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[Rockarosa]

I have a MS 250 Cozeburn with a 70 foot run. It started losing heat and I'm thinking from reading here that it could be my 6 year old nrf 22 bell and gossett pump. What size pump and what brand would work best?

[gtownky]

Why do you think its the pump?

[Rockarosa]

Well, I don't think the hear exchanger is plugged. I did have water penetrate my pex last summer but the furnace was heating fine until last week. I am trying to get ideas before I spend any money. Figured it wouldn't hurt to have a spare if I'm wrong. Planning on digging up the lines and possibly going to a coal burner come summer. Just trying to get through the winter for now.

[hondaracer2oo4]

We need to know what the temps are at certain points in the loop to know where the problem lies. You need to measure the water temp when it leaves the boiler, when it enters the home, before it enters the hx, after the hx and when it returns to the boiler. If you have a high heat drop across the exchanger then your pump is pumping to slow.

[victor6deep]

if you people would change your water every three years you wouldn't have problems like that

[hondaracer2oo4]

Why is that?

[cantoo]

Does water wear out? I have a 100' one way run and a 35' one way run, should I change it more often? Willie G has a real long run, does he change his every year then?

[Sprinter]

if you people would change your water every three years you wouldn't have problems like that

He must mean changing the water that waterlogged the fancy foil wrap underground lines.

Or maybe changing it when it starts turning green in the sight glass.

If it meets manufacture test , it should be good to go.

To the OP, the circ is probably not the problem, unless you are getting NO heat at all.

[victor6deep]

Can you go 100,000 miles in a car without an oil change?

[cantoo]

You could but not sure of damage, that's oil though. What about water, I bet lots of people never change or flush their radiator system on cars for that many miles. I had a mini van with 400,000kms on it. The only time the water was changed was when I hit a deer and wrecked the rad. I put 300,000 kms on it. So water does wear out then? Or does it accumulate iron, rust of something? I've read of guys on here who have ran for years and never changed their water. Lucky I guess or better water maybe? My brass fittings are black inside so I'm thinking I need to look into it more.

[hondaracer2oo4]

Victor, you are comparing apples to oranges. Oil in an engine is for lubricating the parts of the engine, oil by nature breaks down over time and loses its ability to lubricate effectively anymore. Water in an owb is used to transfer heat energy from one place to another, it does not lose its ability to do this over time or through use.

[Sprinter]

Can you go 100,000 miles in a car without an oil change?

Actually , YES. Please check out the Amsoil site on exactly how to do this. You can even go much more. Water doesn't wear out last I checked, and as long as you water quality tests are good.

This is exactly  why pressurized systems last so long, same water for decades".........

[Ratchet Thunderbolt]

We need to know what the temps are at certain points in the loop to know where the problem lies. You need to measure the water temp when it leaves the boiler, when it enters the home, before it enters the hx, after the hx and when it returns to the boiler. If you have a high heat drop across the exchanger then your pump is pumping to slow.

You mention temps in a lot of various places to determine where things are going right and wrong.  What type of sensors are you using?  Dial thermometers or digital with readouts? 

[hondaracer2oo4]

I use an IR gun thermometer. I have posted on a few other threads about how to get the most accurate readings. I would like to get a contact thermometer but haven't gotten one yet. 

[LittleJohn]

Independant of open or closed loop, I would frown upon whole swap out of fluid;
   In closed loop, you just introduced a large amount of new air/minerals into the system and run the risk of not purging properly. 
   In an open loop system, you basically have to start over with adding inhibitors and the whole purging issue again

However if you are running a system with Glycol or other type of anti-freeze test yearly and swap out when pH or freeze protection starts to turn.  The lower your operating temperate the less likely anti-freeze is to fail, but "souring" of anti-freeze is very common in solar applications