air to water heat pump options
Last Post 04 Mar 2015 08:50 AM by ICFHybrid. 22 Replies.
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greenseattleUser is Offline
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25 Sep 2014 01:52 AM
What are the air to water heat pump options out there? I know the Daikin Altherma, what else? My air handler for existing older 3 ton heat pump in Seattle just died. Putting in some hydronic micro zones (bathrooms, kitchen) and 120 gallon indirect in ongoing remodel. Need to feed all of the above. One option is a natural gas mod con, but would prefer to stay off fossil fuels. Any air to water solutions out there without a huge price premium?
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25 Sep 2014 05:28 PM
Our North American market is not competitive in the air-to-water heat pump area. It will come, but for now, yes those systems command a premium.
I just specified the Daikin Altherma for my new house. It's costly, but electric is my only option and we wanted radiant heat without air movement. Another thing to keep in mind that air-to-water pumps do is heat DHW. Most people focus only on the heating aspect, but you do get a great benefit of essentially having a heat pump DHW heater without the negative effects of cooling the mechanical room you get from the HPWH.

Here are the choices I found during my research:
Daikin Altherma
Unichiller RC
Aqua Products Reverse Cycle Chiller
Aermec ANK series
Thermo Matrix CoolFire
Ecologix CCHP
Mitsubishi Ecodan will be on the market perhaps next year

The reason I went with Daikin is because a local company installed quite a few, so I'll have local support rather than being the experimental house for some of the newcomers.

Hope this helps.
Cheers.
ICFHybridUser is Offline
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25 Sep 2014 10:10 PM
I'm pretty pleased with my Daikin and I'm ecstatic I don't have to run an earth loop, both from the point of view of less equipment, less maintenance hassle and less pumping energy.

HOWEVER, I suspect I would use radiant electric in "microzones" like the bathrooms before doing the hydronic floors in those places again.
jonrUser is Offline
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26 Sep 2014 11:39 AM
ICFHybrid: I'm curious - why would you use radiant electric if you have radiant hydronic? You can still microzone it.

The UK has many air to water heat pump choices - I believe that either they would work fine on 60Hz or it would be a minor modification by the manufacturer. So it's a question of demand.
greenseattleUser is Offline
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26 Sep 2014 02:42 PM
I want radiant hydronic. The question is how to heat the water. I'd prefer to do an air to water heat pump over a mod con if I can but those are the two options I'm looking at. Water to water is great, but the cost and permitting of a vertical well is too much for this project. Besides, Seattle has a reasonably mild climate - air to water is a good candidate.
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26 Sep 2014 04:28 PM
Posted By greenseattle on 26 Sep 2014 02:42 PM
I want radiant hydronic. The question is how to heat the water. I'd prefer to do an air to water heat pump over a mod con if I can but those are the two options I'm looking at. Water to water is great, but the cost and permitting of a vertical well is too much for this project. Besides, Seattle has a reasonably mild climate - air to water is a good candidate.

The Daikin Altherma will heat your domestic hot water for you, at a higher net efficiency than a standalone heat pump water heater.  It's not cheap, but it's a very well-engineered setup, and nearly ideal for a Seattle climate. (The very first US Altherma installed was in Portland OR, only modestly warmer than Seattle.)
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26 Sep 2014 08:25 PM
ICFHybrid: I'm curious - why would you use radiant electric if you have radiant hydronic? You can still microzone it.
Well, I should probably explain a bit. My home is passive solar and it works so well, that it appears the air to water heat pump is going to have to run solely to make the bathroom floors warm in the mornings. Of course, the dead of Winter is an exception, but that's fairly short for us. I'm microzoned up the wazoo. The bedrooms (and bathrooms) are on the second floor and there is more than enough residual heat to keep the upstairs the way we like it. If we want the bathroom floors to be comfy, it appears that causes the heat pump to run, but I will know more when we get a full year or so under our belts.

It's possible that the added expense of installing hydronic up there is quite a bit more than resistance mats. What we don't know is if the operational cost savings with the heat pump makes it worthwhile.

I am a big fan of using ductless minis to heat efficient homes and the resistance mats are a good way to get some nice warm floors in small, specific areas.

Seattle has a reasonably mild climate - air to water is a good candidate.
It's an excellent choice in Seattle, especially with the more reasonable electric rates. Someone might try to make an argument for geothermal in the higher foothills, but I doubt it.
Will17109User is Offline
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28 Sep 2014 08:06 PM
"... higher net efficiency than a standalone heat pump water heater"

I assume this refers to having to make up the heat removed by the water heater during winter?

What about summer efficiency? I currently have an oil-fired boiler with a DHW loop in it. I never run out if hot water, and I guess it's reasonably efficient when I'm running the boiler anyway, but when I need hot water in summer I'm firing up enough BTUs to heat the house. I'm looking at options to replace it. Wouldn't a whole-house hydronic heat pump have the same cooling season inefficiency?
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28 Sep 2014 09:46 PM
Wouldn't a whole-house hydronic heat pump have the same cooling season inefficiency?
Inverter driven heat pumps can operate at very low outputs and use correspondingly small amounts of energy. However, the issue you bring up is probably why the Daikin Altherma has a solar integration option. The summer is when the solar panels would be delivering the maximum output.
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02 Oct 2014 10:09 AM
biggest problem with the air to water is the first cost and no tax credits which make the ground source much more accesible in some cases. If load is very modest electric radiant might be a good fit.
Joe Hardin
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02 Oct 2014 06:05 PM
Posted By Will17109 on 28 Sep 2014 08:06 PM
"... higher net efficiency than a standalone heat pump water heater"

I assume this refers to having to make up the heat removed by the water heater during winter?

What about summer efficiency? I currently have an oil-fired boiler with a DHW loop in it. I never run out if hot water, and I guess it's reasonably efficient when I'm running the boiler anyway, but when I need hot water in summer I'm firing up enough BTUs to heat the house. I'm looking at options to replace it. Wouldn't a whole-house hydronic heat pump have the same cooling season inefficiency?
The standby jacket losses of almost all oil boilers are HUGE compared to the losses the DHW storage tank on a Daikin Altherma.  Most oil boilers have R4-R6 insulation, and lots of uninsulated plumbing sticking out of it, for a very high standby loss.  The plumbing on the Altherma would normally be all insulated, and at a lower delta-T to the room air than you'd see with an oil boiler, and the tank insulation is something like R10-R15 (didn't look it up- took a WAG.)

While you don't get the marginal room-cooling effect of standalone heat pump water heater extracting it's heat from the room where it is located, since the heat exchanger coil on the outdoor unit of an Altherma are much larger than of those on a tank-top heat pump,  and the fact that it has a load-variable scroll compressor driven by a VERY high efficiency DC motor it ends up being significantly higher efficiency heat pump than what can reasonably fit on top of a tank (or within the budget of what makes sense for just a hot water heater. The output of the Altherma heat pump is higher too, for shorter recovery times.  Also, whenever it's warmer outside than inside, it's even pushing a lower delta-T than the heat pump water heater would have to.  All in all it ends up being more efficient than an integrated tank-top heat pump even in summer.


Almost all boilers capable of cold-firing without damage can reap a large summertime efficiency gain by heating an indirect-fired tank, and using a heat purge controller on the boiler to bring the temp down to ~140F (or whatever you set the indirect tank to) after the burn, dumping as much of the residual boiler heat in to the tank rather than letting it dissipate as standby loss between calls for hot water.  With an embedded tankless coil you probably have to maintain a boiler temp of 160F or so to have reasonable hot water performance.

Even with non-cold-start boiler that had to idle at 140F to avoid damage would see a large cut in standby loss during the summer when operating with an indirect. There would be fewer but longer burns (== lower start up losses) and lower standby losses, since the delta-T between room & boiler would be ~70F instead of ~90F.  With a cold-start boiler the average jacket losses would be quite a bit lower, since the boiler wouldn't automatically fire up to maintain 140F, and would have a much lower average temp, for a much lower delta-T.
greenseattleUser is Offline
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03 Oct 2014 01:35 AM
Thanks for all the responses so far - good discussion. However I am not making any progress on the heat pump front - I need to keep the cost under the Daiken. Local shops are recommending Viessmann, and it looks like they lead the pack for modulation. But 5:1 is also good. Any others to add?
jchatersUser is Offline
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13 Jan 2015 09:19 PM
Altherma seems have disappeared in fact the only unit that is now allowed in California is the Aermec . The Aermec ANK has set the standard for efficiency whereas the Altherma numbers were not real so it is gone
Melanie OldhamUser is Offline
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14 Jan 2015 09:48 AM
Nice reading!

I would like to know, Since I have seen water-water types of "heat recovery" with even the commercial chillers that air chilling water and using the other side of a system warmer water for something, does this air to water HP make that hot water at the same time as the cooling is running. Is there any control over the outdoor fan to maybe stop running while that "recovery" is on.?
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14 Jan 2015 10:13 AM
Posted By jchaters on 13 Jan 2015 09:27 PM
Altherma seems have disappeared in fact the only unit that is now allowed in California is the Aermec . The Aermec ANK has set the standard for efficiency whereas the Altherma numbers were not real so it is gone

Do you have a source for this?
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14 Jan 2015 10:20 AM
Posted By Melanie Oldham on 14 Jan 2015 09:48 AM
Nice reading!

I would like to know, Since I have seen water-water types of "heat recovery" with even the commercial chillers that air chilling water and using the other side of a system warmer water for something, does this air to water HP make that hot water at the same time as the cooling is running. Is there any control over the outdoor fan to maybe stop running while that "recovery" is on.?

It can only run in one direction at any given time: heating or cooling. So, in the cooling months, the priority is by default to heat the hot water and when that task is done, it switches back to cooling cycle. Some units may allow a change in that priority, but I believe that is the default.
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14 Jan 2015 01:12 PM
It's appears that Daikin has decided to let CA certification standards go, but the Altherma continues elsewhere. And, the notion that the numbers "are not real" is either ignorant or designed to be misleading. My Daikins continue to perform as well as or better than claimed. That's something Daikin has long been known for.
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14 Jan 2015 01:22 PM
It appears I may have offended with my comments about efficiency, I am sorry I did not mean too. As I have been told by people in the CEC Daikin had a waiver and did not need to provide an efficiency rating. The new rules state you must. Simple
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03 Feb 2015 07:27 AM
Well, I should probably explain a bit. My home is passive solar and it works so well, that it appears the air to water heat pump is going to have to run solely to make the bathroom floors warm in the mornings. Of course, the dead of Winter is an exception, but that's fairly short for us. I'm microzoned up the wazoo. The bedrooms (and bathrooms) are on the second floor and there is more than enough residual heat to keep the upstairs the way we like it. If we want the bathroom floors to be comfy, it appears that causes the heat pump to run, but I will know more when we get a full year or so under our belts.

It's possible that the added expense of installing hydronic up there is quite a bit more than resistance mats. What we don't know is if the operational cost savings with the heat pump makes it worthwhile.

I am a big fan of using ductless minis to heat efficient homes and the resistance mats are a good way to get some nice warm floors in small, specific areas.



SOunds nice! I put hydronic in my basement with an air HP with gas backup coil for very cold temps. THe air handler I have has all the bathroom venting running down through it as well. Now that the system has been running for almost two months (without the upstairs thermostat even hooked up), the home (3400sf) is only a few degrees cooler in upstair bedrooms (barely noticeable). I put heat coils in the bathrooms (only one running right now) with a solar system to capture some free sun. My lot orientation and neighbors trees didn't allow for any passive solar but I get some on the West side of the house in the afternoon. With the HP switch pulled out, it was 7 degrees overnight and the house was still warm the next morning with basement set to 10 degrees cooler than normal temps. I lost one degree! (1.5" exterior rigid). Pretty happy so far. I anticipate my monthly bills to be pretty low :) but not free like you!
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06 Feb 2015 06:07 PM
If your space heating loads are tiny enough it looks like there is (finally) soon to be a CO2 refrigerant air-to-hydronic option available in the US from one of the Eco-Cute hot water heater vendors, Sanden.

http://www.greenbuildingadvisor.com/sites/default/files/Sanden%20HPWH%20-%20whywait%20dot%20com%20dot%20au%20-%20cropped.jpg

CO2 refrigerant hot water heaters have been available in Japan for a bit over a decade. More recently they have become popular in Australia where the climate is temperate to hot, the gas grid is limited, delivered propane expensive, and the residential electricity rates among the most expensive in the world.  The Sanden unit gives good efficiency down to outdoor temps of +14F, but falls off quite a bit at temps below 0F.  The NEEA consortium of utilities in the Pacific Northwest has run it through some testing, and are doing in-situ monitoring of the few that are already installed.

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