? on hooking up OWB to HX to existing oil boiler

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Old 12-15-12, 01:32 PM
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? on hooking up OWB to HX to existing oil boiler

I just installed a Portage and Main ML36 outside wood burner. I have an existing oil boiler that I want to use as a back up source. I have a 50 plate heat exchanger that will seperate the two systems. The OWB side is all hooked up and now I am having trouble on the best way to do the oil boiler side.

A Taco 007 f5 pump is on the return side as well as a Boilermate with its own pump for the DHW. Can I use the Taco pump to circulate thru the HX and my 4 zones, am I asking to much of this pump?
Or should I use another pump that runs 24/7 and tap into the drain [return] and extra supply port?

Most sites that I have seen diagrams for have it run with it's own dedicated pump circulating thru the oil boiler, but I have seen some that have a check valve between the supply and return and one pump.

As you can see I'm confussed!
A picture of my boiler for you to ponder.

 
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Old 12-15-12, 02:34 PM
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There should be installation recommendations in the manufacturer install book, no?

Most sites that I have seen diagrams for have it run with it's own dedicated pump circulating thru the oil boiler, but I have seen some that have a check valve between the supply and return and one pump.
Post links to what you are looking at.
 
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Old 12-15-12, 06:27 PM
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Portage and main manual has a three way valve.[ pg 13 ]
http://woodheating.ca/p+m_furnace_man.pdf

This one has a pump on the supply side [new style of hydronic recommendations ] mine has it on the return side.
http://www.centralboiler.com/Tech/C220.pdf

Here is one that has 2 pumps and a check valve. but no HX.
Wood Doctor Hookup, Flat Plate


Just not sure how to hook it up yet!
 
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Old 12-16-12, 07:26 AM
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Here is one that has 2 pumps and a check valve. but no HX.
Toss this one out for starters... this would require one to run their existing boiler as an OPEN system, and there are MANY problems that will arise out of this.

Why OPEN? Because the OWB is open. Without a means to hydraulically separate the two systems by means of a FPHX it means that the existing system will also be opened.

To explain further would require a lot of dialog... just forget it.

This one has a pump on the supply side [new style of hydronic recommendations ] mine has it on the return side.
This is a good setup. It keeps the oil boiler hot anytime the OWB is running by means of the 'wrap around' pump. There is a slight disadvantage in that if the OWB is not running, the wrap around circuit provides a 'boiler bypass' circuit... not necessarily a 'bad thing', but you might not NEED a boiler bypass on your system. One could simply close a valve on the W-A loop when not running the OWB, or it could be 'automated' by use of an electric valve... BUT, a zone valve is generally not designed for 'continuous' duty. If doing this I would recommend a different type of valve. You could do this with your system, but the 'cut in' on the return would have to be below your circ pump where it's all black pipe. You could reposition the pump a bit higher on the pipe and make the cut-in just below the pump.

Remove the lower flange, transition to copper, add tee for cut-in, then flange for pump, etc.

Don't move pump up too far, 12" of straight pipe is recommended on suction side of pump.

Alternately, you could do some repiping and move the existing pump to the supply side. This would require moving the air scoop closer to the boiler and the pump where the air scoop is now. You should probably change to a different style air scoop, such as a SpiroVent, which doesn't require the 18" of straight pipe ahead of, as your current scoop does. You should still observe the 12" ahead of the pump.

Whatever you choose, ABSOLUTELY use the WYE STRAINERS! You don't want to clog up the heat exchanger!

Portage and main manual has a three way valve.[ pg 13 ]
This manual is sadly lacking in details. The 3-way valve detail could be added to Central's diagram (the electric valve mentioned above), except it would only need to be a 2-way because when OWB is cool, all you would need to do is shut off wrap-around pump and close the valve.
 
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Old 12-16-12, 10:17 AM
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Thank you for the response!

Ok, I think I'm going to do the wrap-a-round set up.
Instead of hacking the existing pipes I'm going to pipe it using the other ports that are in the boiler, and they are on opposite side of the boiler towards the back wall.

Should I push or pull the water in the HX with the pump or does it matter much? Where should I put a valve to purge air?
>Pull water from bottom of boiler and dump it into the top.
I did'nt know about the 12'' rule before the pump!
I don't know if I have enough pipe in such a tight space.


I have a ballvalve/wye strainer/union before the HX on the OWB side but I was going to just do ballvalve/union with no wye strainer on the oil side. I did not think the closed system would have that much crud in it.
I should be able to close this loop off in summer and clean/service the HX.


Here's another shot of my set-up.
I have a Grunfos 15-58 mounted outside on the OWB pushing water thru the bottom pipe to the HX.

 
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Old 12-16-12, 12:07 PM
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going to pipe it using the other ports that are in the boiler,
Interesting idea... but, what are those ports actually for? Are they in fact an 'alternate' set of supply and return? (what model is the boiler?)

Should I push or pull the water in the HX with the pump or does it matter much?
I would probably pump TOWARD the HX. Why? Well, for one reason it's what CB has in their drawing. They probably considered the question. I would think that because the HXs are typically fairly high 'head' (i.e. restrictive to flow) that putting the pump to suck from the HX could potentially cause the pump to cavitate due to the "NPSH" dropping too low.

Where should I put a valve to purge air?
You probably won't need one... water will likely be moving fast enough to keep air out, and if you pipe with air in mind, you won't leave places for air to collect. So, I guess the answer would be at the highest point in the loop, or before the water re-enters the boiler.

on the OWB side but I was going to just do ballvalve/union with no wye strainer on the oil side. I did not think the closed system would have that much crud in it.
Put it in anyway. Cheap insurance. There may not be that much crud, but those passages in the HX's are small... easily clogged. Not easy to unclog.

Pull water from bottom of boiler and dump it into the top.
Yes. By feeding the HX with the cooler water from the bottom of the boiler, you will maximize the heat transfer.

Make sure that you observe the COUNTER FLOW piping on the HX! Both sides do NOT flow same direction for max heat transfer.

Grunfos 15-58 mounted outside on the OWB pushing water thru the bottom pipe to the HX.
Did the OWB come supplied with that pump?

I think you are using the insulated underground PEX... how many feet, of what size?

I would question if the 15-58 is going to be enough pump to give you enough flow through long runs of tubing, especially with a restrictive HX hanging on the end of it. You probably want at LEAST 8 GPM of flow from the OWB... maybe more.
 
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Old 12-16-12, 12:12 PM
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Just looked at the specs again...

You could have used the ML 30, I'm sure the BTUs are more than enough...

I looked through the manual and there are no flow recommendations, but if we go with the standard of 1 GPM per 10,000 BTUH for a 20F delta T, then your ML36 with 225-300 thousand BTU would require a 22-30 GPM flow rate... which is ridiculous lot, but if you WERE extracting all those BTUs then you would need that much.

What are the specs on your HX ... BTU-wise... ?
 
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Old 12-16-12, 05:07 PM
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The oil boiler is a Burnham V714 rated @ 113MBH [BTU]
Manual;Burnham V7 SERIES free Manual (Page 8)
Honeywell 8148A aquastat
4 zones of baseboard plus a 40 gallon boilermate with its own pump.
House is a ranch with 1900 SQFT plus the same in a finished basement.

The heat exchanger is a 50 plate 5x12 with 1'' ports rated @ 170k BTU running 10 GPM.
50 Plate 5"x12" Brazed Plate Heat Exchanger [1" MPT] - Brazed Plate Heat Exchangers

The Portage and Main ML36 is definitly overkill but a good deal was made!
It is rated for 8000 SQFT.

The Grundfos 15-58 did not come with the OWB but recommended by Portage and Main. I think it is pumping up to 17 GPM.

I have 70ft of Logstor insulated pex with 1'' ID to the house.
 
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Old 12-16-12, 07:37 PM
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At 10 GPM the tubing is looking like maybe 7.5' of head.

I can't find any head loss data on the HX you are using, did any specs come with the unit?

The Grundfos 15-58 did not come with the OWB but recommended by Portage and Main. I think it is pumping up to 17 GPM.
Did they ask how long your tubing runs were, and the specs on your HX ? If not, I don't see how they could say the pump would be OK.

Maybe up close to 17 GPM, but that's at ZERO HEAD...

I don't imagine there's any appreciable altitude difference between the two boilers, is there?
Imagine the oil boiler is in basement, and OWB at ground level?

I don't have a warm/fuzzy about the 15-58 in this app.
 
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Old 12-16-12, 07:42 PM
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Manual;Burnham V7 SERIES free Manual (Page 8)
You're thinking of using H and J then?

Good luck getting those plugs out!
 
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Old 12-19-12, 10:41 AM
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Just found out my Honeywell 8148A aquastat is not turning the Taco 007 pump on!

No voltage C1-C2 when call for heat, zones open up.
Burner fires and shuts off when supposed to.
Jumped L1 to C1 and pump works.

The relay on it has been buzzing/humming for awhile and this seems like a common problem with the aquastat.
I have twisted/moved the aquastat a little to quit it in the past.
I have searched here and found this;
http://www.doityourself.com/forum/bo...tat-8148a.html

I'm not sure what contacts that might need cleaned.
Is it the little round ones on the copper prongs?
 
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Old 12-19-12, 03:47 PM
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I'm not sure what contacts that might need cleaned.
Is it the little round ones on the copper prongs?
If you are talking about the round contacts on the prongs on the RELAY inside the aquastat, then yes, you can try cleaning those. Do NOT use any abrasives, such as sandpaper or the like. With a bright light and a strong pair of reading glasses, examine the contacts, see if they are pitted.

There could also be a bad connection where the relay is soldered to the circuit board.

The BUZZING issue is a different thing though...
 
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