I plan on using my house as the dump zone. It's a ranch with one big loop in it. It is fed from the oil boiler via a 1" down the center which then splits to each side going to the baseboard heaters then back to the boiler. So if I tap into that 1" line will I see adequate thermosiphon action with all the ups and downs that connect the baseboards together? Also I have a pile of 3/4", would that size pipe move enough hot water to do the job or is it necessary to use 1" to tie that in? Will a thermosiphon move through a swing check?
Another dump zone question
- Thread starter cheapsx
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cheapsx said:
My experience is that thermosiphoning will find a way to happen when you don't want it, but will stubbornly refuse to work at the least excuse when you're counting on it. Any resistance at all will have an effect on flow, and I expect that a swing check would be a problem. The 'ups and downs' represent a barrier that has to be overcome by having hot enough water at the start to push all of the cold slugs uphill. In that scenario, you'd probably get no flow at all for a while, then suddenly get normal flow.
As usual, I have no actual experience with the topic, so we'll have to see if anyone who knows what they're talking about will chime in.
In the meantime, here's a chart showing 'cold lock' in my thermosiphoning solar panels. The temp sensor (blue line) is up by the storage tank. At about 7:30, the panels start to heat up. The panels have to get hot enough to push all the cold water in the buried lines up and through the heat exchanger. It takes from 7:30 until about 10:00 before all the cold water pushed through. From 10:00 on, the panels are heating storage.
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I should have mentioned that the boiler is in the cellar of the house. I can pitch up to where I tap the 1" line and the return will pitch down to the boiler. The swing check is at the lowest point in the system which is near the boiler inlet. Having said that I hope it works well enough with that hot water heading directly up hill. I am hoping will be enough to get it going fairly quickly. I could put the dump zone on the basement ceiling like many do but I don't think it will need to work that often and I would rather get the heat upstairs. The upstairs has 67' of baseboard and I could most likely only get 24' - 30' in the cellar. I suppose I should get a zone valve with the largest flow rate possible too, correct?
cheapsx said:
Thought about this on my own system, I have about the same amount of baseboard on one loop. I don't think it will work to well with the check
but I could be wrong. Why not use a zone valve on the return as well? I thought of using 2 automag valves and coming right off the boiler to my
baseboard loop. When the power goes out both valves open, one feed and one return, to each side of baseboard loop.
Singed Eyebrows
Minister of Fire
I can't comment on the swing check. My heating loop is all thermosiphen though & even considerable restrictions still allow flow as the Mod says. Randy
I just went and did a little experiment. Oil boiler up to 170*, no call for heat, so I opened the main ZV to the house loop. It took a good 10 - 15 minutes to get going but when it did it was working. The boiler temp wasn't exactly falling very fast but it did work. It was also working through a non checked circulator pump. I have to think it would work through that swing check but I am afraid it will be to slow to start. I can push it to half the house if that would make it get moving quicker, but that would only give me 24' of baseboard. I am going to be using 500 gallons of storage so I am thinking this will be most important for a power outage situation. Usually we are here to get the generator going right away and don't intend on burning when I am not here but I am planning for the worst case scenario. For example if we had a fire going and I stepped out for something or got called to work and the power were to go out, I want the wife to be able to handle it and not have it blowing out the relief on her. Does the set up of open baseboards in the ceiling work quicker in that power outage situation?
sdrobertson
Minister of Fire
cheapsx said:
It would be quicker and I would think safer. One small air bubble in the wrong place and even if the circ would push water past, it might be enough to slow down the thermo siphon. I'm not saying one or the other wont work, but this is going to be for the worst case scenario, so I would go with the simplest and most worry-free way possible.
kabbott said:
Two auto mags is how we pipe gravity loops when we're using an existing baseboard zone (or radiator) for the dump. The spring check in the near boiler circulator and the Termovar prevent return water from getting back to the boiler on a gravity feed... and one additional automag is less expensive than piping up a dedicated baseboard zone.
cheers
OK so if the safest simplest way is to get in in the cellar next to (above) the boiler, so how much do I need? I know 10% seems to be the rule of thumb but is a little more better? I have 20' of .75" I can relocate and add to that if need be. The boiler is an old energy mate so I don't know BTU's. I am guessing about 125,000. Does the 10% rule still apply for when the power fails and it's working on thermosiphon too? Speaking of power failure is .75" automag and pipe adequate to flow enough water on it's own for this to work or is it necessary to go to the 1" automag and piping to get it done?
cheapsx said:
10% on a non gasification unit should be more than adequate... there is no 2000° refractory to keep dumping heat into the vessel after the power goes out. Make sure that your draft controls work properly, so that if the power goes out, the draft is closed.
cheers
If I were to use a cast iron radiator what would be an appropriate size for this dump zone to get out the 10% requirement?
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