Re: Gravity to fully pumped and oil to gas !

[Andy Hall]

OK several issues

> >I've had a few heating engineers come and look at my current system with a >view to conversion but am loathe to cough up the 2500 quid that formed the >cheapest quote !!! > >I've surfed many websites to research this project and found > to be as good as >any, however I still have some queries. > >Currently my oil guzzling (30 yr old) boiler lives in a cupboard under the >stairs and has two loops. Gravity loop (28mm or imperial equiv) for the >water tank which is almost directly above the boiler in a cupboard at the >top of the stairs. Heating loop (22mm or imperial equiv) with a pump for >the radiator circuit. > >Now, I am hoping to install a Condensing Conventional Gas boiler on the >external garage wall and run the pipes along the top wall just above floor >level, through the internal garage wall which will take me into the sunken >compartment where the boiler is currently. The plan then would be to bring >the Flow via the pump to a 3-way motorised valve and merge into the existing >pipework for the HW tank and heating manifolds (I have microbore !) > >Is there any limitation on proximity of the pump to the boiler ?

Not particularly. You could consider a system boiler where it is integral.

If you are going to have pipes dropping down such that the boiler becomes a high point, then you will need to make a venting arrangement consisting of manual or automatic vents at the boiler position.

In the garage, you will also need to insulate the pipes very thoroughly and fit a frost protection thermostat if the boiler doesn't have its own arrangements. A pipe contact type is most suitable if you need to add one.

For all pipework, take care that it does not run where it can suffer mechanical damage - e.g. from a car.

The Flow >pipe will fall from the boiler approx 1 Metre then horizontally at floor >level for approx 5 metres before meeting my intended location for the pump >(Cupboard under the stairs). What size pipe should I use from the boiler to >the cupboard; 22 or 28 ?

Unless the run is very long, 22mm should be enough since this size fed the pumped heating before.

>I also have two pairs of Flow & Return manifolds for Upstairs & Downstairs >radiators, would this lend itself to two zones ? How do I cater for that ?

If you wanted to implement this, the usual way is to use an extended version of Honeywell's S plan. With this, instead of having a three way valve, you use 2 port valves. You would have one covering the hot water cylinder and one for each manifold.

at S Plan Plus.

>One of the heating engineers mentioned that he would have to run another >pipe up to the hot water tank. Any ideas ? Surely that would only be if he >planned having the motorised valve in the HW Tank cupboard. >

Hard to say, unless there is a vent or something missing or the feed and vent pipes are connected to the wrong places.

A boiler change like this would be a good opportunity to switch the whole primary system to sealed operation. This is very easy to do and you may find it a prerequisite for your chosen condensing boiler. Quite a lot require sealed operation, but there are some that don't such as the Keston Celsius. Ed Sirett has a FAQ with info. on sealed systems.

Not entirely sure about the requirement for a bypass ! How does that work ? >Where does it run from and to ?

Assuming that the pump is on the boiler flow, the bypass goes from after the pump but before the motorised valves, via an adjustable valve and then to the return. Its purpose is to provide a path to allow water to be circulated through the boiler if the CH or HW thermostat stops demanding heat while the boiler is in full firing. Not all boilers need it, but in those that do the purpose is to make sure there is water running through the heat exchanger to avoid it boiling.

You can use a lockshield for this purpose, although a better solution is to get an automatic bypass valve. These are pressure operated and open when the pump is running and both or all three motorised valves are closed.

>Apart from a little time & inconvenience I envisage this lot to cost me >approx £1K including the £750 for the boiler oh and a couple of hundred to >Transco to provide me with gas. Cant wait to get rid of the unsightly oil >tank on its lovely breeze block stilts !

Don't forget to give the system a thorough flush.

>That'll do for now > >Col > >

.andy

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[Colin Forsyth]

Makes sense, I hadnt thought about that !

Agreed, been thinking of a Gloworm 30Hxi which has built in frost protection.

Only problem area would be the doorway to the utility room, but intend to enclose the pipework.

I'll look into this, however boiler in question can cope with open vented or sealed systems.

Will do ! Its actually empty at the mo while I replace a radiator. Had an experience with a lockshield valve with water flying past the screw. Dare say the poor little seal hadnt been disturbed for a long long time !!! So it was hose on and emty the system and then the main drain off seal failed so I had to drain the lot!!!

Ho hum....

Thanks for the comprehensive reply

Col

[Andy Hall]

Since you mention imperial pipe sizes etc. presumably the rest of the system is 30 years or so old as well?

When I refurbished my system a year ago it was 17 years old and the pipework (22mm feeds and 8mm to radiators) was all in good condition as were the radiators. I had been quite fastidious about using Fernox etc. in the system. However, I did take the opportunity while the system was out of use to do a thorough check through and clean.

I had decided that I was going to replace the DHW cylinder anyway - the existing one was too small for the current requirement and also the pipework in the airing cupboard - done by the original subcontractor was badly laid out.

If the cylinder is 30 years old, it may be worth considering a pre-emptive replacement while the system is down. You can obtain rapid recovery cylinders from the major manufacturers such as Albion, Telford etc. These have a coil with a much higher surface area than old cylinders either by having more turns or by splitting into multiple pipes. This, together with switching to a pumped arrangement anyway will make a large difference to how quickly the cylinder recovers temperature after a large draw of water. This is useful anyway but also if you are going to have a control system with priority to hot water (fairly typical) then the effect is that the heat is diverted away from the radiators for a shorter time.

Before fitting the new boiler, I removed the old one and modified the plumbing for sealed operation. To simplify this, I fitted the expansion vessel/filling loop/pressure gauge in place of the old small feed/expansion tank and connected on to the feed pipe. The old vent pipe was disconnected in the airing cupboard where it connected to the system. It doesn't really matter where this goes as long as there is access to a mains water supply. I temporarily capped off the boiler connections to the system and provided hot water with the immersion heater.

I then organised a simple production line for the radiators. At each radiator I disconnected and emptied it carefully (remember that rust, sludge etc. stain indellibly). I then took it off and outside and flushed through with a pressure washer. The thermostatic radiator valves had been replaced not that long ago and were fine. If you don't have them, they are well worth considering with a condensing boiler because they do help towards better temperature control and more efficient operation. However, the lockshield valves were original and one or two had shown signs of seeping even under gravity pressure, so I replaced them as I went. I then turned on the water to the system and in turn each valve at the radiator position. This flushed out quite a lot of original crud such as copper swarf from the system. Then the radiator went back and I went on to the next. I think that this is worth doing, even if you aren't going sealed - you can still just use the tank supply. Since you can get good quality lockshields for about a fiver, to me it was a no-brainer. I used Pegler Terrier valves with a built in drain c*ck. These are useful in that you can isolate a radiator and drain it a bit more cleanly than by just undoing the valve unions.

On fitting the new boiler, I added a strainer on the return from the system before the boiler. This is a small brass fitting with a removable stainless steel mesh filter which catches any remaining bits in the system. Most new boilers have quite small waterways so it's a good practice, even if the makers don't stipulate it.

FInally, on commissioning, I ran some Superfloc system cleaner for a day to mop up anything else in terms of fluxes etc., did one final drain and flush and after a few days to check for any leaks added Fernox.

Then I think that a replacement exercise is probably worth it rather than having to mess around with each one later.

.andy

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[Colin Forsyth]

Top tips, cheers Andy, so what is it Night Shift worker or insomniac ?

Col

[Andy Hall]

A little of both :-)

.andy

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[Roger Mills]

For starters, don't use a 3-way valve - use individual zone valves. In your circumstances, I would use 3 - one for hot water and one each for upstairs and downstairs heating.

Each zone valve would be controlled from the programmer and would have its own room or cylinder stat, as appropriate. Each valve has an independent pair of contacts which close when the valve is fully open. These are all connected in parallel to switch the boiler and pump - so that the boiler and pump only run when one or more zones are calling for heat. It may make sense to use programmable stats for the two heating zones - so that you can have them on at different times should you so wish. The main programmer would then control the hot water on a timed basis, but would have heating switched to continuous - leaving the actual control to the programmable stats.

As someone else has explained, with this arrangement (zone valves rather than 3-way valve) you will need a bypass loop in order to ensure that the water always has somewhere to go when the boiler over-run stat decides to keep the pump running after the boiler has stopped.

Roger