On Sun, 13 Jul 2003 00:12:20 +0100, "Colin Forsyth"
wrote:

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
http://www.gasman.fsbusiness.co.uk/f...ed_systems.htm 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.

http://content.honeywell.com/uk/homes/systems.htm

Look 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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