Central Heating and Hot Water Pump

Have you just moved in ? Is the system behaving any differently to previously ? Do you have a hot water cylinder / heat store ? If so the radiator in the bathroom might be on a gravity or pumped secondary heating circuit ? Why do you think the pump is running ? Is there more than one pump ? Are you sure it is the pump for the radiators ? Can you switch it off, if so what happens when you do ? Do your radiators have thermostatic valves on them, if so what are they set at ? What is the main house thermostat set at ? What happens when you lower or raise the set temperature ?

 

Let's first of all forget whether it is a gas or oil fired system and simply assume it is a 'wet system'......

The immediate questions are: Have the radiators on the heating system got thermostatic valves?

And, has the radiator in the bathroom got any valves that can be controlled easily by hand, or have the handles been pulled off?

It is normal in a wet system with thermo valves to have a bleed radiator ie; one that is fully open and cannot be closed; but it is usually in the heating side rather than the hot water side.

It is also normal for the pump on the hot water side to run all the time until the hot water correct temperature has been reached (but you could find that if the hot water is set for one hours duration, the pump might stop at least twice)......why the rad in the bathroom is on the hot water side of things, I don't know, unless a DIY plumber thought it was a good idea..........it doesn't make sense to me........unless the valves are screwed right down to nearly closed and it is acting as a heated towel rail.

(saying that, I have two bathroom rads on my system, but it would take too long to explain why)........

 

maybe your motorised valve is stuck..........

 

Yeah, and that...........but I would expect if that was the case, it would either be allowing hot water into the heating system when not required; or no heating when required.

The things that control the pump are the boiler stat and the hot water cylinder stat.............and the time clock, of course.

 

Without standing in front of it, it is hard to tell exactly what controls you have, but based on what you have told us, I am beginning to think it is normal.

AL

 

Are you sure the pump is for the radiators?

I ask because my heating system has a pump on the hot water circuit (as well as the radiators) to help the circulation due to the route of the pipes.

 

A fully pumped system is quite normal.........

The pump will run when there is a demand for hot water or for heating (the demand is created by cold water being circulated passing across the appropriate temperature sensor (when the particular system is switched on).

When the hot water system is on, the pump will run until either the water temperature in the hot water cylinder is reached, or if the boiler setting is reached (Summer / Winter etc) ie; the water in the boiler circuit and coil in the hwc...........It is quite normal for the boiler to stop running for a while and the pump to keep going............It will happen with the heating system as well.

AL

 

There should be 2 temp sensors on a water tank. One to sense temperature and another 'high limit' sensor, which is a safety feature. To stop the cylinder getting too hot. Even when a cylinder is at temp (in your case 45 it seems) a boiler may run hot water to 60-65 to pasteurise the system periodically. Typically once a month depending on controls. Legionella loves 40-45degC but its a sealed system and not dangerous as would be an air cooled chiller or water cooler which typically cause all the outbreaks as it becomes air borne. Besides the pasteurising deals with it.

 

."I only have the one sensor which is about a foot up from the bottom of the tank."

That's the tank stat Mervyn.

If you still have problems and need someone to look at the electrical side of things I can come over and take a look but not until Wednesday afternoon at the earliest.