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Have we forgotten to make heat traps? (2012)

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Re: Have we forgotten to make heat traps? (2012)

#21

Post by Scoundreller »

Declanomous wrote: post #15
tomkinstinch wrote: post #13

Earlier quoted context omitted.

Hot water "hydronic" heating with radiators is very common in the US as well, at least among homes in the Northeastern US constructed before the 1960s. It's a shame more new construction does not use hot water heating in conjunction with central air for cooling because radiators are much quieter, more efficient, and better for those with asthma.

I live in a house with steam heat. Steam systems often get converted to hot water, but in general I have a few observations related to radiated heat. 1) Steam and other radiant systems don't deal with temperature setbacks well. They take FOREVER to warm up a house after a set back, so don't bother with a deep setback overnight, and if you are gonna turn down the heat because you are going to be gone for a while, expe…

> They take FOREVER to warm up a house after a set back, so don't bother with a deep setback overnight

This is incredibly true in intermittently occupied areas. Just heating the air is one thing. Heating everything around it just to get warm is another.

If you're in a private/semi-private office 9-5, having your own heater or window A/C gives you a lot of control and is incredibly efficient since you can turn it on/off with your work hours.

It will cycle a lot because the envelope doesn't change temperature much (eventually heating/cooling the air), but you reduce consumption a lot by not getting to the point of majorly heating/cooling the envelope, just the air (which is what matters unless a mattress is involved).

Re: Have we forgotten to make heat traps? (2012)

#22

Post by kragen »

thefourthchime wrote: post #3

Seems like something trivial to make with PEX these days. I have no idea if it's regular practice or not. The only downside I can see is if there was recent hot water, it might take slightly longer to reach the faucet.

Wouldn't it be better to make the heat trap itself with 45 cm or less of copper, then hook up the PEX to its output? Copper will last centuries in continuous contact with hot water, but I'm not sure PEX will.

Re: Have we forgotten to make heat traps? (2012)

#23

Post by 781 »

kragen wrote: post #22
thefourthchime wrote: post #3

Seems like something trivial to make with PEX these days. I have no idea if it's regular practice or not. The only downside I can see is if there was recent hot water, it might take slightly longer to reach the faucet.

Wouldn't it be better to make the heat trap itself with 45 cm or less of copper, then hook up the PEX to its output? Copper will last centuries in continuous contact with hot water, but I'm not sure PEX will.

I'm pretty sure a house is not expected to run centuries from now with present day electrical/piping systems.

It's a bit like people from 200 years ago debating what to make the candle holder from so that it lasts 100 years.

Re: Have we forgotten to make heat traps? (2012)

#24

Post by Declanomous »

Scoundreller wrote: post #21
Declanomous wrote: post #15

Earlier quoted context omitted.

I live in a house with steam heat. Steam systems often get converted to hot water, but in general I have a few observations related to radiated heat. 1) Steam and other radiant systems don't deal with temperature setbacks well. They take FOREVER to warm up a house after a set back, so don't bother with a deep setback overnight, and if you are gonna turn down the heat because you are going to be gone for a while, expe…

> They take FOREVER to warm up a house after a set back, so don't bother with a deep setback overnight This is incredibly true in intermittently occupied areas. Just heating the air is one thing. Heating everything around it just to get warm is another. If you're in a private/semi-private office 9-5, having your own heater or window A/C gives you a lot of control and is incredibly efficient since you can turn it on/o…

Yeah, exactly. I like to have it relatively cold at night, so with forced air I set the heat to come on about 15-20 minutes before I want to get out of bed, and turn off 15 minutes after I leave for the day.

With radiant heat, if I want it to be 55 while I'm sleeping, and 70 when I leave my bed, my heat will come on 2 hours before I'm going to get up, and the temperature will slowly increase over that time, leading to it being far too warm about an hour before I intend to get up. The heater turns off as the house gets up to temp, but the radiators thermal mass is such that they are still quite hot when I leave for the day, in effect heating the house long after I've left.

Furthermore, it's basically impossible to have zone heat with one-pipe systems, and it's much more difficult with two pipe systems. (This is less of a problem with hot water though).

With forced air, you can install active vents fairly easily, and while you still can't cut off TOO many of the vents at once, lest you cause too much back-pressure in the system, it is fairly easy to heat one side of your house or one floor of your house.

On top of all that, steam doesn't handle short-cycling well, so you have to accept a wider swing in temp than you do with forced air.

Re: Have we forgotten to make heat traps? (2012)

#25

Post by NeedMoreTea »

jetbooster wrote: post #9
mcmatterson wrote: post #4

I designed and installed a complete hydronic heating system in our house last year, replacing a conventional forced air system. It being the first time I'd ever done such a thing (and indeed, the first time I'd ever really been exposed to hydronic heating at all) I learned everything through reading (mostly the excellent idonrics series at https://www.caleffi.com/usa/en-us/technical-magazine ). I went really deep on…

That's interesting, as Hydronic heating is the standard heating method over here in the UK. Reason its not done in the US I image is we don't often ever need AC, so we only need to be able to turn the temp up.

Forced air was very briefly in in the UK. For a few - maybe as few as five - years around the early or mid 60s forced air was fairly commonly seen in new build houses and the type of small blocks that have 6 or 8 flats. By the seventies no one was putting them in new builds any more, and people were already ripping them out - or sealing up the vents - to go back to just a fire - though without a chimney it would have to be electric or gas, or to put in central heating or storage heat.

You will never find one of those houses still using it. Doesn't matter who built the house, where, when, what make of components or which fuel. Usually electric, but there were quite a few gas. Effectively all have been ripped out now. You might find evidence of ducting when rewiring.

Re: Have we forgotten to make heat traps? (2012)

#26

Post by leoc »

Declanomous wrote: post #15
tomkinstinch wrote: post #13

Earlier quoted context omitted.

Hot water "hydronic" heating with radiators is very common in the US as well, at least among homes in the Northeastern US constructed before the 1960s. It's a shame more new construction does not use hot water heating in conjunction with central air for cooling because radiators are much quieter, more efficient, and better for those with asthma.

I live in a house with steam heat. Steam systems often get converted to hot water, but in general I have a few observations related to radiated heat. 1) Steam and other radiant systems don't deal with temperature setbacks well. They take FOREVER to warm up a house after a set back, so don't bother with a deep setback overnight, and if you are gonna turn down the heat because you are going to be gone for a while, expe…

> They take FOREVER to warm up a house after a set back, so don't bother with a deep setback overnight

Steam and other radiant systems don't deal with temperature setbacks well. In the UK and Ireland people perform a deep setback (on their hot water system) overnight then usually just accept that the house will be cold in the mornings.

Re: Have we forgotten to make heat traps? (2012)

#27

Post by maxerickson »

mcmatterson wrote: post #4

I designed and installed a complete hydronic heating system in our house last year, replacing a conventional forced air system. It being the first time I'd ever done such a thing (and indeed, the first time I'd ever really been exposed to hydronic heating at all) I learned everything through reading (mostly the excellent idonrics series at https://www.caleffi.com/usa/en-us/technical-magazine ). I went really deep on…

I see the buffer tank is listed as a water heater? Is that hooked up as a backup?

Re: Have we forgotten to make heat traps? (2012)

#28

Post by gregmac »

gpm wrote: post #11
gregmac wrote: post #6

Earlier quoted context omitted.

My water heater has one made from PEX. From memory, I would guess it adds about 18". With 3/4" PEX at a relatively slow 1.5 GPM flow rate, that adds about 1.4 seconds to 'hot water delivery time', though that's not entirely accurate, because the loop itself has some heated water trapped in it.

Shouldn't you also adding the length of pipe/water you are preventing from being heated to that 18"?

I actually don't think so, because you end up with only a gradient of lukewarm-to-ambient temperature water, which you still have to purge in order to get actual hot water. Even if you're going for just warm water, you still have to purge some of it, then after a few seconds start continually adjusting cold until the hot water from the tank gets to you.

Re: Have we forgotten to make heat traps? (2012)

#29

Post by egypturnash »

jetbooster wrote: post #9
mcmatterson wrote: post #4

I designed and installed a complete hydronic heating system in our house last year, replacing a conventional forced air system. It being the first time I'd ever done such a thing (and indeed, the first time I'd ever really been exposed to hydronic heating at all) I learned everything through reading (mostly the excellent idonrics series at https://www.caleffi.com/usa/en-us/technical-magazine ). I went really deep on…

That's interesting, as Hydronic heating is the standard heating method over here in the UK. Reason its not done in the US I image is we don't often ever need AC, so we only need to be able to turn the temp up.

You’ve never been to the Southwest or the Gulf South, have you? There are parts of the US where you would die without AC. Seriously, like when you get a brownout on a hot summer day in New Orleans or Santa Fe or Dallas, people start dying. Mostly the elderly and kids.

Re: Have we forgotten to make heat traps? (2012)

#30

Post by m463 »

gxx wrote: post #19
LeoPanthera wrote: post #12

Earlier quoted context omitted.

UK hydronic systems usually use radiators. US systems are almost always under-floor.

I once had a new house with hydronic under floor heating - the worst heating setup I've every had - horribly slow to respond and expensive to operate. We turn down the heat to sleep and finally I just shut off the heat to the bedrooms and heated them a different way. Our initial experience with the system was even worse than it might have been. The people who installed it including the thermostats were plumbers and d…

I wonder if better PID tuning would help, maybe adding stuff like ambient outside temperature or weather prediction as a system input.

I know the nest thermostat does a lot of systemic learning and understands the outside temperature. (I'm not recommending that system, just that a little modern control theory might make things workable)

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