Radiators - how many / kw?

[Johny London]

And yet another conundrum - assuming a 62ft nb with 80l calorifier, I'm aiming for 4 rads plus a large towel rad. I know the Webasto likes to be fully loaded and is 5kw.

I'm thinking 4x600w rads (2 in saloon, one in bedroom, one in stern cabin, plus towel rad in bathroom) look about right to me - otherwise next size up is 770w. What have you guys got?

[nb Innisfree]

I fitted 6 x1kw + 2 x 60lt calorifiers in Innisfree (60' nb) heated by 7kw Mikuni and/or 40 hp engine. Bit OTT but better too much than too little, rads can be adjusted down if necessary. 

Edited October 30, 2017 by nb Innisfree

[canals are us?]

Too small really at 600 watts each. Approximately a 600x 600mm single rad.

I have a webasto TTC and have 4 radiators of 1x 450x 1400mm single. 1x 300x 1500mm double panel single convector. 2x 300x900 double panel single convector and a 50 litre calorifier.

My rad output roughly equates to 3.9kw which heats the boat fine. First 2 rads heat my 20ft long by 6ft wide salon and kitchen on my 50ft trad narrowboat.

Issue is I need to turn the boiler off after around 45 minutes to an hour as it cycles on and off to prevent coking up. They get really hot as well as the hot water.

I was governed with 300mm and 400mm high rads as I have linked my webasto to heat my existing gravity heating system of my solid fuel stove with back boiler. My rads are fitted in between the gravity pipes. You will be installing a quick and easy 22mm two pipe fully pumped system I presume with 15mm branches to the rads so can have taller rads.

I personally on a 62 footer, particually if a trad would fit 4  600x800 doubles at around 1.3kw each or 4-5 type 21 double panel single convector at 1kw each in that size plus large towel radiator.

Do not fit thermostatic valves as you don't want the boiler to cycle. When it gets too hot, I just turn the boiler off.

James

Edited October 31, 2017 by canals are us?

[BEngo]

The total output of your rads should be slightly bigger than the max output of the heater. That way it will run in long cycles and not coke up too soon. As others have said control the temperature with the ON/OFF switch and by opening the doors/windows.

Or get a smaller output heater!.

N

[Johny London]

Thanks, it sounds like I need to think of bigger radiators then. The system is to be used to "take the chill off" on those evenings when it's not cold enough to light the stove, plus for a nice burst of heat first thing in the morning (or when I get up).

I'm after the 2 column style rads purely for aesthetic reasons, but yes I was looking at 600x600, also trying to conserve wall space for other stuff. I take the point about needing a bigger load for the Webasto. I'm assuming the 80l calorifier counts as roughly a couple kw worth in terms of the load seen by the heater though of course once it's hot then not so much.

It sounds as though I'm going to get a lot oh heat for my diesel.

[NMEA]

Ignore the calorifier when working out the loading. Though it is a very good thermal dump when the potable water is cold it is soon at a point where it is taking less and less as the coolant and potable temperatures come closer together.

Edited October 31, 2017 by NMEA

[cuthound]

The link below is useful for working out the kW rating of the various types and sizes of radiators.

http://www.simplifydiy.com/plumbing-and-heating/radiators/power