Circulator sizing

[Cashius23]

Just looking for a second opinion and some insight. This winter was my first with an owb. Everything worked great. But now I’m finishing my shop and will be adding a second loop to it. My main concern is I think my pump is oversized for my house. So if that’s the case I’d use the 0011 for the shop and get the correct size for the house.
My boiler is 35’ from the house. Inside it’s 25’ to the boiler room. I have a total of 70’ of 32mm pex (1.25”) and 50’ of 1” pex. About 15 1” pex 90s, 8 full port ball valves, a 20 plate and a 30 plate heat exchanger.
Using Tacos TD10 I’m at around 9 feet of head.
My heat loss for my house is about 40,000 btu on design day. I shot for 50,000btu with a 20 degree drop which gave me 5gpm.
According to the curve for a taco 0011 at 9’ head it’s moving 23 gpm roughly. Is it necessary to move that much water.
Curious on what anyone else thinks. I’ve done enough number crunching the last few nights my brain is fried. Thanks.

 

[Former Farmer]

If you drop your gpm, the head will decrease some as well. You may want to look at the Taco 008 according to your 9' head and 5 gpm. With moving more water, you have a lower temperature drop on your plate exchanger.

 

[maple1]

What was your dt across the boiler?

Not sure how 'bad' oversizing would actually be. It would increase your electricity use for sure. But unsure of significance for you. And I think too much velocity might increase corrosion potential in fittings etc.. But I don't know if or when that might become an issue.

 

[Cashius23]

If you drop your gpm, the head will decrease some as well. You may want to look at the Taco 008 according to your 9' head and 5 gpm. With moving more water, you have a lower temperature drop on your plate exchanger.

That curve is better. Otherwise a 0015 seems like a decent option. Even on low it looks like it should handle it.

What was your dt across the boiler?

Not sure how 'bad' oversizing would actually be. It would increase your electricity use for sure. But unsure of significance for you. And I think too much velocity might increase corrosion potential in fittings etc.. But I don't know if or when that might become an issue.

It was 10 degrees once the house loop steadied out. So I mean it’s fine but like you said I don’t know if velocity would become a factor at some point. It’s not noisy or anything either.

 

[maple1]

What are the needs for your shop going to be? More head there? Heat loss?

 

[Cashius23]

What are the needs for your shop going to be? More head there? Heat loss?

Around 80k btu and that’s at the high end. With a 25 degree temp diff I can do 6.4 gpm at 16.2’ head. With the standard 20 diff at 8 gpm I’m around 24’.

 

[maple1]

So bigger demand for the shop? I would think about using current house circ for shop then. And going smaller for the house.