Multiple Central Heating questions

[willougs]

Good evening all.

I have recently moved into a house and have absolutely no idea how all this central heating stuff works. I would grateful if someone wouldn't mind taking 5 minutes to assist me with the following questions. The system I am led to believe is a standard gravity fed setup, consisting off:-

Glowworm Ultimate 50FF boiler
ACL LP241 Programmer
ACL Drayton RTS2 Thermostat
Gledhill hot water cylinder
12 radiators (without thermostats)

My questions are as follows:

a) With the LED on the RTS2 on ("call for heat" on), is it normal for the boiler to not be on? Sometimes it only fires up for a minute or so and then cuts out again, even though the LED is on.

b) The thermostatic knob on the boiler itself is currently set approx mid-way between min and max... is that correct?

c) The upstairs of the house gets very warm, however with the room thermostat on 22 degrees downstairs, it seems to always be "on" and never reach the required temperature. Downstairs is always noticably colder. Is there anything I can do to alleviate this?

d) There is a tap on a pipe from the bottom of the hot-water cylinder that is neither on or off. I am told this is to balance the flow of the water between the heating and the hot water. Is this correct? And if so, how do I know when its at the correct setting?

I really appreciate any help that anyone can offer.

Thanks in advance,
Steve

 

[Bahco]

a) If the water has reached set temp in the cylinder (60 degrees) the boiler will not fire up until the the cyl stat calls for heat again, assuming that it is working correctly

b) yes

c) Fit TRVs to all your upstairs rads and set your roomstat to 18 - 20

d) Where exactly is this tap?. Is it a gate valve linking flow and return pipes
Hope this helps

 

[kevplumb]

which gledhill ?

 

[willougs]

Many thanks for the quick replies! I am very grateful. In answer to the questions, I'm not entirely sure on the type of Gledhill. I will update the post as some as I have a model number to hand.

The tap that is "unknown" is plumbed in right at the bottom of the cylinder, in that a pipe comes out from right at the bottom of the cylinder and connects to the "half-open" tap... this then just connects to one of the many pipes at the back of the airing cupboard. Sorry I am being a bit vague. Am I able to post pictures onto this forum?

With regards the response to question a) above, the enquiry was actually regarding the Central Heating, where the RTS2 (room thermostat) has the LED on (indicating "call for heat" on) but the boiler switches on and off for random periods, even if the LED remains constantly on and the required temperature is not met. Is this a different matter?

Thanks again,
Steve

 

[croydoncorgi]

Thermostat in boiler controls temperature of water leaving it by turning burner on and off. Control knob on boiler adjusts this temperature.

Room thermostat turns radiators on and off (DOES NOT change the temperature of water going throght them).

So it's quite normal for boiler to cycle on and off when the radiators are on and the room thermostat is still calling fo heat.

The model of Gledhill cylinder is important because it MAY be a heatstore, in which case the whole system works on different principles.

 

[felix]

That 'half-on' valve is almost certainly in your cold feed. If so, it controls the flow of water from your cold storage tank into your hot water system and I can see no possible reason for it to be half shut. Do this experiment with the heating switched off. Open an upstairs hot tap and close that valve. If I'm right, you can expect the hot water flow to stop quite soon.

Radiators are designed to run a lot hotter than you would like for your hot water and boiler thermostats are normal set to maximum. It sounds like you have no cylinder stat - and nothing for it to control even if you did. Look for a small box on the side of the tank. I bet you don't find one.

I think somebody has cut corners here. They've turned down the boiler to get the hot water temperature right and now all your radiators are running too cold. If this is the case then I can't see any easy way out. You can turn up the boiler and have dangerously hot water coming out of your taps or you settle for poor heating or - and this is the expensive option - you can fit a motorized valve and tank stat into the system to control the tank temperature.

 

[willougs]

Hi Felix and all,

Thanks for the tip of testing the cold water feed. I shall do that when I get five minutes and the other half won't want a bath.

In answer to previous questions, the cylinder doesn't have a specific model number on unless 31/025A is one, but it does have "1050x450mm vertical indirect c/w flexilag insulation", thats about all. It has an emersion heater element in the top by the looks of things.

I do have a thermostat on the cylinder (an HTS3), that's currently set to 50 degrees. So if that's the case, then I will be ok to put the boiler thermostat up to the maximum? To put hotter water through the radiators? I read in the boiler manual that is approx 82 degrees.

I have attempted to add some images of the tap setup and cylinder label to the web link below.

http://www.zen33260.zen.co.uk

Thanks again for all your help. Its all very interesting stuff to me.
Steve

 

[felix]

It seems that I lose my bet but this is good for you - possibly. Try this:

Set your controller for hot water only. If you can't see how to do that then turn the room thermostat right down.

Turn the boiler stat up to maximum.

Now carefully turn that tank stat back and forth. With luck you will hear a click as it switches. In a properly functioning system the boiler will switch on and off as well. If the boiler runs on regardless of the tank stat position then something is faulty and your hot water is going to end up far too hot. I can just imagine the previous owner, or a rogue plumber, turning down the boiler stat to get round this problem.

Let's hope that you get lucky. I would recommend that you set that tank stat at 60 degrees but that's a personal choice.

I've looked at the pictures and that valve does appear to be in the cold feed but there's a puzzle. If you follow it back from the tank and through the valve you have a large pipe going up, presumably to your cold tank but there's also a small pipe going down through the floor.

The only thing you can put on the end of a pipe like that is a drain cock. If it feeds some kind of mixer tap downstairs - a shower maybe - think what will happen if your cold tank runs dry. The hot tank will empty into the cold side of the mixer. Bad plan - especially for anybody in the shower when it happens! But we now have a possible explanation for that half-closed valve; it will increase the cold flow to a mixer on that pipe.

You CAN feed a mixer from a branch off the cold feed but it must be higher up than the top of the tank. Better still, take it right back to the cold tank.

Incidentally, the soldering on those pipes is terrible and that green gunge means that a lazy plumber didn't bother to wash the flux off.

 

[willougs]

Hi Felix,

Thanks for your suggestions. I agree that the piping doesn't look pretty. The house itself is only 11 years old so I don't think they even had the excuse of a difficult retro-fit job.

Anyways, I did as suggested... turned to hot water only, turned up tank thermostat and it did click, the multi-valve switched to the "W" setting and the boiler started up. Turning down the stat, a click, and the boiler switched off. Switch stayed on "W" as I guess you'd expect.

I have added another picture to the link above to attempt to trace the pipes (not so easy). We do not have any showers downstairs, and have two mixer taps in kitchen and utility room. Once the pipes go thru the floor they are then behind walls and impossible to trace. All 3 pipes into the cylinder itself are very hot to the touch.

Thanks alot.
Steve

 

[felix]

A picture certainly saves a thousand words. I can see now that the pipe isn't the cold feed at all. It's the bottom end of your cylinder heating coil. Being fitted so low down and with that gate valve it resembles a cold feed in every way but it isn't.

The overall view makes it clear. Follow the pipe from the top of the pump and you come to the three port valve. One outlet from this is coming forwards and into the top of the heating coil, the bottom of which is directly below on the cylinder. What really gives it all away is that other valve behind the pump. This is a bypass on the heating circuit which allows a small amount of water to flow, even if all radiators are off. The point is that this bypass connects with that mystery pipe. Conclusion - it's part of the heating system.

The small pipe going down into the floor is no longer a problem. It's most likely the return pipe for radiators downstairs. You can set your boiler stat to maximum and the tank stat to whatever you like. Fifty degrees is a bit low but it's your choice.

So what about those valves? The one behind the pump should be almost shut. To set it up you turn off all your radiators and select heating only on the controller. This leaves only the bypass open and the boiler will cycle on and off on its own thermostat. If the boiler 'kettles' before switching off, the bypass needs opening. If you open it more than is necessary your radiators will not heat up properly because too much water is taking the easy route through the bypass. The other valve, the one that started this whole discussion, is redundant. You can't even use it to isolate the heating coil for maintenance because you don't have one at the other end. All it's doing at the moment is increasing the time it takes to heat up a cylinder full of cold water. I recommend you open it wide.

 

[willougs]

Felix,

Many many thanks for your help in this matter. It certainly makes more sense to me. I will indeed open it wide and also set the boiler to max.

Thanks again
Steve

 

[kevplumb]

jesus if i had put that in the boss would have had my legs



and rightly so