installing a water heater - series or parallel?

Thanks for the link to the Eberspacher guide. You mention valves to balance the performance of the system; I think these valves need to be in the 22mm ring main (not the 15mm branches) so that it can be constricted thereby forcing the water through the various appliances - would you agree with that? This obviously them turns a 22mm system thougn in to something less so that later applications in the system get a lesser flow? Hmmmm.......

It has been said that it is worthwhile having the engine in the network because it supplies some heat stability (being a lump of steel) and stops the heater "hunting" but comments further down this thread suggest that this will not work because the thermostat will be closed thereby preventing a flow of watedr through the engine.

Thanks for your help.

rob
 
I am using PolyPlumb piping - domestic stuff, it look okay.

You suggest an adjustable valve on the inlet side of the appliance - but I think it might have to be in the 22mm (see my post above) what do you think? If the valve is in the inlet side I imagine that the water will bypass the appliance completely and follow the easy route of low pressure - and follow the 22mm ring main and therefore the appliance would not receive hot water?

rob
 
I agree that I need to be able to isolate the engine with a bypass circuit. See my comments above regarding including the engine for temp stability though. It seems thaty this will not work though because of the thermostat in the engine preventing water flow.

rob
 
Thanks for this. I have looked at twin coil calorifier but have decided to try the system without one because a) a new calorifier is expensive when I have a perfectly good one already fitted in the boat and 2) it is a right royal pain to get it out and replace it!

rob
 
I am beginning to think that your suggestion of excluding the engine is the right (and easiest) strategy. I will post a success or failure report when I have finished!

rob
 
Staying with Minis, the early cars had a rotary rheostat to control the fan speed>If you can get hold of one, this would give you a simple non-electronic control method.

Steve Cronin
 
[ QUOTE ]
Thanks for the link to the Eberspacher guide. You mention valves to balance the performance of the system; I think these valves need to be in the 22mm ring main (not the 15mm branches) so that it can be constricted thereby forcing the water through the various appliances - would you agree with that?

[/ QUOTE ]No, the valves can be on the individual appliances - that way you can isolate one or more if you wish. This is exactly the same principle as the radiator valves on a domestic central heating system.
 
Steve,

As I understand it a rheostat works by reducing voltage through creating resistance. My schoolboy physics then tells me that amps would then increase and I'd end up with a fire! But that doesn't happen (as far as I am aware) so rheostats must not only reduce voltage but also reduce watts consumed somehow?

Some has to ask the stupid questions..................

rob
 
Theoretically yes but the wire wound variable resistor used in the Minis used eureka wire which was of sufficient thermal capacity as to not heat up significantly and was matched to the mini blower motors (a lucas motor). It would work fine. However, if you're using computer type fans then these aren't as easily slowed down but they are preferable due to their vastly superior efficiency in moving air and their quietness. These though are usually supplied with three or four wires now and the use of the correct combination of these wires results in a choice of fan speeds. A simple rotary selector would control the airflow by this means. I have something similar on the fan which controls the evacuation of air in the fridge compressor locker.

Incidentally, a good choice of automotive heater matrix which is robust, cheap and a convenient shape, is the one made for a Land Rover Defender '86-95. They can be obtained for arond £20 in the after-market trade. In fact, the Defender heater unit itself is an ideal boat heater due to it's dimensions and outlet size. It also has "air mixing" temperature control via a simple lever mechanism. Scrap recovered ones are a little difficult to come by as (new statistic just discovered!) 75% of the Series 1-3 "Landys" and Defenders ever made are still on the road!

Steve Cronin
 
<<<<<It seems thaty this will not work though because of the thermostat in the engine preventing water flow.>>>>>

Thermostats don't prevent flow, they only localise heating to part of the engine and bypass the rest of the flow. The exact route depends upon the engine design. When you start your engine the thermostat is closed but there is plenty of water circulating, which you can easily check by squeezing one of the hoses at the pump.

In your case I assume you are intending to circulate from a fresh-water cooled engine? In that case you have a centrifugal water pump which does not prevent flow when stopped. Water will flow quite freely through your stopped engine.

In a raw-water cooled engine, and on the raw-water side of your heat exchanger, you have a positive displacement pump which cannot withstand a restricted output. If the thermostat closed off the supply from this the pump or some downstream hoses would fail.
 
[quote....Thermostats don't prevent flow, ...

[/ QUOTE ]

Rubbish! of course they do. Whet the poppet closes down flow out of the water elbow is stopped until the water around it heats up the bellows or the wax plug and the poppett rises up again. There is a small bleed hole though to avoid boil-ups.

Now there ARE diverting thermostatic valves made (I have one - a Drayton - in a cupboard next to my desk here) but these tend to be used as hot water cylinder temperature regulators in indirect domestic CH system.

Steve Cronin


Steve Cronin
 
You may know something about thermostats but you clearly don't know a lot about engine cooling systems. There are always two possibilities for flow exiting the water pump, either throught the thermostat or through the bypass. When the engine is cold the thermostat is closed, preventing flow through the engine so that rapid heating takes place. The pump at this stage is directing virtually all its flow through the bypass. As the thermostat opens the hot water begins to flow through it, joining the bypass flow. If the thermostat simply closed off all the flow the pump would be pumping against a closed head, not a great idea for a centrifugal pump but disastrous for a positive displacement one.
 
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