thoughts & Qs on TRVs and draining radiators

[jkn]

Hi All We have a simple vented CH system with a back boiler which probably will need replacing soon, but lets not go there ... anyway, some rooms get much too hot, and I am thinking of fitting TRVs all round (except the bathroom rad).

Thinking about this ... is the effect at the boiler of fitting TRVs to cause it to operate at a reduced duty cycle? I presume if the boiler was a 'modulating' type (If I understand the terminology correctly) it would operate at less than 100% capacity, but with a 'bang-bang' system such as ours I'm wondering about possible reduction in heating costs.

Also, the actual fitting of the TRVs, and draining of the radiators ... I know about the Drayton bungs at the tank end, but I have occasionally wondered about making things easier at the actual radiator end. I've come across this product (with the suspiciously similar name 'Draineasy', and an even more suspicious recommendation from, British Gas):

anyone experience of this bit of kit? I'm inclined to make something similar. I also wondered if there existed a sort of drain tray with a 'slot' in it, so that you could ... 'wrap it around' .. the upright pipe going to the rad, so that the water had a greater tendency to drain into the tray than dribble off the edge. If anyone gets what I mean from that dubious description, would be interested to hear of your thoughts.

Thanks J^n

[Tim W]

jkn wibbled on Tuesday 01 December 2009 21:45

Yes. Having had TRVs on 3 dumb boilers (going back to the 70's and one was a back boiler), what happens is the boiler tends to cycle on its internal thermostat. So you might expect increased frequency of firing but with less overall "on time" if several of the valves were closed down.

You'll save money just by not wasting heat overheating rooms. I won't comment on the relative efficiencies of modern modulating boilers because I don't know, but you will be better off with TRVs than without for a given system.

Ideally, if you could stump up to time controlled multiple zones that could save even more money (how many people actually meticulously turn the bedroom rads down in the day? Ok some do, but loads don't) - but that gets either a lot more complicated and/or more expensive to retro fit. It's a good thing to consider if doing any plumbing work on the system though...

Interesting idea - don't see why that wouldn't work.

The other more usual option is a proper drain c*ck at each rad.

[newshound]

If you don't have a wet and dry vac yet this might be a good time to get one.

I can recommend these:

just useful for rad jobs; if you get a blocked sink, don't do as my son just did and undo the trap with a basin underneath, use the wet and dry to empty the sink first. Similarly brilliant for emptying blocked drain gulleys. Also clearing washing machine filters: fire up the wet and dry with a floor attachment before undoing the filter cover.

Someone else will be along soon and answer the Q about TRVs.

[The Medway Handyman]

100% agreed. I carry that very vac on the van. Also handy for slurping the water out of toilet cisterns & runs of pipe that don't drain that well, and can be used to sort out airlocks.

Add the dry filter & it connects to my circular saw. Wouldn't be without mine.

[Roger Mills]

A few years ago, I made a device which screws into the rad in place of the bleed valve (or just the pin, depending on the rad design) which allows air to be pumped in - expelling the water through the pipework and up into the header tank. It looks like this:

connecting a car pump to the schrader valve (taken from an old car tyre) I was able to expel virtually all the water before undoing the unions - with very little mess resulting.

More recently - when I fitted TRVs on all but one radiator - I also fitted drain-off lockshields to the other end of each rad, making it very easy to drain a single rad without any spillage. This method would work with either a vented or unvented system, whereas my schrader valve device will only work with vented systems.

[The Medway Handyman]

But does the header tank not overfill?

[Tim W]

The Medway Handyman wibbled on Wednesday 02 December 2009 00:09

It would overflow yes, but it will (should) have an overflow pipe.

Might discover it's blocked at this point by bugs so worth a check.

[fred]

In article , Roger Mills writes

Nice one Roger, I'll be making one of those. Can't see why it wouldn't work on a pressurised system too as long as there is a drain point somewhere.

[Roger Mills]

It depends on the size of the radiator! Bear in mind that the static level in an F&E tank should be very low - so there's plenty of headroom before reaching overflow level.

If it's an issue, it's easy enough - once the rad has been removed - to open one of the valves and drain some water into a container.

I've just re-connected a largish double rad in the main bedroom this morning after removing it to decorate. In this case, I didn't use the device under discussion because the rad is fitted with a drain-off lockshield - so I drained it that way, and collected the water (to save the inhibitor) in 3 washing-up bowls. After re-installing the rad, I emptied the washing-up bowls into the F&E tank before bleeding the rad. The level went up to the point where the vent pipe just dipped into it - but it wasn't high enough to overflow. Of course, as soon as I bled the rad, it went down to the normal level.

[TheScullster]

"jkn" wrote >

Yes I have made similar. A length of lino (about 200 long by 80 wide) with a 15mm wide x 70mm long round end slot in. Slot the lino around/onto the pipe directly below the valve. Wedge it in place with the bottom end draining into your bowl! Works for me

Phil

[DavidM]

I just use some (thickish) kitcehn tin foil, wrap it around the valve between the nut on the tail and the valve body and then shape it into a funnel to direct the water into a bowl, or oven tray if the rad is low down.

If taking the rad off I also tie a piece of plastic over each tail first to stop any sludgy water spilling out when lifting the rad off and carrying it away.

[Harry Bloomfield]

fred formulated on Wednesday :

I have a lathe, nice little project for it, which I just spotted - thanks.

[The Medway Handyman]

Excellent idea. Another daft question - how do you know when the rad is empty?

Oh, and another question - when you going on Dragons Den with it :-)

[Roger Mills]

That's easy! You pressurise the air in the rad to about 10psi with both valves closed. Then you open one valve, and can hear the water flowing out, whereupon the pressure drops with some water still remaining. So you shut the valve again and re-pressurise, open it to let the water out, repeating as many times as necessary - typically 3 or 4. When the final slug of water goes out - mixed with air, it makes an unmistakable rude noise.

I'm not! I first 'published' it here several years ago for the benefit of you lot - so it's too late to patent it. Anyway, I don't think it would work very well - if at all - with a non-vented system, so it has limited - and diminishing - appeal.