thermostat not starting pump

neil3841

it is happening daily now the thermostat does not start pump but the green light is on the reciever (it normally means pump should be running) But when I turn thermostat down so green light goes off and back up so it comes back on the pump starts. (normally 1st time sometimes I have to do this a few times)

Yes every morning I get up to the reciever having the green light on but the pump is not running.

I do not know if I should blame the thermostat or the pump neither a that old (both definitely less than 15 years old)

Advice please

Ironman

I assume by your description that you mean the pump control when you say "receiver"?

If that's the case, then the problem is not with the thermostat or its wiring' its most likely the circulator or the loop is air bound.

There are dozens of ways a system can be configured and controlled and we're not on site to see yours. If you would post some pics of the boiler, its near piping, the pumps and controls, we could better advise you.

What's the pressure on the boiler gauge?

neil3841

It is a back boiler so does not have a pressure gauge. is must be either the themostat or pump. It is not a new fitting so cannot be the wiring as it was fitted by a gas fitter and has worked fine for years. By receiver I mean the thing that is on the wall that recieves instuctions from the wireless themostat to control the pump. When the green light comes on the pump should be running.

Jamie Hall

If the pump isn't running -- really isn't running; no sound, no vibration, no nothing -- it's as likely as anything that it's not getting power. Check first -- is there power coming to the pump when the green light is on? If not, is there power coming out of the control box to the pump wires when the green light is on? If both of those are "no", then your problem is in the control box. If there's power coming out of the control box, but not getting to the pump, then it's in the wiring. If there's power at the pump but it's not running, then it's the pump.

Never say "it can't be X, it's worked fine for years"!

neil3841

Ok thanks will look into it. The pump is not running at all no sound no vibration not getting hot nothing. I think it probably is the control box as it comes on when I turn it down so green light goes off and back up so it comes back on but not always first time.

Ironman

neil3841 said:

It is a back boiler so does not have a pressure gauge. is must be either the themostat or pump. It is not a new fitting so cannot be the wiring as it was fitted by a gas fitter and has worked fine for years. By receiver I mean the thing that is on the wall that recieves instuctions from the wireless themostat to control the pump. When the green light comes on the pump should be running.

What's a "back boiler"? IDK what you mean by that.

All boilers are required to have a pressure gauge to get ASME certification and meet code.

neil3841

It is behind the gas fire like this https://en.wikipedia.org/wiki/Back_boiler

STEVEusaPA

So there is no boiler, just a coil getting it's heat from the fireplace.
Are you sure the system is full of water? Is it a closed system or an open (to the atmosphere) system. If closed, does it have an expansion tank and relief valve?
Some pictures, or a sketch with all the components would help.
But if there is enough water in the system, either power is going to the circulator or it isn't. If power is going to the circulator, it's the circulator. If power isn't leaving the control to the circulator, it's at least the control-can check circ without power.

neil3841

I think we getting off the point here but yes it is a closed sytem and obviously it is full of water as it works when I turn the thermostat down and back up. The problem is either the control box or the pump. The back boiler is gas powered but it isn't anything to do with that. How the boiler works has nothing to do with the problem

It seems I need to check if power is leaving the control box. I suspect it is some of the time but not others but I need to test for that.

STEVEusaPA

How is it 'obviously full of water'?

neil3841

because the radiators work fine when it comes on if they didn't have water in they would not work. I have said several times about it coming on when I turn it down and back up.

It seems I need to find out if the pump is recieving power when it doesn't come on. There is nothing wrong with the back boiler and the system is full of water.

hot_rod

A volt meter or 120V test light will confirm that you have power to the pump.

However pumps can stick, break shaft or just fail. To know for sure you need to remove the pump (4 allen bolts) from the housing and power it up.

That would maybe require a drain down and re purge.

Those back boilers are famous for flashing to steam if flow is stopped or reduced, then you end up with an airlock. The pump my be spinning but an air bubble is prevent circulation.

neil3841

Hi yes I need to do some tests. I have had the pump stick before but only after it has been stopped a long time after the summer but I pretty sure this is something else though. As when it has stuck after summer it has needed turning manually to get it going.

Once pump starts after tuning thermostat up and down heating works as it should. But now I know what I need to test thanks for the help

Zman

I am guessing that the control side of your setup is 24 volt with a relay that activates the 120 volt side. This is how they normally work.
To trouble shoot, you can check the voltage to the relay and the circulator until you find the issue.
My money is on the circ, it could be a bad relay as well.