heating manifold

Hi there,

a slight complication with underfloor central heating in a new build, 2 story house....which is not built yet........100sq/m downstairs and 80sq/m upstairs.....

because of the house situation it'll have 2 forms of connected heating..,

1, is a v/large wood fire with a back boiler in the living room UPSTAIRS and a insulated hot water tank with 3 immersion heaters fitted in it down stairs, (emergency use) situated in a plant room with all the incoming elec and water etc.....both CONCRETE floors will be heated......the lower floor is the new machine shop and toy room.......the water boiler and the fire will be in opposite corners of the house......plan to use 2 pumps pushing the cooler water back to the heating units.......was kinda thinking of using the hot water heating tank as the manifold or collecting unit.....this system will be a vented with a top up tank in the roof space ......

domestic bathing water is from solar heating and a seperate immersion heater....which is completely seperate from the room heating system.......

what would be the best way to connect the 2 c/heating units together so that either can be used without disturbing the other.....normally I use the elec heating for the odd cooler nights and when the house needs more heat I start up the wood fire, which will run full time......I can offer plans of sorts for a heating engineer to look at in a P.Message....have done this before in my current house but a normal layout not the upside down variety.........works well......you should know that these 3 imersion heaters are fed by a 3phase supply now and in the new house....

thanks for any help offered.......clogs

Clogs, Hi we have a large log burner heating a largish hot water tank as a back up i have an electric heater to heat the water it powers a wet underfloor downstairs radiators upstairs and provides domestic hot water. It works like this the big tank is called a heat store, it is sort of oppositte a normal central heating so the tank contains the hot water directly connected to the heaters and underfloor and the electric heater the domestic hot water is mains fed through a high efficiency heat exchanger in the tank there are 3 pumps one in line with the electric heater to push that water through and into the tank, one to circulate hot water to the underfloor ( which also has its own pump) and one to circulate through the radiators, i guess i am using the tank as a manifold although the underfloor zones are on a seperate one, all works well.

Look up Dunsley Baker neutraliser, it is a tank which is fed from both heat sources, and has all heat demands tapped off it. Have used them before, and they work very well. Beware of underfloor heating using a wood or solid fuel burner as a heat source. The UFH manifold blends flow and return water to match the temp requirements of the UF coils, which is a lower temp than required for radiators. this can result in the heat source overheating if the UF coils are not shedding enough heat., resulting in boiling water going over the expansion loop and filling the header tank with disasterous results! In systems I have installed in the past, I have used pipe stats on the flow to turn pumps on and off, and pipe stats on the return to switch in extra heat sinks (rads etc) to prevent overheating.

A form of heat store is definitely the way but beware some of the specialist ones with multiple coils are staggeringly expensive. They are normally designed to combine solar and wood then have electric as third string. It's a few years since I was looking at this but there used to be fancy units at £2k, less fussy stainless at £1k and plain steel tanks from Poland at £500. Go over to the Navitron forum for some more detailed advice.

good point Phil W........the only time we got into trouble was when a storm shut down the elec supply.......but we are prepared for this, the genny is always ready to go with extension leads for the pumps.......

just to add, having a similar system in the house I'm in already, except for the under floor heating and very large wood boiler, we run rads at the mo.......have found that even running flat out, can't produce more heat than the system can get rid of .......we keep the rad's wide open in all rooms and adjust the heat by the amount of wood we burn.....

this under floor system, I propose to use Hep 2o plastic pipe or something better that will be 15mm dia........def not smaller.........the pipe will be in a 50-60mm sand sandwich between the concrete floor and the insulation......which should help save the pipes if there's a quake.........all the walls in the new place will be "Ytong" themal block (inner and outer skin) the wall's take no loading as the house is steel framed (RSJ'S) like a barn/factory........

the 2 levals of the house will be supplied with just 1 heating loop for each level....no seperate room heating......it's only a small house.........because of seismic loading the min floor thickness has to be not less than 250mm, so plenty for the hot water to do........once the concrete floors are warmed up it's just a case of the heating ticking over........like this stone house I'm in now......walls between 750 and a meter thick.......take about 6 weeks to get the wall's warm and after that were running on a tick over.......

the fire/back boiler is an old but pretty East German cast iron lump that from experience size wise would only heat a 2 bed cottage.......there's no design/capacity plate.......

the winter temps only go down to an average of 3-4 degrees with the odd dip to freezing, so I don't need mass's of heat......plan to use the odd oil filled radiator for a top up if necc....winters are very short 6-8weeks at most......snow once in 25 years........

plan to make or get made the tank from st/steel with the 2 1/4 bsp fitting's welded in along with a drain, vent and the necc pipe connectors.......

thanks for all your replys....will def look at the Navitron site.....

cheers Clogs

For an either/or situation how about a two way changeover valve, that connects one or the other heat source to where it is needed?

If you wanted both heat sources at the same time, you could have a second valve connected in parallel with the first, but connected 180 degrees out of phase.

No 1 is used to select the heat source, the second could then connect the second source. There is, however, always the risk that one heat source tending to act as a feed water heater to the other. So that you are then into installing check valves!

Life never was simple.

Howard

I forgot you were not in UK. Check your regulations for the requirement to have a heat leak radiator above the level of the wood stove for thermosyphon when the power fails. Also allow for water expanding by 10% when heated. UK regs also have rules over emergency vents and cold water replenishment.

thanks Bazyle + Howard L, the plan is to have 20 gallon tank for the feed and overflow.......operating at 1/2 full, should be enough capasity with the necc overflow to the outside.........

as far as I can find out there are only regs for a non-vented systems where oil is the fuel source.....

as for the change over valves, my idea is to keep everything as simple as poss and to use the tank with the emersion heaters in as the maniflold supplying pumped hot water for the heating........

which brings to mind that when the heating is on, up/dpwnstairs are always on together....no good being toasty upstairs and the workshop cold.......

thanks for all the help from everyone, think I've got it nailed now.....

tis a great forum to be sure.....somebody needs to work out how to win the Lottery.........hahaha......

Clogs........

Just a thought, your feed and expansion tank needs to be metal.

A plastic tank with boiling water and steam flowing through it can soon collapse; you then gave a very hot shower flowing down through your ceilings/floors.