Cleaning Heat Exchanger

[yooperdave]

I don't know what you want to do to the heat exchanger that would help. The temps you have sound plenty adequate.

Another thing I just thought of is to check the blower motor for build up of dust on the vanes of the squirrel cage portion .

Is there a way to inspect the other side of the exchanger?

If your return temp at the boiler is 153, thats pretty good.

Five years and never a problem before now, huh? Also, check your registers and grilles (SA and RA) for buildup of dust and or blockage.

I assume that the blower motor of the furnace runs constantly since the house is only 66 on colder days? If thats the case, you have the the heat at the exchanger, its just not getting transferred to the air like it used to. Suggests poor airflow, right?

Keep us informed, please.

 

[brenndatomu]

The temps you have sound plenty adequate.

You think the 12* loss over the coil sounds good? That sounds really low to me...

 

[yooperdave]

You think the 12* loss over the coil sounds good? That sounds really low to me...

I don't think I had much more than that at my old place. ?

 

[Trevdor]

Oh, we’ve definitely had problems, just not this specific problem. Seems like there’s always at least one malfunction of some kind every winter. The pump was running pretty much continually cause the house never got to the right temp, but the blower only kicked on when the water temp dropped.

Yeah, I’ve seen some people talk about a 30 degree drop over their heat exchanger. That’s why I thought that might be the problem somehow.

 

[yooperdave]

Oh, we’ve definitely had problems, just not this specific problem. Seems like there’s always at least one malfunction of some kind every winter. The pump was running pretty much continually cause the house never got to the right temp, but the blower only kicked on when the water temp dropped.

Yeah, I’ve seen some people talk about a 30 degree drop over their heat exchanger. That’s why I thought that might be the problem somehow.

I don't think I ever had such a temp difference. Maybe I was doing something wrong? Dunno, the house was always warm and we never turned the T-stat down when working or bedtime....

I would never have though of draining the water and flushing out the heat exchanger though......

I also ran my circulation pump 24/7 period. Never shut it off, even for summer when the fire was out. Constantly circulating.

 

[brenndatomu]

I don't think I had much more than that at my old place. ?

I might be wrong...I've never heated my own place with a OWB...have messed with a few though...and run a large industrial boiler at work, but that's a whole different ballgame. It drops 30-40* across the HX (water to water)

 

[Tonty]

I have a water to air HX here, I’ve never checked what the temp drop is. It heats well, so I haven’t had the need. But I’ll see if I can get a reading for reference.

 

[Tonty]

Just went and checked. 160 going in, 136 out. 24 different. My forced air has a variable speed fan, and I think it was on high. It’s kind of hard to know, though.

 

[yooperdave]

I spoke with a dealer this morning and the temp difference I was experiencing on my water coil was "Ideal. Don't change a thing!"

But, before he said that, he asked about length of runs, (inside and outside) vertical height differences, blower motor speed.

He also mentioned that as a rule of thumb, temp diff across the coil would be 20-ish and has seen as high as 30. He did say
that blower speed should be increased to recover more heat from the coil. (I guess there are two schools of thought on this as I have heard both approaches)

So then......................the temps drops that have been reported are within range of that dealer's business as he said 15-30 is acceptable. Bear in mind that there are a lot of other variables involved also.

 

[coolidge]

I clean my water to water hx every year before the season begin.
You would be surprised the crap that comes out.

 

[yooperdave]

I clean my water to water hx every year before the season begin.
You would be surprised the crap that comes out.

Yes, I would be surprised. I have never had to clean the water in the OWB. Latest one has had the same fill on it since 2009. Treated every year.

 

[maple1]

I clean my water to water hx every year before the season begin.
You would be surprised the crap that comes out.

This is a W-A hx.

 

[Trevdor]

Well with it being a warm day yesterday I went ahead and took the opportunity to clean the heat exchanger as best I could without completely taking it apart. I vacuumed what I could reach and hooked a hose directly to it and flushed it with water. No gunk or anything came out. I then tried to get some vinegar into it and let that sit for half an hour, did that twice and then flushed it really good again. I was going to use CLR, but I noticed that the instructions said to not use it on brass so I didn't want to take the chance of screwing something up.

Once I got it all set back up and running I measured the water temp again and it seemed to have a slight improvement from the In to the Out water, I was losing about 15 degrees vs the 10-12 before. With it being warm out though it is hard to tell if it is going to make a difference or not. It's set to get cold again tonight so that will be the real test.

One thing I did notice though as I've been measuring the water temp frequently, last night when I restarted the system the water was right at 180, this morning when I checked the fire had died down a bit and the water going into the heat exchanger was 160. Do you all see that big of a swing normally in your systems? Could it be that my Hardy just isn't heating the water up fast enough?

 

[yooperdave]

That'll give you peace of mind for cleaning the water coil anyway. Temps you are quoting from your OWB (180 leaving; 160 returning) aren't that bad. I hope you use the boiler to heat your domestic water also?

Have you inspected the blower motor squirrel cage for debri buildup on the squirrel cage vanes? Or any of the other suggestions I offered?

 

[maple1]

Well with it being a warm day yesterday I went ahead and took the opportunity to clean the heat exchanger as best I could without completely taking it apart. I vacuumed what I could reach and hooked a hose directly to it and flushed it with water. No gunk or anything came out. I then tried to get some vinegar into it and let that sit for half an hour, did that twice and then flushed it really good again. I was going to use CLR, but I noticed that the instructions said to not use it on brass so I didn't want to take the chance of screwing something up.

Once I got it all set back up and running I measured the water temp again and it seemed to have a slight improvement from the In to the Out water, I was losing about 15 degrees vs the 10-12 before. With it being warm out though it is hard to tell if it is going to make a difference or not. It's set to get cold again tonight so that will be the real test.

One thing I did notice though as I've been measuring the water temp frequently, last night when I restarted the system the water was right at 180, this morning when I checked the fire had died down a bit and the water going into the heat exchanger was 160. Do you all see that big of a swing normally in your systems? Could it be that my Hardy just isn't heating the water up fast enough?

Possibly. There would be a considerable difference in heat into the house, between 180 supply and 160. But your boiler should be able to keep it consistent up until you need to put wood in at again.

 

[maple1]

You should also be measuring duct temps. If there is a big temp drop from close to the HX, to duct outlets, you might still have an air supply/flow issue .

 

[Woodman1]

I asked this on the other thread but not sure if I got an answer. Has the system been able to keep the house warmer than 66 in previous years during similar cold snaps. If not it could all come down to a cheap and or undersized hx

Also, how is the hx plumbed? The supply line should be on the bottom.