Wetback - Radiators - Gas Instant

Forums › Home Workshop DIY › Wetback - Radiators - Gas Instant - Heating System DIY

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153 posts

Master Geek
+1 received by user: 7

#1095236 24-Jul-2014 21:20

Radiators arrived.
Beautiful, really happy with them.
Not so happy that I got a puncture on the way home with them in the boot of the car, so had to unload them all on the side of the road to get the tools out to drop the wheel and change it. My poor back. Damn they are heavy.

Anyways...

Modified the drawing somewhat to illustrate it a bit better.
Took out all the fancy stuff which may have been confusing the picture somewhat.

The pipe to the sight glass still confuses the picture a bit, as does the safety bypass through the solenoid, so I have dotted the safety line since it is not the normal flow path and only there for safety purposes, so really it can be ignored for normal operation. Flow switch only there for the solenoid too, so that can be ignored too.
Sight glass isnt really where it would go - all the way out there, but just to illustrate the points it would join on to really, to show the level in the tank for the purpose of manually filling it or topping it up. Added the manual tap and feed to illustrate that. tank would be full right up and up the vent a bit so all the pipes are full. Vent water would raise and lower as the temperature of the water heated and cooled.

Got the 25L hot water cylinder, it has both inlet and outlet on the top of it, which is why I have them there in the picture. That then warranted a little air bleed on the incoming just to be able to get the air out of that line. Most likely just use a T and end cap, and crack that to get rid of any air when setting it up. More than likely it would push it through into the tank and out the vent anyway, but its there for now.

We set up a bit of a test here with odd bits of pipes, and filled the tank up and connected the pump, and fed it back into the tank, and had the vent on there etc. works really well. Tank under no pressure at all due to pump tanking and giving from it at the same rate. Tank can essentially be ignored really and just thought of as a 'Fat' pipe which has a volume of water in it. filled it right up to the top of the vent so we could see it and started the pump, and away it went. Definitely pumping water and the level in the vent stayed nice and still. Very happy with the tests, apart from getting freezing cold hands as it was about 10pm last night and playing with water in the cold evening isn't much fun.

Heres the diagram anyway.

If its too small, try loading it directly: Proposed Idea
Again, comments very welcome.

WanaGo

Hammerer

2480 posts

Uber Geek
+1 received by user: 802

Lifetime subscriber

#1095283 24-Jul-2014 22:41

I'm not as confident as you in relying on manual refill particularly if the tank outlet for the thermosyphon is from the top rather than the bottom.

Anyway, I hope it runs perfectly. I'll be interested to hear how well it works.

WanaGo

153 posts

Master Geek
+1 received by user: 7

#1095304 24-Jul-2014 23:38

Yeah, that is something we have to work through. Unfortunate that our little tank has 2 top ports.

Ill give this some thought, and maybe even look at getting a different tank. Hopefully we can figure out a way this one can work though. Else install another port on it.

Will keep this thread updated.

WanaGo

Aredwood

3885 posts

Uber Geek
+1 received by user: 1749

#1095913 25-Jul-2014 23:13

A few things you should change. Make a 3rd pipe connection into the side near the bottom. Just remove the element and use the hole that it used to thread into as a pipe connection. The thread is 32mm just get a brass reducing bush to change it to the size you want. Run the outlet pipe from the wetback into the element connection. As the wetback outlet pipe must always run uphill from the wetback outlet to the vent pipe. To prevent an air lock or a steam trap from forming. Use the pipe that is the tank inlet in your diagram as the tank outlet. And the connection that the vent pipe is connected to, use only for the vent. If you don't do these things you will have alot of issues with air locks. Hope those radiators have air bleed points on them. As if they fill up with air, the water will still flow but they will be noisy and won't put out as much heat.

And myself - Have a radiator central heating system that uses a home made boiler that burns waste oil. Also heats my hot water and spa pool. Have plans to make my own HRV style ventilation system that preheats the incoming air. And modify a clothes dryer to run off the central heating as well. This system has been my main heating and hot water system for approx 4 years now. The boiler system combined with solar hot water panels means that I only need to use the electric element in the hot water cylinder for only a day or 2 each year.

WanaGo

153 posts

Master Geek
+1 received by user: 7

#1095917 25-Jul-2014 23:44

Thanks for the input, good information.

That is a very good idea to put the wetback inlet into the element hole, and that should solve the problem mentioned above.

We were thinking of putting a little open air container/trough with ballcock/valve on the vent pipe line, with mains water. This will then keep the system topped up automatically and keep the water level right where we want it, which should solve that side of things too. Gets rid of the need of the sight glass too as we will know exactly where the water level is. Were trying to figure out how we may be able to use an Ajax, but the pump just screws all of that up with its negative pressure behind it and it would fool the Ajax into thinking it needs to apply more water I think. Best to stick with the ballcock.

Yes all radiators have air bleeds on them already.

Very handy info, thanks very much.

We were thinking that we could utilise the element in the tank to get the system started with a boost, however changing it to use the incoming on the element hole removes the ability to do that. It wouldn't be terribly efficient however would potentially take an hour off the heat up time, or help to maintain the heat if we were to go out for a few hours as the fire wouldnt last that long. Could dial up the element to run for a hour or something for example. If we left the diagram the same, but replaced the air bleed pictured to be one of those auto air bleed valves, would that help?

This is the new diagram I was working on today (havent taken into account what you said above yet). Let me know your thoughts.
Since the water level is now dictated by the header tank, the line into the tank should never get air in it, so the bleed valve would only be needed at setup time or after a fluid replacement etc. It then essentially makes the tank and header tank 1 vessel, so the incomming from the radiator is therefore actually half way up the 'tank', rather than in the top as it is without the header tank. I think this could actually solve that problem too...

Most likely have the header tank off to the side and still vent out to the roof, but not sure. May not be needed as the header tank is open with a loose lid or something.

Thoughts?

Thanks

Idea 6

Direct Link to make image bigger: Next Proposed Idea

WanaGo

153 posts

Master Geek
+1 received by user: 7

#1095924 26-Jul-2014 00:30

Here is the diagram changed to take into account your idea of the Element hole being the incoming.
I think I like this idea the best.

Notice I have removed the solenoid too. I am going to make the closest radiator to the fire not have a shut-off valve at all, so it is always fully open, so that is the safety path.

Input welcome.

Direct link: New Proposed Idea

WanaGo

Aredwood

3885 posts

Uber Geek
+1 received by user: 1749

#1095954 26-Jul-2014 01:19

Don't bother trying to include the electric element anywhere. If you need backup heating just put electric heaters in the rooms that require it with thermostats set to a low temp. So the electric heaters will only run if the rooms get too cold.

Since you are now including a header tank, Just put a T junction in the wetback inlet pipe just before the wetback, and run a pipe from the header tank to this T junction. Make sure this pipe always slopes up to the header tank. If the pump fails, Steam will go from the wetback up to the cylinder, out of the vent pipe. And water will be supplied direct from the header tank. Instead of having to rely on flow through the radiators, or electronics, or moving parts to keep the system safe. The top of the vent pipe will need to be about 2m above the top of the header tank. Also there is lots of air dissolved in water. The first time you get the system up to temp all of that air will form bubbles. And will cause air locks anywhere it can. Recommend using 20mm or 25mm copper for the pipe between the wetback and the cylinder. And copper for the vent pipe as well. Time spent designing and building it so it will automaticly purge out any air is well worth it. Otherwise it will cause breakdowns at inconvenient times.

If I have to do a drain and refill on my system, It will keep burping out air for almost a week afterwards. Also make sure your header tank is big enough. The water will increase in volume between 1% and 2% when it heats up. And decrease again when it cools down of course.

WanaGo

153 posts

Master Geek
+1 received by user: 7

#1096133 26-Jul-2014 14:15

Thanks again for this info, very informative

Aredwood: Since you are now including a header tank, Just put a T junction in the wetback inlet pipe just before the wetback, and run a pipe from the header tank to this T junction. Make sure this pipe always slopes up to the header tank. If the pump fails, Steam will go from the wetback up to the cylinder, out of the vent pipe. And water will be supplied direct from the header tank. Instead of having to rely on flow through the radiators, or electronics, or moving parts to keep the system safe.

This part. hmm. So you are saying I need to run another copper down from the ceiling down the back of the flue to the wetback - from the header tank. Rather than the header tank being on the vent pipe line...?
I understand what you said and why that would be good, but a bit of a pain to have to run in our case.

The return from the wetpack currently does go via the pump, however it flows through extremely easily, there is very little restriction there at all as the pump is designed to allow flow when its not pumping. The temperature sensors will not be in the pipes, they will be strapped to the copper, so no issues there. Flow switch is part of the pump and has an extremely light weight spring flap, so essentially no restriction there. And the radiators should not offer much restriction at all, but time will tell.

I need to think about this a bit and see if it is practical to run another copper down to the fire. The beauty of the way it is currently pictured is there is 1 copper coming from the ceiling behind the flue, and the return comes from under the floor from the radiators.

Regards

WanaGo

Rcl

1 post

Wannabe Geek

#1106043 10-Aug-2014 20:43

Hi There, I just installed a radiator system off our metro rad fire. The radiators work really well see the image below.

The main pipe is 20mm copper with the branches off to the radiators in 15mm. The third radiator is part of the loop and has ball valves that stay open all the time, they are just there for being able to remove the radiator for servicing, if needed. We used two 2kw side boiler wetbacks (already have a wetback in the back for hot water). Hope this is helpful.

Aredwood

3885 posts

Uber Geek
+1 received by user: 1749

#1109349 15-Aug-2014 22:42

Nothing wrong with your system as long as you have the vent pipe rising continuously from the outlet of your wetback. This is so if your pump fails there won't be any steam traps in your vent pipe. And it will allow air to vent easily.

WanaGo

153 posts

Master Geek
+1 received by user: 7

#1109401 16-Aug-2014 08:56

Building our system today.

Will post some photos and update as to how it works.
Going to run the system in both pump working and pump failed states to see if there are any issues. Will report back how that goes.

Thanks to all who helped with input/information over the last few weeks

WanaGo

153 posts

Master Geek
+1 received by user: 7

#1110836 18-Aug-2014 21:25

System installed and running beautifully.

Tested in both pump on and pump off situations. It thermo-syphons fine just takes longer for the system to warm, so is good for a backup if the pump fails. But when pumped, the fire only has to be on 5 mins and the radiators are warming up.

I put a probe on the outlet of the wetback, and another on the inlet, to monitor temperatures just temporarily. With the fire running normally, not stoked up high, we get about 70 degrees C out of the wetback, and its returning about 55 degrees.
Have 2 'side backs' in parallel. Very very happy with their performance.
Still yet to stoke it right up and see if I can get it to 80C. If I can then I may be able to install another radiator, but I suspect it might be too much for our little fire.

We made the side backs out of 4mm steel plate, sandwiched together with a 4mm gap inside and a 'M' shaped set of baffles inside so the water has to do a M pattern from inlet to outlet to maximise time in the wetback.
After doing reading, we read that just a standard 1/2" copper tube style wetback can be inefficient due to the water in the pipe being hot around the outside of the pipe, but with a flowing cold centre. One way was to squash the round tube, which apparently increases performance quite considerably. We took this theory and applied that to steel plates instead, with a 4mm gap to simulate a squashed tube. I couldn't be happier with the result. 3/4" steel nipples welded on top and bottom, top one one a slight angle to encourage the thermo syphoning effect. Both side backs paralled at the back of the fire, and hot goes up, and cold comes in from under the floor. Top tubes always on an incline, no flat spots anywhere.

Have 2 radiators installed at the moment, 2100W and a 800W, and the fire doesn't seem any smokier than it was before. House was beautifully warm today, I just cannot believe the performance, I am really happy.

So the system takes only minutes to warm up, which is warming up the 25L in the tank up in the ceiling, and about 10L total in the radiators, and then pipe work, so maybe 50L max. Would be very interesting to try and calculate the 'kW' rating of these side backs.

Ended up doing the setup I pictured last, http://www.taktik.co.nz/geekzone/OpenLoop-Idea7.png

We used copper 20mm pipe from the fire up to the cylinder, and then copper out of the cylinder into the pump. out of the pump goes into 22mm plastic PEX tubing with speedfit type push fittings, down through a wardrobe and under the house. It then T's off into 10mm PEX into the radiators in parallel, and the 22mm is capped off. Out of the radiators in 10mm PEX, T'ed back into another run of 22mm PEX and long to the bottom of the fire, back into 20mm copper, through the floor and into the cold side of the wetbacks. All lagged.

Got it running on Sunday, so 2 days of running, no leaks and a nice toasty warm front of the house. Bedrooms don't have heating yet, but even those are benefiting from the larger radiator, which brings the fire heat a bit closer.

Thanks to all who helped with info and input, no matter how small. All positively impacted the end result.

WanaGo

Aredwood

3885 posts

Uber Geek
+1 received by user: 1749

#1110910 18-Aug-2014 23:58

Glad everything is working well. This is reminding me about the extra things I need to do on my system. Main ones being installing radiators in the lounge and bathrooms. As the temp in my room currently is 24deg while the lounge is 16deg. Also need to add active water temp management to my system. So the oil feed rate into the boiler will be varied based on how much heat is needed. And then I will be able to add thermostatic radiator valves to the radiators. So this problem won't happen again

That wall thermostat is not actually connected to anything, It is there solely to monitor the temp. It's not set to the correct time either.

Stan

929 posts

Ultimate Geek
+1 received by user: 183
Inactive user

#1110916 19-Aug-2014 00:13

WanaGo: System installed and running beautifully.

Tested in both pump on and pump off situations. It thermo-syphons fine just takes longer for the system to warm, so is good for a backup if the pump fails. But when pumped, the fire only has to be on 5 mins and the radiators are warming up.

I put a probe on the outlet of the wetback, and another on the inlet, to monitor temperatures just temporarily. With the fire running normally, not stoked up high, we get about 70 degrees C out of the wetback, and its returning about 55 degrees.
Have 2 'side backs' in parallel. Very very happy with their performance.
Still yet to stoke it right up and see if I can get it to 80C. If I can then I may be able to install another radiator, but I suspect it might be too much for our little fire.

We made the side backs out of 4mm steel plate, sandwiched together with a 4mm gap inside and a 'M' shaped set of baffles inside so the water has to do a M pattern from inlet to outlet to maximise time in the wetback.
After doing reading, we read that just a standard 1/2" copper tube style wetback can be inefficient due to the water in the pipe being hot around the outside of the pipe, but with a flowing cold centre. One way was to squash the round tube, which apparently increases performance quite considerably. We took this theory and applied that to steel plates instead, with a 4mm gap to simulate a squashed tube. I couldn't be happier with the result. 3/4" steel nipples welded on top and bottom, top one one a slight angle to encourage the thermo syphoning effect. Both side backs paralled at the back of the fire, and hot goes up, and cold comes in from under the floor. Top tubes always on an incline, no flat spots anywhere.

Have 2 radiators installed at the moment, 2100W and a 800W, and the fire doesn't seem any smokier than it was before. House was beautifully warm today, I just cannot believe the performance, I am really happy.

So the system takes only minutes to warm up, which is warming up the 25L in the tank up in the ceiling, and about 10L total in the radiators, and then pipe work, so maybe 50L max. Would be very interesting to try and calculate the 'kW' rating of these side backs.

Ended up doing the setup I pictured last, http://www.taktik.co.nz/geekzone/OpenLoop-Idea7.png

We used copper 20mm pipe from the fire up to the cylinder, and then copper out of the cylinder into the pump. out of the pump goes into 22mm plastic PEX tubing with speedfit type push fittings, down through a wardrobe and under the house. It then T's off into 10mm PEX into the radiators in parallel, and the 22mm is capped off. Out of the radiators in 10mm PEX, T'ed back into another run of 22mm PEX and long to the bottom of the fire, back into 20mm copper, through the floor and into the cold side of the wetbacks. All lagged.

Got it running on Sunday, so 2 days of running, no leaks and a nice toasty warm front of the house. Bedrooms don't have heating yet, but even those are benefiting from the larger radiator, which brings the fire heat a bit closer.

Thanks to all who helped with info and input, no matter how small. All positively impacted the end result.

Would be interested to see photos of the wetback itself to see how you did it on the little fire :)

WanaGo

153 posts

Master Geek
+1 received by user: 7

#1111608 19-Aug-2014 21:07

Here is a pic I found we took before we installed them. Dont look too closely at the welds, not the prettiest of things but they are water tight and tested to mains water, and we are using 1/10 that in the system.

Wet Sides before installation

They obviously go on each side of the fire with the vertical 'ribs' facing inward to attract more heat. They are sitting away from the walls of the fire by about 6mm or so and have a little foot which sits on the bottom of the fire. They are then fire cemented into the back of the fire to prevent smoke etc going out the holes, and plated with collars on the outside at the back to hold them in place. Used the upper hole that was designed for the wetback on this model, and then drilled 3 additional holes in the fire body, and plated up the other original one which wasn't in the right place.

Ill take a pic of inside the fire in the next few days when I do the next clean out and its not running.

Going to install another radiator tomorrow and just see how the system works. If its too much ill just turn it off, but at least I will know.

The remaining radiators ill put in next year if/when we decide to install the boiler system.
Waiting for a really cold day... if any more are coming, to really see what this is like.

Cheers

WanaGo

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