OWB Can’t keep up after pump change

Had my water pump replaced last year and it seemed that after that, my boiler could not keep the house warm. It was always chasing the thermostat. I live in Delaware so it doesn’t get crazy cold but around 20 degrees, I notice the problem. The water temp is steady 180ish. I’m getting warm air but just not enough and no my front door is closed .This seemed to be an issue after the pump was replaced. Any thoughts around this? I’m on the waiting list to get a guy out to have a look.


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Is there a screen that could be clogged? Pump cavitation? Sounds silly, but pump vanes on backwards or pump running backwards? Do you have a thermostat on the lines inside before they hit the heat exchanger - what's the temp in and out of heat exchanger?

 

What pump was on before, and what pump now? I'm thinking like BigPapi there's something clogging it.

 

You should accurately measure temps in and out of everything the water goes in and out of. Likely starting with your underground pipes.

 

Thanks for the feedback. Let
Me get measuring temps.


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I'd bet a highly valuable Black Walnut log that there is still a slug of air in the system...and that...will drive you nuts getting it out sometimes!

 

Yes, air in a system is a killer.

 

Also a distinct possibility, yessir.

 

speed of pump is too high (fast) perhaps? (Needs more time to complete the heat transfer?)

If the OWB is an open vent system, air in the lines should be non-existent.....

 

Could be a high spot in the loop or piping somewhere that could trap air.

 

Ok, I’m overwhelmed with all the feedback. I’m still trying to figure out how to measure the temps. Just so everyone knows, I bought this house with the system installed. It’s an outdoor wood boiler made by central boiler. I’ve been running it no problem for 4 years until it stopped getting heat last year. Pump was replaced and it was good but could not keep up on cold days. Well, it’s been frigid this week! I don’t know what kind of vent system to be honest. Feedback is welcome. I’m just good at chopping wood and starting fires


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Is the replacement pump the same size as the old one? If a multi speed pump is it on the correct speed setting? If those check out you have air in your lines.

 

Central boilers are open systems. Now, that doesn't mean that you can't get an air lock.

 

IIRC the Central Boilers have a "FireStar" controller option that allows monitoring furnace temps, etc. over time / in real-time: if yours is so equipped, may be something to check out / contact Central Boiler folks for more info.

'Usually' inside the home / where the boiler's (hot) supply line hooks up, there is (some) thermostat (or sensor) at that point (junction and/or manifold), to compare the home's DHW input ... vs. the outdoor Boiler output temps. Might be worth taking a look at what kind of temp. drop is occurring on the supply line.

 

So just to sort this out - it heated good for 3 years, then didn't last year? At which point you replaced the pump, but it still didn't work like the first 3 years? Is that right?

That kind of sounds like your underground pipes may have gone wrong. Like, moisture got into the insulation so now most of your heat is going into the ground. Maybe.

A dual probe bbq or smoker thermometer should measure temps pretty good. Tie the probe right to the pipe (with good contact) with some pipe insulation over it. That way you can see two temps, in & out, of most anything the water goes through.

No matter what, it's just guessing without temp measurements.

 

I agree. Some repeatable, verifiable temp. data to narrow down (where) the issue is happening ... is really needed.

If you need to fit a mechanical temperature and/or pressure gauge into the mix - I can recommend the Weiss line of liquid-filled temp. / pressure / tri-meter gauges from experience: they are highly accurate, well machined, & durable. .. A quality gauge, that won't break the bank.

 

Who did the pump replacement? There are a lot of pumps out there that appear the same.

It may be moving water too fast or too slow and not allowing the heat to transfer as much as it used to.

This would be the first place to look since you said the system worked fine until the pump was changed......

 

Thanks, my HVAC guy did the pump. I should have had him back last year but it took me a while to figure out what was going on then it was May and temps were good. He’s got me on the list to come back out. Is there a way to test this myself? He is an authorized Central Boiler installer.


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If you have the old pump, check it against the new pump. The find the ratings on the interweb.

I use a taco in my system and let it run 24-7 every day of the year. I do not burn the OWB all year long, only the winter months; but the circ pump runs constant.

 

There are ways to troubleshoot stuff, yes. First and simplest is temp measuring. You could also measure amperage draw of the circ when it is running, if you have an ammeter and the how-know.