Questions about radiant heat system

[GLyford]

Dad's controller had a separate controller input and pump for the stove, at least, so didn't need to wait for the panels to warm up. There was a thermal sensor at the stove.

The exchanger was of the stainless box variety, and was actually his 2nd, the first wasn't stainless and eventually leaked.

It all got ripped out when they redid the kitchen, and the house's new owner has taken down the panels as well.

 

[mx842]

Raspy..........you posted a suggestion over on I think it was #47 about how to pipe the HX and water tank. I think I'm a little confused about how to do this. I know I have stated that my system is a two piece setup and may be part of my own confusion. I guess it would be better to say this is a three piece setup rather than just two, the HX, the old water heater tank, then the supply loops to the manifold. I guess I was thinking of the HX and the water tank as one piece because I can isolate those two parts by full flow valves from the rest of the system. My original plan was to somehow get the water that was in the 30 gal water heater up to around 175 to 180 degrees which I still think I can do then somehow mix my return water from the loops with the hot water in the water heater tank to get it down to a more desirable temp for the floor.

I figured out that the HX holds just a tad over 6 gals and the storage is 30 gals.

My confusion with your suggestion is where do I tie in the water in and out of the HX. I like the idea of the top of the tank being used as an air and pressure tank but I already have one of those in the system along with a couple air bleeders at different points in the system. I'll probably be able to get back on this by Wed or Thurs so hopefully I'll have a better understanding of what to do when I get back at it. Thanks!!!

 

[mx842]

I haven't had time to post a lot for the past week or so but I think Im getting close to getting this thing up and running. I spent two days last week re-piping the system only to come up short and having to do it all over again. I had rebuilt my Taco 100 series in line pump that was leaking and had it plumbed in at the manifolds. I guess I should have checked it before I fired up the boiler but I didn't. Anyway, I fired it up and waited for the temp to come up to 150 coming out of the HX and turned on the taco 007e I had just bought to circulate water through the tempering tank and the HX. By then hot water had already been flowing into the tank through the pump so the tank had already warmed some. Everything looked ok so I threw in some more wood and once the tank had gotten to about 160 at the top of the tank and I had 135 degree water coming out the bottom line going back to the HX I went over to the manifold room to cut on the circulating pump for the loops. By then I already had warm water at the pump.

My plan was to cut on this pump and let it run for about 10 minutes just to see how much how much that cooled the water in the storage tank then go from there. It all went down hill from there. When I plugged in the pump water went ever where. Not only was water shooting out the weep hole it was also leaking out of one of the flange gaskets and the flange where the pump housing bolts up to the bearing housing. I fixed the flange gasket pretty quick and adjusted the spring coupler which slowed down the leak out of the weep hole. water was still pouring out of the pump housing and there was nothing I could do but pull it apart and try to fix it. I pulled it apart and everything looked ok, nothing out of place so I put it back together and tried it again but it still leaked like h@ll. By now the water in the boiler room was flirting with 220 degrees and there were some weird noises starting to come out of the storage tank. I ran back over to the manifold room and decided to put that old 100 series pump that i had replaced with this newer leaking pump and once I changed out the pumps and turned it on nothing happened. The leaking pump had tripped a breaker and by the time I figured that out and got the pump running the storage tank temp gauge was passing 240 and was really clanging and banging. I had put a mixing valve on between the water tank outlet and the supply pipe to the manifold and no matter how I adjusted it nothing would come out. I guess I had an air lock somewhere that was blocking either the supply or return line from the manifold. At that point I tried to get as much of the burning wood out of the stove as I could but it was too hot so took the water hose I already had laying on the floor and misted the fire until it had cooled down enough to be not putting any more heat into the water as there was already there. I cracked the fill valve that I had put in the top of the tank to vent air as I was filling the system. This let out let out some of the steam and pressure that was in the top of the tank and then left. The tank was making all sorts of different noises and it did this for about an hour as it was cooling down.

I removed the mixing valve from the system and changed a couple other things since and hopefully will be able to try again soon. I had flushed the whole system and when I filled the system the last time after I had checked for leaks and added conditioner the did a dry run to see how things looked. I had a hard time getting all the air out of the system and even then I still cant get the flow I want through the manifolds. The flow gauges hardly move at all and are reading only .2 gpm. I was hoping for at least 1 gpm through the loops but it don't look like either of these 3 piece pumps has the b@lls to do it or I still have air somewhere in the system that holding everything up.

 

[Raspy]

Exciting times. Good lessons.

Get that tempering valve out of there. A simple bypass will serve you better because it's not so restrictive. You need flow! Find out why the spring drive pump is leaking at the mechanical seal (is it an old worn out pump?).

Look at the manifold and figure out how to adjust the flow. This is VERY important. Don't assume anything, look at it carefully and figure it out. You must have the loops open and flowing correctly. You may not have the adjusters open as the flow is too low and your loop lengths seem right.

Don't buy any more pumps until you know what you are getting and why. The 007 should be fine on the HX, but it's a very low head pump. The floor needs a higher head than the old spring drive model Taco. It's probably OK, but a Grundfos 15-58 or a Grundfos 26-64 would be nice. A Grundfos 26-99 three speed is the Cadillac, but it's a very expensive pump.

Carry on. You've seen the effects of panic overheating with a wood fired system. Now, wait till you have a power failure and a big fire , while you are not paying much attention to the system. Eeek!.

Looking forward to your next installment.

 

[Raspy]

mx,

Regarding plumbing the HX to the water heater: The HX is horizontal and it doesn't matter which line is in or out, but plumb the out to the top of the tank with as little restriction as possible and an up-slope all the way. This will help the thermosyphon affect and, during a power failure, will circulate some water. Assist it with a pump to get the maximum BTUs to your tank. The 007 should be fine for this duty. Use the 3/4" port on the side of the tank near the top, typically, this is the pressure relief port, as the return from the HX.

TEE the output to your floor pump at the same upper side outlet of the tank, where the HX line ties in. Simply screw a brass or galvy tee on a short nipple sticking out of the tank fitting and plumb each line to it. Return the floor loop to the cold inlet on top of the tank. Pull the dip tube out of the cold inlet fitting and set it aside. Put an automatic air vent on the hot outlet. If you insist on an auto fill system, tie it in at the cold tank inlet with another tee.

I suppose the best flow pattern would be to place the HX pump on the bottom line pumping away from the tank toward the HX. Place the floor on the line from the upper side fitting tee, pumping toward the floor. Return it to the cold top fitting as mentioned.

All of this will tend to move air to the tank and get it out of the system. It will not inhibit thermosyphon.

Install tees on the supply and return lines to the floor. One just before the pump, which is pumping toward the manifold. And one after the manifold on the return line to the tank. Connect these with a 3/4 pipe and a ball valve. This will allow you to throttle a bypass and control the supply temperature somewhat. It also reduces restriction in the floor loop. You'll still get all the available energy to the floor, but you'll avoid scalding temperatures and you'll help the pump purge the air. A bit of manual adjusting of this ball valve will get you find the right setting. Probably 1/2 open for starters.

Install a ball valve on the return line to the tank from the floor. Preferably, near the tank. Then tee in a hose bib right before this valve (on the manifold side). You can then close the valve and open the bib to manually purge the floor loops. This will help you get it all started and force out any air.

Again, look carefully at the manifold to make sure you have the loop restrictors fully open. Very important.

 

[quicksandfarmer]

You're on the right tract with experimenting and observing, it's too bad your experiment was ruined by factors that really didn't have anything to do with it -- although it sounds like exciting times!

The reason you need to experiment is you'll only know if you need a higher capacity pump if your return water is coming back stone cold and your boiler water isn't getting too cold. If your return water is coming back warm, more flow won't do much for you. If your boiler water is dropping below an acceptable level, more flow will just take more heat out of the boiler. Or put another way, you want to increase the flow until you hit one of two limits of your system: the ability of the floor to disperse heat, or the ability of the boiler to provide heat. Once you've hit either of those limits more flow does you no good.

 

[Raspy]

you want to increase the flow until you hit one of two limits of your system: the ability of the floor to disperse heat, or the ability of the boiler to provide heat. Once you've hit either of those limits more flow does you no good.

Well, and a couple of other factors: He needs enough flow to evenly heat the entire floor such that it feels warm everywhere. This is why the floor circulation is entirely separate from the heat exchanger circulation. Heating the floor is different than the ability of the boiler to provide heat. Increased flow evens out the experience and it increases the floor's capacity to accept the energy, but it has little to do with how many BTUs are being delivered from the heat source. He needs to EXCEED the ability of the floor to disperse heat. This means the floor will warm up because it is past it's equilibrium with the surroundings. This is what makes floors "greet' us as we step on them, we have added more energy than they are delivering. Then, after the heat source is cut off, they coast down and deliver the excess over time.

These factors give maximum comfort, maximum stored energy, the best stability and the most even heating to the room. Hopefully, the BTU output of the heat source is sufficient to not only carry the heating load, but make the floor feel comfortable in the process. Even better is having enough power to warm it up in a fairly short time. This allows us to program the heating which brings in other desirable features. Of course, in this case, where it's wood heat, the fireplace needs to be as small as possible to do the job and programming is not really an option. That's why, again, that design is fun and always different. So many things to consider in each case.

 

[quicksandfarmer]

Of course, in this case, where it's wood heat, the fireplace needs to be as small as possible to do the job and programming is not really an option.

The other way to look at it is the way you program a wood stove is to put another log on!

 

[Raspy]

Yeah, we need a thermostat that throws another log on the fire in the middle of the night. I'd love that!

 

[CalG]

Call me stubborn, but in reading, I still suggest to shut down all floor circuits but one, and try to work out the system that way.

Why> Now the flow is too low. Shut down the size of the system, and perhaps the flow can be managed by valving.

Simplify,simplify,simplify!