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[Chris M.]

I have a continuous loop pumping from my furnace underground to my house.  It goes through a 20 plate domestic heat exchanger then through a 40 plate heat exchanger for my base board.  The water temp from the furnace when it enters my house is at 185.  It appears that my water temp of my closed loop system is only reaching 150 at best when I need 180 after going through the exchanger.  I just replaced a Taco 009 pump in this cold weather since the old pump was making noise.  This has not fixed my problem.  Any suggestions welcomed.  As a side note, in past winters I have struggled on the coldest of days to get the base board up to temp through the exchanger.  Really need to address this problem. 

[slimjim]

I would bet that the restriction caused by your 20 plate in series with your 40 plate is the issue, how about adding another circ and running the 20 plate in parallel.

[Chris M.]

There in lies the problem.  I only have one line in and out to the furnace and it is 4 feet underground.  Would buying a larger domestic heat exchanger increase the flow?  Would upsizing my pump be an option? 

[slimjim]

In order to solve the issue, I would place 2 closely spaced tees in the supply line from your boiler to the house, the first tee would be to mount the new circ that would supply your 20 plate and the second would be for the return from the 20 plate, the 40 plate circ would run constant with the 009 and the 20plate could be a smaller say 007, if your 20 plate is supplying a tank then it could be switched on + off by the aqua-stat on the tank.

[mlappin]

Would he still get enough flow by placing a mono tee in the line and feeding the 20 plate off of that?

[tawilson1152]

I had air trapped in the top of my heat exchanger. I had to put a valve in for a vent to get rid of it. If not there might be air elsewhere.

[slimjim]

The Mono Flow tee is another way to do it if he wants constant flow through the 20 plate.

[Chris M.]

Hey guys thank you all for your responses.  I am trying to understand the different approaches.  I am trying to figure out what is the best option.  In my current set up, I bypass the hot water tank completely.  I turn off the water to and from it and turn off the breaker. 
If I install the secondary 007 pump, I would only have just a few feet of circulating water in order in and out of the supply loop.  I would have to have it run constantly.  Does that sound right?  I can post a picture of my current set up if needed.   

[Chris M.]

I didn't see the mono flow Tee response when I typed my last response.  That might be a much easier solution if you think that option works. 

This may be a dumb question but when my supply water from the furnace goes through the heat exchanger, should the closed loop water being heated come out at the same temperature as the supply water in?  Or is there an expectation that it will be lower? 

[slimjim]

  It will be a bit lower for sure!

[Chris M.]

Will one mono flow tee be sufficient?  If just one, how far from the other "Tee" do I place this? 

[mlappin]

Will one mono flow tee be sufficient?  If just one, how far from the other "Tee" do I place this?

I believe you'd place the Mono Flo T first, then the return T from the 20 plate can be located anywhere after that.

[GCTerpfan]

Could one or both of your exchangers be scaled up or have air trapped in them?  My loop runs through 400' of pipe, a 50 plate and a 30 plate heat exchanger with a Taco 007, and I am not having any issues.

[Chris M.]

Well I went ahead and plumbed with a mono flow tee.  It is all done in pex so it didn't take too long.  In response to the last post, I think you may be right.  Although after plumbing with the mono flow tee, I got an additional 10 to 15 degrees water temp at 165 now.  I noticed some build up in the pex fittings.  Pretty bad stuff.  I don't know what else to do to treat that.  I will probably have to buy a new  heat exchanger.  I treat my furnace twice a year as recommended with the manufacturers chemical. I got 3 years out of this exchanger.  I think this is where my problem is.  Is there any way to clean an exchanger? 

[slimjim]

The heat exchangers can be cleaned with commercially available coil cleaner, if plumbed to do so it can be done without removal.