I built a Hydronic Dryer. It's not heating. Ideas?

Thaddeus

hello, I built a hydronic dryer from a standard clothes dryer by removing the electric heating element and installing a 110,000 BTU heat exchanger in the pedestal of the dryer and plumbing it into the dryer duct work.

My boiler is a central boiler classic 750. I am using Taco 900 circulating pumps. The boiler supply line enters my house and goes to a sidearm heat exchanger which heats my domestic hot water, then it goes to my hot air furnace, then it goes to my clothes dryer and returns to the boiler.

I am using a Taco 110/240vac 3-way zone valve to supply the heat exchanger in the dryer. When the dryer is powered on the leads that were connected to the heating element are now connected to the Taco 3 Way zone valve and Supply water to the heat exchanger.

The dryer is not building any heat when activated. Here are some things that I've noted. The heat exchanger came with 1-inch Supply and exit lines. My boilers entire system runs on 3/4 inch. Also I noticed that the dryer has the ability to suck enough air through the heat exchanger to cool it fairly rapidly.

I am wondering if my waterline size is not supplying enough hot water for the heat exchanger. Or, if I need to choke the air intake, or if I need to choke the air exhaust.

I understand this is not a regular subject and that some might read this and scratch their heads. I'm hoping that there's somebody out there that has a lot of experience with heat exchangers in rare situations that might be able to help me diagnose my problem.

Thanks for any help or ideas. I really appreciate it

mikeg2015

Need water temperatures. The output of the coil is likely rated at 190f Water, around 65f air temp and 11 gpm. With 3/4” and that pump and other factors I’d guess you have 3 gpm.

However, clothes dryers only need about 15000 btu but the air temp will be 100-120f.

Not sure how well this will work.

Commercial systems are often steam heated. Will need fairly hot water to make it work and more flow rate.

Are you using 100% room air being sucked into the dryer?

Again, what is the incoming and leaving water temperatures?

Thaddeus

Thx, so boiler output ranges between 185 and 170.

The dryer has been installed on the exiting portion of the loop, approximately 80' total distance from boiler. So I imagine that I'm down about 10 degrees from source. But I will try and take a measurement tonight

hot_rod

Others have gone down this path. i think it is doable with some control technology for control and cool down cycles.

Let us know how it works for you.
https://www.engadget.com/2008/02/15/hydromatic-debuts-revolutionary-dryer-miser-clothes-dryer-tech/

Zman

Do you know the rating of the original heating coil? How many CFM does the dryer move? How did you size the heat exchanger?
My thinking is that you need to verify the load and the coil size and then figure out if you are delivering enough energy.

GroundUp

Are you certain that the 3 way is diverting water through the coil during a call? As others have said, need water temps as well as total loop distance and diameter of your piping, and what the construction of your underground piping is. Keep in mind that the water temp on the OWB display is likely nowhere near what you're actually supplying to the house, the Edge has an awful habit of not mixing the water jacket and displaying 10-20 degrees higher than what the actual supply temperature is due to the location of the probe.

Thaddeus

So my temp gun failed last night. I hope to borrow one that works today.

To answer some if the questions above.

1) Yes, 100% room air temp. 74°

2) Will hopefully have the temp of the entrance/exit pipes tonight and will report.

3) How did I size the exchanger? I honestly didnt, I found online from Dodds Brothers outdoor wood boiler supply this exchanger designed for clothes dryers. So it is admittedly my mistake assuming it would work accordingly

4) Is the 3way diverting. Yes, I can put my hand on the entering pipe to the exchanger and it will drastically heat up when the dryer is activated. So I know my installation is proper

5) Total loop is approximately 190'... 65' from boiler to Hot Water tank sidearm exchanger, from there 15' to hot air furnace exchanger, from there 20' to dryer inlet and then a 90' return because I diverted the return line about 20' as I intend to supplement my hot tub with waste heat.

6) Line type and size. I am using 3/4" double line Thermopex to the house Rated heat loss is 1°/100' in the house I am using Pex heat pipe non-insulated as the distance of exposed pipe is very short, under 35' total

7) The heat exchanger I an using uses 1" piping at entrance/exit

8) My Classic Edge settings are 170° call for heat, 185° end call for heat, 20min separated 70sec airpulses

And for the record, I am a competent and skilled mechanic. I am an FAA licensed aircraft technician and a Journeyman Millwright. So my mechanical skills and understanding are suitable, I just have not been trained or have experience in this field which is why I am asking questions in this forum hoping I am talking to pro's

Thanks to all for your help
Thaddeus

Thaddeus

Screen shot of boiler performance. It is performing within specs

mikeg2015

So that Taco 009 is the only circulator and it’s all 3/4” to the house. I’d have to see a diagram of the piping inside the house. But I’d WAG your be around 3-4 GPM with 250’ equivalent (Includes elbows) or more in 3/4” pex (pex ID is smaller than copper).

The 750 rated output is 240,000 BTU. Should have used 1-1/4” the House, 1” minimum after that. You want probably 10-13 gpm to that boiler. (Assume 75% efficiency and 20-25f delta t).

All that being said. You should be able to get enouhh heat as dryers airflow is pretty low, probably 100cfm at most.

I wonder if the duct transition isn’t pushing air evenly across the hot water coil. Worse, the air flows across bottom of the coil and due to low flow all the heat goes across the top not warming any air.


So oddly, your coil may be too big because your flow is too low. Could possibly black off the bottom 1/2 with sheet metal and see if that helps.

Ironman

Your main issue is that the zone valve is not piped correctly. The center port is the common and has to be connected to the system supply or return depending upon if it's mixing or diverting (either way will work). You have no flow through the coil the way it now is.

The second issue is that your piping, pump and the zone valve are too restrictive. You can improve this by piping the appliances as secondary(s) and the boiler as primary, but you'll need a separate circulator for each secondary.

That zone valve has a 3.3 cv rating which means it's very resistant to flow over 3.3 gpm. As others mentioned, you should be moving 10 gpm+ depending upon the house load.

Here are a couple of diagrams, but again, the zone valve should not be in the boiler loop.

Thaddeus

Mikeg2015. I understand what you are saying. What do you think of my thoughts on this... I am going to try and block off a portion of the intake, I was thinking maybe peg board so that air is distributed evenly thru the exchanger... I also considered restricting air output, currently 4", maybe reduce it to 3". Or maybe both. Of course restricting output makes me have to monitor vent for lint build up, but I understand that

Thaddeus

Iron man, thanks for the diagram. I have this valve plummed the same exact way my hot air furnace is plummed. And that works fine... now, that said, is it possible that I have them both wrong but the furnace coil is still heating properly?? Not sure... I did test the valve prior to installing it, the incoming line is fed directly to the valve and the "non call" position is exiting from the bottom.

Thaddeus

On the question of water Flow. Is there a style of heat exchanger, such as a plate heat exchanger, that would allow me to feed it with the 3 gallons per minute, and circulate 10 gallons a minute on the other side, while maintaining an adequate BTU transfer??

Zman

Electric dryer heating coils seem to average about 5,000 watts. 5,000 x 3.415 = 17,075 btu/hr. If you assume the fan moves 100 cfm as someone suggested, 17,075 / 1.09 / 100 =157 degree delta T on the air side. With an electric coil that can get well over 500 degrees, that works just fine. In your case, your coil maxes out at 180 degrees. Unless you can increase airflow, the dryer will underperform. To make this work at all, the heat exchanger size and configuration needs to be studied.

Ironman

Thaddeus said:

Iron man, thanks for the diagram. I have this valve plummed the same exact way my hot air furnace is plummed. And that works fine... now, that said, is it possible that I have them both wrong but the furnace coil is still heating properly?? Not sure... I did test the valve prior to installing it, the incoming line is fed directly to the valve and the "non call" position is exiting from the bottom.

The diagram can't be wrong. If you'll map out the flow, you'll see that. I've put hundreds of 3 way valves in and all of them are the same: the center port is the "Common" connection on American valves. That's Taco's drawing for your valve.

Regarding the piping: you don't need another heat exchanger to integrate different flow rates between two loops. That's the function of primary/secondary piping as shown in the diagram.

The concept may be new and strange to you, but it's something we use and design with every day. Do a search for p/s piping or hydraulic separation to obtain a better understanding.

Thaddeus

Iron man, I didnt say the diagram was wrong. I'll need to study the other valve installation to confirm. But I think your diagram proves me wrong. And as such I need to rectify the issue and then move to the next issue which is the current issue. So thx. Honestly the valves did not come with a diagram just warranty info. So I had to figure it out myself by calling a few people at the time I installed the coil into my furnace. It looks like I made errors. But I'll check the furnace tonight.

On that note, if the first 3way valve in the circuit is installed wrong but still functioning, would that reduce my water flow or is it the same either way?

Ironman

It's gonna drastically reduce your flow because it's only designed for 3.3 gpm.

For example, IF your house needs 80k btus to heat it, then you need 8 gpm @ a 20* delta T. You've got two 3 way valves rated at 3.3. Then you have the equivalent of 250' of 3/4" pipe. A 100' length of 3/4" is good for 4 gpm max. Then you got the resistance of your heat exchangers. You'd be doing well to 3 gpm through all that, probably it's less.

Long, under-sized piping runs and multiple components piped in series is very common mistake with ODWB installations. We see it regularly since we sell and install them and get calls to fix what others have done.

Regarding pipe sizes:
1/2" = 1.5 gpm
3/4" = 4 gpm
1" = 8 gpm
1 1/4" = 16 gpm.
These are at 100' equivalent pipe length. Going longer than that requires increasing the pipe size.

I'm gonna attach a mark up drawing showing a closer detail. You need to remove the 3 way valves and pipe the furnace and drier as secondaries off the boiler loop.



The circled triangles are the circulators. The secondary loops go to the appliances. That means that you would do 2 sets of closely spaced Tees; one for the furnace and one for the drier. A separate circulator on each secondary. The primary loop is the ODWB.

Thaddeus

Iron man, thx! Albeit I am now worried about pipe size and my future plans such as a heated walkway... the thermopex I purchased was $14/foot and I trenched it and secured it before placing the ODWB. so replacing it would be painfull both in labor and cost.

May I ask your thoughts on heat storage? I've heard/read of people talking about building insulated cement heat storage in the ground. Haven't actually seem it in practice. Just wondering.

BTW, what ODWB do you sell?

mattmia2

Hmm, how can i put this without talking specific cost...If you buy the oxygen barrier pex, insulation, and drain tile separately and assemble it yourself it costs far less than the pre-made product.

mattmia2

But the primary/secondary setup lets you keep that loop at a lower flow with a higher delta T to probably get enough heat transfer over your smaller buried piping.

mattmia2

Read this:
https://www.caleffi.com/usa/en-us/technical-magazine

or get a copy of this (a used copy of an older edition is fine for the basics):
https://heatinghelp.com/store/detail/modern-hydronic-heating-for-residential-and-light-commercial-buildings
Haven't I seen John Siegenthaler post on here...

Don't make the mistake I did which was to try to save cost on circulators and do it with zone valves and end up spending about the same to make the zone valves work...

Solid_Fuel_Man

The best heat storage is located inside the building (in the basement maybe). I like pressurized storage, cheapest way is used 1,000 gallon propane tanks. The killer is expansion tanks to deal with the large volume of water.

Your OWB is unpressurized, do you run the entire system unpressurized? If so you can still use a propane tank, just need more chemicals to treat the larger volume of water.

I (and others) can elaborate more if you'd like.

Ironman

Thaddeus said:

Iron man, thx! Albeit I am now worried about pipe size and my future plans such as a heated walkway... the thermopex I purchased was $14/foot and I trenched it and secured it before placing the ODWB. so replacing it would be painfull both in labor and cost.



May I ask your thoughts on heat storage? I've heard/read of people talking about building insulated cement heat storage in the ground. Haven't actually seem it in practice. Just wondering.



BTW, what ODWB do you sell?

Heat storage with a used propane tank is viable, but it may be cheaper and easier to spend $1500 on a second set of underground pipes. 1000 gal of buffer is helpful in getting a long clean burn of wood.

We sell Heatmor.

GroundUp

I must point out that there is no such thing as 3/4" Thermopex. They have 25MM, 1", and 1-1/4". The 25mm is slightly larger than 3/4" nominal pex, and 1" is a little over 3/4" ID so which one you have will be a big determining factor in your flow rate. You can certainly decouple the loads from the OWB and maintain independent flow rates, but with only 3-4 GPM the return temp to the OWB is going to be dangerously low with even your current loads, so snowmelt is out of the question. If you actually have 1" nominal Thermopex however (the outer jacket is approximately 4.5" versus 3" for the 25mm), that drastically changes things and would raise your flow rate closer to 6 GPM including the zone valves. Central Boiler can NOT tolerate low return temps with their urethane foam insulation, it causes condensation outside the water jacket which breaks the bond of the foam and traps the condensation between the foam and steel, rotting it out in short order. I am actually going to swap out a 5 year old 5036 tomorrow, that is leaking profusely from this exact scenario and junked a 3 year old 750 last weekend with the same problem- and no, CB will not warranty a stove without a thermostatic valve in place for boiler protection. Proper flow through the OWB and underground lines is the number one design key for these systems. If you do in fact have 1" lines, I would be inclined to recommend a P/S setup and shorten that primary loop as much as possible to keep flow rate as high as possible, and do away with the 3 ways. At the very least get rid of the one for the dryer. Your sidearm won't have much pressure drop nor will the W2A in your furnace, but those 3 ways are killers.

Thaddeus

Groundup, thank you. I will measure the Thermopex today. I have been using 3/4 pex fittings that's why I say I have 3/4 Thermopex. I do in fact have the thermostatic valve installed properly. The 2 biggest reasons I bought CB was the internet connectivity and monitoring, and the 25 year warranty. So I do not want to do anything to violate the conditions of that warranty.

So you say my 3way valve on the furnace is ok. Can I keep that and do what Ironman days with the circ pump for the dryer?

Thanks for the information on CB, mine is 4 years old. I've maintained the anti corrosion and ph of the water properly and cleaned it regularly. It so far is running good. Being an aircraft tech and a Millwright I am at least prone proper maintenance and care of my investments

Thaddeus

Here is the 3way in the furnace

Thaddeus

mattmia2, thank you. I glanced over the links you sent me, lots of info so I'll be reading that for sure.

Thx for the advice because I was thinking 3ways was the way to go because my system is unpressurized and continuous loop. But with everyone's advice here, I have to start looking at circ pumps

Thaddeus

Please forgive my rough schematic drawing skills but this is the current configuration of my system

Solid_Fuel_Man

You already have a good piping layout to put your dryer on a secondary loop as @Ironman suggested. Keep that ball valve between the Ts open and add a dedicated circulator for your dryer loop. I've attached some edits to your loop.

I'd also suggest doing the same with your furnace HX. You can add some closely spaced T's and a dedicated circulator. This takes all the 3 way valves out of the loop and may help with flows.

Solid_Fuel_Man

Ironically, if you put both the dryer and furnace on secondary loops, you can get rid of the 3 way (bypass) valves.

Ironman

I don't recommend putting a valve between the closely spaced Tees. We're not trying to force water from the primary loop into the secondary. The secondary circulator will extract as much flow as necessary without disrupting the flow of the primary. This is the whole principle of p/s piping: two separate flow rates can be maintained while mixing water.

Example: 10 gpm going through primary; secondary could extract 2 gpm while 8 gpm passes between the closely spaced Tees. The secondary returns 2 gpm and thus the primary maintains 10 gpm.

If you put a closed valve between the Tees, then you accomplished nothing more than what you have now: you're forcing all the flow through the dryer coil which is restricting it way below what it needs to be. The dryer coil only needs about 2 gpm to function properly. The ODWB loop should be moving at least 10 gpm.

Again, please do some research on "hydraulic separation" and "p/s piping" which is the most common method of achieving it.

If you need a means of purging air from a secondary loop, then put a shut off valve in the secondary's return line just before it connects to the Tee with a boiler drain Tee'd in just upstream of it in the secondary.

Zman

These OWB companies are the worst. They are happy to sell you a 250,000 btu boiler with 50,000 btu pipe. Then they give nothing but bad advice on how to tie in the loads.
The heat exchanger you bought for the dryer may be rated for 110,000 btu, however, without more airflow, it will never put out as much as the original electric coil.
As for the rest of this, the lack of btu's to the house is the elephant in the room. You may be able to make it work with the 3/4 pex to the boiler but you would have to do some careful math and run pretty high delta t's.

Thaddeus

Groundup, I measured a piece of the Thermopex not currently in use but from the coil I bought. 21mm (3/4") picture attached. So i don't have the necessary flow to make my project work. As Zman stated, i simply do not have the BTUs to spare.

What I do have tho.... is a large enough boiler to ultimately achieve what I want to do. It has two unused 1" supply ports. One will be for the garage next year and the third I can use for heat storage. I just have some work in front of me.

Thaddeus

I think this is the end of this thread gentlemen.

I would like to sincerely thank you all for your thoughtful advice, experience, expert knowledge and input.

I know now that for my project to work it needs more flow and more consistent BTUs.

I am going to start another thread asking about heat storage. I kinda liked the idea about the propane tank.

Thank you again to all of you who contributed.

Thaddeus

Solid_Fuel_Man I started another discussion about heat storage. I sincerely would love to hear about what you where speaking of previously

EYoder

In case others reading are interested, my dad made one using a smaller coil with a squirrel cage booster fan pushing into the dryer. This raised the cfm's enough to get the drying time to about twice as long as the electric. Without the booster fan it was miserably slow. It wasn't a water flow issue, it only needed a couple gpm, but the low temps required a lot more airflow. He got his air temps to about 160F (way lower than electric), I don't think there's a reasonable way to get it hotter with a hot water system.

Solid_Fuel_Man

Consider a gas or electric dryer cycles the elements or burner at an exhaust temp of 180 degrees. The elevated temp evaporates water in clothing much faster than a water to air heat exchanger can ever get unless you are running super heated water or high pressure steam. Neither one is safe in a home.

mattmia2

You could potentially do it by heating the whole drum, not just the air.