Do ducted split units perform??? + contractor recs

[overhear]

We've been moving along with our research. Yesterday I had an HVAC contractor who has installed a lot of split systems come out to the house.

It was pretty funny: our architect was appalled by the look of the ductless units and ceiling cassettes, my husband was wringing his hands over the cost, and I'm sitting there -- ever the gearhead that I am -- dazzled by the performance of the VRV/VRF systems.

Our house currently has hot-water heat with big, old radiators, but to eke out more space we've been thinking about changing over to in-floor radiant heat downstairs and replacing the upstairs radiators with lower profile units. But instead, I'm wondering if we should be considering using the a VRV/VRF system as a heat pump.

Can anyone speak to the energy efficiency of VRF/VRV systems for heat compared with hot water radiator systems?

[mchild]

We've been moving along with our research. Yesterday I had an HVAC contractor who has installed a lot of split systems come out to the house.

It was pretty funny: our architect was appalled by the look of the ductless units and ceiling cassettes, my husband was wringing his hands over the cost, and I'm sitting there -- ever the gearhead that I am -- dazzled by the performance of the VRV/VRF systems.

Our house currently has hot-water heat with big, old radiators, but to eke out more space we've been thinking about changing over to in-floor radiant heat downstairs and replacing the upstairs radiators with lower profile units. But instead, I'm wondering if we should be considering using the a VRV/VRF system as a heat pump.

Can anyone speak to the energy efficiency of VRF/VRV systems for heat compared with hot water radiator systems?

Without knowing the true delivered heat cost of each system it will be hard to compare. Once you have an idea as to what the true operating efficiency numbers are, plus the delivered cost of energy, you can input some basic data at: http://www.warmair.com/html/fuel_cost_comparisons.htm

Heat pumps decline in heat output the lower the outdoor temps drop and operating efficiency drops too. But, unlike any other method of heat a heat pump gives you more than it is consuming until its breakeven point. This is measured by its COP (Co-efficient of Performance) in which the amount of energy it is consuming is compared to the heat (energy) it is putting out. So the COP drops and once it hits 1 there is no benefit in using the heat pump as a heating source. Most VRV/VRF manufacturers provided extensive data on the heat output and the electric consumption of their systems at numerous different temps.

Based on your location it would likely make sense to use the heat pump as your primary heat source and the hot water as a supplemental heat source once the heat pump can no longer carry the load on its own.

With my home the heat pump can provide the required heat to about 14*F but then electric heating coils located in the ducts just down stream form the air handler cycles as needed to maintain the room temp. Heat pump continues to run and produce heat and the electric coils supplement the heat pump as needed.

The VRV/VRF systems produce more heat at lower temps than conventional heat pumps. I am pleased that my system can produce virtually all the heat my home needs. Our winter design temps are 9*F. The number of hours we spend below 14*F where I need supplemental heat is minimal.

Also, as a consideration, while not a VRV/VRF system you may want to consider this system form Mitsubishi. It produces 100% of its rated heat output down to 5*F and at -4*F it is rated at 90% of its output. http://www.mehvac.com/UploadedFiles/...0Submittal.pdf

[overhear]

Thank you mchild. That's very helpful.

[overhear]

... Also, as a consideration, while not a VRV/VRF system you may want to consider this system form Mitsubishi. It produces 100% of its rated heat output down to 5*F and at -4*F it is rated at 90% of its output. http://www.mehvac.com/UploadedFiles/...0Submittal.pdf

mchild, Can you clarify which Mitsubishi system that is?

[mchild]

mchild, Can you clarify which Mitsubishi system that is?

It is in their H2i Hyper-Heat line up. There are two ducted systems 2.5 and 3 tons and several ductless too. You can look at them here: http://catalog.mitsubishipro.com/cat...ies-heat-pumps

It is my understanding that they are able to produce the higher heat output at lower temps by using an oversized compressor and then limiting it on the cooling side to 3 tons (by keeping RPMs down) but when outdoor temps drop it will allow the compressor to run at a higher RPM to get the maximum output from it.

If you want to review the Mitsu products go to mehvac.com and select the Pro site from there. The homeowner side of the site is lame.

[overhear]

It is in their H2i Hyper-Heat line up. There are two ducted systems 2.5 and 3 tons and several ductless too. You can look at them here: http://catalog.mitsubishipro.com/cat...ies-heat-pumps

It is my understanding that they are able to produce the higher heat output at lower temps by using an oversized compressor and then limiting it on the cooling side to 3 tons (by keeping RPMs down) but when outdoor temps drop it will allow the compressor to run at a higher RPM to get the maximum output from it.

If you want to review the Mitsu products go to mehvac.com and select the Pro site from there. The homeowner side of the site is lame.

Thanks mchild, I'll take a look. I have the energy audit scheduled for next week. I'm hoping that will give us a better sense of what kind of tonnage we need and also serve as a reality check when bids come in.

[mchild]

Thanks mchild, I'll take a look. I have the energy audit scheduled for next week. I'm hoping that will give us a better sense of what kind of tonnage we need and also serve as a reality check when bids come in.

A well done energy audit will provide you with good information on how your home is using energy (Make sure the techs walk around with you and explain what they are finding and what you can/need to do about it. Don't let them just print out a report and leave it with you.) and will give you a much needed point of info for a properly run Manual J load calc which is the air infiltration. Once the audit is done you can decided what items you want to tackle on tightening up the structure. Air leakage is as much if not more of an issue as insulation. Insulation does not stop air flow. Air sealing is the only way to reduce air infiltration/exfiltration.

Then you can have a pro (either HVAC contractor or engineer type) run a detailed room by room Man J. With this you can also do some what if runs to see the impact of making some of the improvements. It will help you decide where to spend dollars first. Don't be surprised if the home needs less heating and cooling than you initially thought.

[overhear]

A well done energy audit will provide you with good information on how your home is using energy (Make sure the techs walk around with you and explain what they are finding and what you can/need to do about it. Don't let them just print out a report and leave it with you.) and will give you a much needed point of info for a properly run Manual J load calc which is the air infiltration. Once the audit is done you can decided what items you want to tackle on tightening up the structure. Air leakage is as much if not more of an issue as insulation. Insulation does not stop air flow. Air sealing is the only way to reduce air infiltration/exfiltration.

Then you can have a pro (either HVAC contractor or engineer type) run a detailed room by room Man J. With this you can also do some what if runs to see the impact of making some of the improvements. It will help you decide where to spend dollars first. Don't be surprised if the home needs less heating and cooling than you initially thought.

And it still makes sense to go forward with the audit now even though we will be replacing doors and adding windows during our renovation later? I can give the building plans to the tech performing the assessment, but want to be sure.

[mchild]

And it still makes sense to go forward with the audit now even though we will be replacing doors and adding windows during our renovation later? I can give the building plans to the tech performing the assessment, but want to be sure.

Some people do a before and after audit to confirm that the installers did a proper job and the window, as an example, don't leak like a sieve.

[overhear]

Hi All,

I'm wondering if someone can offer me advice as I'm still floundering a bit here. After all the research I decided I definitely would prefer a multi-zone mini-split or VRV/VRF system with concealed (ducted) evaporator units. I thought I'd get 3 estimates -- 1 from the company that performed the NYS energy audit which does a lot of work in our area, and 2 other estimates ideally from companies that have experience installing split or VRV residential systems.

But now I'm worried again. We are just a few weeks from putting out whole home renovation project out to bid and I'm not sure that I have a contractor with experience designing a DUCTED or concealed multi-zone split system.

The estimator from the company that provided our energy audit said that Mitsubishi does not make concealed indoor units and after a while said that he had never heard of a VRV/VRF system. He will therefore only give an estimate for a packaged system. That was disappointing because I know this company will do a manual J and has engineering expertise.

The 2nd contractor only installs multi-zone split systems but I don't think he's an engineering type as he hasn't taken any measurements. He is proposing a Samsung variable speed system for the 1st floor using units under the floor. A Mitsubishi multi-zone system would serve the 3 rooms and bath on the 2nd floor by tucking concealed ceiling units into the perimeter of the 3rd floor attic bedroom. He was not inclined to cool the bathrooms, but I asked for the design to have the 2nd floor bathrooms each share an indoor unit with the adjacent bedroom.

He also gave me an estimate for a VRV system, but the price is 25% higher than the already pricey ducted split system, so I don't think we can go there.

I guess I'm just not sure I've found the right person yet. I called the Daikin distributor and got the name of someone they sell to that installs lots of residential VRV systems. I'll try that person but meanwhile we are starting to lose time and I'm wondering if I should just give up and have whoever the GC on the job is just take care of it (sigh).

Any thoughts?

[mchild]

Hi All,

I'm wondering if someone can offer me advice as I'm still floundering a bit here. After all the research I decided I definitely would prefer a multi-zone mini-split or VRV/VRF system with concealed (ducted) evaporator units. I thought I'd get 3 estimates -- 1 from the company that performed the NYS energy audit which does a lot of work in our area, and 2 other estimates ideally from companies that have experience installing split or VRV residential systems.

But now I'm worried again. We are just a few weeks from putting out whole home renovation project out to bid and I'm not sure that I have a contractor with experience designing a DUCTED or concealed multi-zone split system.

The estimator from the company that provided our energy audit said that Mitsubishi does not make concealed indoor units and after a while said that he had never heard of a VRV/VRF system. He will therefore only give an estimate for a packaged system. That was disappointing because I know this company will do a manual J and has engineering expertise.

The 2nd contractor only installs multi-zone split systems but I don't think he's an engineering type as he hasn't taken any measurements. He is proposing a Samsung variable speed system for the 1st floor using units under the floor. A Mitsubishi multi-zone system would serve the 3 rooms and bath on the 2nd floor by tucking concealed ceiling units into the perimeter of the 3rd floor attic bedroom. He was not inclined to cool the bathrooms, but I asked for the design to have the 2nd floor bathrooms each share an indoor unit with the adjacent bedroom.

He also gave me an estimate for a VRV system, but the price is 25% higher than the already pricey ducted split system, so I don't think we can go there.

I guess I'm just not sure I've found the right person yet. I called the Daikin distributor and got the name of someone they sell to that installs lots of residential VRV systems. I'll try that person but meanwhile we are starting to lose time and I'm wondering if I should just give up and have whoever the GC on the job is just take care of it (sigh).

Any thoughts?

GCs normally know squat about HVAC so he will just turn to the low bidder (he probably already knows him) and tell him to slap something in. As in cheap.

Each of the major Japanese manufacturers (watch out for the non-Japanese manufacturers) have contractors listed on their web sites. Also, as you have already done you can contact distributors too. VRV/VRF ssytems are somewhat idiot proof - but then again the installer really does need to know what he is doing to install it properly. Daikin is terrific in supporting their contractors.

If you are concerned by having a quality Man J and duct design by Man D then hire your own engineer to do the work for you and then he can spec exactly what the system must do to be considered properly installed. There is a fair amount of work with all HVAC comfort system to get it rifgt so spend the time and money now and then you don't have to worry about having to redo it later.

[tedkidd]

I can't see your project very well from where I'm sitting, but it sounds like there is some confusion about process.

You need a design BEFORE going to bid, unless you like this gambling approach. Step back and think about this. You think the sales guy is going to spend hours and hours learning about a system, pay for custom engineering and design for your house for FREE, then stand behind that design, all in the hopes he'll get the low bid?

If you want a design for a custom system that is outside the standard cookie cutter poke n hope work, you have to PAY for that design.

If you are concerned by having a quality Man J and duct design by Man D then hire your own engineer to do the work for you and then he can spec exactly what the system must do to be considered properly installed. There is a fair amount of work with all HVAC comfort system to get it rifgt so spend the time and money now and then you don't have to worry about having to redo it later.

Jumped me...
What did the audit recommend? What did it say load was?

[overhear]

Thanks for the reality check, mchild.

I'm not sure how to find an engineer to spec out the job. Since my architect, and presumably also the GC's he works with, doesn't have much experience with split and VRF systems, what's the best way to get a recommendation for a good engineer who has done that kind of work?

[overhear]

You hit the nail on the head, tedkidd. I've been very confused about process. I totally get why a contractor wouldn't want to put the design work in upfront. And the fact that the architect doesn't think I need the system designed has been an added complication.

Sorry but I'm a complete ignoramus and don't see anything about load in my NYS energy audit.

I'm definitely ready to hire someone to design a system.

[tedkidd]

You hit the nail on the head, tedkidd. I've been very confused about process. I totally get why a contractor wouldn't want to put the design work in upfront. And the fact that the architect doesn't think I need the system designed has been an added complication.

Sorry but I'm a complete ignoramus and don't see anything about load in my NYS energy audit.

I'm definitely ready to hire someone to design a system.

The HPwES program and the TREAT software have a LOT of if/then, so none of us can claim to not be somewhat ignorant. That said, sounds like the ignoramus is your architect. Building houses that aren't comfortable to LIVE in misses the point of elegant design, doesn't it?

The load calc is in the software, but probably not part of the report you received. Are you still engaged in conversations with the auditing contractor? Ask them what the base and improved loads were. TREAT comes pretty close to manual J. Both have a fair "safety factor."

Did they come up with any hvac solutions?

[overhear]

The load calc is in the software, but probably not part of the report you received. Are you still engaged in conversations with the auditing contractor? Ask them what the base and improved loads were. TREAT comes pretty close to manual J. Both have a fair "safety factor."

Did they come up with any hvac solutions?

The guy that did the audit seemed great, but sort of deferred to his company's estimator. Then the estimator didn't seem to have ever seen a split system that didn't use a ductless evaporator.

I'll call tomorrow and ask for the load info.

[tedkidd]

the estimator didn't seem to have ever seen a split system that didn't use a ductless evaporator.

I'm starting to get confused too. You want mini-splits, right?

[MM#7]

I'm starting to get confused too. You want mini-splits, right?

some of the fujitsue mini splits can use very limited duct work to do 2-3 rooms
depending on btu's and room sizes. the operative word is limiited duct! some states and localites are even wanting ducted air from outside even with mini-splits!

[overhear]

I'm starting to get confused too. You want mini-splits, right?

I do have that effect on people.:-) I guess what I mean is the "concealed" ducted indoor units that Mitsubishi sells for their P-Series split system (for example, http://catalog.mitsubishipro.com/vie...oners-systems?).

Maybe I am confused. Are those units really not very "concealed" when they're installed?

[MM#7]

I do have that effect on people.:-) I guess what I mean is the "concealed" ducted indoor units that Mitsubishi sells for their P-Series split system (for example, http://catalog.mitsubishipro.com/vie...oners-systems?).

Maybe I am confused. Are those units really not very "concealed" when they're installed?

do you mean ductless units as compared to ducted?