To fit or not a secondary heating circulation pump

[BigBurner]

But if you said "I need a boiler which will be capable of heating all rooms to 21°C from cold within half an hour", and the boiler fails to meet your requirements, then the fault lies with the installer.

That is what a responsible installer does. If the customer specifies something which the installer has reservations on, he puts in in writing to them. Like, "the boiler is inadequate and will not heat the house in the worst case scenario".

 

[jackthom]

Warhammer you say it takes a long time for the room temp to rise from 18C to 22C but it isn't clear how quickly the actual radiators are heating up.
Do they all get really hot in a reasonably short time?

 

[WarHammer]

technically the installers have done everything as specified in the original heating quotation & by the book

It all depends on what you asked the installers to do. If you just said "I need a new boiler" and left him to specify what he would install and you accepted his proposal, which then proves to be inadequate for heating the house, then you have no one to blame but yourself. But if you said "I need a boiler which will be capable of heating all rooms to 21°C from cold within half an hour", and the boiler fails to meet your requirements, then the fault lies with the installer.

However, whatever was requested, a competent installer would have looked at the existing system, realised there might be a problem, and taken this into account when specifying the boiler.

As to the suggestion that the pipework needs replacing, this proposal is ludicrous. The system just needs balancing properly.

Just for information, what was the old boiler?

The old boiler was a gloworm fuelsaver 55f that had been in situ before various extension work/extra rads etc were added to the orginal house design - this fed a range tribune premier 180ltr cylinder on a y plan set-up.

In terms of what/who specified the new system, I suppose it could be subjective (6 of one & half a dozen of the other) - whilst I did ask for a vaillant system to include the unistor 210ltr & the 360f controls - the boiler sizing was the installer recommendation based upon the calculated heating output of the current rads & DHW / house size etc.

unfortunately I did not specify that I wanted the new system to heat the house to 21 degrees with 1/2 hour or so.

TAdditionally, I did also have two existing single panel rads changed for doubles & moved to improve heating in down stairs loo + breakfast area in kitchen.

Furthermore, the shoddy builder employed by the previous house owners had built an extension above the garage and plumbed 3 new rads directly into the main flow & returns well before the MV controls/cylinder - therefore they came on with hotwater demand as well as heating & also caused poor DHW performance by sucking heat out of the sytem when trying to heat the water cylinder. Suffice to say these have now been re-piped into the main heating circuits & fed by 22mm reducing down to 15mm.

I believe the issue I have is with a double rad in the extra downstairs TV room - this does not seem to heat-up fully whilst the other house rads seem to be all working fine now. The 360f is also fitted in this room. This rad seems to receive very hot water to the TRV side (by the way the head is removed due to 360f in the same room) - but conversly the return pipe is always cool - the piping is 10mm which disappears into the skirting board & then runs upstairs somewhere - where the piping goes into the skirting it does look a little squashed as if it's been bent so is more oval than round....but this is on the rad feed pipe not the return...as we know this gets extremely hot so I can't see the kink causing too many issues. I bled the rad and it seems to have no air whatsoever - also when the installers balanced the system, I did get them to check this rad by shutting down all other household rads and only feeding this one with full heat....it got hot both on feed & return piping.

So I'm lost as to why this rad is not performing too well when being asked to work in-conjunction with all the others (it;s a 1yr old stelrad k2 1400x700)

Due to it's slow/difficult performance, teh 360f being in the same room obviously takes it's time to reach 21.5 degrees - whilst in the lounge/other rooms it will be 24 degrees by the time the 360f is reading 21.5 degrees.

Anyone shed any light on this problem - or do I need to lift more upstairs laminate flooring & floorboards to check what's going on with this troublesome rads piping?

Just realised I've written an epic here - hope you manage to stay awake by the end of the read

 

[WarHammer]

Warhammer you say it takes a long time for the room temp to rise from 18C to 22C but it isn't clear how quickly the actual radiators are heating up.
Do they all get really hot in a reasonably short time?

Yes they do jack - all but this naughty one in my above epic post - al other rads heat up quickly & are very hot to touch (even when TRV is set to 4 out of 6)....so in my opinion this is good right? - but this extra TV room stelrad is sluggish, slow to heat up, never too hot to touch, cooler at the bottom than the top - with a red hot pipe feed at the TRV end and a cool return pipe out - problem is teh 360f is sited in this room as well, so you can imagine why it takes time to go from 18-21.5 degrees...I imagine that the rad is slowing heating-up times down??? Am I right?? - if so what coudl be the cause & what would the fix be (besides simply siting the 360f in a hotter room where the rads wrok better - shut the door on the extra TV room and go watch telly in the main lounge

 

[jackthom]

I think you just supplied the answer. This rad has a long run of 10mm pipe and there may even be kinks in places.

Very hot water will run through this feed pipe to the TRV but it will be at too low a flow rate to supply the radiator properly.

I'd suggest replacing any kinked sections first and if that doesn't work you might consider using 15mm over part of the run.

 

[WarHammer]

I think you just supplied the answer. This rad has a long run of 10mm pipe and there may even be kinks in places.

Very hot water will run through this feed pipe to the TRV but it will be at too low a flow rate to supply the radiator properly.

I'd suggest replacing any kinked sections first and if that doesn't work you might consider using 15mm over part of the run.

That's exactly what I'm thinking jack - also this is why the installer might have suggested fitting a secondry heating ciculation pump - to shove more flow around and possibly force more heat quicker into this troublesome rad - he did say it may not solve it, but if it worked it may mean not having to lift yet another rooms laminate floor up and possibly avoid the need to remove plasterboard from the pipe fall wall from upstairs down to the floor where the 10mm pipe feeds appear. - and it may also be a cheaper option all-in?

 

[jackthom]

I've just gone through the same scenario in my own home with a dodgy run of 10mm pipework to one bedroom and ended up replacing one very tight pipe bend with an elbow and running 15mm where access was a bit easier.

I did toy with the idea of an extra pump, probably running at its slowest speed, but decided it could create other problems in the future and it's best to keep it simple IMHO.

 

[D_Hailsham]

... I believe the issue I have is with a double rad in the extra downstairs TV room - this does not seem to heat-up fully whilst the other house rads seem to be all working fine now. The 360f is also fitted in this room. This rad seems to receive very hot water to the TRV side - but conversly the return pipe is always cool - the piping is 10mm

A 700x14002 rad gives 2815 watts at 75/65/20, which is well within the capability of 10mm pipe, which can carry about 5 kilowatts. Are there any other rads on the same branch which would take the total above 5kW?

I did get them to check this rad by shutting down all other household rads and only feeding this one with full heat....it got hot both on feed & return piping.

This shows there is nothing fundamentally wrong with the pipework.

Having read all the alterations you have made to the system, I still think that the problem lies with the balance. This will need to be carried out from scratch - and not by feel. See http://www.diynot.com/forums/viewtopic.php?p=1068597#1068597

Just realised I've written an epic here - hope you manage to stay awake by the end of the read

Yes, but it was (mainly) useful information.

 

[Stewb]

Sorry to revive a 14 year old post but I thought useful for others Googling this to add my experience.

We have 4 zone S plan CH (up, down, UFH (own pump), HW) on a WB Greenstar 40 CDI. About 20 rads plus UFH. My system was cycling often and no more than one zone would get hot at a time and downstairs was particularly bad (longest pipe run).
We replaced the Alpha2 pump in case it had failed for a UPS3, which didn't help, so we added the Alpha2 as a second pump but on the downstairs return pipe on low PP speed. That worked well, the pumps played well together and we could get down and up to heat at the same time.

Anyway fast forward a few months and some re-piping was being done and the Spriotrap MB2 was removed and that revealed it was gunked up high. Emptying it occasionally did not release the magnetite it was all congealed inside and blocking flow. We couldn't get it clean (well we did in the end but broke the Spirotrap in the process by flushing it backwards through its drain - so have scrapped it and fitted a Spriotrap MB3 instead (the one with the external/removeable magnet - much better design)) and lo and behold the system is now working like a dream.

We also fitted a UPS2 25-80 (180) at the time in place of both pumps given the size of the system/boiler with all flow/returns T'd off 28mm now. Pump is only on PP 2 and is more than powerful enough. Boiler range rated at 80% not that it gets near.

So to confirm what others have said, even on a big system it is more likely that you have a circulation problem than need a second circulator.