Calorifier and instantaneous hot water system

[stegra]

From what I've read so far it seems that the most common hot water set-up is to have a twin coil calorifier heated by both engine and solid fuel back boiler. Am I correct in thinking that its normal to have an instantaneous water heater as well, either LPG or diesel?

 

If so, is the incoming water for ever/sometimes/normally fed from the hot output from the calorifier; and if so, does the instantaneous heater adjust to suit the varying temperature of the incoming supply?

 

If this is not normally done, is it feasible? It seems a shame to heat icy cold water when one could be heating water from a higher start point. I guess there would be a bypass valve for times when the water from the calorifier was already hot enough.

[mrsmelly]

From what I've read so far it seems that the most common hot water set-up is to have a twin coil calorifier heated by both engine and solid fuel back boiler. Am I correct in thinking that its normal to have an instantaneous water heater as well, either LPG or diesel?

 

If so, is the incoming water for ever/sometimes/normally fed from the hot output from the calorifier; and if so, does the instantaneous heater adjust to suit the varying temperature of the incoming supply?

 

If this is not normally done, is it feasible? It seems a shame to heat icy cold water when one could be heating water from a higher start point. I guess there would be a bypass valve for times when the water from the calorifier was already hot enough.

 

Hi

 

I had a cauliflower and an instant gas heater on my last boat. A simple hand operated valve was operated to choose hot water from the cauliflower or from the gas heater.

[cereal tiller]

 

Hi

 

I had a cauliflower and an instant gas heater on my last boat. A simple hand operated valve was operated to choose hot water from the cauliflower or from the gas heater.

Same set up on present boat,always hot water.

 

CT

[stegra]

 

Hi

 

I had a cauliflower and an instant gas heater on my last boat. A simple hand operated valve was operated to choose hot water from the cauliflower or from the gas heater.

 

So never diverted the, lets say, slightly warm water from the calorifier to the water heater?

[mrsmelly]

 

So never diverted the, lets say, slightly warm water from the calorifier to the water heater?

 

No, never needed to. We had four options for hot water, these were Morco instant gas, Engine cauliflower, webasto cauliflower and immersion in cauliflower. Brilliant and never any chance of no hot water.

[cereal tiller]

 

So never diverted the, lets say, slightly warm water from the calorifier to the water heater?

Never! 80 degree water from calorifier raised another 50 degrees by water heater could be catastrophic

 

CT

[stegra]

Never! 80 degree water from calorifier raised another 50 degrees by water heater could be catastrophic

 

CT

 

Yes. Hence the bypass valve. Also, possibly a thermostat on the calorifier and a solenoid. Seems a shame to be heating water from near freezing if it could be heated from 25 degrees. I wondered if the water heaters could cope with varying input temperatures and adjust.

[cereal tiller]

 

Yes. Hence the bypass valve. Also, possibly a thermostat on the calorifier and a solenoid. Seems a shame to be heating water from near freezing if it could be heated from 25 degrees. I wondered if the water heaters could cope with varying input temperatures and adjust.

Not sure about More modern water heaters, but the Paloma (ancient) I have has only manual adjustment for flow rate and would likely be unhappy with 80 Degrees,probably cause significant scaling and Thermal stress in it's heat exchanger

 

The Stat. and solenoid valve would be viable,its the sort of thing I would do for others but for myself the preference would be to stick to the KISS method

 

CT

Edited January 27, 2017 by cereal tiller

[BEngo]

 

So never diverted the, lets say, slightly warm water from the calorifier to the water heater?

The boat safety scheme prohibits this. The thinking is that "slightly warm " might be OK but it is far to easy to end up with "melting hot " as the output.

 

N

[blackrose]

All you need is a cold feed calorifier, a cold feed gas water heater and a L-port valve between the two hot water supplies so that only one supply can ever be drawn.

[stegra]

The boat safety scheme prohibits this. The thinking is that "slightly warm " might be OK but it is far to easy to end up with "melting hot " as the output.

 

N

 

Ah. OK, That's that idea out the window then. Thanks for the info.

[Robbo]

I'm planning to have a heat exchanger on the calorfier hot outlet that's heated by a diesel boiler. It won't be instant hot water as the boiler takes some time to turn on, but I won't have to wait for the water to heat up to have a shower.

[cereal tiller]

I'm planning to have a heat exchanger on the calorfier hot outlet that's heated by a diesel boiler. It won't be instant hot water as the boiler takes some time to turn on, but I won't have to wait for the water to heat up to have a shower.

Sounds interesting,what type of boiler?

 

CT

[Robbo]

Sounds interesting,what type of boiler?

 

CT

The Bubble PJ is at the top of the list at the moment. It's 12kw, so should be able to heat the water by enough at a decent flow for something like a shower.

[MtB]

I'm planning to have a heat exchanger on the calorfier hot outlet that's heated by a diesel boiler. It won't be instant hot water as the boiler takes some time to turn on, but I won't have to wait for the water to heat up to have a shower.

 

 

This is how an ordinary household combi boiler works.

[Robbo]

 

 

This is how an ordinary household combi boiler works.

It's where I got the idea from

[MtB]

It's where I got the idea from

 

 

Good idea. You can manually divert the flow from the boiler from the radiator circuit to pass through a plate heat exchanger instead, whenever you want a shower.

 

Bear in mind the water flow rate through the HE will affect the resulting temperature so a thermostatic shower mixer would be a Good Idea. (As with a manual mixer each adjustment you make to the shower temp will affect the flow the therefore the temp coming from the HE, so getting a stable shower temp *could* be quite difficult.)