Head calculations

[heaterman]

Not liking what I'm seeing for flow requirements on the HX. I need to know what water temp you have available in the boiler and what water temp you need to heat your house in order to get a good handle on what flow we have to get through the HX. Right now, using the 50 plate you have, 180 in and 170 out (boiler side) and 155 in/170out on the house side the flat plate software is calling for 14gpm on the boiler side. Does the house heat OK with say 150-160* water temp?

Factoring in all the parameters you listed, I'm seeing the following with a 15-58 Grundfos. 6.9GPM, 13.1 ft of head and a 5.5PSI differential. Throwing a big dog 26-99 or 0011 on it only gets us another 1-1.5gpm and blows the head into the stratosphere. No high head circ is going to live very long on an open system while pushing heads in the 20'+ range.

Here's the bottom line. When I plug the 6.94 GPM into the HX software it shows that we can only transfer about 34,000 btu's given the water temps I listed above. I don't think that's going to cut it for you.

I guess I'd like to say to all who read this that the issues we are running into here are not uncommon at all. Many "pro's" who have been doing this stuff for ages fail to comprehend that all the components have to work as a system rather than just a collection of parts. Typically, the guy selling OWB's just doesn't understand it because he's a salesman not a system design/install person. It ain't rocket science but you have to obey the rules.

 

[MyOutdoors]

The house does heat fine @ 160*. My boiler can put out 165*-190* consistently. I seemed to have lost quite a bit of BTU's through the insulated BHS pipe I installed last season, that is another reason I would like to use that pipe for the "dual" return line and install a better "dual" insulated pipe for the supply. I also figure I won't have the heat loss/transfer through the supply/return touching each other like the present condition. I've downloaded that heat loss calculator and will get a # ASAP for you. Boy, this stuff is complicated...hopefully this will help people in the future to really investigate the installation part of these heating systems.

 

[MyOutdoors]

OK Heaterman, I think I've got the heat loss calculations, Now I need to understand the #'s it has calculated, feel free to point out anything that may look unusual since this was the 1st time I've used this type of program.

 

[heaterman]

Can't recall if we discussed this above anywhere but what type of heating system do you have in your house?

What factor did you use for infiltration?

Did you include your basement in the calc?

If you have baseboard heat..............I don't know if the single use copy has it or not but my copy of HVAC-CALC has a pull down tab that will give you the length of baseboard required by room for your house. You can plug in a "safety factor" of whatever percentage you choose to help simulate working with lower than normal water temps.

 

[heaterman]

Aside from my questions above, you have a couple options to deal with the fact that even with dual 1" lines you won't be able to get the flow needed in the HX.
Low flow in the HX means lower available water temp to the house side of the system.
That being the case you could increase the heat emitter surface area whether that be a coil in a furnace or total feet of baseboard in the house. What that does is get you to where you can drop the temp 25-30* or more in the house side which then decreases the amount of GPM needed to serve a given BTU load.

Remember this little formula; Gallons per minute x 8.33 x 60 x temp drop = BTU delivered / hour
so for example

14GPM x 8.33 x 60 X 5* = 34,986 BTU's
7 GPM X 8.33 X 60 X 10* = 34,986 BTU's
3.5 GPM X 8.33 x 60 X 20* = 34,986 BTU's

How much you can drop the temp in the system is the key to your puzzle.

 

[MyOutdoors]

Here are my temp readings last season that I posted on one of your threads:

"I just checked mine as well. I used Sequoya’s BHS pipe, basically it’s 2-1"pex pipes enclosed in one large peice of pipe foam all in 6” corrugated pipe. The pipe is down 18” in a sand bed and gravel top."

Temp at point of entry to supply (OWB)181*
Temp at point of entry to house piping 175*
Temp at point of return in house 165*
Temp at point of return to boiler 165*

My current heating system is base board FHW. I currently have 3 heating zones with the 4th being for DHW, all run on a seperate Taco 007.

Factor used: Are you talking about the infiltration Tab? I used Average (average, good construction, poor vapor barrier) to be safe, but I'm realistically between best & average

I did not include my basement

The HO version does not have a baseboard tab that I can see?

So it looks like last season I was dropping 10*

 

[MyOutdoors]

bump...Where are you heaterman? Tis the season, I'm sure your all out at work.