New boiler install - Potterton pump too powerful?

[Gasguru]

Check if the flow and return are still as they were with the Puma...even bi-directional TRVs have a limit on "reversed flow" differential pressure up to a point.

The Puma should have had a bypass valve installed across the flow and return, these were generally a gate valve to ensure a minimum flow rate through the boiler. This would reduce somewhat the differential pressure across the TRVs. The majority of modern boilers have a built-in automatic bypass. This is primarily to protect the boiler and may not be sufficient when the system has several TRVs. Some boiler bypasses are adjustable to cope with the system but this is rare.

So you may require an auto bypass valve (correctly set) installed across the flow and return to reduce the pressure across the TRVs especially as they shut down.

The pump in the boiler must be left at its maximum setting since it is required to circulate sufficient water when operating in hot water mode, despite being too powerful for the heating.

 

[liller123]

thanks for everyone's help, I will speak to the heating engineer about the points raised on here and see what he says.

Question though, where would the auto bypass be fitted? and is it an expensive job?

 

[Gasguru]

http://www.honeywelluk.com/products/Valves/Bypass-Valves/DU145/

PLenty of other manufacturers too.

 

[Iddy]

You shouldn't have TRV's on every Radiator. One radiator, normally the one in the hallway, should have just standard valves fitted. This is also where your installer should have fitted a room 'stat to provide what's called 'boiler interlock'. I.e. once your home is up to temperature, the room 'stat will turn your heating off.
If presently you have TRV's on every Rad, then whilst the boiler and pump are running, your house is getting warmer and warmer, each TRV is gradually closing, restricting the flow to each rad. Even though your house is now toasty, your boiler doesn't know any different and keeps the pump running. The 'differential pressure' across each TRV will get higher and higher as they close, eventually causing them to 'chatter' if they've been fitted the wrong way 'round. Bi-directional vales can only cope with so much differential pressure.
If you keep your system as it is, you should definitely fit a by-pass. This should be an automatic one to comply with regs.

http://www.plumbnation.co.uk/site/honeywell-dual-auto-by-pass-valve-22mm-angled/

http://danfoss-randall.co.uk/xxnewsx/bc9b4d5a-bdb9-4d40-9691-43abf6a67fdf.html

 

[Agile]

The current energy efficiency advice is that TRVs should be fitted to all rads except in a room where the room stat is located together with an auto bypass ( ABV ).

Obviously in this case the installer has not bothered to fit a ABV.

Worse, he does not seem to realise that he should have done so even with TRVs rattling to remind him!

Tony

 

[liller123]

thanks and thanks! some good advice to be had here! The engineer did mention as he was leaving that perhaps we should take the TRV off the rad in the hallway next to the wall stat....strange that he did not do this when he installed the boiler 3 weeks ago. I think it's time to get a new engineer....I'm going to put all this to him today to see what he says.

 

[Agile]

Did he complete the Benchmark Certificate for the boiler install?

Did you receive a blue Certificate from Gas safe? He should have notified the installation to them and they in turn advise the Building Control. Thats required by law and not notifying can cause you problems if you sell.

Tony

 

[liller123]

Did he complete the Benchmark Certificate for the boiler install?

Did you receive a blue Certificate from Gas safe? He should have notified the installation to them and they in turn advise the Building Control. Thats required by law and not notifying can cause you problems if you sell.

Tony

He said he did although I have not yet received the cert from gas safe

 

[Gasguru]

The engineer did mention as he was leaving that perhaps we should take the TRV off the rad in the hallway next to the wall stat

Pretty much normal (back practice) to have the room stat near a rad with a TRV...most installers round here are clueless. This rad should have a lockshield valve at each end (ie. valves with plain caps that are not user adjustable). This radiator (along with all the others) must be balanced to ensure an even heat up. In addition, depending on the size of this rad and its location it may need to be throttled down to ensure the rest of the property has come up to temperature before the room stat turns off the heating.

 

[liller123]

anyone know a good plumber??

 

[liller123]

Hi again. Update and further advice request!

The engineer visted yesterday and removed the TRV from the rad in the hall which is where the wall stat is located. He also installed a Honeywell auto bypass valve.

So far so good.

My questions are these:

Now the TRV has been removed from the rad in the hall I was wondering how I was going to leave just the heated towel rail on in the summer months? as this rad is fixed on it will mean that this will also come on every day during the summer months if I want to keep using the heated towel rail. I checked the valves on the hall rad and they are fixed so I can't just switch it off. Should I be able to switch this rad off? Like with a simple on/off valve?

I know that you shouldn't fit a wall stat on the same wall as the rad but how close can you fit it to the rad? As my hall is not that wide.

thanks in advance!

 

[durhamplumber]

I once fitted a baxi 105 and all the radiators banged and clattered ,baxi told me i had the flow and return the wrong way around??,,swapped them,did the trick! weird