HVAC design for apartments - Need Ideas

[cadillackid]

I have been requested to make a design for the owner of an 8 unit townhouse building.

the building is a single row house of older design but is currently gutted out for remodelling.

the building suffered a flood and therefore was required brought up to code.

previously the building was heated by baseboard hydronic hot water heating system and had no Air-COnditioning.

To get decent rents these days one must have Air-Conditioning so thats why he contacted me..

he wants to have installed a hybrid gas / electric HVAC system.. with heat pump and A/C.. and the ability to adjust temperatures per floor with variable capacity.

this would mean 17 indoor units.. (2 for each apartment and 1 for the Lobby area..)

currently there is a mini split handling the Lobby area and that will probably stay so I need 16 additional indoor units..

I need 1.5 Tons per indoor unit and they need to be ducted..

I first suggested a Daikin VRV system for cool and heat pump.. with a Hydronic kit for aux heat.

that was shot down as he wants each tenant to pay for their own electricity.. each unit is metered separate.. so that limits me to having an outdoor unit for each apartment...

The central boiler will have 17 Zones fitted to it and he plans to bill the apartments based on the number of minutes that a zone is calling for heat from the boiler in times of cold weather when heat pump is not operable..

so somehow I need to find a system with ducted ceiling mounted indoor units that can also handle a hydronic coil as well.. and be able to communicate with a central controller..

I was willing to design a custom control system, but he wants me to fit industry standard controls in case i am no where to be found in a few years..

my second thought was to fit a Mitsi city-multi system with a computer interface that could centrally shut down all the heat pumps at a certain outside temperature.. however I still need all the apartments to be able to adjust their temperatures by one controller and not have to worry about 2 thermostats.

those setpoints and room temps need to be reported to the central system as well the unit fans need cycled (or stay in per user request).. and of course the hydronic valves get cycled based on heat call..

what a wild system but I do not see how to do it without custom controls and software...

so I figured id ask if some of the members in europe where boiler heat is common have ever fitted a combination heat pump / Air-Cond / hydronic system such as this?

-Christopher

[goshen]

Hi :
u should look at trane units that can communicate ,or mitsubishi units .
they also have a program that can calculate bills for tenantes for vrf systems,if u choose to use a water unit u should check out climaveneta energyriser units that produce simultaniusly cold and hot water up to 65 deg c! and u bill the tennantes by energy meters connected by comm!
good luck

[frank]

You can use the Daikin VRV option and add the Dbacs package which allows separate metering of useage.

[Tesla]

Hi Christopher
I attended the ARBS exibition in Sydney this week and saw some new technologies which might help. You could fit domestic water flow meters to each appartment with a single coil. The coil could use the new Belimo 6 way walve to provide heating or cooling. You could even provide domestic hot water from the same system. Use a single water heatpump with more than one compressor (for redundancy and efficiency), with two pumps for each hot and cold water. You could use a ringmain water piping system to save on pipe intall costs. Have a hot and a cold water storage tank. Depending on the cost of electricity/gas the heatpump should be cheaper than gas. With a power meter installed on the unit and the water meters the owner would charge about double the cost of the power to cover plant costs. For 17 indoor units I'm sure the above would be the most efficient to run and reliable. As for the control system you could fit a generic controller that most fridgies can opperate - like in Ausie Innotec controllers are simple, cheap, and common. If the owner is bent on gas it could be installed as a booster for colder months.

[mad fridgie]

What are you ambient limits and what is ambients are more normal.
Do you have heating and cooling in the same 24 hour period.
I would look at a diversified load, with phase change thermal storage, both hot and cold,
Simple ring mains, with hydronic energy meters. Seimens (can come with comms) use ambient temps to maintain optimum efficiency.

[Rajkumar]

You can use slurry ice system which is similar to thermal storage and you get the different water temperature at different height on the tank.

[dougheret0]

In my opinion the most cost effective solution would be water source heat pumps. You will still need a boiler, and you will need a cooling tower, but you can pipe moderate temperature water to each apartment. By monitoring compressor operation, charges for the boiler and cooling tower can be based on compressor operation. Since boiler energy use will be the same as heat pump heating use (less offsetting heat rejection from systems in cooling mode), it will also be necessary to monitor reversing valve operation to levy a different charge for compressor heating operation than for the cooling tower, which will be modest.

The down side is that heating COP with such a "boosted" water source system is very poor - usually about .5 or .6. However, cooling operation is very efficient.

[cadillackid]

I hadnt thought about using water for both heating and cooling.. there has to be some sort of fossil fuel for heat as the outdoor ambient temps in this region typically go to -5 to -15 degrees F (im usa i work in degree F).. and in summer we easily reach temperatures of 95 degrees F with dewpoints in the 70s..

so for a comfortable system it almost has to be variable capacity to handle the varying conditions..

each apartment has its own gas and electric Meter and each apartment will be fitted with a Rinnai Tankless domestic Gas fuel water heater..

Currently im talking to Rinnai about Heating loops from the water heaters.. it is an option they offer.. and the control system is promising with it too..

this would eliminate the central heating-only boiler he was going to fit..

the owner seems pretty set on having separate primary system for each unit.. so im looking at the mitsi ducted city-multi 3 ton systems.. one for each apartment with 2 indoor units...

this guy embraces new technologies but only to a point then he gets the fear of the unknown..

as far as heating and cooling the same 24 hour period.. very much Yes in the spring and fall... yesterday for example it was 46 degrees in the morning and was 84 in the afternoon.... last night was 68.. then it went to 82.. and we just had a storm.. it went back to 65.. and will be 36 tonight and only 52 tomorrow so wild swings in outdoor ambient are common..

im really liking some of your guys' ideas for sure... especially the multi-tenant billing systems..

I will approach him one last time about a completely central system.. I too think that would be most efficient.. we will see...
-Christopher

[back2space]

If your fitting heat pump AC systems why not just use them in reverse for the heating also.

You will have good efficiencies from the heating operation and some countries you can buy units that can work down to -25C in particulary cold countries.

This will solve the problem of charging for the heating etc and will be more efficient.

[cadillackid]

the issue is where i am at i need to be able to heat at full capacity down to -15 to -20 degrees F... most heat pumps start to really drop off at 10 degrees F.. and with the often high humidity here... snow, ice, cloudy skies.. they spend more time in defrost than in heat mode..... right now we are looking at rinnai hydronic coils fitted into daikin ducted indoor units...

at 95% efficiency gas heat is far cheaper here than trying to run an electric system flat out.. mitsi hasnt gotten back to me yet on whether their ducted ceiling indoor units can be fitted with hydronic heating coils or not...

there will definately be heat pumps as part of this... for one the unit-facing side of the building will be in the sun during the morning and midday hours when most post-night warm up mode heating goes on... this will allow me to run the heat pumps in a bit colder weather...

the switchover from heat pump to gas will occur somewhere between 10 and 15 degrees F and will be based on temperature, humidity, and current gas / electric rates, as well as heat load, etc...

the owner has greatly warmed up to the idea of custom controls and now finds that some people are interested in living there because of later technologies used in the HVAC, communications, lighting and entertainment systems of the building.... the project has slowed a bit because of some construction issues so that makes it easier as there is more time to come up with a good system...
-Christopher

[dougheret0]

[quote=cadillackid;185011]I hadnt thought about using water for both heating and cooling.. there has to be some sort of fossil fuel for heat as the outdoor ambient temps in this region typically go to -5 to -15 degrees F (im usa i work in degree F).. and in summer we easily reach temperatures of 95 degrees F with dewpoints in the 70s..

>A boosted water source heat pump will work well in >your climate. The source water is heated by a gas >fired boiler during space heating. This is inefficient,
>as I said, because the boiler must provide all of
>the heat needed for the unit, which is producing
>cold water. Piping and hookups for boosted water
>source systems are available from manufacturers of
>the units.


as far as heating and cooling the same 24 hour period.. very much Yes in the spring and fall... yesterday for example it was 46 degrees in the morning and was 84 in the afternoon....

>I was speaking of different apartments requiring
>cooling and heating at the same time - say
>in late afternoon, east facing apts are cold and
>west facing are warm. In that case, the heat
>rejected by the warm apts will supply the heat
>needed for the cold apts. The piping, hookup,
>and controls should be set up to take advantage
>of this situation when it occurs. Again, guidance
>can be found from manufacturer's reps.

[Magoo]

Consider a 4 pipe system, with heat pumps and gas boost and calorifiers, and drycoolers for summer.
Similar to an hydronic system used successfully in high rises, yours goes side ways as opposed to up.

[lomb]

KISS principle. A seperate outdoor unit and gas boiler for each unit. Common areas have their own outdoor unit. This removes cost of controls and engineering which is costly. Gas boilers are cheap.

[cadillackid]

right now this all comes down to which manufacturer is going to fit our ducted splits with hydronic coils..

Lomb: a separate boiler and outdoor unit for each condo is where we are going.. however in the USA Hot air heat is the norma and what people expect so we have to find a solution that allows hydronics in the ducted system... it looks like its going to be mitsi..

the boiler will either be a Navien or a Rinnai which will supply domestic hot water as well as system heat for each apartment..

one outdoor unit and 2 ducted indoor units for each apartment.

using city multi the systems can be connected and allow for central maintenance monitoring....

we have plenty of time as the project is undergoing some serious construction related setbacks..

Daikin is also in the running, however they are a bit pricier than mitsi.
-Christopher

[FreezerGeezer]

Why do you want the hydronic coil in the split? Wouldn't it be simpler & work as well to have it in the duct?

[cadillackid]

I guess I shouldve clarified the hydronic coil doesnt have to be in the split itself physically, esp since it is not a cooling coil there will be no condensate.. however it will need to be accessible for cleaning / repair, etc....

the main thing is that the controls need to be integrated... so the tenant only has to operate a single t-stat for each system.. (1 upstairs, 1 down).

-Christopher

[Zwed]

Hi guys,.
Nice read to get useful information about design the home decoration ,.

[techguy]

Hi CK,

This is not exactly what you were after but____

You could try a SANYO VRF System. We have a controller which can determine how much energy each individual indoor unit uses as a % of the outdoor units consumed energy over a billing period. So if you meter the outdoor unit using a pulse meter and connect this to our controller it can then determine the total KW usage of each indoor unit over the billing period. The system then simply multiplies this by the cost per KW which you can input to the system when commissioning and you have your bill.

This is available in Europe as Sanyo Staims software. This is a full controls package which will do a number of other functions also. But it does allow independent individual remote control from local controllers. Not sure if the USA use it. But you can always ask.
T