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[AnotherNewbie]

Hi All, some time ago I posted a few questions about the efficiency (or lack thereof) of my unit and got many useful responses and I am preparing to make some changes this summer and wanted to once again beg for the assistance of the many years of expertise on the forum.

I'm in western PA, and last winter was a cold one..in the coldest of the cold, I noticed that no matter how much wood I burnt through, I couldn't keep up, so I started some testing. First I measured the supply and return water temps at the furnace with inline thermostats - the delta T seemed to go between 18 - 24 degrees under load and was less than 4 when the house wasn't calling for heat.
I moved the thermostat inside right above the heat exchanger and measured the incoming temp at the heat exchanger, it was within 2 degrees of the supply line - so I know I'm getting the hot water into the house.
This is where the trouble seems to exist. I'm getting 180 degree water into the heat exchanger from the boiler, and I'm running about a 20 degree change by the time the water gets back out. But the internal system (a pressurized boiler system) is only getting water temperatures up to about 140 degrees.
So, the problem....180 degree water from the OWF, 140 degree water in the house - not keeping the house warm in the real cold weather.

A couple facts about my set-up:
I have a grundfos 15-58 variable speed pump;
My run is about 210 feet into the house;
I have a 40 plate heat exchanger plumbed above the hot water tank with 1 inch ports
I have a 90 plate heat exchanger plumbed to the boiler with 1 1/4 inch ports.
The inside boiler system is a pressurized system with 4 zones. The pump (BG Gossett) runs only when one (or more) of the zones calls for heat.

I've come up with two possible solutions, and would appreciate any input, thoughts, suggestions.

1. My heat exchanger has 1 1/4 inch ports, but my supply return lines from the OWF are 1 inch. The internal side is 1 1/4 inch supply/return. One thought is to run a 1 1/4 inch line from the OWF to the house, (I have a second pipe buried with a rope already in the ground, so I should be able to fish the line through, hopefully) and run both 1 inch lines as 'supply' lines through the house and into the heat exchanger and then run one line (1 1/4) back to the furnace as a return - increasing the water flow from the furnace. (I read somewhere that two 1 inch lines flow just slightly more water than one 1 1/4 inch line...).
My questions with respect to this approach are: Can I run two 1 inch lines as supplies off a single pump and through a simple manifold system? Will the increase in water supply really help? Is a grundfos 15-58 variable speed pump going to be sufficient for water flow?

2. Create a 'circulation loop' on the internal boiler side and have the pump run 100% of the time instead of only when the zones call for heat.
A few questions with this option though:  Do I need to have a large circulator loop, or even a buffer tank in order to make the operation efficient? Will a simple tie-in of the supply and return lines outside the heat exchanger create sufficient circulation? Should I have the circulation loop running at 1 1/4 inch, or neck it down to a 1 inch connector that way when the zones call for heat they will get the better flow of hot water and the circulator will continue to mix with return water? 

Is there anything I'm missing, am I overshooting the target with my ideas/options, or am I still way behind the 8-ball? 

My thoughts are that if I increase water flow from the OWF then I should realize better efficiency on a purely volume of water basis, and if I run a circulator loop on the inside of the boiler, then the return water will be mixing with hot water before entering the heat exchanger, which will make my need for additional heat out of the exchanger decrease, improving my efficiency. 

The final question is....do I need to do BOTH options 1 and 2? Would just option 2 be sufficient? It seems, although I can't seem to find GOOD schematics on how to properly set up the inside of the house with a water to water heat exchanger, that I need a circulation loop inside ...

I, of course, bought my unit used, installed it myself, and have been tinkering with it to get it right ever since!

I am sorry for the long post, and anyone who has any thoughts or suggestions I would be more than happy to hear them. If anyone has any questions, I'll gladly answer them!

Thank you

[mlappin]

I’d definitely try option one first, seems the easiest both in time and damage to your checkbook.

[shepherd boy]

For 210 pipe,I would go with a larger pump with at least a 25 to 30 ft. head rating. I would do a secondary loop system and run continuous, but with 4 zones it will be running continuous a lot of the time anyway. There is a lot of other little tricks to max transfer of heat from a heat exchanger but would need to see the system. Slim Jim has done a lot of boilers hope he comments.

[hondaracer2oo4]

Are the water flows from the owb and the indoor boiler flowing in opposite direction or the same direction through the exchanger?

[slimjim]

All three answers are good observations / solutions, I would definitely start with a larger circ on the outdoor boiler side of the exchanger then depending on how you have the piping set up at the indoor boiler I would run that circ 24/7 and lastly be sure that the circs are moving the water in a counter current flow through the exchanger. Could you post a picture of the near boiler plumbing?

[AnotherNewbie]

Are the water flows from the owb and the indoor boiler flowing in opposite direction or the same direction through the exchanger?

They run in opposite directions. That's why I am so surprised that the temps aren't closer than 40 degrees.

[AnotherNewbie]

Thanks everyone for your replies already! This is what makes this site so invaluable to a "do-it-yourselfer, and sometimes twice"-er like me!

Slim, any suggestions on what size circulator on the OWF side? I will work on getting a picture tonight when I get home and getting it posted. When you say the near boiler, you mean the OWF plumbing? Just don't want to waste time with the wrong stuff!

Would a bigger circ pump require bigger pipes too, or would 1 inch pipes be sufficient? 

Thanks again everyone! I appreciate it!

[slimjim]

Near oil boiler to see how you are plumbing it and circs we typically use are Grundfoss three speed 26-99

[RSI]

a 15-58 pump is definitely too small. A 26-99 may be large enough but a B&G PL36 would be better.

If you do switch over to 1-1/4" pex then the 15-58 might be ok. I would use the single 1-1/4" as the supply and the two 1" for return though. I think the other way might cause some weird flow issues and if the pump is in the house you might have problems with air in one of them.

[ambonci]

Near oil boiler to see how you are plumbing it and circs we typically use are Grundfoss three speed 26-99

What is the part number for them because im currently looking for a a bigger circulator to replace my 15-58.  I looked into the 26-99 but find many different options.  Just curious on what the part number of the ones you use are.  Thanks

[RSI]

The full part number is ups26-99fc

[mlappin]

a 15-58 pump is definitely too small. A 26-99 may be large enough but a B&G PL36 would be better.

If you do switch over to 1-1/4" pex then the 15-58 might be ok. I would use the single 1-1/4" as the supply and the two 1" for return though. I think the other way might cause some weird flow issues and if the pump is in the house you might have problems with air in one of them.

Definitely, fluids can do some strange things. When we used to have a tractor with saddle tanks (a large tank mounted on each side of the tractor between the front and back tire) we’d make sure each tank had exactly the same amount of hose between the T and each tank, Make sure each hose was level as possible as well, they’d still have one side fill faster than the other, sometimes you’d have to stop, get off the tractor and close the ball valve a little on one tank as it would empty faster than the other and would suck air before the other was empty.