two pipe p/s

Paul S_3

I'm installing a two pipe primary secondary system.....boiler is a crown bimini Bwc 120....I want insight on this job....so be as critical as you want....never done a two pipe p/s system....the first set of tee's(3/4") is for the radiant in slab for first floor (36,000 btu) it has iseries 3 way with taco bumble bee which will be set up for delta t(unless you guys recommend other)....and the tee's for the radiant do you guys think they are to close to the return pipe? The next set of tees which the cross over bridge isn't piped yet will be for two baseboard zones a total of 57000 BTUs....will be using 1"pipe (5.7gpm)..the bottom cross over bridge/set of closely spaced tees will be for a snow melt system using a brazed plated heat exchanger.....(keep in mind snow melt was not done by me....contractor ran 3 280ft 3/4" pex already explained the way he ran the tubing against my recommendations that it probably wouldn't melt snow and ice evenly....any insight would help....and I will change what I have to thanks Paul s

Steve Whitbeck

piping

wet rotor pumps should be installed with the motor armature horizontal.

The boiler P/S closely spaced tee's - I usually install first and then the air elimination system and then the system pump. Where the supply line comes off of the boiler going up and then down to the closely spaced tee's tends to trap air did you install an air vent at the high point? I try to make the air eliminator the high point of the system. Why didn't you go with the new tire tube design?

Paul S_3

air vent

There is a air vent at the cross fitting at the supply at the boiler where the lwco and relief valve is....I always pipe my p/s systems with the boiler loop closely spaced tees behind the primary pump and the spiro vent....but in the manual from crown shows the closely spaced tees in front of the primary pump and crown says it would void warranty if I don't pipe it there way....I posted a thread about this recently....Paul s

Steve Whitbeck

loop

Instead of the second system loop with the big pump I would have just done a return and supply header and ran a much smaller ( properly sized ) pump for each supply circuit. That second loop just adds a LOT of cost and no added benefit. It doesn't have enough mass to stop short cycling. I would not tie the snow melt into that boiler that is heating the house - it isn't big enough to do both jobs and the house heating will suffer unless you do an injection system that maintains a minimum supply temp. 3 280 foot loops is a LOT of snowmelt for a 120,000 BTU boiler.

Paul S_3

what about

A tekmar 667 snow melt mixing control.....if I use that would that help? Snow melt load is 82,000btus....I was supposed to design and install but homeowner changed his mind to cut cost....(bad move)...andabout just running a supply and return header doesn't the boiler cause a severe pressure drop? And manufacture says it is not recommended and needs at least 8gpm to operate properly....and if only one zone would call wouldn't there be a problem?...thanks Paul s

Paul S_3

oh

I think you meant keep the boiler loop....and for the system just connect a supply and return header for the zones?.....what application would be ideal for a 2 pipe p/s system? Could I have used a caleffi hydro separator? Connecting the boiler loop to one side and the system to the other? Thanks Paul s

Steve Whitbeck

Tekmar

A return header then the closely spaced tees, air eliminator and then the supply header. That way the boiler gets the flow it needs and each load gets the pumped flow it needs. The Tekmar control will solve the boiler not being able to heat the house but it won't melt snow either. I went down this road many years ago when a salesman told me what he had sold. One boiler for both house heat and snow melt. 900,000 BTU boiler to do both and when it got real cold it wouldn't keep the house at 70*. The customer had a long driveway 400 ft with 200 ft up a steep hill.

I couldn't turn the snowmelt off at 0* because of the hill.

Do you have enough money in the job for that Tekmar - they aren't cheap.

Steve Whitbeck

P/S

The boiler loop with the closely spaced tee's is a primary / secondary system.

A hydro separator would work but it costs a lot more than the tee's.

Paul S_3

tekmar

I explained to the customer about the tekmar control.....I know the price its expensive....but even with the control you don't think it can melt snow/ice....but the customer also asked me in the beginning of job if he can just have a on/off switch to control snow melt....which I explained it does not work that way, that it takes time to raise the slab temp....I just don't want another company to come and do some shotty work with the snow melt and get it to work without the control then I lose a customer.....thanks Paul s

Steve Whitbeck

boiler

You just don't have enough boiler to do both. You can do an off switch as long as the customer doesn't expect instant melting. The tekmar will help.