central heating confusion

Springsteen

Hi All,
moved into a second hand house, built circa 1965. Oil fired central heating, and a back boiler from open fire ( open fire and back boiler seem to have been added at a later stage ). I've had many problems with the system, most of which seem to be solved. One last problem I cannot figure out. When the heating is switched on, radiators heat up from from pipe on left hand side of of the radiator. I have a pipe stat fitted to the pump on the back boiler which kicks the pump on at approx 40c, once this pump is running the radiators now heat from from the pipe on the right hand side. The direction of flow reverses, the supply becomes the return, and vice versa It seems as if the oil fired boiler pump and the back boiler pump are working in opposite directions. Excess water is also flowing into head tank in the attic.

Any ideas thoughts or suggestion would be great.

Springsteen

PeteHeat

Hi,

The system may have been fitted that way on purpose, do you know if there are non retrn valves fitted on the two boilers ?

The idea would have been to prevent the heat from the back boiler heating the oil boiler and vice versa as both boilers would taking the equal of a couple radiators.

While the system can work it is not ideal from a safety point of view especially when the system is handed over to someone who does not how it was supposed to work.

Possible dangers are if the oil boiler fires from a timer while the fire is lighting and the back boiler is generating heat, both pumps could be operating against each other which may account for the water venting through the expansion pipe in the attic.

Also check the pump settings it may be set too high causing the expansion to overflow.

.

Springsteen

Thanks for the reply Pete,
not sure if non return valves are fitted, any simple way to check?

Still trying to work out the system, its cryptic for sure. A lot of gun barrel piping, a few add ons with copper and qualpex (spelling!). Two radiators upstairs have been T'eed to supply two extra radiators in extensions downstairs. They're always very slow to heat.

I have tried the pumps on all settings. The higher the setting the quicker the rads heat, but the problem is the overflow. Burner pump on setting 1 and back boiler pump off seems to eliminate the overflow problem, but then the heating takes ages to heat up. Boiler is a relatively new benetone, i gave it a good clean out too.

Would I be better off removing back boiler? How about flipping the back boiler pump? That would allow both pumps to work in the same direction???

I'm very much a novice.
S

PeteHeat

Hi,

If you run the oil boiler and the back boiler stays cold but downstairs rads heat up then there is something stopping the water going through the back boiler, usually a non return valve.

If you look at the pipe coming off the top of your oil boiler you should be able to see a non return valve on the pipe (if there is one) test similar to the above, light the fire and see if the oil boiler heats up.

I would not recommend changing the pump on the back boiler around as heat from a fire is very difficult to control especially if a non return valve was fitted.

An advantage to disconnecting the back boiler would be you may be able to pressurise the system which with carefull balancing of the system could force the heat to the rads in the extension.

I would recommend that you contact a local plumber to advise you.

.

Springsteen

Thanks Pete,
all very sensible advise. I think disconnecting the back boiler is the way to go, especially if I can improve the flow and heat to rads in extension.

If i'd the money I'd love to rip the whole system out and start again with zone valves etc. Some day!

Thanks a mill.
S

Stratocaster

Springsteen wrote: »

Thanks for the reply Pete,
not sure if non return valves are fitted, any simple way to check?

Still trying to work out the system, its cryptic for sure. A lot of gun barrel piping, a few add ons with copper and qualpex (spelling!). Two radiators upstairs have been T'eed to supply two extra radiators in extensions downstairs. They're always very slow to heat.

I have tried the pumps on all settings. The higher the setting the quicker the rads heat, but the problem is the overflow. Burner pump on setting 1 and back boiler pump off seems to eliminate the overflow problem, but then the heating takes ages to heat up. Boiler is a relatively new benetone, i gave it a good clean out too.

Would I be better off removing back boiler? How about flipping the back boiler pump? That would allow both pumps to work in the same direction???

I'm very much a novice.
S

The problem you have with water spilling out the vent is known as "pitching" one way to eliminate pitching is to connect the heating gravity cold feed directly to the vent pipe. By doing this you create more head pressure in the vent pipe to stop the circulation pump forcing water out the vent. Connecting the cold feed to the vent will still allow the system to be filled and vented. But I would advice against doing this yourself as un experience can lead to accidents and safety concerns. Its best practice to completely seal a system. Your expansion is taken up in a vessel which removes the use of your feed and expansion tank. You can fill the system in many ways without the need for the feed and expansion tank. Sealing a system with a back boiler is highly dangerous so you have to make precautions and can only be carried out by an experienced person.

This type of cold feed into vent pitching remedy would occur when a circulation pump was fitted to an old fashioned traditional back boiler. Back in the day pumps were not needed as hot water would circulate naturally. The addition of the pump and extra rads applied forces not suitable for the installation.

By the sound of your posts you have a wide array of things going on with your combined systems so its very hard to find a solution to all the problems without being there. If your only experiencing this problem now you should look back to what additions have been added and who completed the additions and when. The first thing I would look for is how the cross over is occurring maybe during all the changes, modifications etc, someones connected a flow to a return. I have concerns over GB heating systems in house holds here as the instillation's are over 20 years old. Be prepared as its possible for leaks to occur in the near future. GB will not last over 20 years in some installations. GB wont withstand corrosion compared to copper and plastics.

You cant balance a heating system correctly with altering flow and return. As some have mentioned check direction of pumps and the installation of non returns. A non return valve is a cylindrical brass fitting with no levers or valves and has an arrow indication to locate direction of flow.

You should try to hold onto the back boiler as once fitted correctly it serves the best purpose in your house hold. Providing room heat while at the same time providing heat to rads and hot water storage. I know many people who swear by them and those people are normally associated with wood from forests local to the area, carpenters etc.

Springsteen

Stratocaster,

Your solution to " Pitching " is very tidy, I will defo look into it.

Like you, I have a healthy disrespect for GB. I'm waiting for the day..... fingers crossed I can replace it all before it gets angry.

The only Q i have in relation to your remedy for " Pitching ", is this, the " Vessel " you mention, how does it operate? How does it absorb the expansion within a sealed system? and also to top up the system, is this a direct line from the cold feed?

Thanks for the time to respond, i'm learning all the time!
S

Stratocaster

Springsteen wrote: »

Stratocaster,

Your solution to " Pitching " is very tidy, I will defo look into it.

Like you, I have a healthy disrespect for GB. I'm waiting for the day..... fingers crossed I can replace it all before it gets angry.

The only Q i have in relation to your remedy for " Pitching ", is this, the " Vessel " you mention, how does it operate? How does it absorb the expansion within a sealed system? and also to top up the system, is this a direct line from the cold feed?

Thanks for the time to respond, i'm learning all the time!
S

I admire your will to learn but I have to caution the works you are intending on carrying out can lead to dangerous circumstances if not done correctly. I feel your best to leave the works to experienced people.

The pitching remedy is completely separate, should you choose to seal the system you wont have the use of the expansion pipe in its intended form.

I'll give you an idea of how the vessel works. Its shaped similar to a ball or cylinder, also rectangular shaped. Red color for heating with a threaded opening to connect into your heating system. It can be located anywhere once its connected (pref return). Its designed to take up the expansion as a system heats up. Inside the vessel is split in two by use of a rubber diaphragm. One side of the diaphragm is charged with gas/air and the other side is open to allow the expansion of heating water to take place. The expanded water pushes up on the diaphragm and its charged to the right amount to allow for expansion and contraction. The size of the vessel is dependent on how many ltr of water your system holds.

You will find expansion vessels associated with all forms of pressurized plumbing and heating. They take up the expansion created within sealed hot water systems and they are relied upon to activate flow switches in cold water booster pumps.

To fill your heating system you can take a feed from your cold water storage provided you insert a non return valve. The idea of the non return valve is to stop back contamination of heating water going into your storage water. Bacteria can still travel through these non return valves. It is best to completely disconnect a heating cold water feed once the system is full. Should your heating system require more pressure than the cold water storage tank can give, you can pump up the pressure by use of a hand pump or connect to your mains water supply by use of a dedicated heating flex filling loop. This loop will enable you to disconnect from the mains supply once the heating is filled to the required pressure. Should you require top up later down the line the loop can be reconnected with ease.

To save your self some more use of the GB pipes you should go to your local plumbing suppliers and purchase a system cleaner, system inhibitor and a leak seal formula. Fernox is a good brand at a good price and gives detailed instructions for each.

Stratocaster

Springsteen wrote: »

Stratocaster,

Your solution to " Pitching " is very tidy, I will defo look into it.

Like you, I have a healthy disrespect for GB. I'm waiting for the day..... fingers crossed I can replace it all before it gets angry.

The only Q i have in relation to your remedy for " Pitching ", is this, the " Vessel " you mention, how does it operate? How does it absorb the expansion within a sealed system? and also to top up the system, is this a direct line from the cold feed?

Thanks for the time to respond, i'm learning all the time!
S

I admire your will to learn but I have to caution the works you are intending on carrying out can lead to dangerous circumstances. I feel your best to leave the works to experienced people.

I'll give you an idea of how the vessel works. Its shaped similar to a ball or cylinder, also rectangular shaped. Red color for heating with a threaded opening to connect into your heating system. It can be located anywhere once its connected (pref return). Its designed to take up the expansion as a system heats up. Inside the vessel is split in two by use of a rubber diaphragm. One side of the diaphragm is charged with gas/air and the other side is open to allow the expansion of heating water to take place. The expanded water pushes up on the diaphragm and its charged to the right amount to allow for expansion and contraction. The size of the vessel is dependent on how many ltr of water your system holds.

You will find expansion vessels associated with all forms of pressurized plumbing and heating. They take up the expansion created within sealed hot water systems and they are relied upon to activate flow switches in cold water booster pumps.

To fill your heating system you can take a feed from your cold water storage provided you insert a non return valve. The idea of the non return valve is to stop back contamination of heating water going into your storage water. Bacteria can still travel through these non return valves. It is best to completely disconnect a heating cold water feed once the system is full. Should your heating system require more pressure than the cold water storage tank can give, you can pump up the pressure by use of a hand pump or connect to your mains water supply by use of a dedicated heating flex filling loop. This loop will enable you to disconnect from the mains supply once the heating is filled to the required pressure. Should you require top up later down the line the loop can be reconnected with ease.

To save your self some more use of the GB pipes you should go to your local plumbing suppliers and purchase a system cleaner, system inhibitor and a leak seal formula. Fernox is a good brand at a good price and gives detailed instructions for each.

Springsteen

Thanks Stratocaster,
dont get me wrong, I do plan to get a professional in, its useful to know the theory before I decide what way to go. Fernox will be the next purchase.
S