On Sun, 26 Oct 2003 17:57:04 -0000, "IMM" wrote:



1.
Assume a Keston Celsius with load compensation control. When the flow and
return temps become closer together the system assumes the house is nearing,
or up to, temp. It then modulates the burner down. When the return and flow
temps become wiser the assumption is that the house is becoming colder and
winds the flow temp up.

CH is only on the house warms up and the boiler drops the flow temp. Fine.
The pool heater is switched in. The return temp from the pool is very low
(17C) and this blends with the return of the house heating (say 30c) to say
give a combined return temp of 21C. Great for boiler efficiencies. Less
gas is being used. The control system thinks the house is cooling and
ramps up the flow temp to max. Fine, as the pool heater needs this heat.
This means the flow to the house is too high. This is fine as TRV rad
valves will compensate for any heat gain; assuming they are fitted in the
rooms.

2.
The Keston boilers quoted are small commercial jobs with no modulation.

I think that you are thinking of the older models. These two
modulate from 11 to 40 kW and 14 to 55kW respectively.
The rig for them has the option of fully proportional controllers with
weather compensation and remote access and monitoring.



Better still have one boiler do the house and DHW and one do the pool
(assuming a 25kW boiler will heat the house). With a few valves to
alternate boilers if say the house boilers drops out, always having a
backup for essential services. Or if there is a constant large demand for
DHW, it may be best to have the pool and DHW on the one boiler with a
priority system for DHW.

Now it depends on what deals you can get with boilers. The two boiler
option in a commercial concern is by far the best.



---

..andy

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