Back boiler gravity system working in reverse

Spiral Notebook

Currently finishing updating the plumbing system in an old enough house (early 1980's) and we have a problem!

We have a stove with a back boiler. The back boiler heats the cylinder in our hot press (hot water) and when the pipe stat (connected on the flow, about 3 foot from the stove) hits x degrees the circulating pump starts pumping the hot water around our rads.

The problem is that when the circulating pump cuts out, the return from the stove starts getting much hotter than the flow. The return is much hotter the whole way from the stove to the cylinder in the hot press. (We were able to check the whole way along the pipe because the floors upstairs arn't down fully yet).

The flow never heats up enough to kick the pump on again, and it appears the cylinder is trying to be heated from the bottom (because the return is hotter than the flow) and this would take an age to heat.

Anybody ever come across this before, have the plumber coming back Tuesday and from talking to him over the phone, he doesn't seem to know what the problem is?

If I manually turn down the pipe stat to get the pump to kick in, the flow then gets hotter than the return, but when the pump cuts out, it reverts back to the return becoming hotter than the flow!

Also, just to note, the return and the flow run side by side, out the back of the stove, vertically up the chimney to upstairs, horizontally for about 4meters, and then into the hot press. Could this be the source of the problem?

jimjimt

Can you see behind the stove in full and confirm that the return pipe is connected to the bottom of the stove.

Is there a oil boiler or other connected ?

Any non return valves ?

Any other circulating pumps from oil heating ?

Send pictures if you can.

Spiral Notebook

Yes I can see behind the stove, and can confirm that the return is connected to the bottom.

There is an oil burner with its own circulating pump connected to the system.

There are non return valves, but I am not 100% sure on which pipes, i'll go up to the house before lunch, have a look and take a few photos.

Should the fact that there is an oil burner aswell have any effect on whats happening with the stove? When the stove is doing what it is doing we don't have the central heating (oil burner) on?

Thanks for the reply jimjimt.

corkgsxr

Is the pump pumping the right way

Spiral Notebook

Yes, the pump is pumping the correct way. That's actually the first thing we thought of, but had that checked by the electrician.

Dtp79

Spiral Notebook wrote: »

Currently finishing updating the plumbing system in an old enough house (early 1980's) and we have a problem!

We have a stove with a back boiler. The back boiler heats the cylinder in our hot press (hot water) and when the pipe stat (connected on the flow, about 3 foot from the stove) hits x degrees the circulating pump starts pumping the hot water around our rads.

The problem is that when the circulating pump cuts out, the return from the stove starts getting much hotter than the flow. The return is much hotter the whole way from the stove to the cylinder in the hot press. (We were able to check the whole way along the pipe because the floors upstairs arn't down fully yet).

The flow never heats up enough to kick the pump on again, and it appears the cylinder is trying to be heated from the bottom (because the return is hotter than the flow) and this would take an age to heat.

Anybody ever come across this before, have the plumber coming back Tuesday and from talking to him over the phone, he doesn't seem to know what the problem is?

If I manually turn down the pipe stat to get the pump to kick in, the flow then gets hotter than the return, but when the pump cuts out, it reverts back to the return becoming hotter than the flow!

Also, just to note, the return and the flow run side by side, out the back of the stove, vertically up the chimney to upstairs, horizontally for about 4meters, and then into the hot press. Could this be the source of the problem?

You say the pipes run for 4 metres horizontally. Are both pipes rising the whole way to the hotpress on the horizontal??

tickledeb

I have just replaced the pump on the heating system of my mams stove back boiler/hot water tank in her bungalow and I have put the pump on the opposite flow direction to what it was and it still seems to be working fine... It now flows from a 15mm pipe to a 22mm pipe instead of the other way round. not sure if it is flow or return but it is working ok???

Dtp79

tickledeb wrote: »

I have just replaced the pump on the heating system of my mams stove back boiler/hot water tank in her bungalow and I have put the pump on the opposite flow direction to what it was and it still seems to be working fine... It now flows from a 15mm pipe to a 22mm pipe instead of the other way round. not sure if it is flow or return but it is working ok???

As in the pump is now pumping the opposite direction to what is was originally?

tickledeb

Dtp79 wrote: »

As in the pump is now pumping the opposite direction to what is was originally?

Yes, but my mam and stepdad changed it last time the pump broke (about 10 years ago) and they are not sure if they put it on the same way as the one they took off!!??!!

It looks as though it is now pumping the cold water out of the radiators and therefore pulling the hot round the system, eveything seems to be working fine?? Wondered if it maybe will not be a problem because the pump does not seem to be connected straight to the hot tank (can't be sure because the pipes run into the wall) and it is a bungalow so everything is on the same floor.

Dtp79

tickledeb wrote: »

Yes, but my mam and stepdad changed it last time the pump broke (about 10 years ago) and they are not sure if they put it on the same way as the one they took off!!??!!

It looks as though it is now pumping the cold water out of the radiators and therefore pulling the hot round the system, eveything seems to be working fine?? Wondered if it maybe will not be a problem because the pump does not seem to be connected straight to the hot tank (can't be sure because the pipes run into the wall) and it is a bungalow so everything is on the same floor.

Very confusing to say the least!!! Follow the pipes from the boiler the cyclinder. Which pipe is the pump on?? Is it on the top or bottom pipe. ?? As always pics help if possible

tickledeb

Dtp79 wrote: »

Very confusing to say the least!!! Follow the pipes from the boiler the cyclinder. Which pipe is the pump on?? Is it on the top or bottom pipe. ?? As always pics help if possible

Yes I know, the thing is the wood burning stove has a back boiler which is piped into the hot tank which is in the cupboard about 4ft away and the pump is underneath the hot tank shelf on a pipe which runs under the floor to the radiators.... all the 22mm pipes that come from the stove/back boiler come out of the wall in the cupboard so not sure which is which.

If this helps the other day when the heating first kicked in there are two 15mm pipes that come out of the floor from the radiators one has the pump on (flow and return??) they both change to 22mm and go into the wall towards the stove/back boiler, the one that does not have the pump on got hot first.. which made me think the pump was pumping the cold water out of the radiators and pulling the hot round the system??

Is it possible that the radiators are on some sort of loop where it will not matter which way the pump flows???

Dtp79

tickledeb wrote: »

Yes I know, the thing is the wood burning stove has a back boiler which is piped into the hot tank which is in the cupboard about 4ft away and the pump is underneath the hot tank shelf on a pipe which runs under the floor to the radiators.... all the 22mm pipes that come from the stove/back boiler come out of the wall in the cupboard so not sure which is which.

If this helps the other day when the heating first kicked in there are two 15mm pipes that come out of the floor from the radiators one has the pump on (flow and return??) they both change to 22mm and go into the wall towards the stove/back boiler, the one that does not have the pump on got hot first.. which made me think the pump was pumping the cold water out of the radiators and pulling the hot round the system??

Is it possible that the radiators are on some sort of loop where it will not matter which way the pump flows???

Can you take a few pics?

tickledeb

going up to my mams tomorrow to turn the pump round, and renew the pump valves. The thermostat on the pipe out of the hot tank is not kicking in properly and the pump is running longer than it should, so I have got two new pump gate valves and a freezing kit so I dont have to drain the system.

Dtp79

tickledeb wrote: »

going up to my mams tomorrow to turn the pump round, and renew the pump valves. The thermostat on the pipe out of the hot tank is not kicking in properly and the pump is running longer than it should, so I have got two new pump gate valves and a freezing kit so I dont have to drain the system.

Make sure the fire isn't lighting!

tickledeb

Dtp79 wrote: »

Make sure the fire isn't lighting!

funny you should say that he did have it lit!!!!!!

tried running all the hot water off and then freezing one of the pipes but it was still to warm so I just had to turn the pump around and leave the old gate valves on, had a nightmare getting them sealed to the pump but got there eventually.

I have told him to get a proper plumber in because it looks like the hot tank has been leaking when cold and then sealing up when it gets hot :eek:.

thanks for the support-- it's been emotional

DarDow

I HAVE A DUEL HEATING SYSTEM OPEN FIRE AND OIL I FIXED THE BACK BOILER IT HAD A SOLDER AND REPLACED THE PUMP AS IT WAS GONE EVER SINCE IV DONE THIS IT HASNT WORKED RIGHT ITS NOT HEATING THE RADS 1 OR 2 HAVE SLIGHT HEAT IN THEM BUT ITS HEATING THE HOT WATER TO SCOLDING HOT AND ITS BUBLING AT THE BACK BOILER SO CANT LIGHT A BIG FIRE BECAUSE OBVISOULY ITS DANGEROUS IV VENTED ALL THE RADS BALANCED THEM CUT IN AN AAV IN THE ATTIC AND ITS STILL THE SAME ANY IDEAS??IS IT THE BOILER ITS SELF??IM GETTING HOT WATER FROM IT SO IM NOT SURE?? ALSO I PUT IN A NEW OIL BOILER AND BURNER IN SAME SYSTEM AND ITS WORKING PERFECT ANY HELP WOULD BE GREAT AS I AM RUNNING OUTA IDEAS

Robbie.G

DarDow wrote: »

I HAVE A DUEL HEATING SYSTEM OPEN FIRE AND OIL I FIXED THE BACK BOILER IT HAD A SOLDER AND REPLACED THE PUMP AS IT WAS GONE EVER SINCE IV DONE THIS IT HASNT WORKED RIGHT ITS NOT HEATING THE RADS 1 OR 2 HAVE SLIGHT HEAT IN THEM BUT ITS HEATING THE HOT WATER TO SCOLDING HOT AND ITS BUBLING AT THE BACK BOILER SO CANT LIGHT A BIG FIRE BECAUSE OBVISOULY ITS DANGEROUS IV VENTED ALL THE RADS BALANCED THEM CUT IN AN AAV IN THE ATTIC AND ITS STILL THE SAME ANY IDEAS??IS IT THE BOILER ITS SELF??IM GETTING HOT WATER FROM IT SO IM NOT SURE?? ALSO I PUT IN A NEW OIL BOILER AND BURNER IN SAME SYSTEM AND ITS WORKING PERFECT ANY HELP WOULD BE GREAT AS I AM RUNNING OUTA IDEAS

Is the pump on the right way.
It should be pumping into the back boiler on the return

DarDow

Robbie.G wrote: »

Is the pump on the right way.
It should be pumping into the back boiler on the return

The way the system is piped they have the pump on the flow it's strange but i will give tat ago cheers robbie

djr15

OP
Check that the non return is not seized open.

demanufactured

2 year old thread

Dtp1979

demanufactured wrote: »

2 year old thread

It's not a 2 year old problem though. OP did you try bleeding the pump?