radiators on/pump not?

stewie1098

We have a soild fuel heater/gravity fed to hot water tank. As soon as fire goes on the radiators come on, without water in tank reaching therm temp. Pump is still working. Any thoughts ?

keystone

I'm presuming its the upstairs rads that get hot? If you have an anti gravity valve (check valve) on the CH flow and then just give it a couple of taps with a hammer. 9 times out of ten that should sort it. Percussive maintenance pocedures can be a great healer.

First poster to suggest its a busted 3-port valve gets a big slap!!

Cheers

cyclonebri1

Stuck check valve would be my prime suspect, as above, along with a sludged up gravity system. Not a primatic system is it?, ie, do you have a header tank.??

Blast from the past for some guys I guess :D

stewie1098

Yes it does have a header tank, but I keep this quite clean, and it is just upstairs red. Question- where is this value I have to tap?? is it by the main cylinder- what does it look like-Thanks for help !

cyclonebri1

stewie1098 wrote: »

Yes it does have a header tank, but I keep this quite clean, and it is just upstairs red. Question- where is this value I have to tap?? is it by the main cylinder- what does it look like-Thanks for help !

Your problem is it could be situated anywhere on the feed pipe

Mr_Ted

stewie1098 wrote: »

We have a soild fuel heater/gravity fed to hot water tank. As soon as fire goes on the radiators come on, without water in tank reaching therm temp. Pump is still working. Any thoughts ?

1st question is, you say pump is still working!
Do you mean the pump is running all the time, or it works when you want it, in which case it will be controlled by a room thermostat via a timer?

Most gravity system configurations for gravity fed hot water and pumped heating usually require that there are 2 distinctly separate circuits coming from the boiler/heater, a flow and return for the heating(usually a smaller bore pipework, 22mm) and flow and return for the gravity hot water circuit to the cylinder(larger bore pipework, 28mm).
Is this the configuration of your system?


If so the non return valve will usually be on the flow from the boiler/heater and fitted not far from the boiler on the flow pipe on a vertical section.

It will possibly look something like this, depending on the age of the system>>>>>

fitted vertically, or

fitted horizontally?

A tap MAY, repair the problem if it is just stuck in a slightly open position, but if its sludge it may require a drain down to strip out the valve and clean the seating, and a desludge of the system may be needed.

It may well be worth considering having an electrically operated zone valve installed to work off the room stat so that the room stat opens the valve when heating is required which in turn will turn the pump on, this will be a much more positive way of preventing gravity feed to the heating when its NOT required!

It may well be that, depending on age of the system, that there may well be a zone valve on the system hidden away somewhere, possibly behind boxed in pipework?

If so will look something like this >>>>

stewie1098

Thanks Mr Ted. Very comprehensive rely. System seems similar, but not the same. The solid flue stove only has two imputs, one at top one at botttom. Hot goes out of top I assume. (drain also fitted, but not 4 out/ins). From my view of hot tanks I can see only two stopcocks- one turns hot off to taps- other ?? Does effect hot/cold output. Pump works when hot tank gets to required temp and pumps all water to all rads. Thermostat is strapped to tank. In the loft there is a large water tank, and a smaller header tank. Any ideas now ?

Mr_Ted

Mmmm, two options on system type, either cylinder is a Heat Store, or the water in the cylinder is serving heating and hot water in which case it shouldn't as heating water and domestic potable water have to be completely separated depends on pipework configuration and type of cylinder and a piccie of cylinder would help a lot?

If there are only 2 pipes going to cylinder from the boiler which do both heating and hot water, dependent on above, its possible there is NO non return valve and in that case I would suspect sludge in the heater is preventing gravity circulation?

Also, how old is the system, and do you also have another "boiler" as a second primary heat source?

stewie1098

Hope this help-solid fuel/wood stove (20plus years) As water heats in backboiler rises and heats up in cylinder(bathroom),assume as it hits temp ion thermostat it sends message to pump, to start puming around rads. In summer we turn this up high so just have hot tank water(reverse in winter). Problem now is rad(upstairs comes on srtaght away).Lots of other pipes go to cylinder, but only 2 leave stove. The stove is drain(by me) every year-ie hold float up in header tank, drain back boiler, add fresh inhibitor etc.

No secondary boiler.

Any idea-thanks again !!!

keystone

I have a feeling your system probably looks like this:



Am not convinced there is any form of real "connection" between the DHW in the cylinder hitting temp and the starting of the pump. I think you have a coincidence. Facny tracing a few pipes? Do you have a CH roomstat?

assume as it hits temp ion thermostat it sends message to pump, to start puming around rads. In summer we turn this up high so just have hot tank water(reverse in winter).

Could you explain this in a little more detail please?

Cheers

stewie1098

This looks alot nearer to mine- Thanks.
No CH room stats. On/Off on rads only- no stats.
Sorry to sound stupid- 'tracing a few pipes'-What do you mean.?

The cylinder has the onlt thermostat strapped on, what I mean is that in the summer, we turn this to say 60/70, so when the boiler goes on its only on for 1-2 hours for hot water- never reaches 60/70 so rads don't go on.

In winter turn to 30/40 Boiler on all day, rads go on after 30 mns-stay on all day. Hope this explains.

At moment-fault- rad goes on in Summer (60/70 therm setting) straight away !

Thanks again...