Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: gratefulgary on January 25, 2012, 07:08:50 AM
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Hi guys,
I have just gotten on the this site. Looks like a great resource. I need some help sizing a new HX for my system. Disclaimer: I bought this house with all of the system already here already. Some photos are posted here: http://www.flickr.com/photos/toogbrand/sets/72157628953640877/ (http://www.flickr.com/photos/toogbrand/sets/72157628953640877/)
I have a 2001 CL 5648SB that is 200 ft from the house that provides hot water for finned baseboard radiators and domestic hot water. And is integrated with the oil fired boiler. It also provides heat via a water/air HX to a 900 sq ft finished space in the barn.My current HX is a B&G BP412-20. I have always felt that it is significantly undersized. It now behaves as though its flow has become restricted, there are mineral deposits impeding heat transfer, or both. That is, when a cold zone calls for heat, the water temp on the house side drops like a stone and requires the oil burner to kick on to maintain a reasonable temperature. It didn't do that till this year.
There are four zones in a 3100 sq ft split level (4) house with an open floor plan and vaulted ceilings. The total radiator footage is ~182 ft. One of the zones has radiators on three levels totaling ~100 ft. As to how much more pipe comprises the system, who knows, but it's a lot. My local purveyor of CB's had a recommendation something like....Well, that 20 plate is definitely too small and we would usually install a 50 or 70 plate unit for a house your size. I think you need a 70.
My 412-20 has 1 in ports and is 4 X 12 in. The only reasonably accurate temperature I can provide is that the water leaves the WFB at 180 and arrives at the house ~170. The pumps at the WFB are Taco 014's and circulation through the HX in the house is by a B&G PL36. The system is 1 in PEX. The house side is 3/4 Cu with 007 Taco's.
What say you? And I read with great interest the 8 p. post regarding temperature monitoring, something I had just begun to design myself. Some excellent ideas.
Thanks,
G
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I am a bit confused by your post, but wondering about the 180 start temp and 170 by the time it gets into the house. That is a huge drop. I think the consensus here is about 1 or 2 degrees from the furnace to the house.
How many pumps do you have? I only have 1 and use the zone valves to direct the flow. Sounds like you have pump(s) on the furnace as well as in the house. A diagram might be helpful.
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So if I am reading this right you have a 0012 pump that circulates the water through the underground lines and a PL36 that circulated through the plate and indoor boiler? If so, it sounds like those 2 pumps should be swapped.
That is a really small plate heat exchanger you have. Going bigger doesn't hurt anything. The only reason to go with a smaller size is the cost.
Also, going with a larger heat exchanger will allow you to run a much smaller pump on the indoor side.
If what you have had been working ok then I would say a 5x12" 40 plate would work fine but 50 plate would be better. These sizes run in the $300 price range.
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Since this AM I measured the distance from the house to the boiler and it is 205 ft plus about 20 ft inside making the total loop 430 ft. The line from the boiler melts snow on the ground so I suspect it is not buried below the frost line.
Muffin, click on the link in the first post to get you to photos of the system.
They are Taco 014's, not 012's and they replaced the PL36's that wore out since I bought the house. They were provided by the place the CB had been purchased from and were supposedly the same as PL36's.
It is correct that the PL36 circulates water through the HX and oil fired boiler. The 20 plate HX has been too small from the beginning and was wondering if just how much larger an HX should be there could be determined by a method other than a vague...well, 70 plates should do the trick.
There is one Taco 014 pumping water from the CB to the house and another one pumping water in a separate, much shorter, loop to the barn. In those photos, the barn can be seen next to the WFB.
So should there be a larger capacity pump for a 430 ft loop?
Thanks,
G
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I am not sure why I typed 0012. I was looking at the specs for the 0014.
They are not the same. A 0013 would be a little closer but still quite a bit less flow than a PL36.
What happened to the PL 36 pumps that died?
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One began to complain and then had a seizure, the other froze over a summer.
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Were they in a real humid location? It is kind of surprising that it froze from sitting over summer. There is no rotor in contact with the rotor so have much less place to get stuck up.
Do you know how old they were when they died?
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As far as I know, they were the original pumps, so at least ten years old.
It is kind of humid during the summer, but not inordinately so...it's upstate NY, western Catskills.
I'm going to swap the 014 at the WFB with the PL-36 in the house, putting the larger pump in service on the longer run.
I'd still like to get an intelligent recommendation regarding the appropriate HX for my application. I mean, everyone has one...how was it chosen? Or were they provided by the WFB people and that was that?
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Why not omit the hx, not everyone has one !
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Hmmm, that's a thought. Nah, it's fraught with peril. There are a couple of good reasons I that come to mind as to why that wouldn't work so well for me.
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knoing what i no now i would not of put a hx in
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You need somewhere around 1 plate for each 3000 BTU. A 40 plate will work for about 100K btu. I like to go a size bigger just to be safe. Going large will also help keep the temperature differential closer between the indoor and outdoor systems.
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Thanks everyone for all your help and suggestions!
RSI...I called my oil people and from the nozzle specs determined that my oil burner is ~125,000 BTU.
I will swap those pumps. The consensus is, here and elsewhere, that short of replacing the 1 in. pex with 1 1/4 - 1 1/2....really, I'm screwed. Although I clearly do need the larger HX, flow is a major issue and that the pipe is 1 in. is the limiting factor. The pump issue has been discussed in detail here, elsewhere, and with my contact at Syracuse Thermal. None of the alternatives really solves the flow deficiency. So, I'll live with it...for now.
RSI...what are your thoughts regarding going without an HX? Assuming, of course, there was by-pass plumbing to loop the WFB water without going through the oil fired boiler.
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How old is your oil boiler? It may or may not decrease the life of the boiler by depressurizing it. I doubt it would make that much difference if you keep the chemicals in the recommended range.
It would also save you another ~$100 per year on electricity by getting rid of one of the big pumps too.
It will give you about 20 degree hotter water in your indoor system too without the (properly sized) heat exchanger.
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Grateful guy your underground line shouldn't melt snow I don't care if it's laying on top of the ground.. I've installed in snow and let it lay all winter and not melt the snow using triple wrap.
One of the biggest mistakes people assume is deeper means better Insulated.... Wrong. When your heat escapes your insulation, it's gone, it doesn't matter if you lose it to the ground, the air, groundwater. Whatever, once it's gone it's gone.
I have even seen people bury line 5-6ftdeep and brag it's not mounting snow now, little do they know there just heating more dirt .
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Grateful guy your underground line shouldn't melt snow I don't care if it's laying on top of the ground.. I've installed in snow and let it lay all winter and not melt the snow using triple wrap.
One of the biggest mistakes people assume is deeper means better Insulated.... Wrong. When your heat escapes your insulation, it's gone, it doesn't matter if you lose it to the ground, the air, groundwater. Whatever, once it's gone it's gone.
I have even seen people bury line 5-6ftdeep and brag it's not mounting snow now, little do they know there just heating more dirt .
If there is no ground water down the 5-6 feet there will be a little less heat loss there. Heat loss happens from temperature difference. The higher the temperature difference the higher the heat loss. If it is 50 degrees down 5' and 0 degrees at 12" you will definitely get less heat loss at 5'. If you have ground water at 5' you will lose more heat then even if it is warmer because the water will conduct heat away.
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Yea that's true rsi, I've just never seen anywhere in my area where the water table doesn't rise up to within at least 3 feet at times. I'm sure other areas are different.
In my back yard on the edge of the creek the soil is about 2 feet deep before solid rock, 80 feet back to my house it's 4 foot down to rock. Water doesn't have anywhere to go lol
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yeah, if you have a high water table you want to keep above it.
Around here you could go down 30' and not get anywhere near the water table in a lot of places
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a 40 plate ex cost me like 600 i think 2yrs ago, dont think i need it but its there so iam leaving it for now!again knowing what i know now i would not have put it in