rads won`t get hot ?

[malc]

hello all, i`ve been asked to look at a central heating system in a small office block (2 separate offices, one downstairs,one up )
the boiler is located in the downstairs office,the radiators were turned off by the thermostat in the warm weather a week ago or so,but when the radiators were required to heat the offices again after being off a couple of weeks,no heat ?
the upstairs office has no problem with their rads,even though heat comes from the same boiler.
hot water comes from another source.
i haven`t been out yet to look,but was asking if anyone could advise what to check first please.
cheers.

 

[stevetheplumber]

trvs stuck shut is the obvious starting place

 

[Plumbstar Tom]

try banging the TRV with your trusty adjustable or similar

 

[MarkAqua]

Stuck TRV pins would be my first all also. Take the head off and try pulling the pins free. Dont tap them too hard! lol

 

[Bernie2]

Hmm!

Basics: The heated water has got to get away from the boiler. Is the pump okay and nothing turned off on the circuit?

Usually hot water rises naturally so the upstairs getting hot first is quiet usual, but it may need the pump to force the hot water around downstairs because the downstairs pipework probably doesn't rise and so the hot water can't rise to it unless forced by the pump, unless I suppose if the boiler is in a cellar lower than the downstairs.

So if nothing is obvious, then as has been said the next obvious thing is something wrong with the trv's.
As they usually have a pin that forces down to shut the water off when the rad gets hotter than the setting, these pins can stick. Freeing them is usually a case of silicon spray or similar.

You can of course move the pins with pliers, but try tapping them down very gently first with something soft, you don't want to bend the pin, this is of course after leaving them for 10 mins for the spray to work.

If they are stubborn then try the pliers. But only move the pin slightly, don't pull the pin out whatever you do, they are murder to get back in and some trv spray water all over the place if you take the pin out. And don't grip the pin to tight with pliers it can cut the pin sides and make it rough, so it will not operate smoothly and might even tear the seals.

Some pins also have very small O ring seals that can be displaced if you pull the pin out and you then have to turn off and drain down, remove the valve and ty to put the pin and seals back.
The problem is, with trv rings they can become dry and seize onto the pin so they can tear if you pull them out without a lubricant and even sometimes they tear with a lubricant.

Usually though, with plenty of silicon spray they work okay. You may be able to use WD40 but check before you do that it doesn't harm the rubber O rings.

Err! One thing about getting older. You have usually made so many mistakes, you know what happens when things go wrong, so you can tell others to hopefully save them doing the same thing.

 

[malc]

thanks to everyone for your replies, I`ll look at the trv`s. but I
don`t think i made myself clear. the rads in the upstairs office are separately controlled by their own thermostat,the customer has told me the boiler cuts in and heats the rads upstairs when the people in that office want. but when the thermostat downstairs is turned up, it `clicks` as usual,but boiler won`t start.
anymore thoughts ?
cheers,malc.

 

[Mbear]

It sounds as though ur upper and lower office may hav been zoned.

Ie

Thermostat clicks and sends power to zone valve, valve opens while also sending power to pump&boiler. Boiler heats up the zone area.

If ur lower office heating isn't working but the upper is then I'd be looking to see if the lower zone valve is goosed.

All this is providing that the same boiler feeds up&downstairs

 

[malc]

yes same boiler feeds up and down. whats goosed please ?
and how is it fixed ?

 

[Mbear]

yes same boiler feeds up and down. whats goosed please ?
and how is it fixed ?

lololol

sorry, goosed is slang for broken mate.

It could be the head of the valve needs replacing or could just be the synchrom motor that's 'goosed' hehe and needs replaced

synchron motor is obviously a cheaper fix bud

 

[malc]

thanks for that (head lowered )
always glad to provide a laugh !

 

[Bernie2]

As said!

Check zone valve by moving manual operation lever over to open position. If it works it would seem trv's are okay and zone valve is not stuck.

Disengage manual lever and let zone valve shut.

Check zone valve for power. If power there and there are no obvious mechanical problems.

Turn off power and test motor with multi meter about 2,400 Ohms or if other make work out resistance and test. If its open circuit i.e no reading, its usually faulty.

 

[malc]

this is the place to learn !!
thanks to everyone,i`m looking at the job tonight .now i`ve got some idea what to look for . thanks again.

 

[doitmyself]

Resistance = Voltage x Watts.

It wasn't when I went to school - over 50 years ago.

Ohms Law: V = R x I (Voltage = Resistance x Current)

Also W = V x I (Watts = Volts x Current)

So W = I² x R = V²/R

So R = V²/W

That of course only applies to DC circuits. AC is more complicated.

 

[Bernie2]

Yes your right of course doitmyself.

I was trying to make it easy, but never checked what I had written. Sorry about that!

 

[malc]

messege to MBEAR (GOOSE)
absolutely right mate,it was a zoned system and the motorised valve needs a new head.
thanks again.

 

[Mbear]

messege to MBEAR (GOOSE)
absolutely right mate,it was a zoned system and the motorised valve needs a new head.
thanks again.

Glad I could help goose mate