Author Topic: More or Most efficient hydronic heating basic unit? (natural gas)  (Read 12213 times)

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Offline jpanhalt

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #50 on: October 25, 2021, 09:35:24 pm »
As I stated in my post, the purpose of the bypass from return to source is "ostensibly" to prevent condensation in the boiler fire box caused by cold return water.  That is stated in the installation and service manuals.  Nevertheless, the flue gases are still cool, as the flue is barely warm.    The flue is about 16' to the sidewall exhaust in my home.  It is double wall stainless.  There was still a problem with condensate, so I installed a flue drain like this a few several years ago: https://www.ecomfort.com/Noritz-DT4/p31848.html?gclid=EAIaIQobChMI07XWh7_m8wIVw2xvBB1C2gIEEAQYAiABEgL8E_D_BwE

No more dripping from joints.  For the drain tube, I use a typical water-sealed S-bend to keeps flue gasses out of the basement.  I wish Weil-McLain or other identifiable source would issue some update notice to get rid of the bypasses. (plural)  Until then, I will have at least the one my boiler came with.  But, that is next Summer's project.
 

Offline themadhippy

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #51 on: October 25, 2021, 11:40:36 pm »
Quote
Only politics is limiting the mass adoption of heat pumps.
unless your in the uk were its the latest government environmentally  friendly buzz word and another way to divert £450 million to there chums whilst leaving a large percentage of home owners paying higher energy bills for a system that wont keep the house as warm.
 

Online David Hess

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #52 on: October 26, 2021, 01:28:27 am »
In heat umps, where does the heat come from, how is it made available?

Doe heat pumps use electricity to operate?

yes it requires electricity. It works just like a refrigerator except instead of moving energy from inside the  fridge it outside the fridge it moves energy from outside the house to inside the house

the trickery is that it takes less energy to drive the pump than the energy it moves, so if you spend, say, 1000J running the pump and it moves 2000J you get 3000J of heat for 1000J of electricity

The problem with heat pumps is that they are effectively pumping heat "uphill" and the colder it is outside, the taller the hill is.  At some point the temperature difference becomes great enough that efficiency is no better than electric heating, which is 100%, but a lot more expensive than lower efficiency heating using some type of fuel.  The other problem is that heat pumps are more complicated leading to higher cost and lower reliability.

One place were I lived in Southern California, with the associated mild temperatures, had a heat pump.  And one winter we had an unusually cold week where the heat pump was completely useless because the outside temperature was too cold.

Power outages and cold weather happens in winter when the available amount of sunlight is uncertain. If you really are worried about this situation, I don't see much other choice than storing some burnable source of energy, fossil or renewable; gas is difficult to store in large amounts, oil is easier; burning wood is always a great choice but requires some manual work. There are automated pellet solutions etc. but I wouldn't go there. Then you need some quite small amount of electrical power to run the burner, circulation pumps, etc., this could be like some 100W on average, this is possible to store in batteries overnight and get from a decent sized solar array.

Power for full electric heating under such circumstances, direct or heatpump, is practically impossible to store in batteries or generate with solar.

After living through the January 2007 North American ice storm with no power to operate the furnace for a week, I bought backup kerosene and propane heaters, and a backup power generator.
« Last Edit: October 26, 2021, 01:34:33 am by David Hess »
 
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Offline james_s

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #53 on: October 26, 2021, 02:27:01 am »
The problem with heat pumps is that they are effectively pumping heat "uphill" and the colder it is outside, the taller the hill is.  At some point the temperature difference becomes great enough that efficiency is no better than electric heating, which is 100%, but a lot more expensive than lower efficiency heating using some type of fuel.  The other problem is that heat pumps are more complicated leading to higher cost and lower reliability.

While it's true that efficiency of a heat pump drops as the outdoor temperature gets lower, I don't think it will ever quite reach parity with electric resistance heat. Even when it's very cold out, you still get most of the heat that comes from the electricity that goes into the unit. Refrigerant is used to cool the compressor and that heat ends up getting pumped into the house, plus whatever heat it is able to extract from the ambient air. Also newer units are effective down to surprisingly low temperature, I don't remember the spec from the Mitsubishi split system he had installed but I think it's supposed to be good down to -20F. His system has no auxiliary heat at all. Just about anything is more complicated than electric resistance heating, but heat pumps are not known for being unreliable, when properly installed they can be expected to last about as long as a gas furnace. They are after all just an air conditioner with a few added bits and that's a pretty mature technology. They do work best in mild climates though.
 

Online Siwastaja

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #54 on: October 26, 2021, 10:15:38 am »
COP1 parity will be reached in cold climates such as Northern Finland easily but I for example live in Southern parts of the country, Google up "Tampere climate" for a rough idea what we are talking about. Much colder than NYC, for example, but not that bad. Some do install ground-source heatpumps but I don't think it's usually necessary here. Go some 500km North (google "Oulu climate") and things get very different. Yet people do install air source heat pumps even there and with a well adjusted system, are able to reach and exceed Seasonal COP of 2. Cost of heating oil and electricity is now basically 1:1 per energy here, so such 2x energy saving pays back.

For example, my heat pump, a modern quite well designed but still a cheap Chinese unit kind-of-but-not-quite designed for Nordic climate, reaches COP1 at dT=80 degC, i.e., at ambient -25degC water +55degC. Obviously at that point it's wiser to turn the compressor off and run resistive elements, because such usage is also hardest on the compressor, eating more of its life hours.

The change has to be done somewhat earlier from simply the power sufficiency viewpoint. My 9kW nominal machine supplies 4kW at -15degC out / 45degC water, and it also happens my home requires just this, 4kW at -15degC. Below that temperature, resistive support heating would be needed, unless I bought a larger heat pump, but that would be an expensive extra investments just to get slightly higher COP for a few weeks per year. Combining 4kW at COP1.84 and 1kW resistive aux power at COP1 is COP1.58.

But yeah, 3x price difference between electric energy and burnable thermal energy (gas, coal, oil, wood, whatever) pretty much negates the whole point of getting a heatpump. But this is a (stupid) political/business decision; I believe - or hope - it's going to change. If the aim is to Save The World by reducing CO2 and burn less fossils, burning all the same fossils in modern power plants to run distributed heat pumps at households is already a massive improvement; adding renewables such as wind, solar, hydro on top only helps.
« Last Edit: October 26, 2021, 10:18:44 am by Siwastaja »
 

Offline ogden

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #55 on: October 26, 2021, 03:17:52 pm »
The problem with heat pumps is that they are effectively pumping heat "uphill" and the colder it is outside, the taller the hill is.

Right. That's why for heatpump systems heated floors are better choice compared to radiators.

Quote
And one winter we had an unusually cold week where the heat pump was completely useless because the outside temperature was too cold.

Even scarier story - when for some reason many neighbor houses have heat pumps, you all may get grid overload brownouts during extreme cold.
« Last Edit: October 26, 2021, 03:21:04 pm by ogden »
 
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Online Siwastaja

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #56 on: October 26, 2021, 05:04:58 pm »
The sufficiency of grid - or actually production, as the grid itself is very good here - is being discussed here in the heat pump circles because the government is subsidising air-to-water heat pumps with the condition that the oil burner must go. This is totally nuts because even if the oil burner was left as a backup, the heat pump would reduce the oil consumption by some 10x on average, the CO2 emission of that is totally negligible. Even in Southern Finland where most of the population is, it's possible to have several weeks of -25 degC straight although that doesn't happen every winter or even every decade. This means that save for a few in-floor heating houses with carefully tuned flagship heatpumps, most of those "converted" oil houses are running direct resistive electric heating, consuming nearly 10kW per household on average for heating, when they used to consume 50W for the oil burner. At the same time, electricity is needed everywhere else. Last winter, backup fossil plants were already needed (although it was officially "just testing" but somehow happened exactly when the demand exceeded production by 2GW) and we were totally on the mercy of the kind Swedish who had their near-collapse as well and still delivered us power all the time. (We are nowadays continuously importing from all our neighbors. It didn't use to be that way.)

Heat distribution system makes a huge difference. Heat pump is interested about the delta between the outside air, and heating water. If +60degC water is already needed at mere -10degC, that's already the final limit when the pump's definitely out, and COP is crap even before that. But a well designed in-floor heating might be happy running +30degC water even at -30degC out, that's quite an achievement for a heat pump.
« Last Edit: October 26, 2021, 05:06:51 pm by Siwastaja »
 
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Offline NiHaoMike

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #57 on: October 26, 2021, 10:59:44 pm »
Perhaps instead of banning oil or gas heat, just require it to be CHP? It would complement solar very well in that it would be used the most when solar is generating the least and vice versa.
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Online David Hess

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #58 on: October 27, 2021, 03:51:25 am »
Perhaps instead of banning oil or gas heat, just require it to be CHP? It would complement solar very well in that it would be used the most when solar is generating the least and vice versa.

Or apply the true external cost of oil or gas fuel instead of ignoring economics:

https://en.wikipedia.org/wiki/Pigovian_tax

 

Online Siwastaja

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #59 on: October 27, 2021, 09:17:42 am »
Taxation in Finland is a nightmare (basically everything has "pigovian" tax on top of every other tax), but one thing has worked out as it should, IMHO, and has been that way for a long time: electric power has low pigovian tax, and fossil fuels have significantly higher taxes, resulting in approximate energy price parity between oil : electricity. This means it's roughly 4x cheaper to run an EV (that runs at 80% efficiency instead of 20%), or approximately 3x cheaper to run a heat pump with SCOP=3.

And having 1:1 energy price parity isn't excessively unfair for those who need or want to use oil. It sounds fair to me, you pay the same for the energy you use. In many countries it's super cheap to burn fossils to the point that converting into 3x less energy usage by 3x more efficient equipment is not financially viable. This is almost funny because we here run air source heatpumps, in climate where their operation is marginal, and where they would work really well they are not used because of politics.
« Last Edit: October 27, 2021, 09:19:37 am by Siwastaja »
 

Offline richard.cs

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #60 on: October 27, 2021, 09:25:57 am »
In many countries it's super cheap to burn fossils to the point that converting into 3x less energy usage by 3x more efficient equipment is not financially viable.
Certainly in the UK a COP of around 3 is near the break even point. Add in a history of very simple, low-cost gas boilers with a public perception of reliability, and the fact that various green subsidies are added to electricity costs and not to gas (a political problem) and we end up where we are now - the general public does not want heat pumps even with heavily subsidised install costs.

Gas prices are very much on their way up though, which may change things.
 

Online Siwastaja

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #61 on: October 27, 2021, 09:52:34 am »
Subsidizing the install cost is exactly the wrong way to do it. Here subsidising the already excessive 8000EUR investment by 4000EUR caused the price to jump to some 14000EUR, increasing the leftover investment and making it financially unviable.

Because the thing really saves energy, a lot of energy, and energy cost is significant, the only right thing to do is to treat different forms of energy equally (or based on their harmfulness, so on that logic you could make electricity a tad cheaper than fossils because there are at least some renewables in the mix). But now in many European countries, UK included, it seems to be the opposite, fossils are cheap compared to electric energy so people do not want EVs or heatpumps, they don't save enough to break even.

But this isn't getting any better, shortage of electric power is driving prices even higher and people burn fossils in a distributed way, with very poor total efficiency such as 15-70%, when 70-250% would be easily achievable (for transportation and heating, respectively)

In this situation, even building more modern combined cycle facilities and start burning fossils there, to push down the price of electricity, would be an improvement regarding total CO2 produced!
« Last Edit: October 27, 2021, 10:01:45 am by Siwastaja »
 

Offline Marco

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #62 on: October 27, 2021, 11:49:16 am »
Heat distribution system makes a huge difference. Heat pump is interested about the delta between the outside air, and heating water. If +60degC water is already needed at mere -10degC, that's already the final limit when the pump's definitely out, and COP is crap even before that. But a well designed in-floor heating might be happy running +30degC water even at -30degC out, that's quite an achievement for a heat pump.

Ignoring boutique overhead, ceiling heating might be interesting. Easy to retrofit in combination with a tensioned ceiling.
 

Online Siwastaja

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #63 on: October 27, 2021, 12:11:50 pm »
Yes, it all comes back to maximizing surface area to provide the necessary heating power with lower temperature. Floor and ceiling are equal here, but floor has additional benefit that you can drop the room temperature by a degree or two as your feet will stay warm.

Installing heating pipes to floor, ceiling and walls with 100% coverage would result in flat line as the heating curve so that water temperature would always equal to the desired room temperature. Would be one heck of a heatpump COP beast. (Not practical, just the idea for reference.) Forced air convectors (fan units) come pretty close, and also for that reason simple air-to-air heatpumps are very efficient and for little cost. It's just inconvenient to install one to every room or so. A friend of mine has five in his house, and likely is considering adding at least one more. I ended up just installing the air-to-water unit even though it's a clear loss of COP in a radiator house. But you get the heat everywhere.
« Last Edit: October 27, 2021, 12:15:03 pm by Siwastaja »
 

Online langwadt

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #64 on: October 27, 2021, 08:30:11 pm »
Yes, it all comes back to maximizing surface area to provide the necessary heating power with lower temperature. Floor and ceiling are equal here, but floor has additional benefit that you can drop the room temperature by a degree or two as your feet will stay warm.

Installing heating pipes to floor, ceiling and walls with 100% coverage would result in flat line as the heating curve so that water temperature would always equal to the desired room temperature. Would be one heck of a heatpump COP beast. (Not practical, just the idea for reference.) Forced air convectors (fan units) come pretty close, and also for that reason simple air-to-air heatpumps are very efficient and for little cost. It's just inconvenient to install one to every room or so. A friend of mine has five in his house, and likely is considering adding at least one more. I ended up just installing the air-to-water unit even though it's a clear loss of COP in a radiator house. But you get the heat everywhere.

there is an office building a few years old here, that as I understand it it uses a heat pump sourced from circulating groundwater from a well to do both heating and cooling with water circulating in walls and floor 

 

Online David Hess

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #65 on: October 27, 2021, 09:36:50 pm »
Taxation in Finland is a nightmare (basically everything has "pigovian" tax on top of every other tax), but one thing has worked out as it should, IMHO, and has been that way for a long time: electric power has low pigovian tax, and fossil fuels have significantly higher taxes, resulting in approximate energy price parity between oil : electricity. This means it's roughly 4x cheaper to run an EV (that runs at 80% efficiency instead of 20%), or approximately 3x cheaper to run a heat pump with SCOP=3.

The usual problem with taxes is that special interests get exceptions written into the law which defeats the purpose of a Pigovian tax.  At least that is how it works in the US.

If you are going to apply a Pigovian tax of emissions, or specifically CO2, to fossil fuels then it needs to be applied per mole of carbon, without any exceptions or subsidies at all.  It should be easy to administer because almost all fuel travels through a limited number of points in bulk.  Of course if the fuel is not burned, then somehow that has to be accounted for, because some fossil fuels are used for other processes where the carbon will not be released.
 

Offline NiHaoMike

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #66 on: October 28, 2021, 12:32:22 am »
In areas that regularly go below freezing, could a heat pump be developed that freezes water to make ice and then throw the ice outside?
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Online David Hess

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #67 on: October 28, 2021, 03:28:34 am »
In areas that regularly go below freezing, could a heat pump be developed that freezes water to make ice and then throw the ice outside?

Sure, but that assumes a source of liquid water, and having to melt water for the heat pump to freeze would defeat the purpose.
 

Offline james_s

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #68 on: October 28, 2021, 03:58:31 am »
Well most areas are going to have liquid tap water, but consider this. In this part of the world heat pump system capacity is measured in tons, for a a modest house 2-3.5 tons is typical. That is tons of ice that can be melted or frozen in a 24 hour period, so if you have a house like mine with a 3 ton heat pump you could conceivably be looking for somewhere to stack thousands of pounds of ice per day.
 

Online Siwastaja

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #69 on: October 28, 2021, 07:26:43 am »
In areas that regularly go below freezing, could a heat pump be developed that freezes water to make ice and then throw the ice outside?

The energy needs to come from somewhere -> you need source of water -> that source of water is providing the energy -> energy is actually coming from ground -> this already exists, is called  "ground source heat pump". langwadt described this above, some literally circulate ground water and cool it down by a few degrees (there's no need to go as far as freezing it and throwing it out). Others just cool down the bedrock, or soil, for example by drilling a deep well. This is more efficient than air source because the ground source is always at approx. +5 degC even in the coldest climates, but the investment cost is usually pretty high because surface area needs to be high, necessitating deep holes (like 200 meters).

For your idea about ice, air source heat pumps are already condensing water from the cold (nearly RH=100%) outdoor air, which gives energy. But then the ice starts blocking the evaporator coil, and defrosting cycle melts that ice, losing the gained energy. Some industrial grade air source heat pumps, AFAIK, use very sparse evaporator coil fins, in a horizontal installation so that the defrosting cycle actually sheds/drops a significant part of the ice, as ice. This obviously improves the efficiency by utilizing the energy gained making that ice in the first place, and only wasting small part of it during defrosting. But this is just a minor optimization, maybe it gives you 0.1 to 0.2 units of COP.
« Last Edit: October 28, 2021, 07:30:01 am by Siwastaja »
 

Offline cdevTopic starter

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #70 on: October 28, 2021, 05:52:57 pm »
Do you mean like in Iceland, where nearby volcanoes have heated the earth up hot enough to heat groundwater and spring water toasty warm?

Mmmm! Sounds nice. Just hope it doesn't erupt and cause a nuclear winter.  Then the bills will really soar.
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Offline cdevTopic starter

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #71 on: October 28, 2021, 05:55:24 pm »
Well most areas are going to have liquid tap water, but consider this. In this part of the world heat pump system capacity is measured in tons, for a a modest house 2-3.5 tons is typical. That is tons of ice that can be melted or frozen in a 24 hour period, so if you have a house like mine with a 3 ton heat pump you could conceivably be looking for somewhere to stack thousands of pounds of ice per day.

Where does the energy to run that pump come from, natural gas, electricity, oil?

Hopefully not solar roadways..
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Offline cdevTopic starter

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #72 on: October 28, 2021, 06:02:00 pm »
Heat distribution system makes a huge difference. Heat pump is interested about the delta between the outside air, and heating water. If +60degC water is already needed at mere -10degC, that's already the final limit when the pump's definitely out, and COP is crap even before that. But a well designed in-floor heating might be happy running +30degC water even at -30degC out, that's quite an achievement for a heat pump.

Ignoring boutique overhead, ceiling heating might be interesting. Easy to retrofit in combination with a tensioned ceiling.

Heat builds up near the ceiling in a conventinally heated room and a small fan placed near the ceiling blowing the warmer air downward mixes the air and reduces heating costs. I used to have one like this, a small vertical fan hung from a piece of wire did the job well.  This was back when energy was cheaper than today. So I'd imagine the savings might be more now.
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Offline james_s

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #73 on: October 28, 2021, 06:48:01 pm »
Where does the energy to run that pump come from, natural gas, electricity, oil?

Hopefully not solar roadways..

It comes from electricity, which in my region is from a mix of sources, about 60% hydro.
 

Offline cdevTopic starter

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Re: More or Most efficient hydronic heating basic unit? (natural gas)
« Reply #74 on: October 28, 2021, 06:58:00 pm »
So, it uses electricity which around here ALREADY costs at least 3 times as much as gas... probably more.

This is smoke and mirrors..

The problem with heat pumps is that they are effectively pumping heat "uphill" and the colder it is outside, the taller the hill is.

Right. That's why for heatpump systems heated floors are better choice compared to radiators.

Quote
And one winter we had an unusually cold week where the heat pump was completely useless because the outside temperature was too cold.

Even scarier story - when for some reason many neighbor houses have heat pumps, you all may get grid overload brownouts during extreme cold.
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