New CH install - couple of questions - newbie

[jrcsheffield]

Hello - We recently had a recommended Heating engineer install a brand new CH system with a Worcester Bosch Greenstar 1.8i boiler configured as a system boiler and 16 rads, with TRV's and room stat.

There are a couple of things he didn't complete to my satisfaction but I appreciate some things take extra time and I am more than willing to put the finishing touches to the system if I can - I have qualifications in electrical engineering, past knowledge of installing several central heating systems with and without computer control systems. I am a competent person but will no longer touch gas.
As the chap doesn't seem to want to come back here we go.....

I have researched that the Grundfos Alpha 2l pump installed should be switched from speed 2 to CP2 (constant-pressure control) for my type of installation so I assumed that the radiators would all need re-balancing.
A task which I did initially and have now done again for the new pump setting.
The 12 degrees required Centigrade temp drop across each of the 16 radiators had indeed changed so I spent most of the day putting this right.

I also decided to look at the excessively hot ‘bypass’ radiator in the bathroom and attempted to adjust this but could not make it drop 12 degrees, only 5 degrees was possible – it is very near to the pump and boiler and is a very small radiator.

There is also an automatic bypass valve fitted close to the boiler across the flow and return.(Honeywell DU144).

Before I completed any of the above work the Condensing System boiler had a 15-20 C temperature drop across the flow and return pipes at the boiler – this varied slightly depending on how many radiator TRV’s were calling for heat.

After I completed the work the house was up to correct temperature and only 2 TRV’s were calling for heat.

Question 1. I noticed there was very little temperature difference between flow and return at the boiler – is this correct for just 2 TRV’s demanding heat under Constant Pressure pump control or could the automatic bypass valve have cut in?

Question 2. Will this automatic bypass need some flow adjustments performing on it as I understand it should have been set up at commissioning stage?
I suspect his ‘bypass’ radiator (no TRV but twin lockshields) was put in this way so he didn’t have to set up this automatic bypass up or buy another TRV.

Any help most appreciated and no I won't be getting him back or recommending him!

Can anyone out there kindly answer these questions and restore my faith in plumbers & heating engineers?

Many thanks John

 

[lame plumber]

how do you know he hasnt set up the auto bypass? the only reason you have an excessivly hot bathroom rad/bypass rad is your boiler water temp is set too high, lower that and the rad wont be so hot, basic physics. The rads need to be set up and balanced on the constant setting 1/11/or 111 as trying to set them up on a variable setting wont work as when you close down the lockshield the pump will modulate down accordingly! as its clever little pump, In regard to the flow return temps if its operating with a 15/20 degree drop as the sytem runs up life is fine, when only 2 rads are operating what do you think the drops going to do?

All I can say is that he left it on the speed 11 setting as these pumps seem to have caused some issues and arent the most reliable things Ive come across, I seem to be replacing newish ones regularly! and leaving them on the sp 11 or 111 settings seems to be the best option in getting the heating system to work sometimes. All you have done probably is knock out any settings the guy had originally, seems a shame to slag someone off like you do but hey ho customers little knowledge is so dangerous.

 

[SimonG]

Phone the heating engineer and tell him to become a member on here, read your post and then give his side of the story.

 

[GasmanxxxR1]

When I read the op I thought a little knowledge is dangerous, why did you meddle with it? was it not working?

 

[Killy Bing]

As said by lame.

Ive found that variable speed is only any good for solar or central heating piped with the reverse return method.

Set everything back as it was imho.
You don't buy a Ferrari out of the factory and then tune it yourself.

 

[village idiot]

Phone the heating engineer and tell him to become a member on here, read your post and then give his side of the story.

I doubt the OP will do that.

 

[doitmyself]

Worcester Bosch Greenstar 1.8i boiler configured as a system boiler

No such boiler as the Greenstar 1.8i. There is the 18Ri, which is an open vent, or the 18i, which is a system boiler and has a built in pump.

I assume you mean the 18Ri, but had it configured as a sealed system boiler.

I have researched that the Grundfos Alpha 2l pump installed should be switched from speed 2 to CP2 (constant-pressure control) for my type of installation.

Where did you get that info from (link)?

The 12 degrees required Centigrade temp drop

There is no requirement that the drop has to be 12 degrees. You may find that the system will work better with a larger drop. The boiler is designed for a drop of about 20C

Before I completed any of the above work the Condensing System boiler had a 15-20 C temperature drop across the flow and return pipes at the boiler – this varied slightly depending on how many radiator TRV’s were calling for heat.

20C is what you should be aiming for, but 15C is better than 10C.

I noticed there was very little temperature difference between flow and return at the boiler – is this correct for just 2 TRV’s demanding heat under Constant Pressure pump control or could the automatic bypass valve have cut in?

Nothing to worry about. Which Constant Pressure is the pump set to?

Will this automatic bypass need some flow adjustments performing on it as I understand it should have been set up at commissioning stage?

Probably. However, if you have only one motorized valve a bypass is not really necessary.

If you have a room thermostat - I hope so - the rad in the same room should not have a TRV, so it would act as a bypass.

I suspect his ‘bypass’ radiator (no TRV but twin lockshields) was put in this way so he didn’t have to set up this automatic bypass up or buy another TRV.

The bypass radiator will be conflicting with the autobypass, which will be conflicting with the pump.

 

[Ermintrude]

As said by lame.

Ive found that variable speed is only any good for solar or central heating piped with the reverse return method.

Set everything back as it was imho.
You don't buy a Ferrari out of the factory and then tune it yourself.

Ooh reverse return ur a bit special!

 

[Howsie]

You lost me at engineer.

 

[IDCHAPPY]

Ooh reverse return ur a bit special!

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

 

[Killy Bing]

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 🙂

 

[erpkid]

You lost me at engineer.

There should be a special Klaxon when we navigate to any page containing this

 

[erpkid]

Sorry missed the " no longer do gas "

 

[jrcsheffield]

No such boiler as the Greenstar 1.8i. There is the 18Ri, which is an open vent, or the 18i, which is a system boiler and has a built in pump.

I assume you mean the 18Ri, but had it configured as a sealed system boiler.
Yes it is the 18Ri configured as a System Boiler


Where did you get that info from (link)?
Sorry meant to put PP2 (proportional pressure control) this was from Grundfos Alpha 2l installation – pdf – PP2 rather than PP1 was mentioned somewhere – could have been the fact there are 16 rads?


There is no requirement that the drop has to be 12 degrees. You may find that the system will work better with a larger drop. The boiler is designed for a drop of about 20C
I2 Centigrade seems to the best I can achieve on any radiator any further even small incremental turn of the lockshield and it is shut.

20C is what you should be aiming for, but 15C is better than 10C.
If I get a maximum of 12C drop across most radiators and others not so great how do I get a 20C drop across the system please…have tried pump speed.

Nothing to worry about. Which Constant Pressure is the pump set to?
It is set to Proportional Pressure 2

Probably. However, if you have only one motorized valve a bypass is not really necessary.
There are two single way motorised valves

If you have a room thermostat - I hope so - the rad in the same room should not have a TRV, so it would act as a bypass.
The original lounge installation had two radiators one with a TRV one without, the room stat was also fitted in the lounge. We found that the lounge would heat up and switch off the boiler,pump etc via the room stat and the rest of the house would be cold. We had a second TRV fitted to stop this and set the lounge room stat higher than the lounge needs to be. The lounge is the coldest room in the house and has two large radiators


The bypass radiator will be conflicting with the autobypass, which will be conflicting with the pump.

Should a TRV be fitted to the bathroom ‘bypass’ radiator once the autobypass has been set up?

 

[doitmyself]

I suggest you read the Grundfos Alpha Documents.

 

[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.