Heatmor owb. Temps arent where i want them in house...pump size wrong?/head calc

[Timbercreek]

Been running a heatmor owb for 2 seasoms now, was just freeze protection 1st year, now im living here and i domt want temps to dip.
Anyway, i flushed the heat exchanger 2 days ago for a hr each side with sizzle, it made it better, temps are up, but not where they should be.
Im seeing 146 ish on the incoming owb line and outgoing oil, which is saying a good transfer, but boiler isnt hot enough.
Heres my problem, house was previously rigged for a central boiler, 126ft of 3/4"
Foam insulated pipe in the ground.
Central boiler 70 plate exchanger, 1.25" y strainer, pex has a 3/4" 90 where it comes into basement, copper 1" 90s at the side arm.
Back of boiler is plumber in 1.25" brass, has a T for pump with boiler drain, one 90 on return.
My calcs are showing 32ft of head, and i only have a 0013 taco pump.
Is it possible that the pump is moving so slowly im losing heat from the supply to the return thru bleed in the pipes?
Boiler is showing 185-200 degrees on front gauge, aquastat set at 190.
Supply house was trying to say i should be running a taco 20-40, a freakin 1/3hp pump.
Can anyone verify my head calcs for me?
I cant find a spec on the plate exchanger, im really curios what that is.

 

[jebatty]

Is the 3/4" pex one way or round trip?

 

[hondaracer2oo4]

You can please post boiler temps when they leave and return to the owb with no heat load in the house and with the house calling? Also what underground pipe product is it?

 

[Timbercreek]

Its 126' each way, to house and back,
Both pipes are 3/4" id pex.
Typical central boiler stuff
4" smoothbore black outside, solid yellow foam inside, 2- 1"od green pex lines inside.
Inside diameter only 3/4"

 

[Timbercreek]

Owb temps at the exchanger, 146 in, 141 out

 

[Woodfarmer1]

I’ve had this similar question with my Garn, the general consensus is that the boilers how water temp is not what you get at the supply. I had more than 20* difference, it is what it is.

 

[maple1]

Betting wrapped pipe.

Edit: I missed the above post.

 

[maple1]

Pump chart says flow goes to zero with a 0013 at 34.5 head. Which you might be darn close to. The 3/4 pex is severely limiting your potential.

 

[maple1]

I’ve had this similar question with my Garn, the general consensus is that the boilers how water temp is not what you get at the supply. I had more than 20* difference, it is what it is.

I didn't see that consensus. I only see a degree or two drop in mine.

 

[hondaracer2oo4]

What are you using to measure these temps? You temp reading is 146 on the incoming owb line when the aquastat outside runs 175-195? You aren't losing more than. Degree or so with quality thermopex that is closed cell foam. If you were using black drain tile with the wrap type insulation than there is the possibility of that Gettjng ground water in it then causing you to only get 146 degrees at the house.

 

[Timbercreek]

Pipe is good stuff.
Burried at 30-36" with a 1' sand bed and 1'sand above then gravel. I am above water table, should be no issue

Note:
Just noticed today water level was down from flush, topped unit off, so first time full since flush, def running much better.
Boiler showing 185(front gauge) and idle,
161 in on owb side of plate, 154 out,
Oil furnace showing 156.
The owb temp is a well mounted gauge on the front.
The exchanger and furnace temps in the basement are by a mastercool ir temp gauge.
Running over multiples surfaces in measurement area, taking highest recorded.
I find rusty iron usually.reads best.
Copper and black painted copper reading worse.

 

[Timbercreek]

What im really seeing is the owb pump is struggling.
It def works best when the boiler is full to the brim, indicating it needs the most pressure on the suction side it can get.
Def makes me think a pump designed for open loop operation and anti cavitation would benefit me greatly.

 

[Timbercreek]

Hi maple.
You are spot on. Im thinking at 30ft of head, this pumps moving 4gpm on its best day.
From what ive found, 7-8 is the most im gonna move with 3/4 at this length anyway
Shear limited.

 

[maple1]

IR temp guns don't work very good on anything close to a shiny surface. A spot of flat black spray paint where you're measuring will improve things. Most of the time with these types of threads, temps aren't being measured accurately enough to give an accurate diagnosis. A few degrees out here & there can mask problems or potential solutions.

Accurate measurements of ins & outs everywhere are usually needed - in this case, accurate measurements of the supply & return pex at the OWB where it enters/leaves the ground together with the same at the other end (in the house) should tell if heat is being transferred from one pipe to the other. I could see that being a possibility if flow was low enough.

 

[Chris Hoskin]

If I understand correctly, you are only dropping 5 degrees through the boiler supply and return at the flat plate. Is that right? If so, it seems to me that the pump on the house side of the heat exchanger is too small too. You should be able to pull 20 degrees out of the boiler supply.

 

[jfriesner]

If I understand correctly, you are only dropping 5 degrees through the boiler supply and return at the flat plate. Is that right? If so, it seems to me that the pump on the house side of the heat exchanger is too small too. You should be able to pull 20 degrees out of the boiler supply.

Or is that the temp difference he's reading with out a heat load on the hx? I have a heatmor 200css with the same size water lines you have and hooked up to a 40plate exchanger rated at 350,000BTU. I use it for on demand hot water for a house of 7 people and when someones filling the bath tub/taking a shower the plate exchanger will knock a good 20-25 degrees off my boiler temp. You should see an even higher temp reduction with a 70plate. Sounds like water on house side is not moving or barely moving.

I don't know how to calculate the head for you but it seems to me a pretty simple system. My system is a 300' round trip loop through 42 fittings, 4 different heat exchangers, and the water drops down 9' to my spa and back up the wall for one of those exchangers. I run the system on 1 Taco 007. I added a second for insurance incase the first fails but its not needed. The system works flawlessly.