New radiators, new pump but still not warm!

Chrispie

We don't have any of the air vents you describe:(. Since my last posting we have replaced the pump and one of the two motorised valves. Last week my OH did a power flush using a machine he hired. There is still no difference to our system. We are unable to run the boiler on Max or near max as it starts kettling. Would the problems we're experiencing be caused by the Heat Exchanger failing on the boiler?

keystone

Chrispie wrote: »

We don't have any of the air vents you describe:(. Since my last posting we have replaced the pump and one of the two motorised valves.

So your system doesn't look my earlier diagram as iut has two mororised valves rather than a single three port mid position valve. It looks a little like this one (much simplified) in respect of the motorised valves then:


otherwise it will be like the previous one with tanks in the roof. Which valve did he replace? The HW zone valve feeding the cylinder or the CH zone valve feeding the radiators.

Last week my OH did a power flush using a machine he hired. There is still no difference to our system.

I have no idea what possessed him to do that to be honest. That's one pump, one zone valve and one PF machine hire that you've spent your hard earned dosh on that you might not have needed to plus the time he spent doing all this and certainly would have covered the cost (and some) of getting someone in to look at it and tell you what was wrong after a hands-on investigation. How long did he powerflush for as a matter of interest?

Have you got thermostatic rad valves like (or similar to) this on your radiators:



the one on the left is the thermostatic valve. The one on the right is the lockshield valve which goes on the other end of the rad. If you don't have thermo valves then the one on the left would be exactly like the one on the right except it would have a knob on it in place of the smoothe plastic cone to enable you to open and close it manually..

If you have TRVs have you checked they are all operating properly and none of them are stuck in the closed position? To check this remove the head by unscrewing the knurled nut at the base of the head and check the pin inside moves up and down freely.

If your valves are operating correctly now turn down all TRVs to the off position except on one rad. Run the system. Does this one get hot? If so do the same with all of them - one at a time - and if they all get hot then run the system with them all open.

What happens when you do this?

Cheers

Mr_Ted

From experience(which is not always acceptable to others) a blockage is the most likely cause!
The blockage usually tends to be at the most common point of the system return, such as a "tee" piece where the return pipework from the 2 circuits, upstairs and downstairs meet as this is a point where the water in the system joins and mingles thereby causing a swirl effect(to keep it in simple terms) within the fitting!
This then tends to concentrate any sludge, magnatite at that point where it eventually thickens and solidifies!

As has been said you could get a scenario where you get reverse circulation in part of the system or even within a single section of pipework?

I had this experience once whereby the pump impellor appeared to be rotating in the wrong direction when it went off, when what in fact was happening was it was rotating in the right direction under normal running, but as it was stopping, due to the reverse circulation effected(slight back pressure) the impellor actually reached a point before stopping when the impellor was forced to rotate in the wrong direction?

I would start at the point as I said, where there is a "tee" piece on the return pipework!
You may be able to unblock it with some force however this is likely to leave debris in the system again, but I would locate the blockage and replace the section!

keystone

Mr_Ted wrote: »

From experience(which is not always acceptable to others) a blockage is the most likely cause!

Now I'm going to frighten you. I agree but I wanted to eliminate the air possibility before going on a magnetite hunt.

OP - by the way there is no way on earth you will shift a magnetite blockage (if that is what is is) with a powerflush. My usual suspect is where the feedpipe from the F&E tank joins the circuit or in the airsep but you've already said you don't have one of those.

Cheers

Chrispie

Hello Keystone and Mr. Ted, thanks for your patience and continued advice with our problem. Neglected to say earlier, we did have a heating engineer to visit us just before Christmas. He spent about an hour checking what we had already done but couldn't suggest what the problem is being caused by. Only thing he recommended was the PF.
Keystone our system is as your diagram and the valve that was replaced was on the CH side. We do have TRVs on all rads except one. We have been able to get individual rads hot by shutting the others off but can't get any heat to all at the same time. Is this due to not being able to run the boiler anywhere near max? Would a blockage cause the boiler to kettle?

keystone

Chrispie wrote: »

We have been able to get individual rads hot by shutting the others off but can't get any heat to all at the same time. Is this due to not being able to run the boiler anywhere near max?

No. It is due to a circulation problem. If all the rads heat up individually there is no major problem IMO - the system needs balancing. Each rad needs doing in the order that the system heats upand finally adjusting pump speed so that the flow and return at the boiler are also balanced.

Would a blockage cause the boiler to kettle?

Am not now certain you have one tbh (certainly nothing really major) now we know each rad works when on its own. Boiler kettles due to scale within it just like er well a kettle. Boiler kettles when it gets hotter and has no idea what temperature you are trying to achieve in the building as the roomstat doesn't tell it. A blockage won't make any real difference. If its is restricting flow everything near the boiler will get hotter earlier so boilerstat will kick in and shut it down.

Cheers

Chrispie

Thanks Keystone. Any suggestions how we get rid of the scale within the boiler? I guess this is something a Gas Safe engineer would need to tackle? We have tried balancing countless times but can never get the all the rads hot. The individual one will get nice and hot but when all rads are on they are just about warm.

Mr_Ted

This would still indicate a blockage as the lack of flow could cause this and the kettling?
If there is insufficient flow through the boiler it will kettle, if there is insufficient flow through the system there will not be enough flow to balance properly!
The pump will probably also cavitate giving a false indication of air in the system?

keystone

Theres always this possibility as clearly there is a circulation problem as was said right at the top of the thread. Personally I think I'd spend an hour or so balancing then go on the magnetite hunt. It really needs hands on for half a day.

Cheers

Chrispie

Hello Keystone, Mr. Ted and all others who kindly took the time to help us diagnose our CH problems. Just wanted to let you all know as of today we are warm and toasty!! On Friday we had a WB recommended heating engineer visit us. He first thought our system was configured wrong which was restricting the flow. He rearranged some pipework and removed some valves that shouldn't have been there and fitted an automatic bypass. Still no joy so he came to the same conclusion you had suggested, that we had a blockage. Over the weekend my husband removed floorboards upstairs and saw that we had T section which the engineer thought must be there. He came back today and replaced several metres of pipework and T section which was completely gunked up. Engineer also fitted a TF1 to our boiler and ta dah, our system is now working.
So thanks again for all your time, it's appreciated.