Boss Therm 2 port valve

[andyandy2]

I'm having problems with my heating system, hot water seems to be ok but heating will only work with the hot water on as well, i'm wondering if one of the 2 port valves might be at fault, but can't understand the lever set up on them, the lever seems to have little resistance in its normal position, more resistance is felt as the lever is moved towards "open" but it will not stay in this position.
Is there anyway i can override the motor to check its functioning, not sure if these valves can be dismantled to replace head or motor. Any help much appreciated

 

[jackthom]

Is there a step in the slot which will hold the lever against the spring when the valve is fully open?
I'm more familiar with the Honeywell valves but I'd be surprised if this wasn't possible.

I would compare the ease with which the lever can be moved when the system is switched OFF compared to ON and calling for heating.

It should be fully closed and harder to move against the spring when OFF.
When CH is switched ON it should be obvious the motor has worked and the lever should be more floppy.

The boiler not firing for CH only, suggests that either the motor is duff, the valve is sticking and not activating the internal microswitch, or the microswitch itself is faulty.

 

[andyandy2]

Bit of an update, not sure if i'm on the right track, Hot water has come on with timer this morning and cylinder is hot, switch heating on and boiler fires, rads get slightly warm and boiler switches off, there is no room stat just trv's on the rads, Any ideas please

 

[dextrous]

Is the zone valve open (i.e. is the lever floppy?)

 

[andyandy2]

I've just taken the covers of both 2 port valves and had someone switch heating a nd hot water on and off, both valves seem to be operating, but as soon as rads get slightly warm boiler switches off, so seems more like a thermostat problem, its a baxi back boiler

 

[dextrous]

Once you have determined the model number, then try here http://www.heatingspareparts.com/boilerpart.aspx?ProductId=25280&Part=VENT AUTO

 

[andyandy2]

Thanks for your help dextrous, i'm still a bit confused how this system is working, Hot water is controlled by cylinder stat, and when only hot water is on works ok with plenty of hot water, When both h/w and c/w are on together then both are only getting warm, does the boiler thermostat overide the cylinder stat
Is there anyway to test the thermostat (bypass) before i order one, ordering online is a problem at the minute as someone has tried to fraudulently obtain a card in my name so my cards are stopped untill i've been into the bank with photo id, lets hope its not to cold tonight

 

[jackthom]

The boiler thermostat will be OK if you are getting hot water in the cylinder.

The external controls don't usually operate on the temperature of the boiler water, they just switch the boiler ON/OFF.

The most likely source of the problem is the zone valve that controls the CH.

Do you have a multimeter or mains tester screwdriver and are you competent with mains electrical wiring?

 

[andyandy2]

Hi yes i have a multi meter and mains test screwdriver (don't let the electricians read that lol ) and i'm ok with mains wiring
The zone valve seems to be operating when switched on

 

[jackthom]

The normal setup is that the valve microswitch makes the orange wire LIVE once the valve has fully opened. This is what should fire up the boiler when CH only is on (and the hot water cylinder isn't calling for heat).

The orange wires from each valve will be connected together in the wiring centre so that if either of them goes LIVE the boiler ignites.

From what you have described it probably isn't going live except when the DHW cylinder thermostat is calling for heat.

 

[andyandy2]

Ok thanks jack will go and try that, so is the heating just controlled by the trv's and is the boiler thermostat just setting boiler output

 

[jackthom]

Yes.

If you don't have a room thermostat you really should get one and save some money into the bargain.

 

[andyandy2]

Just tried testing the orange wires, switched heating on, went upstairs zone valve had opened, pump was running, checked power to orange wires and showing live, was just checking what wires went where and the heating switches off, loose power to orange wire, back downstairs and red light still on programmer but boiler silent and rads cool (heating only run for a few mins at most
the two orange wires are together in a connector with one black which seems to head off towards programmer, and one brown which seems to go to cylinder stat

 

[kevplumb]

might help

s plan

• kevplumb
• 19 Sep 2009
• 8

 

[Gasop]

I've just taken the covers of both 2 port valves and had someone switch heating a nd hot water on and off, both valves seem to be operating, but as soon as rads get slightly warm boiler switches off, so seems more like a thermostat problem, its a baxi back boiler

Would be a good idea to check the pump.

Could be that the hot water working on gravity only and you have not noticed this.

When heating is called for then the boiler fires up and tries to work on gravity but of course going down on boiler stat as it is doing on HW but cannot circulate round the rads.