger in one of these & blow an oil gun flame on it. Ideally I think your Seton clone exchanger should have been formed from one piece of pipe of the proper diameter for 130,000 btu. My previous advice was to try to salvage the exchanger you have & get it closer to this. Hopefully you can understand that your exchanger is nothing like a one pipe unit. Your exchanger will not positively flow through all the pipes as evidenced by the kettling. Inspecting your exchanger won't tell you anything unless you really screwed up & had welding slag blocking a tube etc. Randy

 

[2.beans]

i guess draft probably isnt an issue for you. ive been trying different stuff since you started these threads. im now using a 007 for my primary pump between my boiler and storage and turn on the 011 when my boiler temps hit 175* plus. i have the 011 in series. this has changed things around for me a little bit. when i just left my boiler i had a delta t of 60* and it was quite. when it gets hotter the kettling begins, but its after the boiler has run longer. now im going to try some different pumps, or a 3 speed to dial it in a little better. i have my boiler isolated from my storage tanks when the boiler temp is lower than my tank set point with fast acting zone valves. this was im not mixing tank water losing my stratification.

 

[Singed Eyebrows]

You could try two 3 speed pumps in tandom. The one operated normally & the 2nd with an aquastat to kick it in when temps rise. I know you can pump through a Grundfoss because I thermosiphen through a shut down one. You would have a lot of adjustment & simple controls, Randy

 

[Pat53]

Pat, Have you ever seen the water tube exchanger in a hot water pressure washer? They are one piece of pipe formed in a coil. I have never seen different. They work flawlessly, no banging no kettling. They cannot trap air, they cannot circulate internally & steam. No one in their right mind would put a parallel exchanger in one of these & blow an oil gun flame on it. Ideally I think your Seton clone exchanger should have been formed from one piece of pipe of the proper diameter for 130,000 btu. My previous advice was to try to salvage the exchanger you have & get it closer to this. Hopefully you can understand that your exchanger is nothing like a one pipe unit. Your exchanger will not positively flow through all the pipes as evidenced by the kettling. Inspecting your exchanger won't tell you anything unless you really screwed up & had welding slag blocking a tube etc. Randy

Hi Randy, well I'm certainly no expert when it comes to HX's, but there has to be some other reason for the kettling. Lots of people are using these type boilers and don't report this problem. When I ran last year without storage I had much hotter fires going (500F stack temps) albeit for shorter duartion, than this season, and never had a sound come from that HX, so I just can't see how a hot fire would alone cause the kettling. I think it was "mole" who said he has stack temps almost 600F on his Seton and a .095 draft and has no problem. Now that is what I would call a "ripping" fire, and yet it evidently operates just fine for him.

However, I do like the idea of using just a one pipe HX. What would you suggest as a possible alternative HX for this unit?

thx, Pat

 

[Singed Eyebrows]

Pat, First off, even if everybody else has a perfect working Seton/Seton clone the fact that you are having trouble does not make this your fault IMHO. Your boiler should tolerate storage/non storage, strong pump, weak pump etc etc & as I said I believe you built to Mr. Setons specs, your problem yes, your fault no. To answer your last question/ because of the difficulty in bending one pipe to the shape of your exchanger you have now I would bend larger diameter tubing to the shape they are now & use something like U fittings to connect them(weld them on, use steel fittings). I don't know the proper size, this is something you would need to research. Probably around 1 1/4" ID. An exchanger like this would respond to increased pump pressure by dropping discharge temperature. Its still going to be a water tube exchanger & without flow will go to steam. You will want to regulate gpm through it to get the discharge temp you want, it will be controllable. It would look similar to what you have now without the 4X4 runners & be just one piece of pipe. I would angle the coils some so the back parts of the coils are not blocked from radiant heat. Randy PS, You might be able to find someone with fancy bending equipment that can just run the whole thing in one piece.

 

[Pat53]

Pat, First off, even if everybody else has a perfect working Seton/Seton clone the fact that you are having trouble does not make this your fault IMHO. Your boiler should tolerate storage/non storage, strong pump, weak pump etc etc & as I said I believe you built to Mr. Setons specs, your problem yes, your fault no. To answer your last question/ because of the difficulty in bending one pipe to the shape of your exchanger you have now I would bend larger diameter tubing to the shape they are now & use something like U fittings to connect them(weld them on, use steel fittings). I don't know the proper size, this is something you would need to research. Probably around 1 1/4" ID. An exchanger like this would respond to increased pump pressure by dropping discharge temperature. Its still going to be a water tube exchanger & without flow will go to steam. You will want to regulate gpm through it to get the discharge temp you want, it will be controllable. It would look similar to what you have now without the 4X4 runners & be just one piece of pipe. I would angle the coils some so the back parts of the coils are not blocked from radiant heat. Randy PS, You might be able to find someone with fancy bending equipment that can just run the whole thing in one piece.

Randy here is a cut-a-way image of the Seton showing the HX in blue. The headers are actually made of square tube, not round, like shown in the diagram.
http://www.rohor.com/page3.html
When I picture a one-tube HX, I was thinking of a pipe that kind of looks like a long snake that runs in horizontal sections up the back of the refractory and then across the top of the firebox. And yes, using "U" fittings welded on for the turns rather than 90 degree fittings. This would give the water a long contact time with the heat and there would be no low flow areas or dead spots within that HX.

What exactly do you mean about "angling" the coils, I don't get that part?

thx, Pat

 

[Singed Eyebrows]

Pat, First off, even if everybody else has a perfect working Seton/Seton clone the fact that you are having trouble does not make this your fault IMHO. Your boiler should tolerate storage/non storage, strong pump, weak pump etc etc & as I said I believe you built to Mr. Setons specs, your problem yes, your fault no. To answer your last question/ because of the difficulty in bending one pipe to the shape of your exchanger you have now I would bend larger diameter tubing to the shape they are now & use something like U fittings to connect them(weld them on, use steel fittings). I don't know the proper size, this is something you would need to research. Probably around 1 1/4" ID. An exchanger like this would respond to increased pump pressure by dropping discharge temperature. Its still going to be a water tube exchanger & without flow will go to steam. You will want to regulate gpm through it to get the discharge temp you want, it will be controllable. It would look similar to what you have now without the 4X4 runners & be just one piece of pipe. I would angle the coils some so the back parts of the coils are not blocked from radiant heat. Randy PS, You might be able to find someone with fancy bending equipment that can just run the whole thing in one piece.

Randy here is a cut-a-way image of the Seton showing the HX in blue. The headers are actually made of square tube, not round, like shown in the diagram.
http://www.rohor.com/page3.html
When I picture a one-tube HX, I was thinking of a pipe that kind of looks like a long snake that runs in horizontal sections up the back of the refractory and then across the top of the firebox. And yes, using "U" fittings welded on for the turns rather than 90 degree fittings. This would give the water a long contact time with the heat and there would be no low flow areas or dead spots within that HX.

What exactly do you mean about "angling" the coils, I don't get that part?

thx, Pat

Pat, The coils need to be angled so the thing looks like a spring, they cannot be one in back of the other unless you use headers again. What is important is to get the diameter reasonably close to correct size for the hottest fires. Too large & the water won't pick up as much heat as it should. How is your Seton controlled now?, as a solid fuel fire is not constant. The exchanger I envision runs vertical up the back of the boiler & across the top, the same as it does now. I would err on the large side though with the tubing as you could put a ball valve on the inlet to throttle flow. Randy

 

[Pat53]

Randy, I don't think I'm following you. Are you talking about a coil-type HX, like something in an unpressurized storage tank ?

There is only about 10" of space between the back of the refractory and the back wall, and even less above the firebox.

Pat

 

[Singed Eyebrows]

Randy, I don't think I'm following you. Are you talking about a coil-type HX, like something in an unpressurized storage tank ?

There is only about 10" of space between the back of the refractory and the back wall, and even less above the firebox.

Pat

Pat, The tubes would look just like they do now only they would be connected with U fittings & be of larger diameter. If instead of your headers you just welded on U fittings you would have the exchanger I"m talking about. This would be 1 continuous pipe & as mentioned could be balanced with a ball valve. You didn't mention as to how your boiler is controlled now. Randy

 

[leaddog]

If you went with a one pipe ex wouldn't it be better to run it back and forth horizonal rather than vertical. Have the cold come in at the top and exit at the bottem so you would be drawing heat with the coldest water. You would also keep the boiler heat more even. The other advantage of this would be the ex would serve as a turbulator and cause turbulation as the gases pass.
leaddog

 

[Pat53]

Randy, I don't think I'm following you. Are you talking about a coil-type HX, like something in an unpressurized storage tank ?

There is only about 10" of space between the back of the refractory and the back wall, and even less above the firebox.

Pat

Pat, The tubes would look just like they do now only they would be connected with U fittings & be of larger diameter. If instead of your headers you just welded on U fittings you would have the exchanger I"m talking about. This would be 1 continuous pipe & as mentioned could be balanced with a ball valve. You didn't mention as to how your boiler is controlled now. Randy

Ok, I see what you mean. So the water would basically go back and forth (up and down) vertically thru the HX? I guess I don't see why you couldn't just run it horizontally in the same manner, with the tubes going back and forth, side to side ?

The boiler is controlled with just an aquastat. I do have shut-offs on both sides of the boiler also.

Pat

 

[Singed Eyebrows]

It should work horizontal as well. I would run it vertical though, because of large differences in heat within the boiler, just a hunch though. Does the aquastat control a fan? Randy

 

[Pat53]

Well, might be a nice little summer project building a new style HX. The Seton has only a natural draft, no fans.

thx for your help Randy, appreciate it.

Pat

 

[Singed Eyebrows]

Well, might be a nice little summer project building a new style HX. The Seton has only a natural draft, no fans.

thx for your help Randy, appreciate it.

Pat

Pat, I still don't know what that aquastat controls. You also mentioned valves on each side of the exchanger I believe. You could PM me if you would rather not post this info, patent concerns? Randy

 

[Pat53]

Well, might be a nice little summer project building a new style HX. The Seton has only a natural draft, no fans.

thx for your help Randy, appreciate it.

Pat

Pat, I still don't know what that aquastat controls. You also mentioned valves on each side of the exchanger I believe. You could PM me if you would rather not post this info, patent concerns? Randy

Sorry Randy forgot that, the aquastat just closes and opens the draft door. I use an Azel 777 on mine. I can set it for whatever I want, a much wider range than a regular aquastat.

Pat

 

[bigburner]

I like the HX design, it's simple, cheap and works. The change I would make is equal pressure drop across the thing. The water needs to travel the same distance for every tube. One possibility might be. put inlet on the left or right of the manifold and the out let on the side of the other manifold.