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[MrUPS]

New to the site and just want to say that it seems like there are some great people here and i have really enjoyed looking around.
      Now for my situation. I just bought a home that had an old OWS. I bought a new CB 1400 to replace it and have it hooked up but I'm having some problems. The old wood stove was hooked up directly through the boiler system in the house. I wanted to keep the systems separate so I plumed in a shell and tube hx on the return side of the boiler. I want to keep the propane boiler as backup. Do I just need to install a aquastat with high and low cut off on the boiler instead of the one that is on there now that just has the high cut off? If I turn the low setting down below what the OWS water is will that allow the circulating pump on the boiler to run without turning on the propane? Next question. The lines from the house to the OWS are 3/4. (30 or 40 foot run) Is that to small for the system to run efficiently?  I only ask because when I had the OWS running the other night I kicked on the boiler in the house to see how hot the water would get in the boiler with the water running through the exchanger and it never got above 140. The OWS is 185.  I'm not sure if the 3/4 lines are to small or if the taco 007 that I'm running is to small or if I'm doing something else that I shouldn't be. 
       I'm sorry this is so long guys but I'm just having a hard time getting over these couple problems and wanted to give as much info as possible. If you need more info please ask. Thanks in advance for taking the time to help! 

[Scott7m]

Wow, sounds like numerous issues going on

007's and 3/4" aren't a good combo

Why the shell and tube exchanger? 

[MrUPS]

Thanks for all the views guys! Scott, the shell and tube is what was sent to me from the dealer. If I could do it over i would go plate style. I wish I'd found this site sooner. I have a taco 009 that just needs a new insert. would that be a better combo or do I need to do something about the 3/4 lines? Any other thoughts?

[Scott7m]

Thanks for all the views guys! Scott, the shell and tube is what was sent to me from the dealer. If I could do it over i would go plate style. I wish I'd found this site sooner. I have a taco 009 that just needs a new insert. would that be a better combo or do I need to do something about the 3/4 lines? Any other thoughts?

Got all kinds of thoughts, just kinda thinking about some possibilities

I'd hate to see ur return temps with 007 and a shell exchanger

U ever checked?

[MrUPS]

never checked. I'm guessing these shell  exchangers are no good?

[willieG]

 i would say the shell and tube exchanger is ok...the pump is undersized (i think)

the 3/4 lines in that short of a distance will work (bigger would have been better)

i would say a pump equivlent to the taco 0014 on the OWB to the shell exchanger, that will take care of any flow problem you have..then add a tee in your return line from the indoor boiler  from this tee to your 07 pump and then into the shell exchanger..then out from the shell exchanger to a tee into the "hot out" from the in home boiler and this tee should be before the  in home boiler pump suction side

what you want to be doing  on the home boiler side of the exchanger is  pulling water from the return side of the homes system..pushing it through the shell exchanger where it will be heated and then pushed back into the boiler's hot outlet (or into the homes feed line if the homes pump is running)

charts i find on teh net say you can push 7 toi 8 gpm through 3/4 pex and you want to be near this max so you are delivering the most btu to that shell exchanger as you can.. both pumps must run 24/7 in order to keep your in home boiler water as hot as possable. i would say run your OWB from about 165 or 168 to 178 or 180  and if you need to you might be able to lower your indoor boiler's kick on temp a little (you will need to ask others on that idea, i know nothing of indoor boilers) jsut my thought..the real pros will have better ones likley

[MrUPS]

Thanks for the reply willie. I'm going to have to look into the possibly of adding the loop pump i guess. I was hoping that I wouldn't have to run two pumps 24/7.

[RSI]

Did I miss it or was the size of the heat exchanger mentioned?

Is the return water to the OWB as cold as the indoor boiler? If it is way hotter then the first issue to fix is getting a large enough heat exchanger.

If the return temp is close to that of the indoor boiler then you need to start with a larger pump.

Instead of going with a 0014 you could put another 007 in series and it would be almost the same flow.
If go with a larger pump I would go for something like a Grundfos UPS26-99

[willieG]

if i read your set up right it appears you have one pump (and i think to small) circulating water from your OWB to the shell exchanger and back to the OWB. you have no pump in the loop of the pipe between the  return  and feed of your boiler, this would mean you have no flow of the boiler water through this loop unless your indoor pump was  running (and this would mean you are using heat) and likely then you would only be pulling part of the water through the exchanger?

by putting a small pump in the exchanger loop of the boiler you would be heating the water in the indoor boiler 24/7 and would always have the indoor water temps as highas your OWB (or close dpending on the exchange rate of your shell exchanger)

RSI is right about the size of the shell exchanger, i was taking for granted it would be of sufficient size as it was supplied by the dealer.... and he may be right on the larger pump for your OWB i was just figuring on about 7 or 8 gmp as that is the recomended max flow for 3/4 pex, perhaps a larger pump  would move more water but it will cause more friction as gpm increase. I know only what i read on the pex pipe sites and they say going over the number of gpm in the charts will cause enough friction for premature wearout of the pipes and fittings? true or false i really don't know

[Scott7m]

Anytime your going through something like a 60-100 plate or a pool exchanger, I always use at least 1" and often times strongly encourage folks to go with pex al pex for it's larger diameter or 1 1/4" pex.  Most plates over 50 are 1 1/4" fittings on them..  I also team that up with a pump that has some good flow numbers...   Kinda opposite how this one was done

[willieG]

bigger linew would sure be better but he has the  3/4 now..a shell and tube exchanger are (i have heard) less restirctive than a plate of the same btu output (?)

before i changed my underground pipe i would  try  the two pumps and turning the OWB low setting up as high as you could risk..maybe 170 or 175 (?)

i think he said he was only 40 feet away so the head loss shouldn't be too bad...i think he could still get 7 or 8 gpm. it is not the ideal set up but  it is there and i would spend a littl etime on it before i gave up and did anything too drastic(?)

[Bondo]

New to the site and just want to say that it seems like there are some great people here and i have really enjoyed looking around.
      Now for my situation. I just bought a home that had an old OWS. I bought a new CB 1400 to replace it and have it hooked up but I'm having some problems. The old wood stove was hooked up directly through the boiler system in the house. I wanted to keep the systems separate so I plumed in a shell and tube hx on the return side of the boiler.

Ayuh,....   How Big of a heat exchanger,..??  Btu's,..??
(personally, donno why ya split 'em)

I want to keep the propane boiler as backup. Do I just need to install a aquastat with high and low cut off on the boiler instead of the one that is on there now that just has the high cut off? If I turn the low setting down below what the OWS water is will that allow the circulating pump on the boiler to run without turning on the propane?

This depends on how the burner control aqua-stat controls the burner, pump(pumps?) 'n how the T-stat controls what....
Ya might need to divorce some of the functions to other controls...

Lotsa ways to do it, but We'll have to know what yer startin' with,...
Pictures help,...  Alot...

Next question. The lines from the house to the OWS are 3/4. (30 or 40 foot run) Is that to small for the system to run efficiently?  I only ask because when I had the OWS running the other night I kicked on the boiler in the house to see how hot the water would get in the boiler with the water running through the exchanger and it never got above 140. The OWS is 185.  I'm not sure if the 3/4 lines are to small or if the taco 007 that I'm running is to small or if I'm doing something else that I shouldn't be. 
       I'm sorry this is so long guys but I'm just having a hard time getting over these couple problems and wanted to give as much info as possible. If you need more info please ask. Thanks in advance for taking the time to help! 

That's another point,...   pictures will help, How do ya have this thing plumbed up,..??

How are ya move the heat,..??   zone pumps, or zone valves,..??

[RSI]

Going with BTU ratings on the heat exchangers probably won't be of much use if it was a pool heat exchanger. The btu rating on a pool heat exchanger will be for around 70 degree water entering it. (maybe even lower)
On your indoor boiler you are only raising the temp a little under load.

A tube in shell heat exchanger large enough would probably be around 5 or 6 inches in diameter and 2 or 3 feet long.

[Scott7m]

I think we can stack this whole scenario up as why a dealer is important, or a good dealer I should say

System design is nothing short of essential

The way it is now, it's a patch job to get it working alright, it would have been cheaper and much better to do it right the first time

Once we know more, we can help more

[woodywoodchucker]

My dealer or ex dealer sold me 1 1/4'' pex for my 5036. The fitting on the boiler is 3/4''.Im not sure if im getting the fill effect of the 1 1/4'' pex or not but it seems to me that I could have saved money by running 1'' or 3/4'' pex.
 That dealer was in N.H. in Colebrook. Has been useless.