New CH install - couple of questions - newbie

[jrcsheffield]

I suggest you read the Grundfos Alpha Documents.

Thanks for those very interesting and useful reading....this document section raised hopefully last questions.......

Bypass commissioning Alpha2 or 2L document

For variable speed pumps, a manual fixed bypass arrangement is recommended. I HAVE AN AUTOMATIC BYPASS FITTED (Honeywell DU144).
An automatic bypass valve should not be used with the Alpha2 pump in proportional pressure control.
I HAVE AN ALPHA 2L CAN IT BE USED WITH PP CONTROL?
IF NOT SHOULD I PUT IT BACK TO CP2 OR JUST SPEED 11 PERHAPS
For condensing boiler, the operation of an automatic bypass with proportional pressure control is counter productive to maintaining condensing boiler efficiency at high load conditions. As the pump pressure increases, the bypass flow will also increase which
raises the boiler return water temperature and reduces boiler efficiency.
In constant pressure operation a fixed manual bypass for will maintain a constant bypass flow.
WHAT ABOUT THE ‘BYPASS RADIATOR AND A TRV?

Many thanks for your help to date..John

 

[solutions]

Not seen a reverse return system in years, big commercials jobs was the last time i seen them

We had an almighty house to sort out and install new boilers too.
Upstairs zone was fine.
never could balance the downstairs.
crawlspace under the entire house.

little bit of re piping into reverse return and issues solved

Dont think I have ever seen one in the real world. Supposed to be considerably more efficient I was lead to believe, although never quite understood why. would apreciate if any one who does know would share. Is it just lower pumping resistance?

 

[doitmyself]

I HAVE AN ALPHA 2L CAN IT BE USED WITH PP CONTROL?
IF NOT SHOULD I PUT IT BACK TO CP2 OR JUST SPEED 11 PERHAPS

Because you have two motorized valves you do need a bypass, so there is a path back to the boiler when both valves are closed and the pump is overrunning. CP mode is what it says - the pressure is Constant. Now the ABV opens when the pressure across it exceeds the set value. So, it will be either permanently open or permanently closed, depending on the which pump setting is used, CP1 or CP2, and the ABV setting. This is obviously undesirable, so using CP is not a solution.

You could use a fixed speed, but you are then losing any of the advantages of the Alpha Pump, particularly low power consumption.

The solution is to put a fixed bypass in series with the ABV. The ABV only allows water to flow through the bypass when it is necessary and the fixed bypass prevents the flow exceeding the required rate. Grundfos recommend the Taco setter, presumably because it has a built-in flow meter so you can set the rate without any guesswork.

WHAT ABOUT THE ‘BYPASS RADIATOR AND A TRV?

Provided the rad in the room where the wall stat is located doesn't have a TRV, there's no reason why you need another rad to act as the bypass. In many ways a bypass rad is not really needed; they are a relic from the days of cast iron or solid fuel boilers which continued to produce heat for sometime after they went out, so there needed to be something available to dissipate the heat. So here's no reason why you should not put a TRV on the bathroom rad.

When a modern gas boiler is turned off, that's it: heat generation stops immediately. So all you need to do is cool down the heat exchanger, which will occur fairly rapidly even if the water is just pumped through a loop of pipe.

 

[jrcsheffield]

Because you have two motorized valves you do need a bypass, so there is a path back to the boiler when both valves are closed and the pump is overrunning. CP mode is what it says - the pressure is Constant. Now the ABV opens when the pressure across it exceeds the set value. So, it will be either permanently open or permanently closed, depending on the which pump setting is used, CP1 or CP2, and the ABV setting. This is obviously undesirable, so using CP is not a solution.

You could use a fixed speed, but you are then losing any of the advantages of the Alpha Pump, particularly low power consumption.

The solution is to put a fixed bypass in series with the ABV. The ABV only allows water to flow through the bypass when it is necessary and the fixed bypass prevents the flow exceeding the required rate. Grundfos recommend the Taco setter, presumably because it has a built-in flow meter so you can set the rate without any guesswork.


Provided the rad in the room where the wall stat is located doesn't have a TRV, there's no reason why you need another rad to act as the bypass. In many ways a bypass rad is not really needed; they are a relic from the days of cast iron or solid fuel boilers which continued to produce heat for sometime after they went out, so there needed to be something available to dissipate the heat. So here's no reason why you should not put a TRV on the bathroom rad.

When a modern gas boiler is turned off, that's it: heat generation stops immediately. So all you need to do is cool down the heat exchanger, which will occur fairly rapidly even if the water is just pumped through a loop of pipe.

So all this is because I chose to buy a variable speed pump to work with my newly installed boiler? Just to clarify if I buy and fit this Taco device in Series with the ABV What do i set the pump mode to be?? CP or PP or fixed speed afterwards? Many thanks once more John

 

[stevetheplumber]

most of that was right over my head but correct me if im wrong
energy saving mean we can only fit the new type of pumps
the new types of pumps need a non automatic bypass
part L demands we fit a automatic bypass

 

[Ray Stafford]

most of that was right over my head but correct me if im wrong
energy saving mean we can only fit the new type of pumps
the new types of pumps need a non automatic bypass
part L demands we fit a automatic bypass

Or put on an A rated pump, but one that has a fixed speed setting.

 

[doitmyself]

if I buy and fit this Taco device in Series with the ABV What do i set the pump mode to be?? CP or PP or fixed speed afterwards?

You set the pump to the appropriate PP.

Normally the ABV will be closed, so there is no flow through the bypass. If the pressure exceeds the setting on the ABV, the valve will open and allow flow through the bypass. If the pressure increases any further the Taco Setter will limit the flow in the bypass circuit.

WB do not state a minimum flow rate, so it might be worthwhile contacting them and asking their advice on the correct setting of the ABV and Taco Setter.

 

[jrcsheffield]

You set the pump to the appropriate PP.

Normally the ABV will be closed, so there is no flow through the bypass. If the pressure exceeds the setting on the ABV, the valve will open and allow flow through the bypass. If the pressure increases any further the Taco Setter will limit the flow in the bypass circuit.

WB do not state a minimum flow rate, so it might be worthwhile contacting them and asking their advice on the correct setting of the ABV and Taco Setter.

Hello again….you will recall I am trying to use a Grundfos Alpha2L in Proportional Pressure 2 mode on my newly installed central heating system in order to achieve maximum cost efficiencies from the pump and heating system. Unfortunately an auto bypass valve has been installed by my plumber.
From my conversations with Grundfos and doitmyself on this forum , I am advised that I can use the Worcester Bosch Greenstar 18RI and the Grundfos Alpha2L in PP mode but I will need to fit a Taco Setter (flow regulator and gauge) in series with the Automatic Bypass Valve.

WB have advised me that the minimum boiler flow rate is 5 litres per minute so, using the pump tables I have set my ABV to 0.25mb.

I do not understand what I should set the Taco Setter to? I am guessing 0.25mb???

Can you also advise if the Taco Setter should come in any series connected order ie: pump outflow – Taco-Setter - ABV – return pipe work or pump outflow – ABV - Taco Setter - return pipe work.

Does it matter?

I think I am amost there once I have these pieces of information I will try to purchase a Taco Setter.

Thanks John

 

[lame plumber]

if your going to the trouble of fitting a taco setter as mentioned, why not fit a gate valve instead of the auto bypass. Its omho but your trying to establish a system running as efficiently in the manner that car manufacturers tell us their vehicle efficiencies are in perfect conditions, overall your just wasting your time, as a bit of corrosion and sludge will soon mean you have to reset the whole setup in 6 months time!

 

[Ermintrude]

if your going to the trouble of fitting a taco setter as mentioned, why not fit a gate valve instead of the auto bypass. Its omho but your trying to establish a system running as efficiently in the manner that car manufacturers tell us their vehicle efficiencies are in perfect conditions, overall your just wasting your time, as a bit of corrosion and sludge will soon mean you have to reset the whole setup in 6 months time!

Yep u want as few variables as possible otherwise every one is going to be adjusting every 3 seconds. Get rid of auto bypass and install a manual buy pass old skool.