heat exchanger question

[efornshell03]

ok, i have a central boiler 6048. I have three large heat exchangers running off of the system. each is equipped with a squirrel cage style fan behind them.
i have my boiler temp set at 175 right now, and i feel like the air coming out of the heat x's is no where near that temp. any ideas on why this might be? 2 of the x's are on one zone and 1 x on the other zone.

any ideas what kind of air temp should be coming out of the exchangers? any help would be great! thanks.

 

[mga]

what are the CFM's of the blowers?

you might be pushing too much air too fast.

 

[xrayman]

Is this the first time running the system? If you've been running the system try back flushing the heat exchangers. Are you running them in series or off a manifold? could be loosing alot of heat if not running off a manifold.

 

[blackdogon57]

Bigger blowers should be on a separate line from the boiler or run through a manifold. I have a 100k btu blower in my garage. The return water goes back stone cold when the fan is running. If there was another hx down stream it would be useless.

 

[efornshell03]

Ok, please forgive me for not knowing a whole lot about any of this. The guy who installed my system did not instill a whole lot of confidence with me, hence why i am now asking all of you for help. to be honest, he was sloppy with his work, and seemed to "cobble" things together.

Anyways , from the best of my knowledge i believe he set me up with two 140k space heaters right from central in the one shop, running on one of the zones and running in series. and i have 1 140k space heater in my other shop with its own feeder line.

he told me that i could run them in series in the one building with "no problem".

i am not sure of the cfm's of the fans, but they do have three speeds and i have tried them on all of the settings.

what exactly does a manifold do? and where in line do you install them?


sorry for all the questions. i feel like i should take a boiler 101 class. anyone teaching that?

 

[superwd6]

second rad will be cooler than the first but my guess is you have an air lock somewhere and aren't getting proper water flow.Time to look @ how to bleed system:msp_smile:

 

[xrayman]

a manifold will allow you to run water from your main line split it off so you'll have separate lines going to each heat exchanger. Think of your car engine the exhust manifold takes the exhust from each cylinder and pipes it down to a single pipe, this does the opposite.

 

[atlarge54]

And what size lines are you feeding these exchangers with? You're expecting 420,000BTU/hr of heat? In a properly designed system 1" pex is rated for 80,000 BTU/hr, you can push more through it but it requires pumps that suck up more electricity and the water velocity in the lines goes up.

The two exchangers in series really sounds bad. I'd wager your gut feeling about the installer is correct.

You might want to do a search on primary/secondary piping of a hydronic heating system.

 

[efornshell03]

Ok, so after feeling the return line it is still warm heading back to the stove after running through two of those 140 k exchangers. Is this an issue with air in the system?

 

[Iska3]

Hey 03, I'm in MN and my buddy in Onamia runs 3 HW exchangers with his Central like yours. One goes to the house, one goes to the 3 car garage and the third goes to a 30x28 shop and he gets more than enough heat in all three buildings. We did run new pex this year because of his heat loss and he had several air locks but all is fine now. Run your fans at low speed. Check your return lines and make sure they are hot. If need be, back flush your lines with a garden hose to your water line and push the air back in to the system.

My OWB is the next smaller size and I run to Heat exchangers and a 10 plate exchanger for my hot water and I have my temp at 160 for now and more than enough heat in this old farm house. In fact, I'll let my water temp go down to 120 degrees and the blowers still keep the house well above 72.

Check to make sure the exchangers are hooked up right. Hot water goes in the top and out the bottom so the air leaving the exchanger is hot. You should only have a loss of 15 to 20 degrees from the exchanger between the hot side and the return line .

What is your water them at the exchanger? Is your heat loss in the lines? My guess is air lock. Hook up a garden hose the run water through the lines to push out all the air.

My water them is only at 160 for now..

 

[Iska3]

I just checked my temps. My OWB water is at 160 degrees. I run an 009 pump to the house 155 ft with 1 inch pex. The water tem at the exchanger is 159 degrees. The air temp at the last register is 139.8 degrees. My pipes are uninsulated in the basement.

Water going in to the exchanger is 159 degrees the return line is 142 degrees.

I run a 009 pump to the house and a 007 to the garage with valves and a "T" between the 2 pumps so if one goes out when it's -18 below I can open up the valve and feed both exchangers.

Turn your fan on low and even then you should have hot water going to the second exchanger that would be around 20 degrees less than the first exchanger.

Make sure the air is out of the lines. This is a Big Must...

 

[woodman6666]

Is the exchanger thats running on it own loop doing any better than the two in series? Im guessing air lock. Garden hose and full well pressure both ways.

 

[efornshell03]

ok guys i am going to check my temps tomorrow with a infrared thermo. I did hook a hose to my system late last winter and pushed water back to the stove and through the system. seemed to help a little bit after that. but i still dont think its quite right.

I understand that the second exchanger will be a little cooler, but i should still be able to get some heat out of it, right? I would just think that once the water goes through both of the exchangers it would be cooled more yet. but i will take some temp readings in the morning and see what we have.

I really appreciate all the help!!

 

[William Balaska]

Turn your set temperature up tp 185 degrees and make sure your thermostatic valve is not air locked. For 140k units you would need three seperate one inch lines feeding directly from a boiler and not off of one line. My 6048 feeds one 70 plate exchanger through 1 1/4 central pex (true 1-1/4 using a taco f14) I deliver a constant 180,000 btu to it an f7 would deliver 135,000 btu so you see where i'm going you need either three lines and three pumps or huge pex and a huge pump.

 

[efornshell03]

Turn your set temperature up tp 185 degrees and make sure your thermostatic valve is not air locked. For 140k units you would need three seperate one inch lines feeding directly from a boiler and not off of one line. My 6048 feeds one 70 plate exchanger through 1 1/4 central pex (true 1-1/4 using a taco f14) I deliver a constant 180,000 btu to it an f7 would deliver 135,000 btu so you see where i'm going you need either three lines and three pumps or huge pex and a huge pump.

I have two zones set up.

the zone running to my big shop has the two exchangers running in series.

zone 2 is in my smaller shop, running on its own pex directly from the boiler.

 

[Fifelaker]

Ther are some diagrams on cb's website that might help.

 

[efornshell03]

Turn your set temperature up tp 185 degrees and make sure your thermostatic valve is not air locked. For 140k units you would need three seperate one inch lines feeding directly from a boiler and not off of one line. My 6048 feeds one 70 plate exchanger through 1 1/4 central pex (true 1-1/4 using a taco f14) I deliver a constant 180,000 btu to it an f7 would deliver 135,000 btu so you see where i'm going you need either three lines and three pumps or huge pex and a huge pump.

How do you make sure the valve isn't air locked? There is a serious issues because my temps at tje exchanger are only at about 115 with the stove set at 170

 

[Fifelaker]

Try turning the valve on and off a few times quickly or shutting the pump off then back on the pressure can dislodge the air.

 

[mtfallsmikey]

a manifold will allow you to run water from your main line split it off so you'll have separate lines going to each heat exchanger. Think of your car engine the exhust manifold takes the exhust from each cylinder and pipes it down to a single pipe, this does the opposite.

Get Dan Holohan's book " Primary-Secondary Piping Made Easy".. Same principle. Use a circ. on your primary line, circ. on the secondary line, size accordingly

And what size lines are you feeding these exchangers with? You're expecting 420,000BTU/hr of heat? In a properly designed system 1" pex is rated for 80,000 BTU/hr, you can push more through it but it requires pumps that suck up more electricity and the water velocity in the lines goes up.

The two exchangers in series really sounds bad. I'd wager your gut feeling about the installer is correct.

You might want to do a search on primary/secondary piping of a hydronic heating system.

Get Dan Holohan's book " Primary-Secondary Piping Made Easy".. Same principle. Use a circ. on your primary line, circ. on the secondary line, size accordingly. I've dissertated on this before. Sorry to say, a lot of OWB dealers don't know squat about proper pipe/pump sizing, heat loss, etc. God Bless the ones that do.

 

[efornshell03]

Just forced some water into the system, shut down the pumps and opened and closed all of my valves...

My stove seems to be making a gurgling sound, water temp is only at 174 and almost sounds like its boiling inside, I know there is enough water in there, maybe even a little too much.

Just tried to call CB and got passed around to three people just to eventually get a voicemail, all they asked me was to contact my dealer...well my dealer is not getting a call from me!