Not all Radiators getting hot !!

[bwel]

Hi,

Some of my radiators are not getting hot at all or some are just hot at the top and from one side.

System Description.
- Downstairs mostly Wet Under Floor Heating. 14 Flow Circuits, with 8 Room Stats / Zones - WORKING OK
1 Towel Rad fed from upstairs

- Upstairs - Radiator based, single zone valve. 12 Rads from 3 pairs of 4 port manifolds to 10mm plastic. + 5 Rads from 2 Pairs of 4 port manifolds to 10mm plastic (other ports capped off).

Current works
Over the past two weekends I have run the system with X800 and flushed I have been flushing the system throughout. I have disconnected and flushed every Rad at mains pressure. I replaced all the JG Speedfit 4 port manifolds for flow and return to the Rad10mm circuits). I have used a radiator vibrator on an SDS drill :38:, to remove any blockages and sludge. I have flushed every circuit and also the core CH pipework which starts with 22mm from boilers (2x Valliant Eco max) to 35mm down to UFH or Rads main 28mm, then 22mm to the Rad Manifold Ports (4 Port Jg Sppedfit), the 10mm to rads.

Yes, I have removed lots of crud and sludge, but have proven full flow ability through every Rad circuits and the feeds to the distribution manifolds.

I also run run a pair of Magnaclean 28mm Pro's in parallel on the main feed to the boilers. I.e. Piped in 35mm.

I'm thinking my Rad problems may be due to poor flow rates to some rads and have tried balancing but am unsure if this is the problem or perhaps the flow is being challenged by some other factor.

One thing in to note is that after of had completed the flushing and refilled / pressurised the system, initially every Rad went up to full heat so I thought I had cracked it, but over the next few hours as it settled down, some rads began to cool down. All TRV's were removed at that point and lockshields were initially fully open.

With my system the has high flow from the boilers but 10mm plastic to individual rads, should I even be trying to Balance via lockshield restriction or just relay on the TRVs doing their job and perhaps try turning some of the TRVs down for rooms that are producing more heat ?

Any thoughts ?

thx Bob

 

[chris watkins]

Hi Bob
How are the boilers linked to the system & controlled ?
Did the upstairs system ever work correctly?
What is the circulator installed how do you know that is able to over come the system frictional resistance so that there will be circulation through all emitters?
There is going to be a lot more required to get it round the rads rather than the UFH.

 

[bwel]

Hi Bob
How are the boilers linked to the system & controlled ?
Did the upstairs system ever work correctly?
What is the circulator installed how do you know that is able to over come the system frictional resistance so that there will be circulation through all emitters?
There is going to be a lot more required to get it round the rads rather than the UFH.

Hi Chris,

The boilers are in parallel and feed to 35mm that then gets reduced in the steps of distribution 35mm, 28mm, 22mm,10mm. The Rads all hang of pairs of JG Speedfit 4 port manifolds. I.e 22mm to 10mm. All distribution manifolds have been replaced but some were previously contaminated.

Boilers are are controlled in parallel via Heat Demand from an upstairs Timer / Stat - Honywell CM67. Also downstairs also has a main Honywell CM67 in the hallway but then also has another 7 room based stats that control the heating circuit actuators from an EZC Microcentre.

I have been in the property for 18 months. Upstairs has worked partially, but I have always had problems with some rads but found this this was because I had some blockages in 10mm radiator feeds or sludge in the 4 port rad distribution manifolds. All however is now clean as a whistle

There is no extra circulator pump for the upstairs rads. UFH has it own circulator pump, but Rad circuits are driven by the Boiler Pump/s.

Thoughts ?

 

[chris watkins]

Hi Chris,
There is no extra circulator pump for the upstairs rads. UFH has it own circulator pump, but Rad circuits are driven by the Boiler Pump/s.

Thoughts ?

Thats the problem then, residual head on boiler pumps for getting water around the system will only be a Metre or two, not enough to get it around rads.

Poor design unfortunately you will need to get the system redesigned / altered to ever get it to work correctly.

 

[bwel]

I'm not saying that there are no design problems, but it's a 15 year old property and was built with the best systems installed at the time with a very particular first owner. I think the problems have been more recent since the contamination blockages which has now been cleared.

 

[chris watkins]

Well you will still need to get someone in who understands systems like this as with out being there with it in front of us &/or having the system designs to work on there is nothing that more that someone on a forum can do for you.

I have dealt with a good number of large systems with just the types of problems you have, I can defiantly confirm that the boiler pumps will not be big enough which I am sure others on here will also confirm.

Sorry

 

[bwel]

Well you will still need to get someone in who understands systems like this as with out being there with it in front of us &/or having the system designs to work on there is nothing that more that someone on a forum can do for you.

I have dealt with a good number of large systems with just the types of problems you have, I can defiantly confirm that the boiler pumps will not be big enough which I am sure others on here will also confirm.

Sorry

I have had a few companies in allready. Initially when I purchased the property, I had tracked down the original installers. They came and recomissioned all the systems and repaired one of the other boilers I have for a separate annex. I them back a few times, but when the bill hit £2500, I stopped using them as they would send a different team each time whom would start understanding the system from a fresh and charge again for the learning time.

I need to find someone who's best at systems design, although saying that, I have been using the Vaillant tech team, whom adviser on the system and specified one of the boiler replacements.

Thanks for the advice.

 

[oz-plumber]

When you removed the TRV's, did you check that the pin was fully out.
You may want to pull each pin with some pliers to make sure they are opened fully.

If the pin is not fully out - flow restrictions will occur.

Being a system of 15 years, and assuming that it was installed so that it was working originally, with the work you have done, the system should be operating better that you are describing.

 

[chris watkins]

Why not post your details up on here they may be someone close that can help !

[DLMURL="http://www.ukplumbersforums.co.uk/im-looking-plumber-gas-engineer/"]I'm looking for a Plumber or Gas Engineer[/DLMURL]

I am sure you understand (now if you didn't before) that your large system is not run of the mill for a domestic property, it is more like a commercial one but commercial companies are often not interested in domestic work especially if you are only willing to pay domestic rates.

You do indeed need a specialist, not a large company who send out different bods each time, not a boiler company who are only interested in selling their boilers & don't know your system, not someone who works for a couple of quid an hour and certainly not someone who is prepared to have the customer doing or advising on the work required.

They are increasingly difficult to find.
Best of luck

Chris

 

[bwel]

Many thanks for all the advice guys

 

[Sparkgap]

Hi Chris,

The boilers are in parallel and feed to 35mm that then gets reduced in the steps of distribution 35mm, 28mm, 22mm,10mm. The Rads all hang of pairs of JG Speedfit 4 port manifolds. I.e 22mm to 10mm. All distribution manifolds have been replaced but some were previously contaminated.

Boilers are are controlled in parallel via Heat Demand from an upstairs Timer / Stat - Honywell CM67. Also downstairs also has a main Honywell CM67 in the hallway but then also has another 7 room based stats that control the heating circuit actuators from an EZC Microcentre.

I have been in the property for 18 months. Upstairs has worked partially, but I have always had problems with some rads but found this this was because I had some blockages in 10mm radiator feeds or sludge in the 4 port rad distribution manifolds. All however is now clean as a whistle

There is no extra circulator pump for the upstairs rads. UFH has it own circulator pump, but Rad circuits are driven by the Boiler Pump/s.

Thoughts ?

Normally for large domestic/small commercial systems with multiple boilers I would hydraulically separate the boilers, so have the two boilers into a low loss header with their own pumpset and a separate pump to supply the UFH and rads. That way you keep the flows through the boilers constant and not affected by whatever bits of the heating are on/off. I usually have most systems running about 25-35kPa system resistance depending on size but actual resitance would depend on the layout. I would not rely on the boiler pumps to handle the system as well, especially one as large as yours sound to be.

 

[Frog67]

Are all pumps working correctly? 15 years old and subjected to corrosion may have worn them out. Could you not isolate the different zones (manifolds) and then run the heating to get each individual zone up to temp in turn?
You stated that the upstairs rads are either hot at the top or sides, this would suggest that there still maybe sludge present in the system. I would definately change the pumps and consider a power flush.

 

[bwel]

Are all pumps working correctly? 15 years old and subjected to corrosion may have worn them out. Could you not isolate the different zones (manifolds) and then run the heating to get each individual zone up to temp in turn?
You stated that the upstairs rads are either hot at the top or sides, this would suggest that there still maybe sludge present in the system. I would definately change the pumps and consider a power flush.

Hi there,
I have had the pump replaced in one of the boilers and the other boiler was replaced completely within the last year.

Re the Rads. Each Rad has been fluhed with X800, then each rad flushed on its own both directions with mains water and been vibrated during flush. When I first reconnected all the Rads, filled and fired up the system, all rads fully heated (top to bottom) but as they settled down some began to cool down at the bottoms hence the thoughts on flow. If I turn down the TRVs on some, others that were cooler at the bottom, heat up fully. So I think the rads are ok but am questioning flow rates.

I'm now thinking of having and extra circulator pump on the CH feed following the Zone Valve for upstairs rads. I'm not sure if I should also fit a low loss header between the boilers and the new circulator pump as well ?

 

[Sparkgap]

I'm now thinking of having and extra circulator pump on the CH feed following the Zone Valve for upstairs rads. I'm not sure if I should also fit a low loss header between the boilers and the new circulator pump as well ?

I would recommend the low loss header simply to separate the boilers from the system and get away from the boiler flow being affected by TRVs or things being turned off. You could go for a combined header with air/dirt separator such as the Spirocross or others. Then get a pump sized to suit the system resistance. The resistance through the UFH should be minimal if they have their own pumped manifolds.
Rough guess for system resistance -not knowing what your system is like/flow rates/pipe sizes- would be about 200Pa/m of pipe if its been designed correctly, so a rad 10m from the boiler would have a resistance of about 4kPa (2x10mx200Pa) plus a few kPa for valves. Only size for the index circuit (usually the rad furthest from the boiler). A bit rough but if anything should mean the pump is oversized and you'll get plenty flow. If you put in something like a Grundfos Magna then you can set the pump to reduce speed as TRVs and suchlike shut down and less flow is needed. Hope that helps.

 

[bwel]

Many thanks Sparkgap,

I've had the LLH on the to do list so am pursuing that priority along with the circulation pump.

I am looking Grundfos UPS2 32-80 for Rad CH Circulation.

 

[Sparkgap]

Many thanks Sparkgap,

I've had the LLH on the to do list so am pursuing that priority along with the circulation pump.

I am looking Grundfos UPS2 32-80 for Rad CH Circulation.

I take it you mean Magna1 32-80?

 

[Billy Bob Bob]

had a similar issue,just as many rads and ufh circuits,one 6 mtr pump trying to get it to the manifolds,no chance,this was off a 50 kw ferroli,put a grundfos in,i forget the size but it was about 350 quid,job done