Bigger Pump - Yes or No?

[DIYMarky]

Hi Everyone

Could I please ask for some advice? I have an Electric central heating system in a flat that feeds 6 largish rads and a towel rail. Its piped in 22mm above the false ceiling which then drops to 10mm pipe as it runs down to the rads behind the dry wall. Its piped in plastic pipe all except the tails where they come through the wall to the rads and there its 10mm copper. Its pump is a Grunfos 15/60 - 130 and the system runs pretty well on speed 3 with all of the rads getting hot. The pipes are nice and clean with no sludge and there is a magna flow filter fitted and its always had inhibitor in it. Its also balanced quite well with all of the rads getting to a similar temperature.

Sounds perfect yes? Well no the problem that I have is noisy lock shield valves. I've had to really squeeze them down in most of the rads to push the water to the furthest rad and this has made them hiss. I'm pretty sure that the balancing like this is just over coming the pipework design. I've tried various pump speeds and different ways of balancing but to no avail. All of the rads have a TRV fitted and they work fine too.

So I was thinking about changing the pump to a Grunfos 25/80 so that there was a greater head of pressure behind the water flow. I was thinking that if there was more pressure I would be able to open up the lock shield valves a bit to stop the hissing but not affect the flow. So what do you think? Would this pump push the water around the system better than the one already installed?

Thanks for reading this - Mark

 

[ShaunCorbs]

Doesn’t need more flow would suggest you change the trvs to flow limiting ones eg imi or the new danfoss ones

 

[ShaunCorbs]

RAS-B2

Danfoss radiator thermostats maintain constant desired room temperatures, individually room by room. The RAS-B2 is a 2-in-1 temperature control and automatic balancing valve, combining a thermostatic radiator valve and pressure controller for two-pipe heating systems.

www.danfoss.com

 

[John.g]

Hi Everyone

Could I please ask for some advice? I have an Electric central heating system in a flat that feeds 6 largish rads and a towel rail. Its piped in 22mm above the false ceiling which then drops to 10mm pipe as it runs down to the rads behind the dry wall. Its piped in plastic pipe all except the tails where they come through the wall to the rads and there its 10mm copper. Its pump is a Grunfos 15/60 - 130 and the system runs pretty well on speed 3 with all of the rads getting hot. The pipes are nice and clean with no sludge and there is a magna flow filter fitted and its always had inhibitor in it. Its also balanced quite well with all of the rads getting to a similar temperature.

Sounds perfect yes? Well no the problem that I have is noisy lock shield valves. I've had to really squeeze them down in most of the rads to push the water to the furthest rad and this has made them hiss. I'm pretty sure that the balancing like this is just over coming the pipework design. I've tried various pump speeds and different ways of balancing but to no avail. All of the rads have a TRV fitted and they work fine too.

So I was thinking about changing the pump to a Grunfos 25/80 so that there was a greater head of pressure behind the water flow. I was thinking that if there was more pressure I would be able to open up the lock shield valves a bit to stop the hissing but not affect the flow. So what do you think? Would this pump push the water around the system better than the one already installed?

Thanks for reading this - Mark

You certainly don't need a 8m pump, judging by the your noisy L/shield valves you are probably running with a head of 5M or so with your existing pump, most systems run perfectly well with a head of 2.5/3M, your problem sounds something basic like a partial blockage in the flow/return to that rad or some restriction in the l/shield or TRV, remove the actuator from the TRV, use the handle of a reversed hammer to push the pin in (it should spring out), it should move ~ 4/5 mm, if OK I would back flush the rad individually into a bucket with the flow/return and the rad blank vent removed.

 

[DIYMarky]

ShaunCorbs - Thanks very much for the info on the valves. I didn't know that these were even made so cheers . I'm happy to change to these I would just have to buy a decent 10mm olive puller to do the job. I'll look into them a bit further and see who supplies them.

John.g - Thanks for the reply. I have measured the flow through every valve with each rad removed. There are no restrictions in the pipework at all they all flow at roughly the same rate. I also measured the flow back to the boiler and its exactly the same as the valve flow. The noisy valves are the lock shields on the rads which I've had to restrict to push the flow further down the system.

 

[John.g]

Presume no restriction in rad itself, how far away is this rad from the the next nearest rad?.
Even though noise suggests plenty of pump head, consider isolating pump and remove the head and ensure pump ports and impeller vanes clean.

 

[DIYMarky]

No sorry I should have said that I have flushed them all out too. I spent a weekend just cleaning it all out after running some X800 through it but didn't find much - not even a lot of sludge just a few bits of rust.

Aah I've just remembered that the existing valves have 15mm - 10mm reducers fitted. Is it possible to remove these reducers or are they permanent? I'm just thinking forward in case I do change the valves?

 

[John.g]

Don't think those reducers should make much difference as the flow through each rad is ~ 1.5LPM but if you can, no harm in removing them.
If you run that problem rad only, then you should still get adequate circulation even with the pump on speed1 which may tell you something.

 

[ShaunCorbs]

Are they the snap type or olive type ?

 

[DIYMarky]

Unfortunately they are the snap type

 

[ShaunCorbs]

You should be ok as you will be able to reuse them the nuts might look different to the body but they should fit aslong as you get 15mm trv bodies

 

[DIYMarky]

I thought about doing that but as they make a 10mm valve it kind of makes sense to swap them over. I don't mind the extra work but if they don't pull off I'll have to have a think about it. I can't put heat onto the copper tails as it will damage the o rings in the plastic pipe that they fit in. I know that Pegler make some nice non demountable copper fittings so I guess I could use those if I have too.

 

[ShaunCorbs]

The 10mm valves will have the same Reducers you have now in eg

You could use these but you need straight pipe no bend or kinks in the 10mm

https://www.NoLinkingToThis/p/pegle...h-fit-reducing-90-elbow-f-10mm-x-m-15mm/28509

 

[DIYMarky]

Thanks very much for your help on this. I just wrongly assumed that they would not have the reducers if you ordered the 10mm. Thats a nice easy job now I'll get some ordered. Can't thank you enough

 

[DIYMarky]

Just to update this thread now that I have changed the valves

Firstly they were a special order and Worsley's got them in for me which two weeks. I also discovered that one of my rads had the TRV on the return side so I took the opportunity to swap it around to the flow side.

So now they are fitted how's the system? Great!!!!

They were nice and simple to install and I used the Danfoss installers app to work out which setting to put the flow adjustment on. Its so simple I couldn't believe it. Just enter the size of the rad and output and it tells you what the setting is.

I now have a silent running CH system with all of the lock shields fully open. All of the rads seem to heat up at roughly the same rate and are giving out plenty of heat. The one rad (towel rail) which always seemed to steal loads of heat also heats up at about the same rate too.

As a bonus the electric boiler modulates quite a bit more now so I think there's some electric savings coming too. I did try and slow the pump down to speed 2 but the flow at the furthest rad got a bit too slow so its back on 3. I guess this is down to the 10mm pipe at the drop downs.

These are great valves that have balanced out my system far better than screwing down the lock shields. Cheers again for the advice

 

[John.g]

Do these balancing valves do just that? or do they have a thermostatic function as well?.

 

[DIYMarky]

They have a thermostatic function too. They look just like normal TRV's but also control flow and pressure. So when the other TRV's close down due to heat there is no increase in flow through the other rads. They keep the flow, pressure and temp constant

 

[gmartine]

What, balancing lockshields? Can you post a link please.

 

[John.g]

Post #3. (Shaun)

 

[DIYMarky]

What, balancing lockshields? Can you post a link please.

They are TRV's with a balancing function. They are Danfoss RAS-B2 valves

 

[DIYMarky]

Here's a couple of pictures