Cold Radiator tried almost everything

[Billz]

Hi,

First of all let me say that this is a brilliant forum. I have been able to resolve many issues by it.

The problem i am having now is that we have moved to a new house with a large open plan kitchen and conservatory. It was brilliant in summers but has been freezing in winters. The problem is that the radiators in the conservatory only get luke warm. There are two radiators. I have tried the following.

1. Drained the system and re fill it.
2. Drained the system till it ran clear, put cleaner in it and run it for 2 days and then drain it and refill it by adding the inhibitor.
3. Closing TRVs on all other radiators and then checking the conservatory radiators which became really hot.
4. Balanced all the radiators.
5. Turned down the feed to minimum on most radiators.

The result has been only a few degree increase in the temperature of the radiators. They are still luke warm. I can feel the feed pipe to the radiators and can say that it is really hot but not as hot as compared to the feed on the lounge which is next to kitchen. The return pipe is same as the room temperature.

What could it be? My guess is
1. Pump? Less likely as its perfectly heating all around the house.
2. Heat loss? Could be the case but as the pump is on full speed surely it should outflow the heat loss.
3. Lack of return? Dont know may be gravity is playing some part in restricting the flow?

It has made the kitchen useless as well as it is freezing in there.

 

[bengasman]

cleaner should be in there for a month, not 2 days
if all rads get hot with all others closed, it is balancing that is wrong.
how did you balance the rads?

 

[Billz]

Thanks for the reply. The cleaner which i bought explicitly stated it should only be left in the system for 8 hours. So i thought 2 days was going to be more than enough as i didnt want any pipes leaking as a result.

I started off balancing with the digital thermometer on all of them feed and return had a different of about 12C. Then i closed them up a bit more as there was no difference. Now most of the radiators have their feed and return set to a minimal value. Upstairs ones are almost 1/4 turn feed and return and the downstairs are 1/2 or 2/3.

The feed wasent starved that much when balancing. I did it as an after thought to see if it improves anything.

I must say the cleaner has really improved the efficiency of the radiators.

 

[gigz]

Turn all the other rads off plus one of the problem ones, see if it improves then open the other one, let this run for a few hours (could be air or sludge) this might work.

 

[gas4you]

What pump have you got?

Could be that the rads have never been installed with correct size pipe, or teed into the existing circuit in the wrong place.

 

[namsag]

Consevatory so rads added afterwards where did they tee in . what size pipework how many rads already on that drop/leg

 

[Billz]

I have turned all the radiators off and alternatives in the conservatory but this hasn't helped. I will try again though.

GAS4YOU>> I will check the pump again today and will post. I am at work at the moment. As far as i know it is the same pipesize all around the house. But i dont know if it is fed from a larger pipe. Its the standard pipe size as it is not micro bore. The conservatory was built around 5 years ago and i am sure it must have been working as the previous owners would have got it sorted out if it wasent.

There are two radiators on one pipe. They are in parallel. Second is brached off after the feed on the first one. Then same with return.

One thing which i noticed when i was draning the system was as the drain valve is in the conservatory and is on the second rad, when draining there was cold water for a about 40 seconds before the hot water starting coming out. Does this mean the return isnt strong enough or may be the pump isnt powerful enough. The pump is on setting 3 which is the fastest.

 

[MANDATE]

Hi Billz! I removed a problem radiator, which after cleaning did not improve one bit.
I then found a by-pass pipe with a valve that was open far too much. Closing this down got the radiator warm for the first time in ages, but it still was not as hot as other radiator in same room but on opposite side.
As all other radiators were hot, the pump was a bit noisy, so decided to invest in new pump.
On removal of old pump together with the two gate valves, which could not be closed off fully, it became clear what the problem had been.
There was sediment built up and the hole size for water to pass through was about 6mm. It should have been in the region of 18mm and with this resistance the flow was restricted. New pump and pump valves cured the problem.

 

[Billz]

Hi Billz! I removed a problem radiator, which after cleaning did not improve one bit.
I then found a by-pass pipe with a valve that was open far too much. Closing this down got the radiator warm for the first time in ages, but it still was not as hot as other radiator in same room but on opposite side.
As all other radiators were hot, the pump was a bit noisy, so decided to invest in new pump.
On removal of old pump together with the two gate valves, which could not be closed off fully, it became clear what the problem had been.
There was sediment built up and the hole size for water to pass through was about 6mm. It should have been in the region of 18mm and with this resistance the flow was restricted. New pump and pump valves cured the problem.

Thanks mandate i know what i will be doing this weekend Will post my results and let you know.

 

[MANDATE]

Hi billz! Did you have any success with your pump?

 

[Billz]

Happy new year everyone. Sorry for not getting back. I was away.

Coming back to the point. I took the pump off. It had very little black sludge in it. I gave it a good clean and checked the inlet and outlets as well. They were both fine. I cleaned them as well. I then went to the hardware store for replacement pump. The guy said that there is no point replacing the pump as yours seems to be working ok. The solution might be a bigger bore pump or it may be that the pipe work to the radiators is not right.

What do you think? baring in mind that my observation was that the hot water does go to those rads but there is not enough to make them hot they just stay luke warm.

Any help would be appreciated as it is -6 here now a days.

 

[D_Hailsham]

bearing in mind that my observation was that the hot water does go to those rads but there is not enough to make them hot they just stay luke warm.

Sounds as if the boiler or the rads are not up to the job.

To checked that the boiler is large enough, use Sedbuk Boiler Calculator to find out. (Assumes you do not have a combi boiler)

To find out the total kW of your rads, use Stelrad Elite Catalogue

Heating systems are usually designed for a worst case outside temperature of -1°C with a temperature rise of 20°C. So if the outside temp is -6°C, the house is unlikely to rise above 14°C or 15°C - unless the radiators are about 40% oversized.

 

[daveaf]

I would like to know how the guy at the shop knew there was nothing wrong with your pump just by looking at it. My last pump was running fine, not making a noise and the impellar looked ok. But on very close inspection, I noticed that the impellar had a small amount of scale build up right at the bottom of the vains. New pump fitted and now it performs a better task running at half the speed of the old 1.

Nobody wants to waste money so I understand your concerns, but you have to start somewhere. £40-£50 for a new pump is a good place to start.


Could it maybe be that your 3 way valve is not shutting off to the hot water tank completely? This would then reduce the flow through the rads as it would try to take the easiest route back to the boiler???

 

[Billz]

Could it maybe be that your 3 way valve is not shutting off to the hot water tank completely? This would then reduce the flow through the rads as it would try to take the easiest route back to the boiler???

Thanks for the reply. You are almost there. I had a plumber in today he inspected the whole thing and was quite impressed with the balancing i did. Anyway he said the same thing the conservatory rads were not getting the flow properly. He said as we cannot have the CH without Hot water. The system always starves. Hence the flow is reduced. He said there are two options. One i get the system rewired for the two to work seperately or he can put a valve on the hot water to regulate the hot water.
Since the three port valve is fairly new. I asked him to put a valve on the hot water side and bingo that did the trick. Now we have a house which is habitable.
What do you think about this solution. I know it is not the most desirable solution but it works for now. We have so much flow that now i can hear the water running through rads. I have turned the pump down to setting 2. For the first time we had the dinner on the table in the conservatory.
Anyway how easy is it to rewire the system. I have already spent 150 today and dont want to spend more at the moment as my wife is on maternity and i am the one who is paying two mortgages and everything else.

BTW when the water gets upto temperature it shuts of central heating as well.

Thanks a lot for your help.

 

[D_Hailsham]

I had a plumber in today ... He said as we cannot have the CH without Hot water. ... Since the three port valve is fairly new.

There are two types of 3-port valves: the diverter and the mid-position. The diverter allows you to have heating or hot water; the mid-position allows you to have heating or hot water or heating and hot water. To say that you cannot have heating without hot water suggests that the system was not wired up correctly or that your time switch/programmer would only allow heating and hot water. There was certainly no need to put in an additional valve.

What do you think about this solution. ...I have already spent £150 today

No comment.

Anyway how easy is it to rewire the system.

Very - you should be able to DIY if you are comfortable working with electrics. That's what the plumber should have done in the first place.

BTW when the water gets up to temperature it shuts of central heating as well.

I take it you mean when the Hot Water gets up to temp. In that case, the plumber has not really solved your problem - this should not be happening.

If you want help with the rewiring, you will have to post complete info on your existing wiring and the components - programmer, thermostats, valves etc. If a wiring centre (junction box) has been used, a photo of the inside with the connections labelled would be very helpful.