Print

[willieG]

iam sorry iam loosing 30 across the EX .  I dont loose hardly  anything from the wb  its only 14 feet away from house well 28 if you count there and back.  my house is 3000 sq . with new replace ment windows this summer. most of my house is very warm execpt my liveing room i cant get it past 65 -68 with the thermastat set at 75 the cirulater pump running all the time witch in turn cooks us out of the room that gets the heat first feels like iam chaseing a ghost

would be good thing to either use a smaller exchanger in the first one so you dont pull so much heat from it before going to the second one or...as my house is i use a feed  header and a return header then pipe both rooms seperatley ( i take i  you have 2 exchangers and 2 blowers now?)

could you for testing purposes block of part of your first exchanger with cardboard or a piece of tin to only draw off the heat you need and see how that works...if you are dropping 30 degrees on the first rad your second rad  can not pull the heat required because the feed water is now too low for the rad to supply the needed btu

[MattyNH]

RSI -  again you bring very good points to light. You are right about the return line and the controller sensing point.  I have noticed it overshoots on burns about 1-2* with the lower flow rate. I need to look into this unless someone knows the minimum flow for a cb classic?

Fireboss- this discussion is about heat load across a heat exchanger. To confirm, your losing 30* before the heat exchanger? Sounds like a underground pex issue. Many discussion already started on it.

I don't know  how there could be a minimum flow for a CB..Reason why I say that..Every set up is so different.. Ive seen CB's literally tuck right up to the house..Probally don't need much flow rate..Somebody 100ft away def needs a much higher flow rate for heat demand..

[willieG]

[/quote] I don't know  how there could be a minimum flow for a CB..Reason why I say that..Every set up is so different.. Ive seen CB's literally tuck right up to the house..Probally don't need much flow rate..Somebody 100ft away def needs a much higher flow rate for heat demand..
[/quote]
i think what you mean to say is someone who has their stove close to the house would get more GPM than someone farther away if the pumps and the lines were the same size.  flow rate could be adjusted by the size of the pump if the distance is farther from the house to match that of the closer stove.

flow rate has a lot to do with btu per hour delivered to the home (that and the water temp) if you keep your water hot (say at factory setting of 180) you could get by with a lower flow rate than if you ran your water temp lower. however you need to keep your water tmep high enough that your blower can extract enough heat to accomodate for your homes heat loss. there are many variables to a homes (and yoru stoves) "sweet spot"

i say dont gamble and keep your water temp at your boiler no lower than 150 (coldest) and keep your gpm  high enough to lose no more than 20 degrees drop on the return line to your blower. ( i know there are exceptions depending on how well your home is insulated and the outside air temps and the wind and such)

i guess you could lower your gpm by the heat yoru home requires on a daily or hourly basis but why not just make sure you are getting enough to heat yoru home on the coldest winter days and leave it alone?

[RSI]

No, I was talking about minimum flow rate for proper circulation in the boiler. It may or may not matter on a CB but they probably designed it so the water would travel in a certain pattern inside the boiler to keep the water mixed. If it is not flowing like it should then sediment may accumulate and cause corrosion and interfere with proper heat transfer.

This may or may not be an issue just something that should probably be checked on if running only a few GPM.

[MattyNH]

I don't know  how there could be a minimum flow for a CB..Reason why I say that..Every set up is so different.. Ive seen CB's literally tuck right up to the house..Probally don't need much flow rate..Somebody 100ft away def needs a much higher flow rate for heat demand..
[/quote]
i think what you mean to say is someone who has their stove close to the house would get more GPM than someone farther away if the pumps and the lines were the same size.  flow rate could be adjusted by the size of the pump if the distance is farther from the house to match that of the closer stove.

flow rate has a lot to do with btu per hour delivered to the home (that and the water temp) if you keep your water hot (say at factory setting of 180) you could get by with a lower flow rate than if you ran your water temp lower. however you need to keep your water tmep high enough that your blower can extract enough heat to accomodate for your homes heat loss. there are many variables to a homes (and yoru stoves) "sweet spot"

i say dont gamble and keep your water temp at your boiler no lower than 150 (coldest) and keep your gpm  high enough to lose no more than 20 degrees drop on the return line to your blower. ( i know there are exceptions depending on how well your home is insulated and the outside air temps and the wind and such)

i guess you could lower your gpm by the heat yoru home requires on a daily or hourly basis but why not just make sure you are getting enough to heat yoru home on the coldest winter days and leave it alone?
[/quote] Exactly Willie..I got a buddy who has the exact OWb as me.. Mine is a yr older..I run a 007 taco pump..Im approx 128 ft + or - to my oil boiler.. unlimited hot water.. house  72- 74F.. My buddy on the other hand... He's 85 ft + or - to his oil boiler.. Ran the factory 007 taco pump.. 007 pump could not keep up with heat demand.. thermostat set to 72 at night..wake up and it would only be like 66 F in his house.. ...Up graded to a 011 taco.. World of difference...Every situation is so different..

[RSI]

I don't understand why the distance from the house would have anything to do with a minimum required flow rate.

You need the same GPM to get the same amount of heat to the house. Distance makes no difference on how much you require. It does make a difference on what pump may be needed and possibly what size pipe.

[willieG]

I don't understand why the distance from the house would have anything to do with a minimum required flow rate.

You need the same GPM to get the same amount of heat to the house. Distance makes no difference on how much you require. It does make a difference on what pump may be needed and possibly what size pipe.

exactly.. and what would be (in my opinion) the "sweet spot" would be knowing how many btu you would require to heat your home on the coldest day of the year and making sure you could deliver that. if you were sure you could deliver this amount then you can deliver enough the rest of the year and that would be "sweet"

perhaps one of those 3 speed pumps and you could run it one speed for average cold days and turn it up on those extreme cold days...but for my money i like the "plug and play" technique...plug in the wood and go play..leave all else alone

[MattyNH]

 I don't get how a outdoor wood  boiler manufacture can give a minimal flow rate.. I can't imagine  they would say for example: You need 3 gallons per min so you won't have a build up on iron and manganese..If your well water has a very high concentration iron..Your gonna have a build up of iron somewhere..Its all whats in your water really..

[Bill G]

Here is my rather amatuer opinion, first time fire up on a new system, you should have at least a y strainer in line and check to see what you may have "caught" if a problem arises.  Weld slag, spider webs, mouse nest, all possible.

Just a thought....

[Ridgekid]

Been doing some reading.

 Central boiler provides a hydronic component selection guide. On the bottom of every page it states not to exceed 30* dt. Mbtu will vary based on actual dt. 

On my install the Total 1" pex installed is approx 230'. That's round trip from/to Green Dragon.

The Taco 009 rated Gpm for that amount of pex is 6.8 gpm.

Maximum flow rates: ( for CB )
1" pex = 11.5 gpm
1 1/4"  pex = 17 gpm

There is a listing on minimum lengths that are dependant of pump selections. In my case the taco 009 requires at least 80' or you overload the pump.

Ok. That's it I'm tired....going to bed.

That's just some data I wanted to share..........

[artbaldoni]

Well my low tech experiment told me this:
Low speed = oil boiler runs alot.
Medium speed = oil boiler runs only in AM when calling for heat and lots of hot water.
High speed = oil boiler never runs.

Ok, high speed it is!

[Trint]

As with anything with multiple variables, there is a sweet spot.  Since we can't control all the variables, we can control certain variables such as return water speed, setpoints on our boilers and furnaces.  Somewhere in this is an optimal performance...maybe

I've got another question to add to this...does anyone try to insulate their heat exchangers?  I have two 50 plate exchangers that put off alot of heat in my basement.

Insulated the heat exchanger I made for hot water, it made a world of difference in the amount of heat in the room and I don't have to worry about burning myself on it.  The metal gives off alot more heat than the pex lines feeding it.