Pool heater

Jackchips · August 2002

Hello,

Being a licensed plumber from Ma. who is a CPD with ASPE I convinced my wife that I could heat our swimming pool for a couple of weeks on each end of the season with our 50 gallon, gas water heater.

I purchased a Therma-Flow Everhot RM-10-SP copper heat exchanger and two Taco 110B circulators with 3/4" flanges. One pump goes through the coil, into the water heater on the cold side and is drawn through the hot side and works off an aquastat. The second pump goes through the exchanger (low pressure side) to two 11/2" x 3/4" tees spaced three inches apart on the return side of the pool line and runs on a time clock. There is an auto vent on the top of the exchanger.

For some reason the line through the exchanger to the pool will not maintain hot water circulation even though there is hot water through the coil from the water heater. If it is purged at the pool it will circulate hot and then after a while it seems to stop.

The other more dramatic issue (other than my wife is do home from business this PM) is while the circulator through the coil is on I am by-passing the water heater and getting cold water into the house. This was established last evening 2 minutes into a shower and was verified by turning off the circulator and getting instant hot water.

I realize there is not much to go by but if there is any creative interest in solving my puzzle I wil answer any questions.

On a note to Dan, I have used your Pumping Away on a number of occasions and saved my employer not only financially but in much good will. Thanks.

Jack

Canuck · August 2002

Lose the pump

on the pool side of the HX and put one of your tees on the discharge side of the pool pump (to sand filter). This will cause flow through the HX on its own (pressure differential). I usually put valves on these tees to regulate flow and allow shut-off for filter maintenance. Cold-in-hot problem - Is the tank, top connection? Do you have hot-hot, cold-cold? Is the dip tube broken? I know if you're getting hot in cold it's usually just a matter of a check valve being put in the line. You'd better hurry, mama's gonna have your butt if you don't get this resolved!!

Jackchips · August 2002

Hi Canuck,

The only accessible spot for my tees was on the discharge line to the pool. That is why I put two tees together and added the pump. The piping I used was 3/4" and I have valves and draw-offs at the pool line. Could the problem be related to losing prime because when I came out of the HX I ran the discharge line higher than the auto vent before looping back down. Looking at it I don't understand why I did this other than appearance. I am thinking of disconnecting it and turning the elbows down so they are below the auto-vent. Although this seems to simple to be the problem of not sending heated water to the pool?

After stareing at the problem for quite a while I see where a check is needed because when the domestic is drawing, the water is short circuiting through the coil and not going through the water heater.

Is there any way of posting a picture?

Thanks

Mark Eatherton1 · August 2002

Posting a picture...

Click on the attachments button on the lower right hand side of the POST REPLY window, then click on BROWSE, then click on the source of your photo, then click on ADD button, then click OK button and you're taken back to the POST REPLY window. There, at the lower left hand side of this window you can then check the little box for the photo (JPG works best) that you want to show without having the reader click on the picture. Otherwise, the reader will have to click on the highlighted area for the picture.

To be quite honest with you, I suspect the heat exchanger is working quite well. When you have a low temp low flow source, and a low temp high flow demand, the delta T on the load side of the heat exchanger is usually pretty low too.

Here's an example. Which moves more energy, 100 GPM at 1 degree differential or 1 GPM at 100 degree differential...

You're scenario is probably the first part of the sentence.

Here's another question, when you're running this rig, does the water heater fire up and stay fired up? If yes, then what I said is happening.

Let us know.

ME

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Canuck · August 2002

Mark has a point

Certainly there is a small delta T on the HX, which then shows up as a 'cold' unit. I'd double check though that the tee closest to the pool pump discharge goes to the inlet of your HX pump and not vice versa. Good luck.

Jackchips · August 2002

Jackchips · August 2002

Hello again,

I dropped the raised line coming out of the HX below the auto-vent, installed the check valve in the heating source from the water heater and everything appears to be working great. It helped to just talk things out and get the feedback you provided. The water heater is not running continuously so I am half way to a successful venture. Now I just have to raise the pool water to a level my wife considers adaquate, although 90 would be her ideal. Thanks for the suggestions.

Jack

Dave Yates (PAH) · August 2002

questions????????

How many gallons of water are in that pool? Is it outside exposed to the air? Is there a solar or insulating cover on the water? What are the surface dimensions? What's the Btu input on that 50-G water heater?

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Mark Eatherton1 · August 2002

Picture of system

He sent me a picture, and I'm attaching it to this post.

ME

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Earthfire · August 2002

inexpensive heater

we've heated a couple of pools fairly inexpensively by taking a 500 ft. coil of blk.poly.well pipe spreading it out on the lawn like a slinky. We used 1 1/2in.pipe & recommend a weedwacker to keep the grass short. Hard to drive a mower over the pipe. Hook one end to pump discharge & the other end to the pool return. Control of circulation can be timer to run during daylight hours or a NC relay hooked to a photocell ( turn pump off when no sun). Fairly inexpensive to build & only additional expense is electric for continuous daylight circulation. A good pool cover helps to keep the heat in at night.

Jackchips · August 2002

Well it looks like I'll have to go back to plumbing and leave the pump designing to Wet Heads. I can not maintain circulation. If I purge for a few minutes the water starts to turn hot but after five or ten minutes there is no longer circulation. I have two 11/2" x 3/4" tees on the return line to my pool with ball valves and draw-offs. The tees are spaced about four inches apart. It has become extremely frustrating but that's what an amatuer gets for crossing fields.
Dave, the pool is a modified 16 x 32 cut down 4 x 16 to add stairs and the deep end eliminated. The deepest part of the pool is only 4/4.5 feet. It is basically a large tub. Great for the grandchildren (and Grandpa). I thought if the 50 gallon didn't quite do it I would twin in a second as the Mrs. loves her hot showers anyway. There is a solar cover on when it is not in use-which looks like it will not be for the rest of this year.
Thanks all for your suggestions.

Jack

Jackchips · August 2002

Well it looks like I'll have to go back to plumbing and leave the pump designing to Wet Heads. I can not maintain circulation. If I purge for a few minutes the water starts to turn hot but after five or ten minutes there is no longer circulation. I have two 11/2" x 3/4" tees on the return line to my pool with ball valves and draw-offs. The tees are spaced about four inches apart. It has become extremely frustrating but that's what an amatuer gets for crossing fields.
Dave, the pool is a modified 16 x 32 cut down 4 x 16 to add stairs and the deep end has been eliminated. The deepest part of the pool is only 4/4.5 feet. It is basically a large tub. Great for the grandchildren (and Grandpa). I thought if the 50 gallon didn't quite do it I would twin in a second as the Mrs. loves her hot showers anyway. There is a solar cover on when it is not in use-which looks like it will not be for the rest of this year.
Thanks all for your suggestions.

Jack

Jackchips · August 2002

Well it looks like I'll have to go back to plumbing and leave the pump designing to Wet Heads. I can not maintain circulation. If I purge for a few minutes the water starts to turn hot but after five or ten minutes there is no longer circulation. I have two 11/2" x 3/4" tees on the return line to my pool with ball valves and draw-offs. The tees are spaced about four inches apart. It has become extremely frustrating but that's what an amatuer gets for crossing fields.
Dave, the pool is a modified 16 x 32 cut down 4 x 16 to add stairs and the deep end has been eliminated. The deepest part of the pool is only 4/4.5 feet. It is basically a large tub. Great for the grandchildren (and Grandpa). I thought if the 50 gallon didn't quite do it I would twin in a second as the Mrs. loves her hot showers anyway. There is a solar cover on when it is not in use-which looks like it will not be for the rest of this year.
Thanks all for your suggestions.

Jack

Mark Eatherton1 · August 2002

Make us a drawing...

we'll get it figure out. It's something simple I'm sure. Heres some mechancial symbols that you can cut and paste with paint and make us a drawing. Save it as a JPG when you're done. They upload to this site real easy.

ME

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Dave Yates (PAH) · August 2002

Jack

Don't be too hard on yourself. We have all, well maybe not Murph, but the rest of us have pulled off some major FUBARB mistakes that would either make you laugh yourself till you wet your pants, or lead you to believe we're totally fried in the knoggin. Don't ever tell Robert Bean I admitted to that!

Math, yeah I hate math cause I'm dyslexic - but dyslexic boo-boos are divisible by the # 9, is the answer! You need to determine how many gallons of water are in that pool. (Circulation & air problems aside.) 1 Btu per Lb of water to raise the temps, not accounting for losses to air and delta T between outdoor temps and pool water. Got to overcome the losses generated by outdoor conditions in order to raise the temps. That's it in a nutshell.

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Mark Eatherton1 · August 2002

Solution....

Hey Jack, Close the automatic air vent on the top of the HX, then re-purge and keep the vent closed. It's acting as a vacuum breaker.

As an alternative, install a ball valve between the two tees coming off the main pool line, and eliminate the pump on the pool side. You'll limit the temp by cycling the input pump.

Let us know how you make out. I suspect the vacuum breaker is killing you.

ME

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Jackchips · August 2002

Mark, You are the man. As soon as I read your reply the vent was closed, the line was purged and the water moving. Currently I have connected a hose to the return draw-off, closed the valve and the discharge is going directly into the pool---warm.

I'll still have to address Dave's concern with the amount of input I'll get out of the 50 gallon water heater but adding BTU's will be an easy one now that water is moving. It has been over an hour and a half so I am confident in sending out this post. I may still install a tee on the suction side of the pool pump but that will be in the spring.

Thank you one and all.

Jack

Jackchips · August 2002

You can tell how new I am to this posting business. Please read my message dated 8/28 above this posting.

Once again, Thanks everyone.

Jack

Mark Eatherton1 · August 2002

Another

satisfied Wall Customer. I told you we'd figure it out and that is was something simple, didn't I;-)

Glad you got it resolved Jack. BTW, Welcome to the Wall.

ME

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