POOL TUBE AND SHELL HEAT EXCHANGER

I installed a heat exchanger for a swimming pool to heat my shop loop. The problem I have is the exchanger is getting 180 degree water ,but it will not put out any water hotter than 80 degrees on the other side (shop loop). It has 1-1/4" ports incoming and 3/4" outgoing to shop. My alpha pump shows that 3 gpms are flowing through the 1-1/4" underground thermopex and to the radiant manifold. Is the pool exchanger the problem or something else?

How big is the heat exchanger? 180F in at 3 gpm, what is the secondary (shop) flow? If you are getting 3gpm of hot water through it and only 80 out, it sounds like it's undersized.

Taylor

IM not sure on the size ,but I can flow 4 gpm through the shop side according to the alpha.

Does it switch to glycol at the exchanger I take it ? Sounds like the hx must be to small.

It is going to switch to glycol ,but for initial flush I only have water. The exchanger itself seems super hot , but the discharge line on the shop side does not get hot. It seems like it should work perfect. The exchanger is mounted horizontal , is that a problem?

I am trying to rack my brain around precisely how you connected the exchanger. The tube side should be connected to the radiant loop and the shell to the heat supply loop. What does the nameplate say for specs on BTU size, flow, temp drop, etc? Do the heat supply send/return lines feel like there is a drop across the exchanger while operating?

It almost sounds as if it could be "air bound". Are you sure all the air is bled out?

I heat my pool with my oil boiler at times and heat a 45gpm flow fairly decent with the boiler up to temp.

I cant find a name or size btu. The tube measures 4.5" wide x 12.5" long. It has 1-1/4" top and bottom supply ports and 3/4" side ports on shop or load side. There is two wires that come out of the tube that have a tekmar label on them. I wonder about air lock? I can hear some air in the tube ?

You said 180 degree water at exchanger, What is the return temp to boiler after heat exchanger?

gg

You need pretty substantial flow on the boiler side of a shell&tube HX and that is likely where your issue is. The actual capacity of the heat exchanger is likely too small also. It's really the wrong type of product for your purpose. A plate HX is better suited to what you are trying to do.

I dont know what temp is after the exchanger , but I think Heaterman is right. I dont think i am transferring enough heat out of the exchanger. It must be too small, which sucks.

Does anyone know where I should get a Plate exchanger with 1-1/4" fittings. I only have a 20,000 BTU/hour heat load ,but also want to try and run a high temp unit heater. I also understand that glycol does not transfer heat as well. With all this said do I have to do a serious upsize on a plate to make a unit heater work?

I don't know if I would call that size tube/shell heat exchanger specifically a "pool" heat exchanger as it seems to be very small compared to mine though 3gpm is not very much flow. I would try running the heating supply loop by itself and see if you get 180 deg in and out with a nice quiet flow. I would also make sure the air is bled out by whatever means I could. If only half the tube is covered it would certainly lose capacity. Also, what is the predicted flow rate of your heat supply side pump? The make and model of the circulator? 180 deg at a very low flow would also be a problem.

I also run glycol at typically 180 deg + through a modine heater for a heat dump from my solar system. It works great.

I did try that and was only able to get 110 degree water using a grundfos 15-58. I was able to get the warmest water on low speed. When i turned it to high I lost a few degrees. The exchanger is being supplied by a Alpha and when it set on auto adapt it seems to be flowing 2 or 3 gpms. I dont think increasing the flow will help if it is not exchanging. My exchanger is the lowest part of the loop, I may have to cut in some boiler drains at the low point to see if air is in there.