I am looking for a low cost way to measure hot water flow in a two inch pipe. Hot water meters are big $$$. I am tempted to buy a cold water meter to see how it holds up to 140 to 150 F water. Any clever and cheap ideas would be appreciated.
I don't think you will get good results (i.e., accurate measurement or very long life) using a cold water meter with 150 F water. Not sure what you are trying to measure...just actual flow rate or totalized flow? If just actual flow rate, you might be able to build a venturi tube:
http://en.wikipedia.org/wiki/Venturi_effect
You would need to calibrate it. Then depending how you using this flow rate info, you might want to use an electronic pressure sensor and scale it for your application.
Bob B.
I want to measure actual flow so i can calculate BTU out put. The boiler has a tempering valve, so the flow will vary a lot.
A friend told me about this flow meter. It should show the flow close enough.
http://www.ppe.com/11cat/0505.pdf
Yes, if your flow rate is between 20 and 100 GPM, that should work very well. 10% flow rate accuracy is more than adequate for most hydronic heating performace calculations. Being a spring type flow meter, I wonder what it's cracking pressure and head loss is?
Bob B.
20 GPM is a lot of water - 1200 GPH.
Have you checked with Badger? They're "Read O Matics" are pretty neat.
Casey
I've used these guys before. Good telephone customer service to aid in selection. They should have some sort of variable-area flow meter (visual indicator of flow) for you for under $100.
No connection to them.
http://www.coleparmer.ca/Category/Flowmeters/1686
I also have used Cole Parmer, They are a top notch outfit. Great support.
Rob
Thanks for the info. I already ordered a flow meter with temp gauge from PPE for close to $160 plus shipping. If you look around the two inch stuff costs a good bit of money. The flow I want to measure will be around 50 GPM.