Daikin Altherma/Viessmann Integration Notes (used … Res... · March 15, 2011 Daikin Altherma/Viessmann Integration Notes (used with schematics M1 thru M5) Our Daikin Altherma project

March 15, 2011

Daikin Altherma/Viessmann Integration Notes (used with schematics M1 thru M5)

Our Daikin Altherma project involves integrating an indoor unit (EKHBX054BA3VJU) with an

existing domestic hot water, high temperature radiant panel, and low temperature radiant floor

heating system. The existing system is built around a Viessmann Vitola 200 propane fired boiler, a

Vitotronic 200 control system, a Divicon mixing station, and a Vitocell 300 domestic hot water

tank. The Divicon serves 6 radiant zones; each zone has a thermostat that controls its respective

circulator through a Taco circulator control. There is one zone of high temperature radiant wall

panels served by a high temperature circulator. Both high temp and mixed temp boiler circuits

utilize heating curves reset using outside temperature. The Vitocell 300 tank is served by a

domestic hot water circulator.

This existing system is approximately 6 years old and represents what once was the state of the art

in hydronic heating. Overall system efficiency is on the order of 80 to 90%. Until recently, there

was no realistic or cost effective way to significantly reduce system operating costs or improve

upon this level of energy efficiency.

We see the arrival of the Altherma in the United States as a tremendous opportunity to rectify this

situation. Our perception is that owners of Viessmann hydronic systems are typically willing to

invest in an efficient heating system and are very interested in energy efficiency and are therefore

ideal candidates for an Altherma retrofit project.

The purpose of the notes that follow is to outline our approach to the integration of the Altherma

with the Viessmann system – what the pre-existing system looks like, different approaches to

integrating the two heat sources, and determining the optimum use of the Altherma’s capabilities.

Pre-existing Viessmann System: Schematic M1 (left illustration)

The existing boiler has a domestic hot water (dhw) circuit, a high temperature circuit, and a mixed

temperature circuit.

The domestic hot water circuit uses the factory default schedule that enables operation from 5:30

AM to 10:30 PM every day. Whenever dhw tank temp falls below the dhw setpoint (currently

130F) the boiler temp rises to 180 F and the dhw circulator operates.

The high temp circuit is a single zone of radiant wall panels served by a high temp circuit

circulator controlled by a Taco switching relay and zone thermostat. The high temp circuit

www.nmdgreen.com P.O. 4778, Vineyard Haven, MA 02568 P & F 508-696-3120/4120, email [email protected]

operates on the factory default schedule that enables boiler operation from 6 AM to 10 PM every

day. Based on an outside reset curve with a high temp of 180 F at 0 F outside, the boiler maintains

the appropriate reset temp at all times of enabled operation. As this high temp circuit is used

infrequently, there are quite a few hours of unnecessary propane consumption to maintain boiler

standby temperature.

The mixed temp circuit has constant circulation provided by the built in circulator in the Divicon

mixing station. Connected to this mix temp circuit are six radiant zone circulators controlled by a

Taco circulator control from zone thermostats. The returns from the six zones (some in concrete

floors and some in wood floors) feed back into the mix temp circuit right after the last radiant zone

supply. Use of large diameter tubing in the mix temp circuit (resulting in negligible pressure drop)

and the pressure gradient from the Divicon mixing circulator help to ensure that system pressures

are fairly uniform and that the zone and mixing circulators work well with each other. Based on an

outside reset curve with a mix temp of 120 F at 0 F outside, the boiler maintains the appropriate

reset temp at all times of enabled operation. As the high temp circuit reset curve is always hotter

than necessary for the radiant zones, the Divicon mixing station is constantly mixing radiant loop

return water with boiler supply to reduce the radiant supply temperature.

Altherma Integration With Viessmann: Schematic M1: (right illustrations)

Parallel versus Series: We feel that installing the Altherma in series with the Viessmann presents

several advantages over alternating or parallel installations. Installation instructions for the

Altherma indicate in Application 5 the use of either a boiler or the hydrobox as a source for a

hydronic system. If return temperatures of the system can be held below 120 F, we feel that there

are several advantages to operating the two sources in series and simultaneously:

Maximize Heat Output from Altherma with the Coldest Return Water:

If the Altherma hydrobox and Viessmann boiler are in series then we can ensure that the coldest

return water will go to Altherma first resulting in the greatest opportunity to extract heat from the

hydrobox (if return temperature is too high, the hydrobox will reach a point where it can no longer

heat the hydronic flow through the heat exchanger).

Maximize Heat Output from Altherma as First Stage:

Given a fixed hydronic input temp, the hydrobox output temp will rise and fall with the capacity of

the heat pump as a function of outside temperature. As the hydrobox output temp drops the

Viessmann Divicon mixing station will add hot water to bring the supply temp up to the reset

setpoint. Having the hydrobox first in a series arrangement will automatically ensure that the

Altherma will always have the opportunity to add as much heat as possible to the hydronic flow.


Increased Heat Pump Annual Run Time:

If the hydrobox and boiler are installed in parallel, we feel that the instantaneous burner/Divicon

mixing station output of the boiler would be much greater than the output of the hydrobox. Mix

temp circuit target temperature would be achieved quickly and the overall runtime of the heat

pump would be reduced. A series installation may reduce instantaneous heat input to the mix

temp circuit but will increase Altherma run time as stage 1 to almost 100% or continuous operation

during the coldest parts of the heating seaon.

Our perception is that operation of the Altherma is more economical than operation of the

Viessmann boiler – as the Altherma annual operating hours increase, the annual operating cost of

the entire system will decrease.

Altherma/Viessmann Integration:

(Schematic M1 inset, upper right illustration and Schematic M2)

The return flow from the mixed temp circuit goes to a 40 gallon buffer tank (necessary to ensure

adequate hydronic system volume) and into the inlet of the hydrobox. The Daikin motorized 3

way valve directs hydrobox output to either the Daikin domestic hot water tank or the heating

system. (Application 3) The heating output from the Daikin 3 way valve goes to a motorized 3

way valve (labeled RadMV1) that directs flow either directly to the radiant system or through the

Viessmann Divicon mixing station.

In the Altherma only heating mode, hydronic flow bypasses the Divicon mixing station and

circulates through the mixed temp circuit. Operation of the Altherma is controlled by the normally

open end switch of the Taco circulator control (as “room thermostat” ) that operates the radiant

zone circulators. Target temperature for the hydronic flow is determined by the reset curve

calculated by the Altherma user interface.

In the Altherma Viessmann series heating mode, motorized valve RadMV1 connects the Altherma

hydrobox output to the Viessmann Divicon mixing station inlet and the Divicon circulator starts.

(Though the motorized valve has a 90 second actuator we feel that the addition of the Viessmann

circulator to the Altherma circulator will ensure that flow will be sufficient for the hydrobox

throughout the valve travel). The Divicon mixing station will add boiler hot water as necessary to

the Altherma input to raise the supply temperature to the mix temp circuit reset setpoint.

Due to the ample size of the mix temp circuit the additional flow from both hydrobox and Divicon

circulators operating in series (with additive pump head) should not create interaction problems

with the existing radiant zone circulators. Both hydrobox and Divicon circulators will be on

together during the periods of highest building heat loss when more radiant zone circulators will be

operating. During periods of lower building heat loss, only the hydrobox circulator will be

operating.


Buffer Tank Connection Choices: (Schematic M1, right illustrations)

There are several ways to connect the heat sources (Altherma hydrobox and Viessmann boiler) to

the mix temp circuit that serves the radiant zones. A buffer tank is used to ensure that the hydronic

system volume is adequate for hydrobox operation. A buffer tank can also be used to isolate

system circulators and reduce undesired flow issues by creating a region of common pressure.

This approach requires a somewhat different control strategy with consequent benefits and

drawbacks.

Buffer tank in series: (Schematic M1 inset, upper right illustration and Schematic M2):

In this approach, the buffer tank is in series with the Altherma and Viessmann circulators. The

radiant zone thermostats activate the zone circulators via a Taco circulator control. The normally

open end switch of the Taco control calls the Altherma directly (as a “room thermostat”) and the

user interface activates the Altherma hydrobox circulator. This hydrobox circulator runs in

addition to any radiant zone circulator anytime there is a radiant call. This will somewhat increase

annual hydrobox circulator run time but the ability of the Altherma to modulate hydronic output

saves energy (compared to a typical “on/off” American heat pump). Temperature control is also

improved as there is very little system lag between the radiant zone call and heat pump operation.

When temperature outside drops below Radiant Stat setting and the Taco end switch is calling,

the Viessmann is brought in as the second stage. This arrangement runs the Viessmann Divicon

mixing circulator in series with the Altherma hydrobox circulator. As the Divicon mixing station

is fully modulating and fairly fast acting, temperature control is not affected and there is little

system lag introduced by starting the second stage. Due to the ample size of the mix temp circuit

piping the operation of the radiant zone circulators should not be affected by the operation of the

Altherma and Viessmann circulators.

Buffer tank hydraulically separating: (Schematic M1 inset, lower right illustration)

In this approach, the buffer tank serves as a hydraulic isolator between the radiant zone circulators

and the Altherma and Viessmann circulators. The supply and return sides of the radiant zones are

separated (note the connection is removed in the illustration) . This arrangement would permit the

operation of the radiant zone circulators independently of the Altherma and Viessmann circulators.

We use this connection approach with non-modulating heat sources (typical American “on/off”

heat pumps) that have one heat output level. A buffer tank decouples the heat output level of the

heat pump from the heat input level going to a radiant zone and reduces short cycling of the heat

source. It can also reduce annual circulator energy use by permitting radiant zone circulators to

remove heat from the buffer tank without always running the heat source circulator.


The buffer tank temperature would drive operation of the Altherma and Viessmann sources. One

possibility would be to use a Tekmar 264 staging control to look at buffer tank temp – the 264

would take the radiant zone Taco end switch input and operate the Altherma as a first stage and the

Viessmann as a second stage. It would use the radiant supply manifold input temp as a control

input.

Typically, a buffer tank installed this way permits multiple circulators of different sizes to

peacefully coexist and lets non-modulating heat sources cycle more efficiently independent of

small heating loads. This approach usually experiences an increased lag in system response

(buffer tank and radiant zone temperatures vary to a greater degree) and increased cost of system

controls when compared to a modulating system (as with the buffer tank in series as depicted in the

upper illustration).

Domestic Hot Water System: (Schematic M2: (upper inset))

A Daikin domestic hot water tank is connected to the Altherma hydrobox via the Daikin 3 way

motorized valve. An existing Viessmann domestic hot water tank is connected to the boiler via a

dedicated dhw circulator. A DHW Stat is used to select a changeover point between Altherma and

Viessmann production of domestic hot water (initial setting of 40 F outside). Below this setting,

we wish to dedicate all of the heat pump output to space heating through the radiant zones. The

Viessmann boiler will be responsible for the entire dhw load. Above an initial setting of 40 F, we

wish to disable Viessmann dhw production and have the Altherma continue with both space

heating and dhw production.

A motorized 3 way valving arrangement switches between the preheat and final dhw tank; below

the initial setting of 40 F, the Daikin dhw tank is preheat and the Viessmann is final – above 40 F

their roles reverse. As the climate of Martha’s Vineyard experiences great temperature swings in

the transitional seasons, this switching arrangement ensures that any energy spent heating domestic

hot water is not lost as the outside temperature rises above and falls below the 40 F setpoint.

From a sanitary perspective, this arrangement also ensures that both tanks are always filled with

potable water fit for human consumption.

Building and DHW Loads: Schematic M3

The upper illustration is a depiction of the building heat loss as a function of outside temperature

(at a maximum at 0 F outside down to a minimum at 68 F warm weather shutdown). Plotted

against this is the heating output of the Altherma as a function of outside temperature (blue shaded

area). There will be a balance temperature above which the Altherma output will be able to meet

the entire building heat loss. Below this balance temperature, the Viessmann boiler output will be

added as a second stage (orange shaded area) to meet the increasing building heat loss.


The Vitotronic control on the Viessmann has two outside reset temperature curves that serve the

high temp and mix temp circuits. An additional Viessmann control, the Switching Module V,

permits the external control of the boiler burner. Below the initial setting of 40 F outside, the

Radiant Stat enables the burner and the boiler will maintain the high temp reset curve. While this

is somewhat inefficient, it is the Viessmann approach so that the boiler is ready if there is a call

from the high temp circuit radiant panel zone. Above the initial setting of 40 F, the Radiant Stat

will disable the boiler burner and the building heat loss will be met by the Altherma output.

The lower illustration is a depiction of domestic hot water production by either the Viessmann

boiler or the Daikin Altherma. The orange shaded rectangle indicates the temperature range in

which the Viessmann boiler will perform dhw heating; the blue rectangle represents Altherma dhw

heating. On the y axis we show hourly domestic hot water output – the Viessmann hourly output

of dhw will be somewhat greater than the Altherma output. We expect that due to projected use,

the Altherma dhw output will be entirely satisfactory.

Below an initial setting of 40 F, the DHW Stat will enable boiler burner operation and switch the

motorized valves so that the Daikin dhw tank serves as preheat to the Viessmann tank. The

Vitotronic control will sense tank temperature and operate the burner and dhw circulator to

maintain 130 F in the Viessmann tank. The Altherma output will be devoted to space heating and

domestic hot water production will be disabled via a field setting. Above 40 F, the DHW Stat will

switch dhw roles by changing the motorized valve positions and disabling the Viessmann boiler

burner. The Viessmann dhw tank will now serve as preheat and the Daikin dhw tank will maintain

125 F.

Smart Grid Integration: The project location is also part of a SmartGrid integration project with

General Electric and the Vineyard Energy Project, a local energy group. We are serving as their

technical liaison with the 50 families in the pilot project. Real time information about current

electricity pricing (3 price tiers) will be available at a local GE interface device and can be used as

an input to the Altherma.

We wish to use this kWh pricing information and the benefit rate kWh power supply field settings

on the Altherma to determine backup and booster heater operation. A comparison can be made

between the price of propane (at a projected system efficiency of 90% for the Viessmann

installation) versus the current electricity price tier (at a projected COP of 1 for the booster and

backup heater).


Control Details: Schematics M4 and M5

This schematic shows one approach to the controls necessary to integrate the Daikin Altherma with

the existing Viessmann system. As described above, the external interface to the Viessmann

system will be their Switching Module V which permits remote control of the boiler burner. When

the contact X7 on this module is closed, burner operation is disabled. Therefore, the domestic hot

water, radiant, and hi temp relays all have their burner disable contacts in series. Any one of these

relays may call for burner operation independently of each other.

Domestic Hot Water Controls: Schematics M4 and M5

A DHW Stat responds to a drop in outside temperature below the initial setpoint of 40 F and

closes an internal contact which powers the “DHW Relay”.

(For the sake of simplicity we depict this DHW Stat as a Honeywell remote bulb controller

T675A1508 with adjustable differential and operating range of 0 F to 100 F. We expect that this

switching function can easily be provided by a web based DDC system that we hope to use to

trend system operation.)

When powered, the DHW Relay will power the motorized valves DHWMV1, DHWMV2, and

DHWMV3 to their Daikin dhw preheat/Viessmann dhw final position. The DHW Relay will also

close the circulator contact and connect the Viessmann dhw circulator to the Vitotronic 200 on the

boiler. The normally closed contacts on the burner disable points will open and enable burner

operation. The Vitotronic control on the boiler will monitor Viessmann dhw tank temperature and

will now be able to heat domestic hot water as necessary.

Similarly, when the DHW Stat experiences a rise in outside temperature above the initial setpoint

(plus the adjustable differential) of 40 F, the internal contacts will open and the DHW Relay will

return to its unpowered state.

The DHW Relay will then power the motorized valves DHWMV1, DHWMV2, and DHWMV3

to their Viessmann dhw preheat/ Daikin dhw final position. The DHW Relay will also open the

circulator contact and disconnect the Viessmann dhw circulator from the Vitotronic 200 on the

boiler. The burner disable points will return to their normally closed position. The field settings

on the Altherma hydrobox will ensure that domestic hot water is now generated by the heat pump

system.

Radiant Heating Controls: Schematics M4 and M5

A Radiant Stat responds to a drop in outside temperature below the initial setpoint of 40 F and

closes its internal contacts. Local radiant zone thermostats connected to a Taco circulator control

operate their respective radiant zone circulators and close a normally open end switch on the Taco


control. This end switch and the Radiant Stat contacts are in series; if both contacts are made

then the “Radiant Relay” is powered.

(As with the DHW Stat we depict the Radiant Stat as a Honeywell remote bulb controller

T675A1508 with adjustable differential and operating range of 0 F to 100 F. We expect that this

switching function can easily be provided by a web based DDC system that we hope to use to

trend system operation.)

When powered, the Radiant Relay will power the motorized valve RadMV1 to direct hydronic

flow from the Altherma hydrobox outlet to the Viessmann Divicon mixing station inlet. The

Radiant Relay will also close the circulator contact and connect the Divicon mix circulator to the

Vitotronic 200 on the boiler. The normally closed contacts on the burner disable points will open

and enable burner operation. The Vitotronic control on the boiler will monitor Viessmann boiler

and will heat the boiler to the high temp reset curve (only because this reset curve is always hotter

than the mix temp reset curve).

Similarly, when the Radiant Stat experiences a rise in outside temperature above the initial

setpoint (plus the adjustable differential) of 40 F or all of the radiant zone thermostats are satisfied

and the Taco end switch opens, the Radiant Relay will return to its unpowered state.

The Radiant Relay will then power the motorized valve RadMV1 to direct hydronic flow to

bypass the Viessmann Divicon mixing station. In this mode, only the Altherma hydrobox output

will be connected to the mix temp circuit and the radiant zones. The Radiant Relay will also open

the circulator contact and disconnect the Viessmann Divicon mix circulator from the Vitotronic

200 on the boiler. The burner disable points will return to their normally closed position.

Hi Temp Heating Controls: Schematics M4 and M5

The hi temp thermostat connected to a Taco switching relay circulator control operates the hi temp

zone circulator and closes a normally open end switch on the Taco control. When this end switch

closes the “Hi Temp Relay” is powered.

When the Hi Temp Relay is powered, the normally closed contacts on the burner disable points

will open and enable burner operation. The Vitotronic control on the boiler will monitor

Viessmann boiler temp and will heat the boiler to the high temp reset curve.

When the hi temp thermostat is satisfied and the Taco end switch opens, the Hi Temp Relay will

return to its unpowered state.

The burner disable points will return to their normally closed position.


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Daikin Altherma/Viessmann Integration Notes (used … Res... · March 15, 2011 Daikin Altherma/Viessmann Integration Notes (used with schematics M1 thru M5) Our Daikin Altherma project