Trying to help a friend with his woodmaster AFA900 hook up. This is the setup the plumber hooked up. It doesnt seem to be working right. The OWB is running @ 180 deg. and the oil boiler doent get above 140. Could the pump for the HX be pushing water through the system rather than to the HX? If so how could this be fixed? Should the pump be on all the time or should it be on by demand. If by demand how can that be wired?
OWB Hook up Question
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[quote author="oliver5528" date="1228200429"]Trying to help a friend with his woodmaster AFA900 hook up. This is the setup the plumber hooked up. It doesnt seem to be working right. The OWB is running @ 180 deg. and the oil boiler doent get above 140. Could the pump for the HX be pushing water through the system rather than to the HX? If so how could this be fixed? Should the pump be on all the time or should it be on by demand. If by demand how can that be wired?[/quoteI
In order of progression:
No, if it were, you would have a failed HX which would be immediately apparent because the boiler water in the oil side of the system would be exiting the top of the "open" or non-pressurized wood boiler.
I typically run the wood side circ constantly when using a piping plan such as you have drawn here. This serves to keep the HX at maximum available temp. You could use intermittent circulation by wiring the wood boiler circ into the same relay as the oil boiler circ but it would not help your situation.
Temp drop across any type of HX is determined by 3 things. A: the surface area (size) of the HX B" GPM of flow on BOTH sides of the system and C: Temperature difference of the fluid on side A vs. side B.
I find on many installations I get called to look at that the the HX is too small or undersized to achieve close approach temperatures. If you want to have your wood supply at 180* and the oil boiler run at 170 or so you will need a pretty substantial HX. We are installing one this week to serve a 185,000 BTU load and given the other system parameters we are working with on this job, the HX called for is a 10" x 20" with 50 plates. Most of the ones I see are are 5" x 12" with 30-50 plates. With standard flow rates delivered by 1" tube and a 009 or 0011 you will see a 20-40* differential from side A to B. It's just physics.
In order of progression:
No, if it were, you would have a failed HX which would be immediately apparent because the boiler water in the oil side of the system would be exiting the top of the "open" or non-pressurized wood boiler.
I typically run the wood side circ constantly when using a piping plan such as you have drawn here. This serves to keep the HX at maximum available temp. You could use intermittent circulation by wiring the wood boiler circ into the same relay as the oil boiler circ but it would not help your situation.
Temp drop across any type of HX is determined by 3 things. A: the surface area (size) of the HX B" GPM of flow on BOTH sides of the system and C: Temperature difference of the fluid on side A vs. side B.
I find on many installations I get called to look at that the the HX is too small or undersized to achieve close approach temperatures. If you want to have your wood supply at 180* and the oil boiler run at 170 or so you will need a pretty substantial HX. We are installing one this week to serve a 185,000 BTU load and given the other system parameters we are working with on this job, the HX called for is a 10" x 20" with 50 plates. Most of the ones I see are are 5" x 12" with 30-50 plates. With standard flow rates delivered by 1" tube and a 009 or 0011 you will see a 20-40* differential from side A to B. It's just physics.
The Operation of the boiler is ok, the problem is on the oil side of HX. The Boiler is a corn boiler burning grain. The boiler heats on its demand. The boiler is using to much fuel so thats why IO was wondering about the cir pump on the oil side of the HX run on demand.
[quote author="heaterman" date="1228208093
No, if it were, you would have a failed HX which would be immediately apparent because the boiler water in the oil side of the system would be exiting the top of the "open" or non-pressurized wood boiler..[/quote
I understand that part but wouldnt the pump push through the path of least resistance? Could the water be pushed through the heating system instead of the HX.
The pump in the OWB is a 0011, and all 1.25 pipe. The HX is a 5x12 50 plate with a 009 pump.
[quote author="heaterman" date="1228208093
No, if it were, you would have a failed HX which would be immediately apparent because the boiler water in the oil side of the system would be exiting the top of the "open" or non-pressurized wood boiler..[/quote
I understand that part but wouldnt the pump push through the path of least resistance? Could the water be pushed through the heating system instead of the HX.
The pump in the OWB is a 0011, and all 1.25 pipe. The HX is a 5x12 50 plate with a 009 pump.
Couple of things to check and some ideas. Most plate HX's should be plumbed counterflow: boiler in at top and out at bottom, system in at bottom out at top (or vice versa). They also have two possible configurations: in and outs are on the same sides of the HX, or they are on opposite sides (cross-over). Look at the instructions for yours to determine.
Get four inexpensive meat probe thermometers from a kitchen supply store, cable tie the sensing probe of each to the in's and out's of the HX, wrap with insulation, and then you can visually see what's happening. Should help to isolate your issues.
I have a 5 x 12 x 30 plate HX. When my boiler is up to temp, typical readings for me are: boiler side - in 180, out 140; system side - in 135, out 160-170.
Get four inexpensive meat probe thermometers from a kitchen supply store, cable tie the sensing probe of each to the in's and out's of the HX, wrap with insulation, and then you can visually see what's happening. Should help to isolate your issues.
I have a 5 x 12 x 30 plate HX. When my boiler is up to temp, typical readings for me are: boiler side - in 180, out 140; system side - in 135, out 160-170.
oliver5528 said:
Looking at the piping schematic you have illustrated a little more closely, it would appear that it's piped in a way that would allow some of your heating system return to flow through the oil boiler without being forced through the HX. I don't know for sure because the circ location is not shown. What ensures that the returns shown on the right side of the oil boiler actually gets pulled through the HX?
heaterman said:
The Oil Burner is a New Yorker and it has two system returns in the bottom of the boiler, three pumps on each side of the boiler. The plumber added the 4th pump on the Left of the boiler to cir. the water through the Plate Exchanger. But my question is how do we know the water is being forced through the HX, not forced through the heating system? I showed the direction of flow the cir. pumps run on drawing.
oliver5528 said:
Basically the only thing you need to know is that high pressure goes to low. The circ outlet is the highest pressure in the system and the inlet or suction side is the lowest. Find the path of least resistance between those two points and you have your answer.
I'm assuming there are flow checks on each of the zone circs.
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Having the boiler in the "middle" of the return flow really messes the situation up when you think about it. What a person wants to achieve is having all the return flow go through the HX before entering the boiler. This preheats the system fluid and prevents the boiler from running. The manner in which it is piped presently would almost guarantee the a fair percentage of the system flow is never going to pass through the HX. What does make it to the HX is going to be blended with the return coming back to the boiler from the right side For example: what would cause the water returning on the right side "as shown" to even think about visiting the HX. The way it looks to me you may need to do some re-piping around the boiler to gain the desired result.
Thats how I set up mine. All return goes through the HX. If we removed the two returns from the boiler and tied them together cap one end then run the other end to HX. out Hx to the return in boiler. Do I need to hook the circulator pump to help push return water through HX, or will the Zone pumps have enough to do that? If I need it where do I make that loop. When I installed my boiler I hooked into my radiant heating system (open System) heated by water heater, so I didnt need to pump through the HX. EDITED 6:44PM Ive added another with a loop from boiler to return line with a check valve . Maybe I'm just crazy!heaterman said:
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Does the boiler have a tankless coil? If not I'd pipe the heat exchanger in parallel to feed into the system without flowing through the boiler.
hr
hr
in hot water said:
How would you control that in the event a person wanted to leave and have the oil boiler fire automatically when the wood drops below the desired temp?
AFA re-arranging the near boiler piping this would be a clear cut case for primary secondary piping IMHO. Your sticky up on top illustrates it quite nicely HR.
So wich drawing do you think should be used or are they all wrong?. The firtst one is how its plumbed now but it isnt working correctly.heaterman said:
Hi, this is a nice diagram, you need to pipe your returns to the HX NOT just one line from your feed..... note on the photo the cross line from the feed side and the return side on the boiler.. with the flow check valve.... the way it shows it shows how you will have a constant circulating flow of cold to HX to boiler to feed and the cross line will allow the whole thing to keep circulating and stay hot even when the system is not calling..... good luck!
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Methinks you need 3-way zone valves on the returns and supply. Avoid running water thru the oil boiler...just have all supply/returns go thru the HX.......chimney effect, will suck heat out of the boiler.....I'm probably off base tho...
I think I would plumb the HX so you have both sides running counterflow instead of the same way.
It was re-plumbed like Drawing Boiler4.jpg without the cir pump to circulate all the time. It uses the zone pumps to circulate through the hx. Working a lot better now. thanks guys
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