Navitron Renewable Energy and Sustainability Forum

BIOMASS => General => Topic started by: Burnt toast on February 01, 2016, 05:30:27 PM



Title: Flushing radiators
Post by: Burnt toast on February 01, 2016, 05:30:27 PM
My radiators are not getting to the temps they used to. My infra red thermometer is saying 55C, when I used to get 74C with water fed at 90C.

Got a 40kW log gasification boiler feeding 2nr 1000 litre tanks with a 200 litre expansion vessel.

Can this be flushed the conventional way by attaching the machine in place of the pump?

Thanks in advance.


Title: Re: Flushing radiators
Post by: sb79 on February 01, 2016, 11:14:27 PM
I suggest you take a rad off and have a look inside before going at flushing. Also you were using a blending valve of some description I take it to reduce the flow temp from 90c if you were getting a flow temp of 74c? Have you tested the operation of that valve?


Title: Re: Flushing radiators
Post by: Burnt toast on February 04, 2016, 05:39:52 PM
The boiler was modulating between 90 and 92C. The water in the tanks was at 90C.

So the water feeding the rads would have been 90 C.

I bled a couple of the rads and the water was clear. So no rust.


Title: Re: Flushing radiators
Post by: Stochengberge on February 04, 2016, 08:11:21 PM

I bled a couple of the rads and the water was clear. So no rust.

Depends were you bleed it from. If it was from the top then it may well be clear. The problem will be all the gunk and general detritus blocking all the water ways at the bottom of the rads, boiler water jacket and any other convenient little hidy hole it can find.
And the other place it likes to sit is in a hole that would otherwise be an escape route for the water. Many a time has a system been flushed only to wash away the "good gunk ". Not that I would say don't do it, you just need to be prepared to deal with any consequences.

Curious why you are running the system at such a high temperature though. And as SB79 says, if you have a blending valve, I would start there, particularly any filters or strainers that should hopefully be on each of the supply sides.

SB.


Title: Re: Flushing radiators
Post by: Burnt toast on February 04, 2016, 11:10:53 PM
Rads were bled from the top of the circuit.

I am not aware of any filters. I don't recall a discussion about them or having seen them.

We run at 90C as rads a wee bit undersized for the volume that needs heated.


Title: Re: Flushing radiators
Post by: Stochengberge on February 04, 2016, 11:48:53 PM
I am not aware of any filters. I don't recall a discussion about them or having seen them.


They may only be a piece of gauze with a rubber/ epdm seal ring on the outside edge that are installed between the mating faces of the connection unions, ie you won't know they are there until you start taking things apart!!!

SB.


Title: Re: Flushing radiators
Post by: knighty on February 05, 2016, 02:01:43 AM
do you have the circulating pump turned on max ?   

well worth trying that first


Title: Re: Flushing radiators
Post by: Burnt toast on February 05, 2016, 07:58:53 AM
The pump is on the mid position. But it always has been. So it's something other than the pump has changed.


Title: Re: Flushing radiators
Post by: knighty on February 05, 2016, 07:03:52 PM
put it on max

if it is just a build up of cr*p in the system, it might shift it 
(if it's built up in a low point etc..)



the fact that the water was clean when you blead the radiator means the system probably isn't full of sludge (water would turn black)... no next best guess is a little big of sludge, or rush, or whatever in one small area


I take it all radiators are the same temperature ?

check the temperature at the pump and a few other locations before/after the mixing valve etc..)

more info you have the easier it is to narrow down the problem :-)


Title: Re: Flushing radiators
Post by: sb79 on February 06, 2016, 06:11:12 PM
The boiler was modulating between 90 and 92C. The water in the tanks was at 90C.

So the water feeding the rads would have been 90 C.

I bled a couple of the rads and the water was clear. So no rust.

There really should have been a blending valve otherwise the nearest rads would get to 90c ish rather than 74c. If it is a professional install then there will most likely be a blender between the store and heating pump whether thermostatic or the electronic rotary type.

Clear water bled from a rad is definitely no guarantee of a clean system. Sludge will not necessarily show when bleeding as it tends to settle in rads and also coat surfaces until it causes a problem. I removed a couple of rads in a bungalow on Thursday to swap for new rads in new positions. As I drained down that section of the system through those rads the water ran clear. Disconnecting the rads however revealed thick black sludge of a treacley viscosity. Powerflush is on the cards now before I finish working on the place.

If there is a blending valve this should have gauze filters inside the inlet connections. Check these first.



Title: Re: Flushing radiators
Post by: dhaslam on February 06, 2016, 11:55:40 PM
Is the  room temperature  different than when you measured the temperature  previously.  The temperature  reached by the  radiators depends on the heat loss as well as heat gained.  However such high temperatures  would always be a lot  higher than the room temperature  so it wouldn't entirely explain such a large difference. 


Title: Re: Flushing radiators
Post by: Burnt toast on February 07, 2016, 08:27:41 AM
Hi
 Thanks for all the replies replies.

If by blending valve, you mean a valve near the boiler and pump which determines how much water goes to the tanks and how much to the heating system, from the boiler, then we have one, but it's manual. In winter we tend to run in slumber mode so,all the water is at 90C.

The rads are at different temps. The ones upstairs are cooler.

The temp in the house is cooler than before, which is why I checked what the rads are doing. The heating had been running non stop at 90C, and the house was losing temp or only maintaining temp. Despite being on all the time. The thermostat was not modulating the pump, we set it to be on permanently.



Title: Re: Flushing radiators
Post by: martin W on February 11, 2016, 06:31:27 PM
hmmm....

if all rads are cooler and the store is at 90C, I would think you've got a flow problem... could be pump, could be sludge.... (or blending valve.

Also have all the rads ever been the same temperature, i.e. the heating system was correctly balanced? If correctly balanced all rads should be above the same temperature until TRV's operate...Do you have any at the normal temperature that you are use to (90C).

Also have you checked your measuring instrument? Is it on the same emissivity setting as before?

Do you have trv's fitted to any rads? are they working correctly / covered, etc... went to once house who had a faulty TRV.... moved curtain that was covering it and the rad.... problem solved  wackoold



Title: Re: Flushing radiators
Post by: martin W on February 11, 2016, 06:39:42 PM
On the flushing question...

I would ensure you isolate the tanks from the heating system when flushing... I suspect you won't be able to just stick a flushing head onto the pump base as usual.

I would think if you flushed with a 1000l tank connected you are gonging to get sludge, etc dropping out of the flow into the tanks...its a big void...

depending on the number of rads a proper flush is going to take upto a day and cost 300-400...more if a lot of rads...

When I do a boiler change most systems seem to be clean until you stick the power flush unit on.... then its like liquid chocolate...or worse!

you can get good results with taking a rad off and sticking a hose on it.....





Title: Re: Flushing radiators
Post by: offthegridandy on February 11, 2016, 09:14:48 PM
And

if you remove the rad to clean it, don't Heinz of and drink tea cos the sediment will start to set hard in the presence of air, get the job done in a oner.

Andy


Title: Re: Flushing radiators
Post by: Ivan on February 20, 2016, 08:57:19 PM
Check your flow coming out of the tanks - I bet it's not the temperature you think it is