Issues with new radiators heating up!

[Ben Walters]

Hello!

I've recently installed 4 new radiators in an extension onto an existing system. The system was put in by a builder which made me suspect to the pipework. I T'd off the 22mm primaries (after zone valve) and ran 22mm into the new extension then ran 15mm pipe in the floor (lagged) for the new radiators.
The new extension is an open kitchen with a little utility room. I did a BTU's calculation using an online website i got around 16, 000 BTU's. Which i took to city plumbing and they gave me rad sizes i needed. The customer didnt want to pay that much for the rads and so found 3 column rads off amazon (non- convector) and i fitted a stelrad in the utility.

They wanted a new boiler so i fitted a Grant Vortex outside boiler 26kw. The system is an S- plan.

I was abit suspect when the rads arrived because of the small size of them.

I also didnt get a chance to put airvents on my pipework which came through the wall because the builders boxed it all in.

I had lots of problems with air at the beginning so forced all airlocks out and added plenty of inhibitor.

The customers came back to me last week saying the rads just dont get very hot at all. I went back an balanced the system to see if that helped. The new rads took around 1.5 hrs until they reached a good temperature. The existing house takes less then half that time.

This still hasnt helped and ive now got pretty frustrated customers!

Im going back to put a thermometer on the flow and returns of the rad pipework and precisely balance the system

- going to check which nozzle is in the boiler and range it up

The pump is a 15/50, there are 14 rads on the system.

Sorry for the long post but after i've tried these next two things i will be stumped!!

Can anyone give me any more advise!?

Thanks!

 

[Gasmk1]

how old is the 15/50 pump i would say pump undersized for 14 rads but others might say should do it.

 

[Ben Walters]

I replaced it like for like about a month ago... just double checked it was a 15- 50/60 grundfos

 

[Riley]

Was the extension definitely run in 22mm dropping down to 15mm for the rad tails or have they teed off 15mm to 15mm

 

[Ben Walters]

Was the extension definitely run in 22mm dropping down to 15mm for the rad tails or have they teed off 15mm to 15mm

As they drop into the floor it reduces down into 15mm then T’s off one way for 2 rads and the other for the other 2 rads. Both runs are about 3meters

 

[Riley]

Undersized potentially then what sort of combined KW are we talking on rads and separately. Try proving this by turning off all bar one then seeing if that one gets toasty

 

[Ben Walters]

Undersized potentially then what sort of combined KW are we talking on rads and separately. Try proving this by turning off all bar one then seeing if that one gets toasty

The rads apparently equalled approx 5600BTUS

Even if they are undersized why are they taking such a long time to heat up?
I want them to heat up in a good amount of time and if the room doesn’t warm up prove that they are undersized...

 

[Riley]

I meant the pipe work is undersized

 

[Darren Jackson]

Try turning off every radiator in the building and just leave on the ones in the extension and see if they heat up properly. There still could be air trapped in the new pipework restricting the flow so be prepared to vent a good few buckets of water out to get rid of the air, then re-balance the whole system from scratch.

 

[Riley]

Also that’s about 1.6kw for the extension which doesn’t sound right to me if 4 rads have gone in??

 

[Ben Walters]

Also that’s about 1.6kw for the extension which doesn’t sound right to me if 4 rads have gone in??

Okay, yeah in total 18,234 BTU’s in total...

 

[Riley]

😀 I would still be thinking that 4 radiators run of 15 mm pipework is your problem

 

[SimonG]

Why did you let somebody else dictate size of radiators?

I would have put extension on its own zone and pump.

Forget nozzle size in the boiler, the boilers not the problem.

 

[Ben Walters]

Why did you let somebody else dictate size of radiators?

I would have put extension on its own zone and pump.

Forget nozzle size in the boiler, the boilers not the problem.

Yep a costly lesson learnt.
I’ve done this sort of setup before and never had issues

 

[SimonG]

Have you room to get the extension onto its own zone?

 

[Riley]

If it’s on a drop I’d say so

 

[SJB060685]

The burner output could be undersized resulting on the last rads on circuit struggling for heat, the pump could be undersized or not on correct setting and not giving enough pressure/flow rates, again resulting in this problem as could undersized pipework. I would shut down all rads in original house and see if circulation improves in extension and go from there.
Like Simon said personally I would of put extension on own zone and possible own pump if needed.

 

[Ben Walters]

The burner output could be undersized resulting on the last rads on circuit struggling for heat, the pump could be undersized or not on correct setting and not giving enough pressure/flow rates, again resulting in this problem as could undersized pipework. I would shut down all rads in original house and see if circulation improves in extension and go from there.
Like Simon said personally I would of put extension on own zone and possible own pump if needed.

Thanks, when I shut off the oringinal house the extension rads get very hot.
They do currently get hit but they take around 1.5hrs to reach that temperature. That’s why I think it could be a simple balancing issue?

 

[Riley]

But do they get hot quickly when you turn everything else off

 

[Ben Walters]

But do they get hot quickly when you turn everything else off

Yes

 

[Ben Walters]

Yes

[QUOTE="Ben Walters, post: 1024995, member: 105045

Is it possible the flow is by- passing my T I’ve cut in and just prioritising the original heating circuit?

Thanks for your help guys!

 

[Riley]

Potentially as that section is all in 15mm but I’d say you’d only be losing minimal flow. How many rads in total and what’s the KW out put of boiler

 

[SJB060685]

Water takes the path of least resistance, so no I don’t think so. The fact these new rads heat up when everything else is off suggests again like I said either undersized burner output and extension rads are only receiving adequate heat when other rads are up to temp, or again the pump/pump setting. Have you personally calculated the system load demand when full and compared to burner output?

 

[Ben Walters]

Potentially as that section is all in 15mm but I’d say you’d only be losing minimal flow. How many rads in total and what’s the KW out put of boiler

14 rads in total, 26kw heat only

 

[Ben Walters]

Water takes the path of least resistance, so no I don’t think so. The fact these new rads heat up when everything else is off suggests again like I said either undersized burner output and extension rads are only receiving adequate heat when other rads are up to temp, or again the pump/pump setting. Have you personally calculated the system load demand when full and compared to burner output?

Okay, it’s an oil boiler so I’ll find out what injector is fitted and range it up.

Pump is on 3. So I will probably look at putting a pump and zone valve on the extension flow.

I don’t know how to do those calculations. Could you point me in the right direction please?

 

[Ben Walters]

Water takes the path of least resistance, so no I don’t think so. The fact these new rads heat up when everything else is off suggests again like I said either undersized burner output and extension rads are only receiving adequate heat when other rads are up to temp, or again the pump/pump setting. Have you personally calculated the system load demand when full and compared to burner output?

There’s also brand new pump on system

 

[SJB060685]

The burner output might be the problem, I’m not saying it is! However if you adjust nozzle and pump pressure output you will obviously need to redo FGA and adjust accordingly. With regards to calculating heat load I’m not an installer so others who do may have quicker ways to calculate but You can find either stuff online or even apps I believe to input numbers and it will do it for you, however it’s not as simple as adding rad outputs up, other factors like wall insulation, types of windows etc etc are all needed to get an accurate representation of output required. To be honest this should have been done before a new boiler is chosen and installed anyway. Sizing the pump is again quite a lengthy process and like I say although I understand that process others on here are better to ask.