Downstairs radiators cold - pump is fine

[fraz]

Hi,

I have three downstairs radiators in my house and they are all stone cold. Up until last week they were luke warm but now they seem to have totally given up. The upstairs radiators are pumping out loads of heat but I can't seem to get the downstairs ones to work at all.

My central heating system is (I think) a little unusual as the boiler, hot water tank and pump are all downstairs in the kitchen. Last night I took the screw out of the pump and I could see the thing spinning around really well.

I also tried a few bleed points that I have on radiators and in the plumbing. The rads were full of (cold) water. The bleed points had a little bit of air. The ones that are used for draining the system had water although the water seemed clean.

I intend to drain the system totally then refill it and see if I can get the radiators to come on. I can't do this for a couple of weeks so was wondering if anyone had any ideas I could look at first?

Please help, I am getting married next year and really can't afford to pay someone to fix our heating.

Thanks,

Fraz.

 

[tomy]

Water will take the easiest route so shut all the upstairs rads off at one end and turn all the downstairs rads off except one and this should force the heating around it leave it like this for a while then do the same for the other downstairs rads then reopen all the upstairs rads , your system may also need balancing .

 

[fraz]

Water will take the easiest route so shut all the upstairs rads off at one end and turn all the downstairs rads off except one and this should force the heating around it leave it like this for a while then do the same for the other downstairs rads then reopen all the upstairs rads , your system may also need balancing .

Sorry I forgot to mention that I have tried shutting off all the upstairs rads and leaving the downstairs ones on. It made no difference but I will try what you suggest and just leave one radiator on. May as well make it the one nearest the boiler downstairs. Will try that tonight.

 

[tomy]

if that doesnt work either your pump has gone or a motorised valve isnt working ,

 

[fraz]

if that doesnt work either your pump has gone or a motorised valve isnt working ,

I have one of these pumps:

http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=102027&ts=03094&id=46018

Last night I took the screw out of the centre and looked inside. I could see what looked like another screw. It just turned when I used my screwdriver on it. I then turned the heating on and I could see the screw head spinning very fast. The pump isn't very noisy unless I turn it on max speed. Then you can hear it humming.

It still surprises me that if the pump had gone with the boiler downstairs it would mean that the downstairs rads would be cold. If someone can explain I would appreciate it. I would have thought that the upstairs rads need the pump to push the water to them?

When I switched the heating on I could hear and see the internals of the motorised value moving last night. I don't know if it is working correctly but it did something. It has a little switch on it and looks like this:

http://www.honeywell.ca/water-controls/images/v4044.gif

The switch is on automatic at the moment and it can be moved to the manual side where the switch can be either up or down. I don't know what the manual side does so I have left it on automatic.

Thanks for your help,

Fraz.

 

[Softus]

...I could see the screw head spinning very fast. The pump isn't very noisy unless I turn it on max speed. Then you can hear it humming.

I've replaced many a pump that hums and turns, but that has turned out to be worn out - how old is it, and how dirty is your system?

It still surprises me that if the pump had gone with the boiler downstairs it would mean that the downstairs rads would be cold. If someone can explain I would appreciate it. I would have thought that the upstairs rads need the pump to push the water to them?

Although gravity has an effect on moving water, this force is relatively small and is easily overcome by convection in a gravity system.
Circulating pumps largely rely on the fact that pressure in a liquid acts equally in all directions. Invariably a non-functioning, or worn, pump results in poor flow to those parts least able to benefit from a gravity flow, which is the downstairs radiators. It matters not where you have your boiler in your scenario.

When I switched the heating on I could hear and see the internals of the motorised value moving last night. I don't know if it is working correctly but it did something.

This is a three-port valve, and although the actuator may be moving the valve could be blocked on one or more ports. Does your hot water get hot?

I would pick the lowest radiator in the house on which you believe both valves work properly, shut both valves, get a wet-vac and/or lots of paint trays and buckets and towels and plastic sheeting, and remove that radiator. Observe the quality of the water/rust/sludge that comes out. Flush it out in the garden using a hosepipe, put it back, and post the results back here.

 

[fraz]

I've replaced many a pump that hums and turns, but that has turned out to be worn out - how old is it, and how dirty is your system?

This is a three-port valve, and although the actuator may be moving the valve could be blocked on one or more ports. Does your hot water get hot?

I would pick the lowest radiator in the house on which you believe both valves work properly, shut both valves, get a wet-vac and/or lots of paint trays and buckets and towels and plastic sheeting, and remove that radiator. Observe the quality of the water/rust/sludge that comes out. Flush it out in the garden using a hosepipe, put it back, and post the results back here.

No idea how old the pump is. We moved into the house 2 years ago and it hasn't been changed in that time.

The hot water gets plenty hot although something I will mention is that during the summer when the central heating is off the rads get hot. We have been switching them off using the taps. A couple of plumbers have seen this and told us that it isn't the valve that is broken although I can't see how it isn't.

I will try to remove the radiator in the kitchen this weekend. At least that way the floor isn't going to get wrecked.

Thanks for the help,

Fraz.

 

[Softus]

The hot water gets plenty hot although something I will mention is that during the summer when the central heating is off the rads get hot. We have been switching them off using the taps. A couple of plumbers have seen this and told us that it isn't the valve that is broken although I can't see how it isn't.

I agree with you - the three-port valve isn't working properly.

The fact that rads get hot with the CH in off mode mode means that the CH port is not closing, so it might also not be opening. This can be either dirt in the valve or a faulty valve - either way I would replace without any further messing around. Even if you don't replace it then you'll have to drain the entire system in an attempt to clean it out.

Whatever your decision, drain down with all with all rad valves open, then when refilling flush out repeatedly with only one rad open at any one time - this will move most of the muck out.

Two points of word advice: firstly, if the system is really dirty, then empty the F&E cistern before draining to remove any solid matter that could later cause a blockage.

Secondly, if your system has been neglected for a while then you will start seeing the latent faults emerge. For example, flushing out the muck can expose radiator leaks at corroded points.

I'm sorry to be the messenger, but you may at the beginning of a long road leading to a healthy heating system, but if it's been neglected and left unprotected then anything you do will be an improvement.

Don't hesitate to come back here for more detailed advice before you tackle each stage.

 

[Softus]

<duplicate post removed>

 

[fraz]

Thanks for the advice. Looks like I will be pretty busy. I will let you know how I get on with my problems.

Ta.

Fraz.

 

[Gasman1015]

Look on the bright side, it's a good excuse not to get married.

 

[fraz]

Look on the bright side, it's a good excuse not to get married.

If I try that something tells me that the heating will be the least of my worries.

 

[fraz]

Just got home tonight. All the downstairs rads are warm. They are nowhere near as hot as upstairs but at least they are warm.

Sounds like a blockage that keeps getting cleared. Any ideas?

Thanks,

Fraz.

 

[Softus]

Just got home tonight. All the downstairs rads are warm. They are nowhere near as hot as upstairs but at least they are warm.

Sounds like a blockage that keeps getting cleared. Any ideas?

Thanks,

Fraz.

Fraz, thinking while typing....

A complete blockage at the valve would normally result in no heat to any rads. The fact that there is some heat to downstairs indicates that there is some pumped flow, but, possibly, a partial blockage. However, rads that are cooler downstairs than upstairs usually indicate a worn pump.

If you replace the pump then you'll only avoid the need to drain down the system if the pump valves are working [enough]. However, if you have any suspicion that the system is corroding, then sooner or later you'll have to drain it, flush it and then add inhibitor when refilling.

If it were me I would drain the system and replace the pump valves at the same time as the pump. However, I've got the advantage of having a selection of pump valves to avoid the need to alter the pipework, and you're not me, so in a quick about turn, I suggest that you leave the pump valves in place and go for the minimum component change.

Springtime would be a good time for a full review and overhaul of the system, but in the meantime I would still do a full drain down and add inhibitor when refilling.

Sorry this is so wordy but perhaps it's better you have the underlying thought process rather than just stark advice.

 

[fraz]

Thanks for the help. I didn't do anything to the system this weekend. Now it is vaguely working I am a bit happier. I think I will replace the pump at the next available time. For the moment I will leave it at that then in Spring when we aren't too worried about having the heating on I may drain the system.

Talking to a friend at work he thought it would be ok to drain the water out of the system and just let it refill from the header tank at the same time. This way I would avoid any nasty air locks. I think I have read that you should prevent the system refilling and refill it from the bottom up using a hosepipe. The later sounds quite a bit harder, which would be best for me?

Thanks,

Fraz.