# Circulating pump question



## Bugzapper (Sep 19, 2009)

Good evening folks.  
I am installing a used Central Boiler system in my house.  I took out my old ad-on wood furnace and Momma is SOOOO happy.
I just tonight hooked up the DWH exchanger and probably next week will get the furnace exchanger installed.
O-k.  For my question.  The man I bought it from said the pump is new this past winter.  I filled her up, fired her up, hooked everything up and turned on the power.  The pump didn't seem to come on, so I thought maybe there is a sensor switch that doesn't allow the pump to come on until the temp is up.  I left the pump plugged in and came back ten minutes later to find the pump quite hot.  I followed the plumbing and found that some dummy had left a valve in the line closed.  I opened it up, but no water flowing.  I put my ear to the pump and there is a very quiet hum.  
Thinking the pump overheated, I unplugged it to cool it down.  Got it to where I could hold my hand on it and it's still not pumping.  It's humming, not pumping.  Well not enough to move the water through the line anyways.  
I really don't think I could have hurt the pump in that short of time having the valve and therefore the loop closed could I?  The run is 50' to the house with about 10' to the water heater.
I'll go out in an hour or so to try again after it has had plenty of time to cool.
I am anxious to see how the water heater works and really excited to try the furnace.
Any ideas?  I have to assume that this pump will purge the air out of the line itself. The outdoor furnace is about level with the DWH with maybe a four foot rise to come into the house.
Of course I recieved no manual.  He said he didn't get one and the dealer doesn't even know if they come with one...

JB


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## Duetech (Sep 19, 2009)

The pumps are very quiet when operating correctly and new (given all is well). From my understanding water is the lubricant for the pump so if you can isolate the pump to test if for flow you should be able to satisfy the question of its functionality (if it was not getting water it would seem you would burn up the seal or lock up the bearing so I would not "assume" the pump is shot). Once the water in my system is hot the pump is too hot to touch for more than a second or two so if your system was hot then perhaps your pump was functioning. There is an air/water heat exchanger in my oil furnace plenum and if there is air in it I get a "lock" and my water will not flow. The pump/circulator in my system will not purge the air out. If your line has to travel up hill to get to the house you may have air in your system that the pump is incapable of purging out. If you have an indoor filler valve for your unit you may be able to turn your control valves to force the flow from the filler valve and purge out any air in the system. Pictures or diagrams of your system will help diagnos your problem and there are many here that can get you going with a few steps or mods. Welcome to the forum. Hopefully your problem is an easy and inexpensive fix (like not needidng a new pump). Stay warm!


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## Bugzapper (Sep 19, 2009)

I figured it out.  The pumps were frozen.  I drained down the tank and removed the pumps (former owner heated garage and house) and worked the impellers free.  Some black scale on the blades which I cleaned off and they both run fine.  The things were humming, but more like a transformer humm and it didn't seem right.  Now, as far as the second pump, should I take it off if I'm not using it?  I guess I'm afraid of freezing, or should the water from the tank keep it warm enough?  I also have a short nipple about 6 inches of pex at the bottom of the pump which I am concerned about freezing.  Of course, this will all be insulated, but I don't want to be replacing a cracked pump at 20 below.
I think I am answering my own question, huh?
What about putting a shut off valve between the tank elbow and the pump?  

Anywho, the tank is refilled, the fire is going again and I should be seeing free DHW within a couple of hours.

I'll post if I have any problems hooking up the furnace heat exchanger.

Thanks for the help!

JB


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## sdrobertson (Sep 19, 2009)

Bugzapper said:
			
		

> What about putting a shut off valve between the tank elbow and the pump?
> 
> Thanks for the help!
> 
> JB



You should put a shutoff on each side of the pump as then when it does die at 1130 pm and its 30 degrees below zero out and you have to change the pump you don't want to have to screw around and drain down the tank to get the circ changed out.  With the shutoffs, you just shut the lines down, replace the dead circ and then open both valves and the air in the line should just raise up and you should be pumping again fast.


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## Gooserider (Sep 21, 2009)

They make "isolation flanges" for mounting circs, which are probably your best bet - they combine the mounting flanges with a shutoff valve so as to make changing out a failed circ as quick and neat of a job as possible...  For the rest of your questions, I would agree, posting a system diagram is your best way to get us to help you out.

It may be too late from your description, but you might also want to look at some of the past threads about sizing the lines to / from the boiler, as we see lots of OWB owners with problems related to undersized lines...

I would also try looking at the CB website, or contacting them - they should have manuals for their products and you might be able to get one for nothing more than a download.

Gooserider


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## Bugzapper (Sep 21, 2009)

Thanks Cave, SD and Goose.
Things seem to be working pretty well.  I see that I will definately insulate the lines inside the house as well as the DHW exchanger.
As far as the lines go, since both the exchangers are 3/4, I went with a step down to 3/4 once the line was inside.  From where it comes in the wall to the water heater is 6' and another 5' or less to the furnace.  It's not keeping the water as hot as I would like, but hey, there are three adults and four grand kids in the house, so I guess any help is help.  I put in a mixing valve above the water heater, but it really hasn't gotten hot enough to need it. I plan to get several thermometers to track the temp of the DHW coming out of the exchanger, out of the tempering tank and out of the gas water heater.  Should be interesting.
I've been running the boiler water temp 170 to 180 with just one piece of wood going.  Pretty amazing.  I know, it's not cold out yet but to just keep those water temps with so littl fuel is pretty amazing.  Two days, maybe half a dozen logs so far.  
We are cleaning up the crappy twigs and sticks in the wooded yard.  Keeps the grand kids busy and it will make great kindling.
I'll put those valves in the lines.  The previous owner said he changed a pump last winter, so I'll ask him if he had to drain down.  I'm sure he did.  I really don't want to go through that mess and refilling, running a garden hose out there at 20 below...  Not my idea of fun.
Thanks again for your advice.

JB


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## jebatty (Sep 21, 2009)

Glad you're making progress on your system. Weather is likely to break anytime now, but the last 3 weeks of summer have been pretty nice. Fall colors are moving into prime.

For what purpose are you using each of the 3/4" hx's? and what size/plates are they? Have you done a heat load calc to determine what your need is and whether the hx's can meet that at a flow rate and pump head which your circ can supply? Head on hx's increases rapidly as gpm's increase, often beyond the capacity of the typical home boiler system. Also, achieving transfers closer than 20 degrees to boiler supply gets to be problematic. You may want to check the selection tables for your hx's to help out understanding this, if you haven't done that already.

I started with 3/4" fittings and 3 x 8 x 24 plate, and it didn't have the btu transfer I needed for my application. I then went to at 1" fittings and 5 x 12 x 30 plate and that did better, although I think a 70 plate would probably have been about right. Everything out of ignorance and a long learning curve as a diy-er. Finally, I eliminated the hx and switched to an all pressurized system and performance improved significantly.


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## Bugzapper (Sep 21, 2009)

Jim:
I'm about to leave for work, but I am going to have to re read your post several times.  I am totally new to this and frankly, I have no idea what you just asked.  Like I said, I'll read it again and I'm sure it will make more sense.  I haven't had my coffee yet.  ;-)
Where do you live Up North?
This is a great forum.  I'm glad I found it.  About as happy as I am for buying a CB and not the one from L&M;.

JB


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## Gooserider (Sep 21, 2009)

Essentially BZ, you need to look at the entire setup as a system, where all the parts have to work together properly, and be sized and chosen to work well with all the other parts of the system.  If you fail to do this, and put in a single part that is not right for the application, it can drag down the performance of the entire system, and often make it look like the problem is in a different area.  Some of your posts have been a bit concerning in that it sounds like you are just kind of glomming things together without giving a lot of thought to how all the parts are going to interact.

This is one of the reasons we like to see people post system diagrams - it gives us an easier way to see what they are talking about, and also makes you think about how it is all going to go together.

What Jim is saying boils down to the fact that a heat exchanger needs to be properly sized to match the load, or it is not going to transfer enough heat to perform well...  There are a lot of factors that go into this, including the size of the inputs and how much restriction the piping inside the heat exchanger creates - as this can have a severe impact on the overall head resistance, and thus flow in the rest of the system.  In addition, the size and number of plates, along with the difference in temperature between what the two sides of the exchanger will have a big impact on how much heat you can transfer through it...

One of the other numbers you will see us constantly asking about is the Heat Load - which is how many BTUs per hour you need to heat your house and so forth to the desired temperature on the coldest day of the year - if your system isn't capable of delivering this much heat to your load, you will not be happy with it.

One of the problems we see a LOT of, especially with OWB installs, is the situation where the boiler is capable of putting out way more heat than is needed, but because of bad component choices, it can't get the heat from the boiler to the load.

Gooserider


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## jebatty (Sep 21, 2009)

BZ - PM me with your contact info and I will reply. I feel much of what you are going through -- I've been there and I think mostly beyond now.


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