Any reason to keep steam with a Hyper Heat Ducted System

jguinta

I am renovating and old house in Boston which has a 100 year old steam system. The original plan was to install a Mitsu Regular Ducted Heat Pump system and replace the steam boiler (also converting this from oil to gas.) The Steam would be the low temp heat source while the Heat Pump would cover the cooling and moderate temp heating. Due to the available energy rebates, we are considering instead going with a Mitsu Hyper Heat Ducted Heat Pump System and eliminating the steam boiler entirely.

Please share your thoughts, opinions and experience.

Thanks.

Jamie Hall

The reason to keep it is to stay comfortable and warm with reliable heat. All of which steam is, and heat pumps ... not so much, although so long as the power stays on you probably won't freeze. The reason to take it out is all that lovely money. Maybe looking at that will keep you warm enough...

Hot_water_fan

I heat exclusively with a hyper heat ducted heat pump and have used it into the single digits. I have no complaints. That said, if you want a backup the steam would work. 

Or! Give it a winter first. Then you can decide to add a furnace backup or replace the boiler. That way it’ll be your decision, not ours. 

Mustangman

I sell many Ductless and ducted mini splits. I am up front right off the get go as there is a lot of misleading information about the low ambient performance of Mitsubishi Hyper Heat and LG Red systems.
Before I piss off the heat pump guys, these ductless systems are amazing pieces of equipment... no doubt. My issue is with the Derating of the equipment during cold weather. You have to look at those performance charts to find out what the unit actually does in cold weather. Lets say we have a 2 ton system with 2 heads. According to the performance charts, you may still have 24,000 of capacity at 30 degrees ambient. As the temperature drops, you will see the performance drop off and what was once 24,000 BTUs you may have 15,000 BTUs available to use for heating at 0 degrees outdoor ambient. That is Derating. I just saw an ad that said, operates at -14 degrees. All that means, is at -14 its not going to shut down, just won't produce much heat.
Like I said, I love the new ductless and ducted systems. However, you should have a secondary heat source to use during the colder days. I realize we don't hit -14 here in PA very often but, when it does, the phone calls for unit not keeping up will come.
The trend now is shifting to deal with this issue. They match a very efficient outdoor section with a full sized air handler. The AHU can be fitted with a bank of electric heat. If its cold and the unit can't keep up, the electric heat will come on to assist.
Its your call but I think I would keep the steam too.
Steve

SuperTech

The Mitsubishi systems are nice, they are my favorite inverter systems.  But I would never rely on them as my only source of heat. A boiler is a lot more reliable and easy to service.  Parts are universal and  readily available for a boiler. I've had situations in the past where replacement parts for a inverter system were not available for over a week when I needed them for a customer with no heat.

GGross

Mustangman said:

I sell many Ductless and ducted mini splits. I am up front right off the get go as there is a lot of misleading information about the low ambient performance of Mitsubishi Hyper Heat and LG Red systems.
Before I piss off the heat pump guys, these ductless systems are amazing pieces of equipment... no doubt. My issue is with the Derating of the equipment during cold weather. You have to look at those performance charts to find out what the unit actually does in cold weather. Lets say we have a 2 ton system with 2 heads. According to the performance charts, you may still have 24,000 of capacity at 30 degrees ambient. As the temperature drops, you will see the performance drop off and what was once 24,000 BTUs you may have 15,000 BTUs available to use for heating at 0 degrees outdoor ambient. That is Derating. I just saw an ad that said, operates at -14 degrees. All that means, is at -14 its not going to shut down, just won't produce much heat.
Like I said, I love the new ductless and ducted systems. However, you should have a secondary heat source to use during the colder days. I realize we don't hit -14 here in PA very often but, when it does, the phone calls for unit not keeping up will come.
The trend now is shifting to deal with this issue. They match a very efficient outdoor section with a full sized air handler. The AHU can be fitted with a bank of electric heat. If its cold and the unit can't keep up, the electric heat will come on to assist.
Its your call but I think I would keep the steam too.
Steve

LG RED systems post their performance at low ambient and those numbers you posted are not accurate for any LG RED outdoor unit, not sure if those are for the hyper heat models, or you may have just made them up, but the RED multi outdoor unit still puts out 21,310 BTU/hr at its lowest rated temperature ( which is lower than design day here in Northern Michigan).

Accurate sizing of ANY heating appliance is important, if you undersize a boiler you would also need backup heat. This is not a unique characteristic of heat pumps.

Mustangman

Great point Supertech. Parts availability is a major issue. The trend seems to be, have small supply houses spread out all over and one super warehouse. Lets say your problem is a thermistor. The supplier has one at their hub in NY. It may take a few days to get that thermistor into your hands so you can restore heat. Another reason to have a back up heat if possible.

tim smith

Put electric back up strip heat in. If od unit fails you can still have emergency heat. Just verify it will still operate fans with blown od unit.

Steamhead

@jguinta , don't rip out the steam. As others have said, you won't be comfortable when it gets cold. And a heat pump trying to run in weather that cold will eat up a lot of expensive electricity.

Try @New England SteamWorks to look at the steam system.

ChrisJ

GGross said:

Mustangman said:

I sell many Ductless and ducted mini splits. I am up front right off the get go as there is a lot of misleading information about the low ambient performance of Mitsubishi Hyper Heat and LG Red systems.
Before I piss off the heat pump guys, these ductless systems are amazing pieces of equipment... no doubt. My issue is with the Derating of the equipment during cold weather. You have to look at those performance charts to find out what the unit actually does in cold weather. Lets say we have a 2 ton system with 2 heads. According to the performance charts, you may still have 24,000 of capacity at 30 degrees ambient. As the temperature drops, you will see the performance drop off and what was once 24,000 BTUs you may have 15,000 BTUs available to use for heating at 0 degrees outdoor ambient. That is Derating. I just saw an ad that said, operates at -14 degrees. All that means, is at -14 its not going to shut down, just won't produce much heat.
Like I said, I love the new ductless and ducted systems. However, you should have a secondary heat source to use during the colder days. I realize we don't hit -14 here in PA very often but, when it does, the phone calls for unit not keeping up will come.
The trend now is shifting to deal with this issue. They match a very efficient outdoor section with a full sized air handler. The AHU can be fitted with a bank of electric heat. If its cold and the unit can't keep up, the electric heat will come on to assist.
Its your call but I think I would keep the steam too.
Steve

LG RED systems post their performance at low ambient and those numbers you posted are not accurate for any LG RED outdoor unit, not sure if those are for the hyper heat models, or you may have just made them up, but the RED multi outdoor unit still puts out 21,310 BTU/hr at its lowest rated temperature ( which is lower than design day here in Northern Michigan).

Accurate sizing of ANY heating appliance is important, if you undersize a boiler you would also need backup heat. This is not a unique characteristic of heat pumps.

So,
Regarding my house, as it's the only real info I have.

I need roughly 36,000 btu/h cooling in the summer. This falls behind a bit during heatwaves but does pretty good otherwise. For heat I need 72,000 and that's actual load, not a calculation.

How would I size minisplits to deal with that load? I need roughly 6 tons of heating, but won't that result in the system being grossly oversized for cooling, or does that still workout with these systems?

I'm currently using a 2 stage split system so even that can only go down to, I think 24,000 minimum.

GGross

ChrisJ said:

GGross said:

Mustangman said:

I sell many Ductless and ducted mini splits. I am up front right off the get go as there is a lot of misleading information about the low ambient performance of Mitsubishi Hyper Heat and LG Red systems.
Before I piss off the heat pump guys, these ductless systems are amazing pieces of equipment... no doubt. My issue is with the Derating of the equipment during cold weather. You have to look at those performance charts to find out what the unit actually does in cold weather. Lets say we have a 2 ton system with 2 heads. According to the performance charts, you may still have 24,000 of capacity at 30 degrees ambient. As the temperature drops, you will see the performance drop off and what was once 24,000 BTUs you may have 15,000 BTUs available to use for heating at 0 degrees outdoor ambient. That is Derating. I just saw an ad that said, operates at -14 degrees. All that means, is at -14 its not going to shut down, just won't produce much heat.
Like I said, I love the new ductless and ducted systems. However, you should have a secondary heat source to use during the colder days. I realize we don't hit -14 here in PA very often but, when it does, the phone calls for unit not keeping up will come.
The trend now is shifting to deal with this issue. They match a very efficient outdoor section with a full sized air handler. The AHU can be fitted with a bank of electric heat. If its cold and the unit can't keep up, the electric heat will come on to assist.
Its your call but I think I would keep the steam too.
Steve

LG RED systems post their performance at low ambient and those numbers you posted are not accurate for any LG RED outdoor unit, not sure if those are for the hyper heat models, or you may have just made them up, but the RED multi outdoor unit still puts out 21,310 BTU/hr at its lowest rated temperature ( which is lower than design day here in Northern Michigan).

Accurate sizing of ANY heating appliance is important, if you undersize a boiler you would also need backup heat. This is not a unique characteristic of heat pumps.

So,
Regarding my house, as it's the only real info I have.

I need roughly 36,000 btu/h cooling in the summer. This falls behind a bit during heatwaves but does pretty good otherwise. For heat I need 72,000 and that's actual load, not a calculation.

How would I size minisplits to deal with that load? I need roughly 6 tons of heating, but won't that result in the system being grossly oversized for cooling, or does that still workout with these systems?

I'm currently using a 2 stage split system so even that can only go down to, I think 24,000 minimum.

Personally I wouldn't recommend a heat pump only system for that house (but I also happen to know you have an existing well functioning heating system). Depending on what outdoor temperature your heat load is calculated at, that would possibly change the setup, but let's assume its 72,000 at -13f for ease of numbers, you would need at least 2 outdoor units, the largest 1:1 residential RED system is going to put out around 35k BTU/hr at -13 with minimum cooling of 18,400 if you go to the multihead model you would be around 39k BTU/hr at -13f, but then you need multiple units hooked up, it's possible but this would be very expensive, a minimum of 2 outdoor units, and these are very pricey. This is assuming you are hooking to a standard style air handler, not wall units. It gets worse if you attach multiple wall units to a single outdoor unit, your minimum will actually go UP for cooling mode, this is something you do not see advertised very often with manufacturers.

Let's say for a minute that I was absolutely set on installing an electric only heating system for a house like this (which I am not lol) I think the best balance between performance and cost would be 2 1:1 air handlers that will get you to around 68k BTU/hr at -13f each with backup heat strips. the largest heat strip LG offers is 20 kw, which is still going to be a bit light for your full load, so I think you would need at least 2 units, which would put your minimum cooling at about 1.5 ton for each unit

No matter which way you cut it you are going to be oversized for cooling. Sure you could theoretically install 1:1 units in each room and be able to modulate to their fullest but that is not reasonable for anyone to install

ChrisJ

GGross said:

ChrisJ said:

GGross said:

Mustangman said:

I sell many Ductless and ducted mini splits. I am up front right off the get go as there is a lot of misleading information about the low ambient performance of Mitsubishi Hyper Heat and LG Red systems.
Before I piss off the heat pump guys, these ductless systems are amazing pieces of equipment... no doubt. My issue is with the Derating of the equipment during cold weather. You have to look at those performance charts to find out what the unit actually does in cold weather. Lets say we have a 2 ton system with 2 heads. According to the performance charts, you may still have 24,000 of capacity at 30 degrees ambient. As the temperature drops, you will see the performance drop off and what was once 24,000 BTUs you may have 15,000 BTUs available to use for heating at 0 degrees outdoor ambient. That is Derating. I just saw an ad that said, operates at -14 degrees. All that means, is at -14 its not going to shut down, just won't produce much heat.
Like I said, I love the new ductless and ducted systems. However, you should have a secondary heat source to use during the colder days. I realize we don't hit -14 here in PA very often but, when it does, the phone calls for unit not keeping up will come.
The trend now is shifting to deal with this issue. They match a very efficient outdoor section with a full sized air handler. The AHU can be fitted with a bank of electric heat. If its cold and the unit can't keep up, the electric heat will come on to assist.
Its your call but I think I would keep the steam too.
Steve

LG RED systems post their performance at low ambient and those numbers you posted are not accurate for any LG RED outdoor unit, not sure if those are for the hyper heat models, or you may have just made them up, but the RED multi outdoor unit still puts out 21,310 BTU/hr at its lowest rated temperature ( which is lower than design day here in Northern Michigan).

Accurate sizing of ANY heating appliance is important, if you undersize a boiler you would also need backup heat. This is not a unique characteristic of heat pumps.

So,
Regarding my house, as it's the only real info I have.

I need roughly 36,000 btu/h cooling in the summer. This falls behind a bit during heatwaves but does pretty good otherwise. For heat I need 72,000 and that's actual load, not a calculation.

How would I size minisplits to deal with that load? I need roughly 6 tons of heating, but won't that result in the system being grossly oversized for cooling, or does that still workout with these systems?

I'm currently using a 2 stage split system so even that can only go down to, I think 24,000 minimum.

Personally I wouldn't recommend a heat pump only system for that house (but I also happen to know you have an existing well functioning heating system). Depending on what outdoor temperature your heat load is calculated at, that would possibly change the setup, but let's assume its 72,000 at -13f for ease of numbers, you would need at least 2 outdoor units, the largest 1:1 residential RED system is going to put out around 35k BTU/hr at -13 with minimum cooling of 18,400 if you go to the multihead model you would be around 39k BTU/hr at -13f, but then you need multiple units hooked up, it's possible but this would be very expensive, a minimum of 2 outdoor units, and these are very pricey. This is assuming you are hooking to a standard style air handler, not wall units. It gets worse if you attach multiple wall units to a single outdoor unit, your minimum will actually go UP for cooling mode, this is something you do not see advertised very often with manufacturers.

Let's say for a minute that I was absolutely set on installing an electric only heating system for a house like this (which I am not lol) I think the best balance between performance and cost would be 2 1:1 air handlers that will get you to around 68k BTU/hr at -13f each with backup heat strips. the largest heat strip LG offers is 20 kw, which is still going to be a bit light for your full load, so I think you would need at least 2 units, which would put your minimum cooling at about 1.5 ton for each unit

No matter which way you cut it you are going to be oversized for cooling. Sure you could theoretically install 1:1 units in each room and be able to modulate to their fullest but that is not reasonable for anyone to install

Yeah, I have no intention of going that route, I was just curious how this actually plays out in real life.

My 72K loss was at -8F with a slight breeze from what I recall.
Out of curiosity, how cold do these minisplits run the evaporators? I.E. would a unit running at it's minimum of 1.5 ton run the evaporator(s) cold enough to give good dehumidification even though the unit is oversized and cycling? Obviously my 3ton system in low stage still cycles plenty, but the evap runs good and cold.

GGross

ChrisJ said:

GGross said:

ChrisJ said:

GGross said:

Mustangman said:

I sell many Ductless and ducted mini splits. I am up front right off the get go as there is a lot of misleading information about the low ambient performance of Mitsubishi Hyper Heat and LG Red systems.
Before I piss off the heat pump guys, these ductless systems are amazing pieces of equipment... no doubt. My issue is with the Derating of the equipment during cold weather. You have to look at those performance charts to find out what the unit actually does in cold weather. Lets say we have a 2 ton system with 2 heads. According to the performance charts, you may still have 24,000 of capacity at 30 degrees ambient. As the temperature drops, you will see the performance drop off and what was once 24,000 BTUs you may have 15,000 BTUs available to use for heating at 0 degrees outdoor ambient. That is Derating. I just saw an ad that said, operates at -14 degrees. All that means, is at -14 its not going to shut down, just won't produce much heat.
Like I said, I love the new ductless and ducted systems. However, you should have a secondary heat source to use during the colder days. I realize we don't hit -14 here in PA very often but, when it does, the phone calls for unit not keeping up will come.
The trend now is shifting to deal with this issue. They match a very efficient outdoor section with a full sized air handler. The AHU can be fitted with a bank of electric heat. If its cold and the unit can't keep up, the electric heat will come on to assist.
Its your call but I think I would keep the steam too.
Steve

LG RED systems post their performance at low ambient and those numbers you posted are not accurate for any LG RED outdoor unit, not sure if those are for the hyper heat models, or you may have just made them up, but the RED multi outdoor unit still puts out 21,310 BTU/hr at its lowest rated temperature ( which is lower than design day here in Northern Michigan).

Accurate sizing of ANY heating appliance is important, if you undersize a boiler you would also need backup heat. This is not a unique characteristic of heat pumps.

So,
Regarding my house, as it's the only real info I have.

I need roughly 36,000 btu/h cooling in the summer. This falls behind a bit during heatwaves but does pretty good otherwise. For heat I need 72,000 and that's actual load, not a calculation.

How would I size minisplits to deal with that load? I need roughly 6 tons of heating, but won't that result in the system being grossly oversized for cooling, or does that still workout with these systems?

I'm currently using a 2 stage split system so even that can only go down to, I think 24,000 minimum.

Personally I wouldn't recommend a heat pump only system for that house (but I also happen to know you have an existing well functioning heating system). Depending on what outdoor temperature your heat load is calculated at, that would possibly change the setup, but let's assume its 72,000 at -13f for ease of numbers, you would need at least 2 outdoor units, the largest 1:1 residential RED system is going to put out around 35k BTU/hr at -13 with minimum cooling of 18,400 if you go to the multihead model you would be around 39k BTU/hr at -13f, but then you need multiple units hooked up, it's possible but this would be very expensive, a minimum of 2 outdoor units, and these are very pricey. This is assuming you are hooking to a standard style air handler, not wall units. It gets worse if you attach multiple wall units to a single outdoor unit, your minimum will actually go UP for cooling mode, this is something you do not see advertised very often with manufacturers.

Let's say for a minute that I was absolutely set on installing an electric only heating system for a house like this (which I am not lol) I think the best balance between performance and cost would be 2 1:1 air handlers that will get you to around 68k BTU/hr at -13f each with backup heat strips. the largest heat strip LG offers is 20 kw, which is still going to be a bit light for your full load, so I think you would need at least 2 units, which would put your minimum cooling at about 1.5 ton for each unit

No matter which way you cut it you are going to be oversized for cooling. Sure you could theoretically install 1:1 units in each room and be able to modulate to their fullest but that is not reasonable for anyone to install

Yeah, I have no intention of going that route, I was just curious how this actually plays out in real life.

My 72K loss was at -8F with a slight breeze from what I recall.
Out of curiosity, how cold do these minisplits run the evaporators? I.E. would a unit running at it's minimum of 1.5 ton run the evaporator(s) cold enough to give good dehumidification even though the unit is oversized and cycling? Obviously my 3ton system in low stage still cycles plenty, but the evap runs good and cold.

An Air handler inverter system would be similar, I see more problems when someone installs a bunch of wall units on a single ODU and they are all oversized for their space.

WMno57

How confident are you that the local grid can supply enough power to run all those new heat pumps. The colder it gets, the more electricity they use. Fortunately the Northeast has been proactively adding Nuclear power for the last 40 years (sarcasm alert).
A steam boiler needs very little electricity. Any 12v car battery and inverter could run it for hours to days. Also a small solar array, a basic box store portable generator, or a computer UPS.
Generic makes automated gas standby home generators. Don't have to lift a finger. Seamless power.
The powerpile parts to modify a gas atmospheric steam boiler to run on no electricity are still available. For the advanced prepper - DIYer.

Paul S_3

In my opinion, I wouldn't remove the steam system unless there have been major upgrades to the building envelope. I've been to plenty of service calls in the dead of winter where a steam/hydronic system was removed for a heat pump. Even though it was maintaining the setpoint. They felt colder in a way because of drafty windows, poor insulation, etc.Also if something goes wrong with it, you would need a seasoned technician to properly fix it. Most people can install them, few can fix them.

SlamDunk

I have both steam and an 80% efficiency forced air furnace. During The two-three week annual cold snap we get we switch to steam and it is heaven. The system is properly sized and well maintained so not expensive at all to operate. Last week, the furnace quit, so we switched to steam until parts arrived. It is really nice to have a back up system.

Keep the steam. Keep it maintained.

Mustangman

72K is extremely large for a home system. I got scorched about some numbers above that I want to explain. I NEVER publish brand names or their performance. It pisses everyone off when you run down LG or Mitsubishi especially if you post actual performance. Everything posted above shows deration... that was my point. That 2 ton unit is not producing 2 ton of heat at -13. Someone mentioned put in strip heat as a back up. The only way to do it is to use a full size air handler. You can't install electric coils in wall units, ceiling cassettes, floor units. I was simply explaining why its a good idea to have a back up.

ChrisJ

Mustangman said:

72K is extremely large for a home system. I got scorched about some numbers above that I want to explain. I NEVER publish brand names or their performance. It pisses everyone off when you run down LG or Mitsubishi especially if you post actual performance. Everything posted above shows deration... that was my point. That 2 ton unit is not producing 2 ton of heat at -13. Someone mentioned put in strip heat as a back up. The only way to do it is to use a full size air handler. You can't install electric coils in wall units, ceiling cassettes, floor units. I was simply explaining why its a good idea to have a back up.

72k is my actual heatloss at -8F in a 1600sqft 1860-1870s house.

I wouldn't by any means call it "extremely large".
It's certainly on the larger side, but considering most modern houses similar to mine have 60K furnaces in them it's far from extreme. My dad's 2000sqft house built in 2006 has an 80K furnace and most older ones often had 120K.

Maybe down south it's extremely large but not anywhere it actually gets cold.