Grant 50/90 Boiler - How to increase pressure / cold radiator

a4007035 · 4 Oct 2020

Hi,

I have recently moved house.

We have one cold radiator in the living room - the other one is fine. I've bled it and opened the valves on either end - still nothing.

I went to check and up the pressure of the boiler and it appears we have a mega old boiler that I'm not exactly sure how to do it. Its a Grant 50/90 boiler. On the combi boiler in my old house you would just open the valve. I can't even find the pressure gauge on this.

So any help on how to increase pressure / identify the pressure gauge would be much appreciated. I'm hoping this will solve the cold radiator issue.

Gavin

terryplumb · 4 Oct 2020

The water pressure is unlikely to be the reason one rad doesn't heat. Have a look in the attic for a small water tank ,that may feed water into your system.
To get rad working ,turn off all other radiators by their thermostatic rad valve ( if fitted ) but don't touch the other valve on them. Run heating and advise if the problem rad now heats up.

oilhead · 4 Oct 2020

And if you find a header tank, make sure it has water in it. Ball valves often stick.

a4007035 · 4 Oct 2020

Hi

I tried your advice and turned off all the radiators except the one in question and it heated up like it should do.

What does this mean then? What do I need to do to rectify it? Obviously need to turn the others back on now.

Also is there any way I can check the pressure. Just want to make sure it's at 1.5bar

Gavin

Terrywookfit · 4 Oct 2020

If the system is open vent (Tanks in loft ) it wont have one.
Read up on system balancing . Basically turn down the lockshield valves on the hot rads until you get flow to all of them the cold one should be fully open.

terryplumb · 4 Oct 2020

a4007035 said:
Hi

I tried your advice and turned off all the radiators except the one in question and it heated up like it should do.

What does this mean then? What do I need to do to rectify it? Obviously need to turn the others back on now.

Also is there any way I can check the pressure. Just want to make sure it's at 1.5bar

Gavin

Turn on all the other rads now . You may be lucky and the problem rad will heat like the others from now on. If it doesn't ,you will need to balance the system ,as Terrywookfit
Advised above ,also note the ref to loft tanks

a4007035 · 28 Oct 2020

Thank you for your advice. It worked in that the cold radiator heated up.

Now I have tried to balance the system. Its been quite difficult to do as I dont want every room to be the same temperature and it seems that the slightest turn on the lockshield valve can have a big effect. Ive turned some radiators completely off like the spare room and bathroom. Now all the radiators are getting warm but I wouldnt say hot i.e. I can keep my hand on all of them.

One question I did have is: how should the radiators be set in the room with the thermostat? There are two radiators in the room with the thermostat: 1) One is small and looks to have identical valves at both ends and 2) The other is a big one with a lock shield valve and setting dial on.

The thermostat is set to 71 degrees fahrenheit which is about 21 degrees celsius. But I think its too low as house isnt particularly warm.

Last question. What temperature should the oil boiler be set at?

Terrywookfit · 28 Oct 2020

The stat set at 70°Will turn off at that temp. What actual temp is the room reaching.

Try turning the boiler temp up.

a4007035 · 28 Oct 2020

I put a thermometer in the room and the actual temp was reading 17 degrees celsius (63 degrees fahrenheit).

Harry Bloomfield · 28 Oct 2020

a4007035 said:
2) The other is a big one with a lock shield valve and setting dial on.

The 'setting dial' sounds like a TRV - a thermostatic valve. Idea is that once the room warms to the temperature set on the dial, the TRV automatically closes the valve - so no more heat to the radiator until the room cools down again. Set the dial to around mid-way, if there are any others, set them similarly - you can adjust them a little higher or lower once you get the hang of the system and the needs of the room. That assumes that the TRV's are functional, they do fail.

Sometimes they just jam closed and you get no heat to a radiator. If you remove the TRV head, under it will be tiny pin sticking up. You should be able to push the pin down against spring pressure, with something flat like a pair of pliers. If it will not push down, it is stuck down and needs a little persuasion to free it to spring out. The pliers will help ease it out, but don't pull it all the way out, just a couple of mm - enough to free it.

a4007035 · 29 Oct 2020

Here are the pics of the valves of the radiators in the room with the thermostat

1. Upstairs radiators. These get very hot quickly. I have either turned the lockshield valves on these completely off or slightly open. These are all ok as I want them to be luke warm.
2. Room with thermostat. Both radiators are turned fully open for lockshield valves and TRV. Both are currently luke warm. Thermostat set to 71. Current temp is 63.
3. Hall radiator. Lockshield valve is partially closed. Radiator is giving out good heat (ideal temp)
4. Living room radiators. 1 is luke warm and 1 is giving out good heat.

oilhead · 29 Oct 2020

Your valves are just wheelheads and exercise no control except for restricting flow if turned down. Open up all the wheelheads all the way and control with the lockshields.
If your room thermostat is calibrated in Fahrenheit, then it is old and may be out of calibration. Is it still in 'demand' whilst your room is cold or has it switched the boiler off?
How big is your room and how big are your radiators? Are they single panel, double panel or convector? Are they both fed off the same flow pipe from the main pipes or are they connected to the flow circuit independently?
Water set to 70oC at the boiler will be significantly less by the time it reaches your radiators. Turn it up. If youe upstairs radiators are too hot, then turn the lockshields down.
What speed is your pump set to? If 1 or 2, then turn it up.

a4007035 · 29 Oct 2020

oilhead said:
Your valves are just wheelheads and exercise no control except for restricting flow if turned down. Open up all the wheelheads all the way and control with the lockshields

I have opened up all the wheelheads and will adjust the lockshields once I know which radiators heat up/dont heat up and which ones I want to stay cold, etc.

oilhead said:
If your room thermostat is calibrated in Fahrenheit, then it is old and may be out of calibration. Is it still in 'demand' whilst your room is cold or has it switched the boiler off?

It looks like the boiler is still in demand.

oilhead said:
How big is your room and how big are your radiators? Are they single panel, double panel or convector? Are they both fed off the same flow pipe from the main pipes or are they connected to the flow circuit independently?

Room is fairly standard size (3.5m x 3.5m x 3m). In the house all but one radiators are double panel. The room with the thermostat has 2 radiators. 1 big, double panel and 1 small, single panel. Not sure on the connections to be honest.

I will turn up the boiler.

How do I check/change the boiler pump speed?

Harry Bloomfield · 29 Oct 2020

a4007035 said:
How do I check/change the boiler pump speed?

If the speed can be varied, there will be an adjustment switch or knob on the pump itself marked with numbers. If it's a very old pump, it might just have a single speed.

a4007035 · 5 Nov 2020

Hi All. Thanks for all your help.

I think I made a mistake. I didnt want the heating on upstairs so I shut all of the lockshield valves. But this seemed to inhibit the radiators getting hot downstairs (I thought it would be other way round).

So I've gone back to square one. I have opened up all lockshield valves and all wheelheads in the house. Heating is hot upstairs and warm downstairs.

Now what would you recommend is the next best course of action? i.e. do I need to adjust the lockshield valves or wheelheads?

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Grant 50/90 Boiler - How to increase pressure / cold radiator

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