HS Tarm MB55 Solo for pool heater?

sardo_67

Member
Sep 19, 2017
170
mid CT
i have an old MB 55 Solo 140k BTU natural draft wood/coal boiler I’m not going to be using in my house. Friend who has a concrete companh was looking for a pool heater, I suggested he lets me borrow his skid steer and compacfor for a week to finish a parking area and I’ll give him the boiler. Even deliver and hook it up for him.

Question is will this work to heat the pool if we get the right amount of flow going thru it or would this just be pissing in the wind?


To me it seems like using a smaller pump that’s controlled with a close on rise thermostat would move just enough water where it would heat the pool but not pump so fast thru the boiler that it never gets hot.
 

JMihevic

New Member
Feb 3, 2018
17
Medina, Ohio
Yes, the pool water would be corrosive to the boiler walls that are exposed to the circulating pool water which has oxygen plus a lot of chemicals. My MB 55 is still in like new condition, but my system is pressurized and the original water I put in in 1980 is still there minus all the oxygen that is no longer in the water.

My MB55 has a copper tankless hot water coil. The spec on the coil is 2.9 GPM. You may be able to use that by circulating the pool water thru it for heating. I think the copper coil should be able to handle the chemicals in the pool water. I would still install a circulator with a simple throttled bypass loop on the boiler from supply to return. This will ensure that you have a uniform water temp on the 55 gallons of water that is in the boiler.

John M.
 

sardo_67

Member
Sep 19, 2017
170
mid CT
what size heat exchanger would be needed for this if one wanted to do it the right way?

as big as possible or a 140,000 BTU exchanger to match the size of the boiler?
 

E Yoder

Feeling the Heat
Jan 27, 2017
294
Floyd, VA
If you look on eBay they have tube and shell heat exchangers sized by BTU output and pool gallons, aiming for a 1° F temp rise per hour. But the boiler flow rates they use to get the BTU output is pretty high.
Oversizing won't hurt, you can always throttle the boiler flow to slow down the BTU rate.
Use stainless for a chlorine pool, titanium for salt water. Absolutely don't want pool water in the boiler. I saw a heat exchanger fail and eat holes in a boiler once.
 

maple1

Minister of Fire
Sep 15, 2011
9,879
Nova Scotia
What would you do for overheat protection?

If everything always flows as intended & designed, it shouldn't overheat given pool water temps. But you should never count on things always flowing as they're supposed to with a boiler. Or the design being exactly right.

You would also likely want to maintain the boiler side stuff as a closed pressurized system for corrosion prevention. So expansion tank and all that stuff. Or else a rigid boiler treatment regime.

There would also be off-season considerations. Wouldn't want it freezing & busting stuff in the winter.

Then there's the esthetics side of things which some may have a concern about. View around the pool might be less appealing if there's a wood boiler in the picture plus a messy woodpile plus some smoke it may make. Might need a building to put it in?

(Not saying this is a totally bad idea by any means though...)
 

Fred61

Minister of Fire
Nov 26, 2008
2,429
Southeastern Vt.
I'm using one of these units. Not for pool heating but for a heat exchanger and buffer tank on my radiant installation. Picked it up cheap from a guy that had his pool removed.

http://www.htproducts.com/ssp-pool.html
 

sardo_67

Member
Sep 19, 2017
170
mid CT
I'm using one of these units. Not for pool heating but for a heat exchanger and buffer tank on my radiant installation. Picked it up cheap from a guy that had his pool removed.

http://www.htproducts.com/ssp-pool.html

that looks expensive. i am giving him my old boiler for free so he's not looking to spend a lot on this, basically just throw some old chit together then throw in some wood and heat the pool. he gets as much free wood as he can ever use/want/need so efficiently isn't a major issue. his house is landscaped so the boiler would be hidden or he might put it in his shop/garage i am not sure
 
Another option would be a heat exchange coil hung in the pool.
 

flyingcow

Minister of Fire
Jun 4, 2008
2,545
northern-half of maine
140k boiler? Just curious , how big is the pool? While a 140k boiler is a good sized one, will it be big enough to do what the pool owner expects. Quick rise in a few hours? Or will he be doing a daily fire(s) to maintain pool at a constant temp?

I briefly thought about doing the same thing with my innova boiler. But it's only 102k.

I installed a 250k propane pool heater. That will give my 18x36 in ground a 1 to 2 degree rise in an hour. Sometimes 3 degrees on a nicesunny day.

. While the terms of the deal sound favorable for you both? The cost of the install, amount of wood needed to be cut, split, stacked may surprise you. And will it heat the pool as expected? We don't use our pool very often, but when we do the 250k heater will take a while to get it up to where we want it to be.
 

TCaldwell

Minister of Fire
What is the output of the current heater and the capacity of the pool, above ground or I ground, covered or not when not in use.
Answers to these can help to see if it’s viable, and at what cost.
I was heating a 22k gal in ground gunite, uncovered pool with the garn, it would take 2 fires a day in the shoulder seasons and 1 during the summer months, about 4 cord. The pool was kept at 83 deg, using a 350kbtu shell and tube hx and a taco 007. The pool side was run through the existing propane pool heater.
It worked well, the propane truck stopped showing up.
 

sardo_67

Member
Sep 19, 2017
170
mid CT
hes going with a converted 55gal drum stove and an added heater core inside of it.

it sounds like a terrible idea no?
 

E Yoder

Feeling the Heat
Jan 27, 2017
294
Floyd, VA
Running the pool water through the heater core?
 

maple1

Minister of Fire
Sep 15, 2011
9,879
Nova Scotia
hes going with a converted 55gal drum stove and an added heater core inside of it.

it sounds like a terrible idea no?
I wouldn't expect what that sounds like, to perform very good at all.
 
You know, for all this complication, a solar pool heater is a very valid choice. No corrosion issues and no hustling wood and what sounds like a smoky mess with the current conversation.
There are some very effective DIY designs on www.builditsolar.com.
We did some of them years ago and they were comparable to commercial collectors at a fraction of the cost for a lot less work.
In Maine, they get the pool up to temp by Memorial Day and maintain it all season.
In Connecticut, it should be even earlier. (If the sun ever shines again.)
A solar pool blanket should be used regardless of heat source at the fringes of the season.
 
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