OWB struggling to heat the house

[MH49]

I have a 6048 Central Boiler that was installed new by the dealer in 2009. It is hooked into a side arm DHW heater and then goes to an HX in the plenum of my forced air furnace. When it was first put in you could cook yourself out of the house if you wanted to by turning up the thermostat even in cold weather. Lately it seems to be struggling to just maintain the temperature in the house even with half of the house shut off. Reading back through the archives I believe I have narrowed my issue down to either the pump going bad or my HX is internally clogged up. Things that I have checked so far:

• Water level is fine in burner
• Burner cycles correctly at it's factory settings
• When I partially close the ball valve at the pump outlet, it will make a noise like water if flowing
• I pulled the HX and the air side is clear
• Furnace filter on intake side of fan is new
• DHW seems to work fine and I have good supply of hot water at approx 150° per meat thermometer

My question is there anything else I should do to diagnose this thing before I start tearing things apart for visual inspection of the pump and HX? I hate to shut down for any more time than necessary because it is dang cold!

 

[Kevin in Ohio]

I have a similar setup/situation. I'm running a water to water HX and have been online for 13 years. How is your HX installed?

My dealer gave me a "map" of the order thing should be installed and I then did it myself. I found out later that a HX should be installed vertical instead of horizontal as I did(shown above) Dealer said it will plug quicker. I have replaced it this year as mine couldn't keep up and was getting worse. I also had a 3 way zone valve go bad at the same time which confused the whole thing. It was overheating when outside temps wee warmer as it was bypassing the valve but when cold, I couldn't keep up.

That said, with these extreme temps I have had a cooler inside house temps. Like you said, it's COLD out. LOL

Your boiler is ramping up fine or is it slower? If slower or smoke rolls out the door more, check your flue for obstructions. Cooler temps bring in more moisture via the air going into the boiler and lets it build up on the flue. Just something else to check.

 

[panolo]

If you have a thermostatic valve inline that would be another item to check. Sounds like you are on the right track. That would be pretty easy to check with a infrared thermometer at the valve. Also remember you can lose a fin or two in a pump and it will still have some flow. Other than the items that Kevin suggested I think you are on the right track.

 

[Deleted member 117362]

My new Woodmaster did that after first year, had a 434 previous 10 years. Pulled my pump, had a big plug of rust and scale. Cleaned pump, flushed heat ex-changer and installed inline filter, problem solved.

 

[Iska3]

Do you happen to have those "Y" screens on your lines? I have this one out in the garage and when I lost some of my heat I found the screen was clogged. What is your water temp going in to the HX vs the temp going out? If need be tape a meat temp to the pipe and check it Also check the temps on the lines per Kevin's pics..

 

[NSMaple1]

Could also possibly be that moisture has worked its way into your underground piping. Said without knowing anything about it.

Might get a better handle on things with some accurate temp measuring on the ins & outs of the HXs, and piping. If it comes down to the HX, make sure you plumb in some shut offs & drains on either side so it can be flushed easy in place in the future - if it doesn't already have them.

 

[bowtechmadman]

Infrared gun is very helpful (and reasonable). Check temps going into your HX and out as NSM has suggested this will tell you how much "heat" is being extracted (for lack of better term) from the water.
Other two possibilities that I can think of have also been mentioned:
- pump not working as it should restricting the amount of flow
- heat loss from burner to the HX (underground) also can be checked with infrared heat gun...check temp out of boiler and right before HX.

Good luck!

 

[MH49]

Thanks for the input so far. I will look into these and I went at lunch and bought a infrared gun so I can check my temps. One thing I didn't mention earlier is that the house sits below the OWB so I am thinking (hoping) that I don't have a air bubble in the system causing fits.

What kind of temp delta should I be looking for across the HX? I know that can be a loaded question but rough numbers are fine. Thanks!

 

[NSMaple1]

Might depend on where exactly & the situation but generally speaking dTs of 20° are ballpark.

On the IR gun, they don't measure shiny surfaces very good. So if you have any of those (e.g. copper), shoot a blotch of flat black spray paint first where you want to measure at.

 

[lefturnfreek]

I’d say you need to run the boiler hotter than 150.

Mines and ol antique POS heating the house and a 1600 sqft shop and in fall with 28ish weather it’s set to 150, now that we had a burp of -30+ it’s about 175-180 and the furnace would run almost all night.

I think your temp delta isn’t wide enough to keep up to your house.

 

[ChoppyChoppy]

May be worth having the dealer look at it, after all it is their install.

 

[NSMaple1]

I’d say you need to run the boiler hotter than 150.

Mines and ol antique POS heating the house and a 1600 sqft shop and in fall with 28ish weather it’s set to 150, now that we had a burp of -30+ it’s about 175-180 and the furnace would run almost all night.

I think your temp delta isn’t wide enough to keep up to your house.

I thought he meant his DHW was 150.

 

[MH49]

That is correct, the 150° number was measured at the tap with a meat thermometer, the burner itself is running at a 175° to 185° cycle. Last night I dropped the pump out of it and everything looked brand new. All the vanes were in the impeller (plastic) and the motor spun freely so I don't think it is the pump. I am getting right at a 20° drop across the HX in the plenum of the furnace so I guess the next step is to drop the HX out and check for scale. I will say the water that came out when I pulled the pump looked really good, clear except for the CB rust inhibitor.

The only other comment I can make is that based on what I have read here in the forums that you need to run your fan on slow speed to get your air temps up. I am sure mine is on high but again it has been that way from day one so I don't know how much of an issue that is. I don't really know how to change it so if ain't broke....

 

[avason]

I've noticed I'm having a hard time keeping temps also. I don't have a HX because the installer said I didn't need one. Mine goes directly to my air handler. I think I'll look into it next year. It's defintately been a struggle this winter season. I think my air handlers are under sized for my house and a drafty gas fireplace isn't helping. Good luck!

 

[panolo]

What was your temp on the input side of the plenum exchanger vs directly below the pump on the OWB?

My fan runs on high and my house is pretty dang big. Thermostat is set at 72 when it's -5 or colder and 74 when warmer.

 

[bowtechmadman]

Noticing any difference in wood consumption, could your temp probe in the stove be bad? I think your delta on temp is in the ballpark...depending on how far of a run from your stove to the HX. My delta is greater but I'm running nearly 300' from stove to hx and I'm water to water exchange.

 

[Gundy]

Same thing happened to me last year. After looking into a few things I figured out it was my wife had crap piled up in front of every return vent. Probably over half had boxes right up against them and the other half had some form of furniture near by. I doubt it is from the same problem but thought I would through it out just in case.

 

[MH49]

Ok, quick update, I still don't have my problem fixed. I completely pulled the water to air HX and found no scale building up. I did go ahead and flush it and nothing came out of it. I am back to thinking I may have a pump problem so going to replace that and cross fingers.

 

[Deleted member 117362]

Since you will have it shut down, install an inline filter. That's if you do not already have one. Hope pump solves your problem!

 

[Bobby Kirbos]

Is it possible that the impeller on the pump is no longer firmly attached to the shaft? It holds on enough for you to spin it by hand, but when it tries to push feet of water column, the shaft spins on the impeller without actually spinning the impeller (or only spins it at a fraction of the speed it should).