Rads take ages to warm up

[HERTS P&D]

You have an air lock. Get your garden hose and fit it to the drain cock, open the drain cock and open the garden tap to push mains water into your heating system. Go round and bleed the rads. Don't let your expansion tank over flow, it might leak into your loft. This will also test the overflow pipe. Once air is removed, turn off garden tap and drain cock. Remove any excess water in the expansion tank. Should be approx 100mm higher than out put on bottom of tank.

Andy

 

[cinman2003]

Think I might've cocked up a bit (about right!) Connected hose, turned on tap, left for 30secs then turned it all off again. Disconnected, went round rads to bleed (only a small amount from 2 rads) and continued bleeding from airing cupboard bleed valve for a bit. Seems the waters a little frothy, probably due to the fernox flush that's in there right now. So far the boilers working (5 mins now!) without popping on setting 3 of 6. Keeping fingers crossed .....

I'm thinking I might've actually pushed air from the hose into the heating circuit, as I didn't run the hose before plugging it to the heating drain point.

 

[cinman2003]

Latest situation: boiler's just overheated again, set to 2.5 of 6 on its thermostat pot. Been running for about 1.5hrs before it did this though. Upstairs got 2 single rads, 1 double and 1 bathroom towel dryer type rad. Bathroom rad used to work up to about 6 months ago - now is dead cold - but did fill with water when I refilled the circuit as air was bled then water seeped from bleed screw. I suspect its under very low pressure though, as as the circuit is under such low pressure, it might be possible the weight of the water in the "victorian stylee" rad might be peventing flow through it? Two single rads upstairs are nice and toasty, the large double is lukewarm at best. Feed pipe into the double is scorching, but for some reason its not making its way through very well. Could it be another combo of low pressure in circuit coupled with double-rad weight of water keeping a decent flow from going through the rad itself? Could it be as simple as a rubbish valve that's somehow knackered? Downstairs got 2 rads, one small double, one large single. Both are lukewarm at best. No air in the system that I can hear now, and based on the above, I'm also assuming the popped boiler is due to slower than normal flow through the circuit? Does all this make sense? Does anyone know a reputable, reliable and trustworthy engineer in or around Hythe in Hampshire?

 

[ajrobb]

Have you turned the hot rads off to see what happens?

 

[cinman2003]

Wow ... would you believe it! I balanced all the rads and it all seems to be working fine now. I would not have believed that balancing could have such an effect!

My sincere thanks for your fab advice and guidance. It's always heart warming to meet (if onlyvirtually) people with a genuine willingness to help thank you

 

[ajrobb]

Well done, I'm glad you got your radiators working.

A quick scan of a Baxi Solo 3 manual suggests that the temperature rise across the boiler should be 11°C. If there is limited flow through the radiators, the temperature rise across the boiler will be higher than 11°C, putting extra strain on the heat exchanger. If that is the case, you could fit a by-pass to increase the flow through the boiler.

 

[cinman2003]

I'm with you on the physics, but where would the bypass be located to achieve this?

In fact, since the heating started working, in a fashion, I've noted a few things of interest. Firstly, balancing makes a bloody massive difference which I would never have thought. Secondly, having the water pump on speed 3 of 3 (my previous pump was on speed 2 of 3) seems to help. Thirdly, keep the water tank thermostat as low as necessary to get a bath of hot water without having to cool it with cold.

I'm curious to know what impact the speed setting on my water pump might have on the heating circuit, if any. I don't want some kind of dangerous pressure building up somewhere, nor do I want to shag my new water pump in 6 months by running it too fast for too long.

I'm hoping that with Fernox flush in the system right now (until next weekend) the extra "pressure" will help free-up any gunk. Its doing something, cos I flushed the system clear, but since Fernoxing it flowed grey water into the header tank when I back-syphoned using a tap, showing that the Fernox is at least picking up some crap on its travels, which must be a good thing!

Shame there's no simple way to identify a heating circuit (which pipe goes to which rad, etc.) without lifting floorboards - or is there?

 

[ajrobb]

keep the water tank thermostat as low as necessary to get a bath of hot water without having to cool it with cold.

I think current regulation require that more than 15 litres of hot water must be stored above 60ºC (for at least an hour a week?) to prevent the growth of legionella bacteria to prevent death by pneumonia. However, new bathrooms must be installed with a temperature limiter (thermostatic mixer) on the bath hot tap to prevent death by scalding.

If you have an immersion heater with a 7-day timer, you might run your boiler cool and have the immersion heater sterilise your hot water for a few hours once a week.

Shame there's no simple way to identify a heating circuit (which pipe goes to which rad, etc.) without lifting floorboards - or is there?

If you turn all the radiators off and let the system cool down, turn one radiator on and only its circuit will heat up.

 

[cinman2003]

Wasn't aware of that, thank you once again for your valuable advice - its much appreciated

I note that my happiness over sorting it may have been slightly premature. The heating works fine when its on in isolation from the hot water, but when the hot water is also on, the heating is MUCH less efficient (i.e. rads are lukewarm at best, rather than hot). I'm assuming the 22mm circuit to/from the hot water tank is flowing much more freely than the heating circuit, thereore when the 3 port valve is mid position, the water's taking the path of least resistance and all going to the hot water tank. Looks like there is still a "restriction" somewhere in my heating circuit. Goodness knows how I find it without lifting floorboards up. It's almost like I wish I could fit a flow-meter or pressure-meter to each rad inlet valve, so I can see where the pressure is markedly falling short, at least pointing me to a particular "segment" of the circuit? What do you think? Am I mad?

 

[Hugh Jaleak]

If the cylinder coil is on 22mm pipes on both flow and return then when HW and CH are on, the water will take the easiest route through the coil, and starve the heating. To counteract this you can either fit a gate valve to the return from the cylinder or replace a section of the return from cylinder with 15mm pipe to restrict the flow through the cylinder, or easiest method, set the HW 'on' times outside of the heating 'on' times.

It may be preferable to have the HW set to switch off after the CH anyway, as I believe the 3way valve uses a voltage to hold itself in position when open to CH only. (AFAIK this voltage remains even if the CH timer switches to off, though unsure whether this could cause premature failure of the valve over time.)

 

[cinman2003]

Now that makes sense. So rather than replumb the HW return which is quite compactly stuffed in the airing cupboard, could I drain the system (easy enough), remove each rad one by one (easy enough - connector each end and lift-off) and take it out the back garden and hose out? If I did this for all rads (only 5 in the whole house) then I could effectively "eliminate" the rads from the list of "restriction/blockage" candidates couldn't I? That'd just leave the actual plumbing, and that's less likely to be sludged/blocked/rusty isn't it? Plus I don't have to destroy the house lifting floorboards?

 

[cinman2003]

Going to "practice/experiment" with one rad, by closing of valves either side of it, loosening connector so it drips empty then lifting off the wall and trying to flush outside with a hose. Will use rubber mallet gently to "persuade" stuborn crud to come out, and then put back by reverse of the above. Bleed and see if it makes any difference. I don't expect one rad to make that much difference, but if lots of crud comes out, it's probably safe to assume there's loads more to be had in the others and I should proceed. Will update you all with my findings, as you've been kind enough to share your time and advice with me

 

[cinman2003]

An update, as promised. Duly removed one rad and WHAT A LOAD OF CRUD IN IT! You WOULDN'T BELIEVE THE AMOUNT! Flushed it through, using rubber mallet to dislodge stubborn bits, and took about 20mins to do. Will do another today when I get home, and hopefully by the weekend we'll be ready to flush the system through once more and refill, syphon and add inhibitor!

 

[cinman2003]

Another update, as promised. Took a couple more rads off the wall, flushed 'em (tons of black sludgy crud came out!) and put back. Boiler kept overheating until I get some of the air out the system (by turning the boiler pot to zero and turning off/on/off/on/etc. the power switch to the boiler and pump, which disturbed the system enough to get the air out. Rads still take ages to warm up, plus they cool down when the h/w comes on, so I'm left with thought of hiring powerflush and giving it a go myself. Probably leave that until Spring though, just in case it goes wrong (don't wanna be without heating through winter!)

Thanks once again for your useful advice - its very much appreciated indeed and my probs would be much worse were it not for your kind help.

Will stop my updates now so's not to fill the forum with my ramblings ... Cheers and Happy Xmas to all