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cycler
10-09-2009, 06:48 AM
I am completing a complete DIY bathroom remodel and the final touch is to install a runtal hydronic towel warmer by patching it into an existing radiant heat loop in place of a section of fin-tube baseboard.

Although I'm comfortable with the piping part of it, I've never drained a boiler loop before and although I've read the theory, I'm wondering if this is something a reasonably competent DIY'er can tackle.

It's a Weil McLane boiler with four zones (I'd only be draining one zone) It's a closed system with what I assume is a bladder type expansion tank (big silver thing about the size of a propane canister). I presume it has an auto-feed valve, but I'm not completely certain.

My understanding is that I would shut off the boiler, drain the zone (from the return manifold side?) connect the radiator into the zone, turn the boiler back on, crank up the heat with the bleed valve open, and wait until water comes out of the valve, then shut it down (repeating with the other two radiators on the zone).

My main question is what are the potential downside. If I don't do it right are the consequences noisy and inefficient radiators, or will I ruin the boiler? The first I can live with fixing, the second, not so much.

jadnashua
10-09-2009, 07:45 AM
You want to ensure you shut the water off to the autofeed valve, assuming you have one. How much you drain depends on the height of the room you are dealing with and if there's anything above it as there might be some leakage from other zones. Assuming you have a good air extraction device, and how the pipes run, you may not have to do much more than turn the autofill valve back with the bleed valves open until you get water, then shut off the bleed valves and turn on and activate the pumps. If you can do that without firing the boiler, that works too. Run it long enough to get as much spitting as you can then close the bleed valves. If the system was designed well, that, along with the air extraction, will clear out the air.

Once you get most of the air out, fire up the boiler and check for heat at each radiator. You might have to rebleed things a couple times, as an air lock might prevent water from circulating.

See what the pros have to say...but, each system is a little different, and may have its own quirks depending on the layout and installation of the piping.

nhmaster
10-09-2009, 02:53 PM
The radiator should be piped using a mono flow tee arrangement so's not to restrict flow to the rest of the loop or at least not overly restrict it.

johnjh2o1
10-09-2009, 03:25 PM
I am completing a complete DIY bathroom remodel and the final touch is to install a runtal hydronic towel warmer by patching it into an existing radiant heat loop in place of a section of fin-tube baseboard.

Although I'm comfortable with the piping part of it, I've never drained a boiler loop before and although I've read the theory, I'm wondering if this is something a reasonably competent DIY'er can tackle.

It's a Weil McLane boiler with four zones (I'd only be draining one zone) It's a closed system with what I assume is a bladder type expansion tank (big silver thing about the size of a propane canister). I presume it has an auto-feed valve, but I'm not completely certain.

My understanding is that I would shut off the boiler, drain the zone (from the return manifold side?) connect the radiator into the zone, turn the boiler back on, crank up the heat with the bleed valve open, and wait until water comes out of the valve, then shut it down (repeating with the other two radiators on the zone).

My main question is what are the potential downside. If I don't do it right are the consequences noisy and inefficient radiators, or will I ruin the boiler? The first I can live with fixing, the second, not so much.

What type of heating system do you have? Your talking about radiant heat & copper fin baseboard. That's two different systems. To be able to drain just one zone you must have two valves, on each zone. One on the feed & one on the return. There are many variables in hot water heating. With out being able to see what you have it's hard to give you advice. If you could take a picture of the boiler and piping I may be able to help.

John

cycler
10-10-2009, 07:50 AM
Thanks for the responses.
I mis-phrased my original question. I was thinking "radiant" in terms of heat radiates from the hot water, not the low temp radiant heat that you run in pex tubing under floors. There is no low-temp radiant on the system (although I'd love to add some, it won't be with this boiler as I'm worried it would drop the return temp too much and cause condensation. The system is all copper fin tube that runs in the 160-180 degree range, and the runtal is designed to run at that temperature.

I 'm attaching photos of the 30" piece of fin tube I want to replace, and the boiler supply and return manifolds and the expansion tank and what I assume is the air extractor?

cycler
10-10-2009, 07:57 AM
Thanks for the response, NHmaster
I understand that monoflow tees are used for putting high resistance items like kickspace heaters, or items in parallel to other heaters. I would think that the resistance on the Runtal Radia would be pretty low (it's a bunch of parallel 3/4" tubes with 3/4" supply and 3/4" return), but I'm not sure where to find that information.
Also I was planning on putting it in series with the fin tube. If I put it in parallel with just a plain 3/4" pipe between the monoflow tees at the supply and the return, what would keep it from short circuiting and all the hot water just taking the low resistance path of going through the straight pipe and not the radiator?
I'm attaching a photo of the fin tube to be removed. I was going to cut the pipe at the supply side (right) pipe up to the towel warmer, pipe down from the other side of the towel warmer, to the existing return on the left. I was going to replace the existing bleed valve on the left with the bleed valve that comes with the runtal, but I thought I might also add a bleed valve before I go up to the Runtal as insurance.

johnjh2o1
10-10-2009, 08:58 AM
Thanks for the responses.
I mis-phrased my original question. I was thinking "radiant" in terms of heat radiates from the hot water, not the low temp radiant heat that you run in pex tubing under floors. There is no low-temp radiant on the system (although I'd love to add some, it won't be with this boiler as I'm worried it would drop the return temp too much and cause condensation. The system is all copper fin tube that runs in the 160-180 degree range, and the runtal is designed to run at that temperature.

I 'm attaching photos of the 30" piece of fin tube I want to replace, and the boiler supply and return manifolds and the expansion tank and what I assume is the air extractor?

From what I can see in your pictures it looks like you have a four zone one pipe system. Are there vents one each section of baseboard? Each zone is valved off so you can just drain the zone you are working on. You can just remove the one section of baseboard and replace it with your towel warmer. Be sure to install a new vent at the highest point on the warmer. After your done open the valves on the zone and vent all the baseboard on that zone. Keep an eye on the water pressure as you are refilling the zone. Some times if the auto feed is old they refill very slowly. If the pressure drops to low you will have to vent all the baseboard on the system.

John

cycler
10-10-2009, 09:34 AM
Yes, it's a 4 zone, single pipe system, and as far as I've checked there's a vent on each section of baseboard.
I'm still not sure if I need to use monoflow tees, as suggested above?
It doesn't really make sense to me, but better to do it right the first time..
Thanks for all the help

johnjh2o1
10-10-2009, 11:07 AM
Yes, it's a 4 zone, single pipe system, and as far as I've checked there's a vent on each section of baseboard.
I'm still not sure if I need to use monoflow tees, as suggested above?
It doesn't really make sense to me, but better to do it right the first time..
Thanks for all the help

I was under the impression you were going to remove the baseboard in the bathroom and use the existing tees. If not then you will need another set of tees in the main, one being a mono flow.

John

cycler
10-10-2009, 01:27 PM
Again, thanks for all the help.

I was going to remove about half of a run of baseboard. I considered removing the whole run, as the towel bar is almost enough BTU to heat the space, but not quite enough, and with tile floor, 3 exposed sides and flat roof above, I'd rather be safe than sorry. The pipe comes up from the floor on the supply side, the baseboard goes about 4'6 along one wall, turns a corner and then there's another 2'6" stretch along the wall, then there's a bleed vent/ elbow down into the floor. No tees visible above the floor. I can hope that the tees below the floor are monoflow. No way to get to them without opening the ceiling below which I'd prefer not to do.

Presumably if there wasn't a problem before, there won't be one now.

cycler
10-13-2009, 07:56 PM
Finished the installation, everything went more or less smoothly, except for a minor incident when the boyfriend couldn't figure out how to close the bleeder valve, and it sprayed across the room. That's what towels are for, and why I do the home repair work in this family. I've bled what I hope is most of the air out of it, will probably check it again tomorrow, although it's not making any noise, so hopefully it's OK.

Thanks for the advice, folks!